Journal articles: 'Adiabatic production of single photons'

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Fernandez, E., W. T. Ford, N. Qi, A. L. Read, J. G. Smith, T. Camporesi, R. De Sangro, et al. "Search for Single Photons from Supersymmetric Particle Production." Physical Review Letters 54, no. 11 (March 18, 1985): 1118–21. http://dx.doi.org/10.1103/physrevlett.54.1118.

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Brange, Fredrik, Adrian Schmidt, Johannes C. Bayer, Timo Wagner, Christian Flindt, and Rolf J. Haug. "Controlled emission time statistics of a dynamic single-electron transistor." Science Advances 7, no. 2 (January 2021): eabe0793. http://dx.doi.org/10.1126/sciadv.abe0793.

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Quantum technologies involving qubit measurements based on electronic interferometers rely critically on accurate single-particle emission. However, achieving precisely timed operations requires exquisite control of the single-particle sources in the time domain. Here, we demonstrate accurate control of the emission time statistics of a dynamic single-electron transistor by measuring the waiting times between emitted electrons. By ramping up the modulation frequency, we controllably drive the system through a crossover from adiabatic to nonadiabatic dynamics, which we visualize by measuring the temporal fluctuations at the single-electron level and explain using detailed theory. Our work paves the way for future technologies based on the ability to control, transmit, and detect single quanta of charge or heat in the form of electrons, photons, or phonons.

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GOGYAN, ANAHIT, STÉPHANE GUÉRIN, HANS-RUDOLF JAUSLIN, and YURI MALAKYAN. "DETERMINISTIC GENERATION OF INDISTINGUISHABLE SINGLE-PHOTON PULSES IN THE SINGLE-ATOM-CAVITY QED SYSTEM." International Journal of Quantum Information 09, supp01 (January 2011): 239–49. http://dx.doi.org/10.1142/s0219749911007253.

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We present a mechanism to produce indistinguishable single-photon pulses on demand from a single atom-optical cavity system. We use sequences of two laser pulses of alternate circular polarizations at the two Raman transitions of a four-level atom. They allow the production of the same cavity-mode photons without repumping of the atom between photon generations. Photons that are emitted from the cavity with near-unity efficiency in well-defined temporal modes, feature the same polarization, frequency and identical shapes, controlled by the laser fields. The second order correlation function reveals the single-photon nature of the proposed source. A realistic setup for the experimental implementation is presented.

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Wei, Yu-Jia, Yu-Ming He, Ming-Cheng Chen, Yi-Nan Hu, Yu He, Dian Wu, Christian Schneider, et al. "Deterministic and Robust Generation of Single Photons from a Single Quantum Dot with 99.5% Indistinguishability Using Adiabatic Rapid Passage." Nano Letters 14, no. 11 (October 30, 2014): 6515–19. http://dx.doi.org/10.1021/nl503081n.

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MARIOTTO, C. BRENNER, and V. P. GONÇALVES. "NONLINEAR GLUON EVOLUTION AND PHOTON PRODUCTION IN HADRONIC COLLISIONS." International Journal of Modern Physics E 16, no. 09 (October 2007): 2984–88. http://dx.doi.org/10.1142/s0218301307008872.

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In this contribution we consider the influence of nonlinear gluon evolution in the production of prompt photons at the LHC pp collider. We consider the EHKQS parton distributions, which are based on the GLR-MQ evolution equations, and imply in an enhanced small-x gluon distribution at Q2 ≤ 10 GeV 2 relative to the LO DGLAP gluon distribution. We find an enhancement of low-pT photons for both single and double photon production. Consequences of this effect for the Quark-Gluon Plasma searches and for the QCD background to Higgs are also discussed.

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BIANCHI, NICOLA. "EXCLUSIVE MESON AND PHOTON PRODUCTION AT HERMES." International Journal of Modern Physics A 18, no. 08 (March 30, 2003): 1311–18. http://dx.doi.org/10.1142/s0217751x03014654.

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First promising results for exclusive electroproduction of vector mesons, pseudoscalar mesons and real photons from HERMES are presented. Different observables like cross sections and single spin azimuthal asymmetries have been investigated. Results have been discussed within the recent formalism of the Generalized Parton Distributions.

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Ford, W. T., N. Qi, A. L. Read, J. G. Smith, T. Camporesi, I. Peruzzi, M. Piccolo, et al. "search for single photons from radiative neutrino or supersymmetric-particle production." Physical Review D 33, no. 11 (June 1, 1986): 3472–75. http://dx.doi.org/10.1103/physrevd.33.3472.

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Adam, W., T. Adye, E. Agasi, I. Ajinenko, R. Aleksan, G. D. Alekseev, R. Alemany, et al. "Search for anomalous production of single photons at and 136 GeV." Physics Letters B 380, no. 3-4 (July 1996): 471–79. http://dx.doi.org/10.1016/0370-2693(96)00671-5.

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Sawyer, R. F. "Production of single plasmons and photons by neutrinos in a medium." Physical Review D 46, no. 3 (August 1, 1992): 1180–85. http://dx.doi.org/10.1103/physrevd.46.1180.

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Astraatmadja, Tri L. "Detecting TeV γ-rays from GRBs with km3 neutrino telescopes." Proceedings of the International Astronomical Union 7, S279 (April 2011): 321–22. http://dx.doi.org/10.1017/s1743921312013154.

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AbstractObserving TeV photons from GRBs can greatly enhance our understanding of their emission mechanisms. Under-sea/ice neutrino telescopes—such as ANTARES in the Mediterranean Sea or IceCube at the South Pole—can also operate as a γ-ray observatory by detecting downgoing muons from the electromagnetic cascade induced by the interaction of the photons with the Earth's atmosphere. Theoretical calculations of the number of detectable muons from single GRB events, located at different redshifts and zenith distances, have been performed. The attenuation by pair production of TeV photons with cosmic infrared background photons has also been included.

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Vogelsang, W. "Next-to-leading order hadronic single-spin production of polarized prompt photons." Physical Review D 50, no. 7 (October 1, 1994): 4436–46. http://dx.doi.org/10.1103/physrevd.50.4436.

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Dom, Rekha, Hyun Gyu Kim, and Pramod H. Borse. "Investigation of Solar Photoelectrochemical Hydrogen Generation Ability of Ferrites for Energy Production." Materials Science Forum 764 (July 2013): 97–115. http://dx.doi.org/10.4028/www.scientific.net/msf.764.97.

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Ferrites have been predicted to be potential material for photo catalytic and photo electrochemical (PEC) hydrogen generation under visible light photons. The article briefly reviews, as well as compares the supremacy of ferrites over titanates and sulfides with respect to their photo-electro catalytic hydrogen producing ability. It shows that though the band energetic of a material plays a vital role to induce the photo-splitting of water; but its optical structure, at the first instance is very important to utilize it to absorb the visible light photons. Among all the PEC materials, the low-band gap ferrites (Fe-d orbital) favor absorption of visible light photons; at the same time offer an advantage of being an eco-friendly material system. A specific focus is given to the single phase, nanostructure and composite forms of typical ZnFe2O4system. Though a concise report, but also throws light on the importance and tunability of PEC properties.

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Lombardi, Pietro, Maja Colautti, Rocco Duquennoy, Ghulam Murtaza, Prosenjit Majumder, and Costanza Toninelli. "Indistinguishable Photons from a Single Molecule under Pulsed Excitation." EPJ Web of Conferences 255 (2021): 06002. http://dx.doi.org/10.1051/epjconf/202125506002.

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Quantum light sources are crucial for the future of quantum photonic technologies and, among them, single photons on-demand are key resources in quantum communications and information processing. Ideal quantum emitters providing indistinguishable photons in a clocked manner, negligible decoherence and spectral diffusion, and with potential for scalability are today still a major challenge. We report on photostable and indistinguishable single photon emission from dibenzoterrylene molecules isolated in anthracene nanocrystals (DBT:Ac NCs) at 3K. The visibility of two-photon interference is preserved even when they are separated more than thirty times the excited-state lifetime, or ten fluorescence cycles. One of the advantages of organic molecules is the low-cost mass production of nominally identical emitters, that also allow for on-chip integration. These aspects combined with high spectral stability and coherence make them promising for applications and future quantum technologies.

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KOZLOV, G. A., and I. N. GORBUNOV. "DILATON DECAYS INTO UNPARTICLES AND A SINGLE PHOTON." International Journal of Modern Physics A 26, no. 23 (September 20, 2011): 3987–96. http://dx.doi.org/10.1142/s0217751x11054024.

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We study the production of the vector U-unparticle stuff and a single photon in decays of a dilaton. The signals of an unparticle can be detected through the missing energy and momentum distribution carried away by U once it was produced in radiative decay of a dilaton. The continuous energy spectrum of the emitted photons encoding the recoil unparticle can be measured in precision studies of rare decays of the dilaton or Higgs-boson after their discoveries.

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Hearty, C., J. E. Rothberg, K. K. Young, A. S. Johnson, J. S. Whitaker, R. J. Wilson, G. Bartha, et al. "Search for the anomalous production of single photons ine+e−annihilation at√s =29GeV." Physical Review D 39, no. 11 (June 1, 1989): 3207–26. http://dx.doi.org/10.1103/physrevd.39.3207.

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MKRTCHYAN, A. R., A. A. SAHARIAN, and V. V. PARAZIAN. "COHERENT PAIR PRODUCTION IN CRYSTALS IN PRESENCE OF ACOUSTIC WAVES." International Journal of Modern Physics A 25, supp01 (June 2010): 47–54. http://dx.doi.org/10.1142/s0217751x10049906.

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Coherent electron-positron pair production by high-energy photons is investigated in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The conditions are specified under which the influence of the deformation is considerable. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for SiO 2 single crystal in the case of the deformation field generated by the acoustic wave of the S type. It is shown that, in dependence of the parameters, the presence of deformation can either enhance or reduce the pair creation cross-section.

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Caliskan, A. "Single production of composite electrons at future SPPC-based lepton–hadron colliders." Canadian Journal of Physics 98, no. 4 (April 2020): 349–56. http://dx.doi.org/10.1139/cjp-2019-0216.

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We consider the production of excited electrons with spin-1/2 at future SPPC-based electron–proton colliders with center-of-mass energies of 8.4, 11.6, 26.6, and 36.8 TeV. These exotic particles are predicted in the composite models. We calculate the production cross sections and concentrate on the photon decay channel of the excited electrons with the process of ep → e∗X → eγX. The pseudo rapidity and transverse momentum distributions of the electrons and photons in the final state have been plotted to determine the kinematical cutoffs best suited for discovery of the excited electrons. By applying these cutoffs we compute 2σ, 3σ, and 5σ contour plots of the statistical significance of the expected signal in the parameter space (L, m∗), where L denotes the integrated luminosity of the collider and m∗ is the mass of the composite electrons.

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PITONYAK, DANIEL. "DOUBLE SPIN ASYMMETRY ALT IN THE PRODUCTION OF PHOTONS, HADRONS, AND JETS." International Journal of Modern Physics: Conference Series 20 (January 2012): 29–36. http://dx.doi.org/10.1142/s2010194512009063.

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We calculate the double spin asymmetry (DSA) ALT in proton-proton (pp) collisions for the production of photons, hadrons, and jets in the collinear twist-3 framework. These processes allows us for the first time to access a complete set of collinear twist-3 functions. We also give numerical estimates for the asymmetries of which photon production shows the most promise of a measurable effect. Furthermore, we comment on how these asymmetries would allow us to probe the gluon helicity down to as of yet unexplored x values, remark on the importance of these effects in determining the evolution of the Efremov-Teryaev-Qiu-Sterman (ETQS) function TF(x, x), and discuss their usefulness in resolving the true mechanism behind the large transverse single spin asymmetries (SSAs) measured in pp collisions.

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de Menezes, Raniere, Raffaele D’Abrusco, Francesco Massaro, and Sara Buson. "The Isotropic γ-ray Emission above 100 GeV: Where Do Very High-energy γ-rays Come From?" Astrophysical Journal 933, no. 2 (July 1, 2022): 213. http://dx.doi.org/10.3847/1538-4357/ac771d.

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Abstract Astrophysical sources of very high energy (VHE; >100 GeV) γ-rays are rare, since GeV and TeV photons can be only emitted in extreme circumstances involving interactions of relativistic particles with local radiation and magnetic fields. In the context of the Fermi Large Area Telescope (LAT), only a few sources are known to be VHE emitters, where the largest fraction belongs to the rarest class of active galactic nuclei: the blazars. In this work, we explore Fermi-LAT data for energies >100 GeV and Galactic latitudes b > ∣50°∣ in order to probe the origin of the extragalactic isotropic γ-ray emission. Since the production of such VHE photons requires very specific astrophysical conditions, we would expect that the majority of the VHE photons from the isotropic γ-ray emission originate from blazars or other extreme objects like star-forming galaxies, γ-ray bursts, and radio galaxies, and that the detection of a single VHE photon at the adopted Galactic latitudes would be enough to unambiguously trace the presence of such a counterpart. Our results suggest that blazars are, by far, the dominant class of sources above 100 GeV, although they account for only 22.8 − 4.1 + 4.5 % of the extragalactic VHE photons. The remaining 77 − 4.5 + 4.1 % of the VHE photons still have an unknown origin.

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MKRTCHYAN, A. R., A. A. SAHARIAN, and V. V. PARAZIAN. "COHERENT PAIR PRODUCTION IN DEFORMED CRYSTALS WITH A COMPLEX BASE." Modern Physics Letters B 20, no. 25 (October 30, 2006): 1617–27. http://dx.doi.org/10.1142/s0217984906012018.

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We investigate the coherent electron–positron pair creation by high-energy photons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The conditions are specified under which the influence of the deformation is considerable. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for SiO 2 single crystal and Moliere parametrization of the screened atomic potentials in the case of the deformation field generated by the acoustic wave of S type. In dependence of the parameters, the presence of deformation can either enhance or reduce the pair creation cross-section. This can be used to control the parameters of the positron sources for storage rings and colliders.

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Cardano, Filippo, Francesco Massa, Hammam Qassim, Ebrahim Karimi, Sergei Slussarenko, Domenico Paparo, Corrado de Lisio, et al. "Quantum walks and wavepacket dynamics on a lattice with twisted photons." Science Advances 1, no. 2 (March 2015): e1500087. http://dx.doi.org/10.1126/sciadv.1500087.

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The “quantum walk” has emerged recently as a paradigmatic process for the dynamic simulation of complex quantum systems, entanglement production and quantum computation. Hitherto, photonic implementations of quantum walks have mainly been based on multipath interferometric schemes in real space. We report the experimental realization of a discrete quantum walk taking place in the orbital angular momentum space of light, both for a single photon and for two simultaneous photons. In contrast to previous implementations, the whole process develops in a single light beam, with no need of interferometers; it requires optical resources scaling linearly with the number of steps; and it allows flexible control of input and output superposition states. Exploiting the latter property, we explored the system band structure in momentum space and the associated spin-orbit topological features by simulating the quantum dynamics of Gaussian wavepackets. Our demonstration introduces a novel versatile photonic platform for quantum simulations.

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MKRTCHYAN, A. R., A. A. SAHARIAN, L. SH GRIGORYAN, and B. V. KHACHATRYAN. "ON THE THEORY OF COHERENT PAIR PRODUCTION IN CRYSTALS IN THE PRESENCE OF ACOUSTIC WAVES." Modern Physics Letters A 17, no. 39 (December 21, 2002): 2571–80. http://dx.doi.org/10.1142/s0217732302008228.

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The influence of hypersonic waves excited in a single crystal is investigated on the process of electron–positron pair creation by high-energy photons. The coherent part of the corresponding differential cross-section is derived as a function of the amplitude and wave number of the hypersound. The values of the parameters are specified for which the latter affects remarkably on the pair creation cross-section. It is shown that under certain conditions the presence of hypersonic waves can result in enhancement of the process cross-section.

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Compagnin, Federico, Stefano Profumo, and Nicolao Fornengo. "MeV dark matter with MeV dark photons in Abelian kinetic mixing theories." Journal of Cosmology and Astroparticle Physics 2023, no. 03 (March 1, 2023): 061. http://dx.doi.org/10.1088/1475-7516/2023/03/061.

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Abstract We consider the cosmology and phenomenology of a dark photon portal to a simple dark sector consisting of a single, light, fermionic dark matter particle species with mass in the MeV range. We entertain three possible kinetic mixing structures of a new Abelian gauge group U(1)dark with the visible sector through U(1)e.m., U(1)Y and T[SU(2)_L]. We assume the dark photon to be massive and around the MeV scale, thus close to the mass scale of the dark matter candidate. We compute the dark matter relic density via freeze-out and freeze-in, entertaining the additional possibility of a late inflationary period that could dilute the dark matter yield of heavy candidates, and (ii) additional production modes, for models with under-abundant thermal production. We explore the parameter space compatible with a variety of experimental and astrophysical bounds, and discuss prospects for discovery with new CMB probes and MeV gamma-ray telescopes.

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Nanayakkara, Themiya. "A VLT/MUSE analysis of HeIIλ1640 emitters at z = 2 – 4." Proceedings of the International Astronomical Union 15, S352 (June 2019): 78. http://dx.doi.org/10.1017/s1743921320001143.

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AbstractIn the quest to study early star-formation physics in the universe, one of the most sought after tracers is HeIIλ1640, with its presence in the lack of other metal emission/absorption lines generally being interpreted as evidence for metal-poor stellar populations. HeII ionizing photons are produced via sources of hard ionizing radiation and requires photons with energies ⩾ 54.4eV, however, traditional stellar population models lack sufficient ionising photons to match with current observations. Our analysis of z = 2 – 4 HeIIλ1640 emitters from deep 10-30h pointings from MUSE has shown that ISM properties inferred from multiple rest-UV diagnostics are not compatible with requirements necessary to reproduce HeIIλ1640 equivalent-widths. Thus, we have used latest generation of single, rotational, and binary stellar population models with realistic dust physics to explore rest-UV emission line diagnostics and link with H and He+ ionisation photon production efficiencies (ξion (H,He+)) in a variety of stellar/gas metallicities and star-formation histories. I will discus our latest results and show that including ‘exotic’ stellar phenomena such as extreme low-metallicity binary stars, X-ray binaries, and dust dissociation physics may be necessary to lessen the tension between models and observations.

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Baskakov, Alexey, Eduard Boos, Viacheslav Bunichev, Maxim Perfilov, and Igor Volobuev. "Restrictions on the mass of the KK excitation W′ from the Higgs boson diphoton decay and the single top production." EPJ Web of Conferences 191 (2018): 02007. http://dx.doi.org/10.1051/epjconf/201819102007.

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In the framework of stabilized brane-world models we consider the contribution of the W′ boson and the rest of the W boson KK tower to the Higgs boson decay to two photons and to the single top production process. Comparing the signal strengths calculated in this approach with the experimental ones obtained at the LHC and taking into account the expected improvements at future high luminosity HL-LHC, high energy HE-LHC, and FCC-hh projects, we get predictions for the limits on the W' boson mass depending on its coupling to SM fermions.

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Albaltan, Weeam S., Alexei Prokudin, and Marc Schlegel. "The transverse nucleon single-spin asymmetry for the semi-inclusive production of photons in lepton-nucleon scattering." Physics Letters B 804 (May 2020): 135367. http://dx.doi.org/10.1016/j.physletb.2020.135367.

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Utzat, Hendrik, Weiwei Sun, Alexander E. K. Kaplan, Franziska Krieg, Matthias Ginterseder, Boris Spokoyny, Nathan D. Klein, et al. "Coherent single-photon emission from colloidal lead halide perovskite quantum dots." Science 363, no. 6431 (February 21, 2019): 1068–72. http://dx.doi.org/10.1126/science.aau7392.

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Chemically made colloidal semiconductor quantum dots have long been proposed as scalable and color-tunable single emitters in quantum optics, but they have typically suffered from prohibitively incoherent emission. We now demonstrate that individual colloidal lead halide perovskite quantum dots (PQDs) display highly efficient single-photon emission with optical coherence times as long as 80 picoseconds, an appreciable fraction of their 210-picosecond radiative lifetimes. These measurements suggest that PQDs should be explored as building blocks in sources of indistinguishable single photons and entangled photon pairs. Our results present a starting point for the rational design of lead halide perovskite–based quantum emitters that have fast emission, wide spectral tunability, and scalable production and that benefit from the hybrid integration with nanophotonic components that has been demonstrated for colloidal materials.

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Siwal, Davinder, and G. Anil Kumar. "Optical photon transport simulations for SiPM based PET scanner." Journal of Physics: Conference Series 2663, no. 1 (December 1, 2023): 012042. http://dx.doi.org/10.1088/1742-6596/2663/1/012042.

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Abstract Positrons emitted from radioisotope quickly annihilates to two collinear photons that are captured by the array of scintillator detectors to infer about the origin of radioactivity. Coincidence collection of pair of points from the detector modules makes a line of response, their large number reveals a radioactive region of interest. Most of the medical diagnostic research is conducted with position sensitive imaging device whose performance strongly depends on the optical light collection efficiency. A versatile Lutetium–Yttrium Oxyorthosilicate (LYSO) scintillator is used to mimic the optical photon production and transport processes followed by the light collection with Silicon PhotoMultiplier sensor. Charge spectrum from a 2 × 2 × 10 mm3 single LYSO bar is obtained in GEANT4, and reproduces well the scintillation characteristics of LYSO along with photons incidence angle distribution with a single SiPM pad. This excercise is followed by the simulation performance of two PET modules comprises of 12 × 12 SiPM tile coupled with mesh of LYSO bars. The preliminarly results shows the transverse position resolution (FWHM) as 7.82 mm for a point source. Objective of this study is to search for a cheaper detector solution which will have equivalent imaging performance.

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Aiello, S., A. Albert, M. Alshamsi, S. Alves Garre, Z. Aly, A. Ambrosone, F. Ameli, et al. "The KM3NeT multi-PMT optical module." Journal of Instrumentation 17, no. 07 (July 1, 2022): P07038. http://dx.doi.org/10.1088/1748-0221/17/07/p07038.

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Abstract The optical module of the KM3NeT neutrino telescope is an innovative multi-faceted large area photodetection module. It contains 31 three-inch photomultiplier tubes in a single 0.44 m diameter pressure-resistant glass sphere. The module is a sensory device also comprising calibration instruments and electronics for power, readout and data acquisition. It is capped with a breakout-box with electronics for connection to an electro-optical cable for power and long-distance communication to the onshore control station. The design of the module was qualified for the first time in the deep sea in 2013. Since then, the technology has been further improved to meet requirements of scalability, cost-effectiveness and high reliability. The module features a sub-nanosecond timing accuracy and a dynamic range allowing the measurement of a single photon up to a cascade of thousands of photons, suited for the measurement of the Cherenkov radiation induced in water by secondary particles from interactions of neutrinos with energies in the range of GeV to PeV. A distributed production model has been implemented for the delivery of more than 6000 modules in the coming few years with an average production rate of more than 100 modules per month. In this paper a review is presented of the design of the multi-PMT KM3NeT optical module with a proven effective background suppression and signal recognition and sensitivity to the incoming direction of photons.

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Arai, Takashi. "Asymptotic expansion of pair production probability in a time-dependent electric field." International Journal of Modern Physics A 30, no. 35 (December 20, 2015): 1550210. http://dx.doi.org/10.1142/s0217751x15502103.

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We study particle creation in a single pulse of an electric field in scalar quantum electrodynamics. We investigate the parameter condition for the case where the dynamical pair creation and Schwinger mechanism respectively dominate. Then, an asymptotic expansion for the particle distribution in terms of the time interval of the applied electric field is derived. We compare our result with particle creation in a constant electric field with a finite-time interval. These results coincide in an extremely strong field, however they differ in general field strength. We interpret the reason of this difference as a nonperturbative effect of high-frequency photons in external electric fields. Moreover, we find that the next-to-leading-order term in our asymptotic expansion coincides with the derivative expansion of the effective action.

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Ninic, Neven, Branko Klarin, and Ivan Tolj. "Hybrid wind-power-distillation plant." Thermal Science 16, no. 1 (2012): 251–61. http://dx.doi.org/10.2298/tsci111022032n.

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This paper reports and elaborates on the idea of a solar distiller and an offshore wind power plant operating together. The subject under discussion is a single-stage solar distillation plant with vaporization, using adiabatic expansion in the gravitational field inside a wind power plant supporting column. This scheme divides investment costs for electric power and distillate production. In the region of the Adriatic Sea, all electric power produced could be ?converted? to hydrogen using less than 10% of the distillate produced.

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Yung, L. Y. Aaron, Rachel S. Somerville, Gergö Popping, and Steven L. Finkelstein. "Semi-analytic forecasts for JWST – III. Intrinsic production efficiency of Lyman-continuum radiation." Monthly Notices of the Royal Astronomical Society 494, no. 1 (March 14, 2020): 1002–17. http://dx.doi.org/10.1093/mnras/staa714.

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ABSTRACT The James Webb Space Telescope is expected to enable transformational progress in studying galaxy populations in the very early Universe, during the epoch of reionization. A critical parameter for understanding the sources that reionized the Universe is the Lyman-continuum production efficiency, ξion, defined as the rate of production of ionizing photons divided by the intrinsic UV luminosity. In this work, we combine self-consistent star formation and chemical enrichment histories predicted by semi-analytic models of galaxy formation with stellar population synthesis (SPS) models to predict the expected dependence of ξion on galaxy properties and cosmic epoch from z = 4–10. We then explore the sensitivity of the production rate of ionizing photons, $\dot{N}_\text{ion}$, to the choice of SPS model and the treatment of stellar feedback in our galaxy formation model. We compare our results to those of other simulations, constraints from empirical models, and observations. We find that adopting SPS models that include binary stars predict about a factor of 2 more ionizing radiation than models that only assume single stellar populations. We find that UV-faint, low-mass galaxies have values of ξion about 0.25 dex higher than those of more massive galaxies, but find weak evolution with cosmic time, about 0.2 dex from z ∼ 12–4 at fixed rest-UV luminosity. We provide predictions of $\dot{N}_\text{ion}$ as a function of Mh and a number of other galaxy properties. All results presented in this work are available at https://www.simonsfoundation.org/semi-analytic-forecasts-for-jwst/.

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KOTKIN, G. L., V. G. SERBO, and A. SCHILLER. "PROCESSES WITH LARGE IMPACT PARAMETERS AT COLLIDING BEAMS." International Journal of Modern Physics A 07, no. 20 (August 10, 1992): 4707–45. http://dx.doi.org/10.1142/s0217751x92002131.

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At the collider VEPP-4 a remarkable deviation of the measured bremsstrahlung photons from the standard calculation method has been measured in the reaction e+e−→e+e−γ. The decreasing number of photons is explained by the fact that large impact parameters give the essential contributions to the cross section. These parameters are by several orders of magnitude larger than the transverse beam sizes. In that case the standard definitions of “cross section” and “number of events” are invalid. Similar effects are expected for the single photon bremsstrahlung and the e+e− pair production at existing and planned high energy e±e−, ep and eγ colliders. A calculation scheme for particle production in the interaction of two bunches, which allows one to take into account these effects quantitatively, is presented. In this scheme the colliding bunches are represented as wave packets, and quantum distribution functions are used. The modified definitions of the cross section and the number of events contain the features of “nonlocality” and “interference”. Reasonable approximations which can be easily used are discussed. The results are applied to analyze the influence of the finite beam sizes on reactions which have been proposed for measuring the luminosity and the beam polarization at the colliders LEP and HERA.

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Hirotani, K. "Gamma-ray Emission from Pulsar Outer Magnetospheres." Symposium - International Astronomical Union 195 (2000): 171–80. http://dx.doi.org/10.1017/s0074180900162904.

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We study the γ-ray emission from an outer-gap accelerator around a rotating neutron star. Assuming the existence of global currents in the magnetosphere, the charge depletion causes a large electric field along the magnetic field lines. This electric field accelerates migratory electrons and positrons which radiate gamma-rays via curvature radiation. These gamma-rays, in turn, produce yet more radiating particles by colliding with the X-rays, leading to a pair-production cascade. Imposing a gap-closure condition that a single pair produces one pair in the gap, on average, we explicitly solve the strength of the acceleration field and demonstrate how the peak energy and the luminosity of the curvature-radiated GeV photons and the cutoff energy and luminosity of Compton-scattered TeV photons depend on such parameters as the surface temperature, the rotational frequency, and the magnetic moment. It is demonstrated that both the GeV and TeV emissions of Geminga will be harder than those of B1055-52, B0656+14, and Vela, and that the TeV fluxes are too small to be observed by current ground-based telescopes.

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White, John, Victoria Centonze, David Wokosin, and William Mohler. "Using Multiphoton Microscopy for the Study of Embryogenesis." Microscopy and Microanalysis 3, S2 (August 1997): 307–8. http://dx.doi.org/10.1017/s1431927600008424.

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Multiphoton fluorescence excitation imaging is an optical sectioning technique for fluorescence microscopy. At very high photon densities, two or more photons may coordinately excite an energy transition in a fluorophore that corresponds to the sum of the energies of the individual photons. by this means, a fluorophore may be excited by a wavelength that is considerably longer than its single photon excitation wavelength. Ultra-fast pulsed (femtosecond) lasers can produce the peak power densities in the focal volume of an objective lens needed to provide sufficient 2- or 3- photon excitation events for imaging. The use of short-pulse lasers provides the high peak powers necessary for imaging yet with modest mean power levels that do not thermally damage biological specimens. Production of multiphoton events depends on the square of photon density for 2-photon excitation and the cube of photon density for 3-photon excitation. The power density therefore rapidly falls off away from the focal volume of an objective lens, thereby confining fluorescence excitation to the focal volume.

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KOVCHEGOV, YURI V., and MATTHEW D. SIEVERT. "SINGLE SPIN ASYMMETRY IN HIGH ENERGY QCD." International Journal of Modern Physics: Conference Series 20 (January 2012): 177–86. http://dx.doi.org/10.1142/s2010194512009221.

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We present the first steps in an effort to incorporate the physics of transverse spin asymmetries into the saturation formalism of high energy QCD. We consider a simple model in which a transversely polarized quark scatters on a proton or nuclear target. Using the light-cone perturbation theory the hadron production cross section can be written as a convolution of the light-cone wave function squared and the interaction with the target. To generate the single transverse spin asymmetry (STSA) either the wave function squared or the interaction with the target has to be T-odd. In this work we use the lowest-order q → q G wave function squared, which is T-even, generating the STSA from the T-odd interaction with the target mediated by an odderon exchange. We study the properties of the obtained STSA, some of which are in qualitative agreement with experiment: STSA increases with increasing projectile xF and is a non-monotonic function of the transverse momentum kT. Our mechanism predicts that the quark STSA in polarized proton–nucleus collisions should be much smaller than in polarized proton–proton collisions. We also observe that the STSA for prompt photons due to our mechanism is zero within the accuracy of the approximation.

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Tarrús Castellà, Jaume. "Exotic bottomonium hadronic transitions." EPJ Web of Conferences 274 (2022): 04011. http://dx.doi.org/10.1051/epjconf/202227404011.

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We report on a recent computation of the transitions of exotic bottomonium to standard bottomonium and light quark hadrons. We work under the assumption that the ϓ(10753) and ϓ(11020) can be described as the lowest laying and first excitation 1− − hybrid bottomonium states, respectively. The computation has two distinct parts: the heavy quark transition matrix elements, which are obtained in a nonrelativistic EFT incorporating the heavy quark, multipole and adiabatic expansions; and the hadronization of the gluonic operators into the light-meson final states. The single mesons production is obtained through the axial anomaly and a standard π0 - η - ηʹ mixing scheme. Two pion and kaon production is obtained by solving the coupled Omnès problem. We also present result for semi-inclusive transitions.

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Pal, P. S., Arnab Saha, and A. M. Jayannavar. "Operational characteristics of single-particle heat engines and refrigerators with time-asymmetric protocol." International Journal of Modern Physics B 30, no. 31 (December 5, 2016): 1650219. http://dx.doi.org/10.1142/s0217979216502192.

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We have studied the single-particle heat engine and refrigerator driven by time-asymmetric protocol of finite duration. Our system consists of a particle in a harmonic trap with time-periodic strength that drives the particle cyclically between two baths. Each cycle consists of two isothermal steps at different temperatures and two adiabatic steps connecting them. The system works in irreversible mode of operation even in the quasistatic regime. This is indicated by finite entropy production even in the large cycle time limit. Consequently, Carnot efficiency for heat engine or Carnot coefficient of performance (COP) for refrigerators is not achievable. We further analyzed the phase diagram of heat engines and refrigerators. They are sensitive to time-asymmetry of the protocol. Phase diagram shows several interesting features, often counterintuitive. The distribution of stochastic efficiency and COP is broad and exhibits power-law tails.

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Duval, J. M., T. Prouvé, M. Collier-Wright, A. Drechsler, D. Hindley, M. La Rosa Betancourt, R. Kroll, M. Branco, D. Orgaz Diaz, and S. I. Schlachter. "Qualification and test of space compatible superconducting current leads (REBCO) designed for adiabatic demagnetization refrigerators." IOP Conference Series: Materials Science and Engineering 1302, no. 1 (May 1, 2024): 012014. http://dx.doi.org/10.1088/1757-899x/1302/1/012014.

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Abstract Many astrophysics observations require space telescopes, either to reduce atmospheric perturbation or simply to make these detections possible (in the X-Ray spectrum for example). One of these missions, Athena, is led by the European Space Agency (ESA), with additional international contributions, dedicated to X-Ray observation. Two instruments will be part of this mission and among them, X-IFU, will use Transition Edge Sensors (TES) to detect and precisely measure the energy of X-Ray photons. These sensors require a temperature of 50 mK to reach their ambitious sensitivity goals. In space, this temperature can be reached using Adiabatic Demagnetization Refrigeration (ADR) and such a cooling system is currently being developed for the X-IFU instrument. ADR utilizes magnetocaloric materials which, upon variation in magnetic fields, can produce a cooling effect. The magnetic field of the order of 1 T in a volume of 10s of cm3 is produced by a superconducting coil with high winding number and current limited to approximately 2 A. Even though this current is low compared to most earth-based systems, metallic current leads to link the high- and low-temperature stages would cause high thermal loads, unacceptable for the limited capacity of the cryogenic cooling chain of the spacecraft. Therefore, a harness consisting of superconducting current leads is planned to reduce the thermal loads at the low-temperature stage. As part of an ESA contract, our team designed, built and tested such a space-compatible harness. This harness includes the electrical interfaces at both ends as well as mechanical support. Its development is capable of operating between interfaces at 80 K and 4 K. The harness is based on industrially available Rare-Earth-Barium-Copper-Oxide (REBCO) High-Temperature Superconductor (HTS) tapes. The tapes were laser-cut by our group to fulfill our specifications, Parylene coated and reinforced with Kapton laminate tape for mechanical and insulating purposes. After characterization of the single tapes, the assembled harness has been subjected to an extensive qualification sequence including thermal cycling and mechanical testing based on launch loads requirements. This paper will summarize the technical design choices for this HTS harness. It will discuss the test results and propose some perspectives for the next iteration of the development.

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Daud, Suzairi, Muhammad Ilham Ahmad Zaini, Muhammad Safwan Abd Aziz, and Ahmad Fakhrurrazi Ahmad Noorden. "Generation of Multiwavelength Fibre Laser based on Erbium-Doped Fibre Amplifier with Lyot Filter." Malaysian Journal of Fundamental and Applied Sciences 20, no. 2 (April 24, 2024): 378–84. http://dx.doi.org/10.11113/mjfas.v20n2.3091.

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A ring cavity setup consisting of erbium-doped fibre amplifier (EDFA) as the optical pump and lyot filter aids in the production of a multiwavelength spectrum. The wavelength of EDFA pumps in photons range of 1530 nm to 1560 nm, respectively. Using maximum power of 18 dBm and a single mode fibre (SMF) of 10 km length, the number of peak lasing lines produced between 3 dB spectral range is 51. Tuning of the polarization controller (PC) to a specific angle helps provide the most stable lasing line. Stability test is done on the output multiwavelength fibre laser (MWFL) over a time period to analyze the wavelength stability.

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Pandis, Pavlos K., Eleftherios Michopoulos, Charalambos Arvanitis, Christos Argirusis, Vassilis N. Stathopoulos, Gerasimos Lyberatos, and Asimina Tremouli. "Bioenergy Production from Tannery Waste via a Single-Chamber Microbial Fuel Cell with Fly Ash Cathodic Electrodes." Key Engineering Materials 962 (October 12, 2023): 105–12. http://dx.doi.org/10.4028/p-0xwsyq.

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Microbial Fuel Cells (MFCs) are attracting attention for their application in simultaneous energy production and waste treatment, as innovative biochemical reactors. They usually operate under adiabatic conditions, utilizing microorganisms to treat wastewater compositions using mainly carbon-based electrodes as anodes and cathodes. During the past years, various anodic and cathodic electrodes with plenty of variations were used in MFC configurations. On the anode side metal-based electrodes are used while on the cathode, ceramic electrodes are currently introduced. In this study, a stainless steel anode is used in a single chamber MFC. Ceramic cathodic electrodes are used, coated with Fly Ash (FA). The mixed transition oxides of FA are tested as potential cathodic catalysts in the operation of the MFC. The FA powder was deposited by two methods: an ultrasound-assisted method and a conventional brush coating. Tannery liquid waste is used as the waste/substrate to be treated in the single-chamber MFC. The configuration with ultrasound-assisted Fly-Ash produced cathodic electrodes, led to the highest power output in batch operation modes and a high degree of simultaneous COD decrease of the tannery waste reaching the values of 0.44 mW/gcat and 85.6% COD removal respectively.

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Karavola, D., and M. Petropoulou. "A closer look at the electromagnetic signatures of Bethe-Heitler pair production process in blazars." Journal of Cosmology and Astroparticle Physics 2024, no. 07 (July 1, 2024): 006. http://dx.doi.org/10.1088/1475-7516/2024/07/006.

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Abstract The “twin birth” of a positron and an electron by a photon in the presence of a nucleus, known as Bethe-Heitler pair production, is a key process in astroparticle physics. The Bethe-Heitler process offers a way of channeling energy stored in a population of relativistic protons (or nuclei) to relativistic pairs with extended distributions. Contrary to accelerated leptons, whose maximum energy is limited by radiative losses, the maximal energy of pairs is determined by the kinematics of the process and can be as high as the parent proton energy. We take a closer look at the features of the injected pair distribution, and provide a novel empirical function that describes the spectrum of pairs produced by interactions of single-energy protons with single-energy photons. The function is the kernel of the Bethe-Heitler pair production spectrum that replaces a double numerical integration involving the complex differential cross section of the process, and can be easily implemented in numerical codes. We further examine under which conditions Bethe-Heitler pairs produced in blazar jets can emit γ-ray photons via synchrotron radiation, thus providing an alternative to the inverse Compton scattering process for high-energy emission in jetted active galactic nuclei. For this purpose, we create 36 numerical models using the code ATHEνA optimized so that the Bethe-Heitler synchrotron emission dominates their γ-ray emission. After taking into consideration the broadband spectral characteristics of the source, the jet energetics, and the properties of radiation fields present in the blazar environment, we conclude that γ-rays in high-synchrotron-peaked blazars are unlikely to be produced by Bethe-Heitler pairs, because the emitting region is found to be opaque in photon-photon pair production at photon energies ≳ 10 GeV. On the contrary, γ-ray spectra of low-synchrotron-peaked blazars may arise from Bethe-Heitler pairs in regions of the jet with typical transverse size ∼ 1015 – 1016 cm and co-moving magnetic field 50 – 500 G. For such cases, an external thermal target photon field with temperatures T ∼ 4 · 102– 6 · 103 K is needed. The latter values could point to the dusty torus of the AGN. Interestingly, a Bethe-Heitler-dominated high-energy component is mostly found in models of intermediate-synchrotron peaked blazars, for a wide range of magnetic fields and source radii.

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Ding, Ran, Yizhou Fan, Li Huang, Chuang Li, Tianjun Li, Shabbar Raza, and Bin Zhu. "Systematic study of diphoton resonance at 750 GeV from sgoldstino." International Journal of Modern Physics A 31, no. 26 (September 20, 2016): 1650151. http://dx.doi.org/10.1142/s0217751x16501517.

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The ATLAS and CMS Collaborations of the Large Hadron Collider (LHC) have reported an excess of events in diphoton channel with invariant mass of about 750 GeV. With low energy supersymmetry breaking, we systematically consider the sgoldstino scalar S as the new resonance, which is a linear combination of the CP-even scalar [Formula: see text] and CP-odd pseudoscalar [Formula: see text]. Because we show that [Formula: see text] and [Formula: see text] can be degenerated or have large mass splitting, we consider two cases for all the following three scenarios: (1) Single resonance, [Formula: see text] is the 750 GeV resonance decays to a pair of 1 GeV pseudoscalar [Formula: see text] with suitable decay length, these two [Formula: see text] decay into collimated pair of photons which cannot be distinguished at the LHC and may appear as diphotons instead of four photons. (2) Twin resonances, [Formula: see text] with a mass difference of about 40 GeV and both [Formula: see text] and [Formula: see text] decay into diphoton pairs. For productions, we consider three scenarios: (I) vector-boson fusion; (II) gluon–gluon fusion; (III) [Formula: see text] pair production. In all these scenarios with two kinds of resonances, we find the parameter space that satisfies the diphoton production cross-section from 3 to 13 fb and all the other experimental constraints. And we address the decay width as well. In particular, in the third scenario, we observe that the production cross-section is small but the decay width of [Formula: see text] or [Formula: see text] can be from 40 to 60 GeV. Even if the 750 GeV diphoton excesses were not confirmed by the ATLAS and CMS experiments, we point out that our proposal can be used to explain the current and future diphoton excesses.

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Folkard, M., K. M. Prise, C. J. Turner, and B. D. Michael. "The Production of Single Strand and Double Strand Breaks in DNA in Aqueous Solution by Vacuum UV Photons Below 10 ev." Radiation Protection Dosimetry 99, no. 1 (June 1, 2002): 147–49. http://dx.doi.org/10.1093/oxfordjournals.rpd.a006746.

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Klaassen, G. P. "Testing Lagrangian Theories of Internal Wave Spectra. Part II: Varying the Number of Waves." Journal of the Atmospheric Sciences 66, no. 5 (May 1, 2009): 1101–25. http://dx.doi.org/10.1175/2008jas2667.1.

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Abstract It has been proposed by Allen and Joseph, Hines, and Chunchuzov that the kinematic advection produced by superpositions of sinusoidal Lagrangian gravity waves confined to lower vertical wavenumbers m provides an explanation for the quasi-universal m−3 Eulerian spectral tails commonly found at higher m in the oceans and the atmosphere. In support of these theories, Hines has proposed a prototype wave spectrum claimed to meet criteria for Lagrangian linearity and the production of m−3 Eulerian spectra. Although the shape of the Lagrangian spectrum is claimed not to play a major role in this process, Hines has argued that moderately large numbers of waves are required to ensure quasilinear behavior in the Lagrangian frame. The present results demonstrate that, for amplitudes consistent with measurements of saturated waves in the middle atmosphere and for wavenumbers consistent with Hines’ prototype, adiabatic excesses do not diminish with increasing numbers of waves; in contrast, consistency with adiabatic constraints is only achieved in the limit of a single wave, for which the advective nonlinearity u · ∇ vanishes. Moreover, fields with strong singularities yield Eulerian tail slopes as large as −1.6, whereas those with lesser violations of adiabatic constraints yield Eulerian spectral tail slopes that are much steeper (more strongly negative) than −3. The implications for theories based on superpositions of Lagrangian sinusoidal waves, for the Hines quasilinear criteria, and for the Hines Doppler-spread theory and parameterization are addressed. The results are also relevant for experimentalists interested in spectral analysis of internal wave fields.

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Pustyntsev, Alexander A., Victor V. Dubov, and Sergei P. Roshchupkin. "Resonant Breit-Wheeler process in an external electromagnetic field." Modern Physics Letters A 35, no. 03 (January 16, 2020): 2040027. http://dx.doi.org/10.1142/s0217732320400271.

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The contemporary research scrutinizes the resonant Breit-Wheeler process in the field of a plane monochromatic electromagnetic wave. Implementing the weak external field condition the processes of electron-positron pair production advances pre-eminently with participation of restrictively two field photons. Thus, within the resonant state the represented process effectively splits into two first-order processes with respect to the fine-structure constant. In details, the effect indicates the single photon pair production with consequent absorption of gamma quantum by an electron (positron) in the field of the wave. We analyze the resonance kinematics precisely. The study determines specific regions in which the interference of resonant amplitudes is absent. Additionally, the computation obtains a resonant differential cross section for the described areas. The corresponding resonant differential cross section significantly exceeds the correlating Breit-Wheeler cross-section without an external field. Various scientific facilities of pulsed laser radiation may experimentally verify the results of these calculations (SLAC, FAIR, XFEL, ELI, XCELS).

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Utomo, Sukarno Budi, Iwan Setiawan, Berkah Fajar, Sonny Hady Winoto, and Arief Marwanto. "Optimizing of the installed capacity of hybrid renewable energy with a modified MPPT model." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 1 (February 1, 2022): 73. http://dx.doi.org/10.11591/ijece.v12i1.pp73-81.

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The lack of wind speed capacity and the emission of photons from sunlight are the problem in a hybrid system of photovoltaic (PV) panels and wind turbines. To overcome this shortcoming, the incremental conductance (IC) algorithm is applied that could control the converter work cycle and the switching of the buck boost therefore maximum efficiency of maximum power point tracking (MPPT) is reached. The operation of the PV-wind hybrid system, consisting of a 100 W PV array device and a 400 W wind subsystem, 12 V/100 Ah battery energy storage and LED, the PV-wind system requires a hybrid controller for battery charging and usage and load lamp and it’s conducted in experimental setup. The experimental has shown that an average increase in power generated was 38.8% compared to a single system of PV panels or a single wind turbine sub-system. Therefore, the potential opportunities for increasing power production in the tropics wheather could be carried out and applied with this model.

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Godard, B., G. Pineau des Forêts, P. Lesaffre, A. Lehmann, A. Gusdorf, and E. Falgarone. "Models of irradiated molecular shocks." Astronomy & Astrophysics 622 (February 2019): A100. http://dx.doi.org/10.1051/0004-6361/201834248.

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Context. The recent discovery of excited molecules in starburst galaxies observed with ALMA and the Herschel space telescope has highlighted the necessity to understand the relative contributions of radiative and mechanical energies in the formation of molecular lines and explore the conundrum of turbulent gas bred in the wake of galactic outflows. Aims. The goal of the paper is to present a detailed study of the propagation of low velocity (5–25 km s−1) stationary molecular shocks in environments illuminated by an external ultraviolet (UV) radiation field. In particular, we intend to show how the structure, dynamics, energetics, and chemical properties of shocks are modified by UV photons and to estimate how efficiently shocks can produce line emission. Methods. We implemented several key physico-chemical processes in the Paris-Durham shock code to improve the treatment of the radiative transfer and its impact on dust and gas particles. We propose a new integration algorithm to find the steady-state solutions of magnetohydrodynamics equations in a range of parameters in which the fluid evolves from a supersonic to a subsonic regime. We explored the resulting code over a wide range of physical conditions, which encompass diffuse interstellar clouds and hot and dense photon-dominated regions. Results. We find that C-type shock conditions cease to exist as soon as G0 > 0.2 (nH/cm−3)1/2. Such conditions trigger the emergence of another category of stationary solutions, called C*-type and CJ-type shocks, in which the shocked gas is momentarily subsonic along its trajectory. These solutions are shown to be unique for a given set of physical conditions and correspond to dissipative structures in which the gas is heated up to temperatures comprised between those found in C-type and adiabatic J-type shocks. High temperatures combined with the ambient UV field favour the production or excitation of a few molecular species to the detriment of others, hence leading to specific spectroscopic tracers such as rovibrational lines of H2 and rotational lines of CH+. Unexpectedly, the rotational lines of CH+ may carry as much as several percent of the shock kinetic energy. Conclusions. Ultraviolet photons are found to strongly modify the way the mechanical energy of interstellar shocks is processed and radiated away. In spite of what intuition dictates, a strong external UV radiation field boosts the efficiency of low velocity interstellar shocks in the production of several molecular lines which become evident tracers of turbulent dissipation.

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Michl, Josef. "Unconventional Solar Energy: Singlet Fission." Molecular Frontiers Journal 03, no. 01 (June 2019): 84–91. http://dx.doi.org/10.1142/s2529732519400042.

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Described simply, singlet fission is a process in which a singlet excited molecule transfers about half of its excitation energy to a neighbor molecule, both end up in their triplet state, and the two triplet excitations diffuse apart. The process is of interest for solar cells. Used in conjunction with ordinary solar cell material, a layer of singlet-fission material offers an opportunity to utilize higher energy photons more efficiently. The maximum theoretical efficiency is then close to 1/2 instead of the Shockley-Queisser value of 1/3 that applies to an ordinary single-junction cell. The problem that prevents an immediate production of singlet fission solar cells is the dearth of sufficiently stable efficient materials. The formulation of simple rules for the design of suitable compounds for the purpose is discussed.

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Luque, Antonio, Antonio Martí, and Arthur J. Nozik. "Solar Cells Based on Quantum Dots: Multiple Exciton Generation and Intermediate Bands." MRS Bulletin 32, no. 3 (March 2007): 236–41. http://dx.doi.org/10.1557/mrs2007.28.

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AbstractSemiconductor quantum dots may be used in so-called third-generation solar cells that have the potential to greatly increase the photon conversion efficiency via two effects: (1) the production of multiple excitons from a single photon of sufficient energy and (2) the formation of intermediate bands in the bandgap that use sub-bandgap photons to form separable electron–hole pairs. This is possible because quantization of energy levels in quantum dots produces the following effects: enhanced Auger processes and Coulomb coupling between charge carriers; elimination of the requirement to conserve crystal momentum; slowed hot electron–hole pair (exciton) cooling; multiple exciton generation; and formation of minibands (delocalized electronic states) in quantum dot arrays. For exciton multiplication, very high quantum yields of 300–700% for exciton formation in PbSe, PbS, PbTe, and CdSe quantum dots have been reported at photon energies about 4–8 times the HOMO–LUMO transition energy (quantum dot bandgap), respectively, indicating the formation of 3–7 excitons/photon, depending upon the photon energy. For intermediate-band solar cells, quantum dots are used to create the intermediate bands from the con fined electron states in the conduction band. By means of the intermediate band, it is possible to absorb below-bandgap energy photons. This is predicted to produce solar cells with enhanced photocurrent without voltage degradation.

Journal articles on the topic 'Adiabatic production of single photons'

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