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Literatura académica sobre el tema "Photon annihilation"

Autor: Grafiati

Publicado: 10 de marzo de 2023

Última modificación: 11 de marzo de 2023

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Artículos de revistas sobre el tema "Photon annihilation"

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Gajos, Aleksander. "Sensitivity of Discrete Symmetry Tests in the Positronium System with the J-PET Detector". Symmetry 12, n.º 8 (1 de agosto de 2020): 1268. http://dx.doi.org/10.3390/sym12081268.

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Study of certain angular correlations in the three-photon annihilations of the triplet state of positronium, the electron–positron bound state, may be used as a probe of potential CP and CPT-violating effects in the leptonic sector. We present the perspectives of CP and CPT tests using this process recorded with a novel detection system for photons in the positron annihilation energy range, the Jagiellonian Positron Emission Tomography (J-PET). We demonstrate the capability of this system to register three-photon annihilations with an unprecedented range of kinematical configurations and to measure the CPT-odd correlation between positronium spin and annihilation plane orientation with a precision improved by at least an order of magnitude with respect to present results. We also discuss the means to control and reduce detector asymmetries in order to allow J-PET to set the first measurement of the correlation between positronium spin and momentum of the most energetic annihilation photon which has never been studied to date.

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Fanchiotti, H., C. A. García Canal y V. Vento. "Multiphoton annihilation of monopolium". International Journal of Modern Physics A 32, n.º 35 (20 de diciembre de 2017): 1750202. http://dx.doi.org/10.1142/s0217751x17502025.

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We show that due to the large coupling constant of the monopole–photon interaction the annihilation of monopole–antimonopole and monopolium into many photons must be considered experimentally. For monopole–antimonopole annihilation and lightly bound monopolium, even in the less favorable scenario, multiphoton events (four and more photons in the final state) are dominant, while for strongly bound monopolium, although two photon events are important, four- and six-photon events are also sizable.

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3

Gertsen, Anders S., Mads Koerstz y Kurt V. Mikkelsen. "Benchmarking triplet–triplet annihilation photon upconversion schemes". Physical Chemistry Chemical Physics 20, n.º 17 (2018): 12182–92. http://dx.doi.org/10.1039/c8cp00588e.

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Lingenfelter, Richard E. y Reuven Ramaty. "Annihilation Radiation and Gamma-Ray Continuum from the Galactic Center Region". Symposium - International Astronomical Union 136 (1989): 587–605. http://dx.doi.org/10.1017/s0074180900187091.

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Observations of the time-dependent, electron-positron annihilation line radiation and gamma-ray continuum emission from the region of the Galactic Center show that there are two components to the annihilation line emission: a variable, compact source at or near the Galactic Center, and a steady, diffuse interstellar distribution. We suggest that the annihilating positrons in the compact source, observed from 1977 through 1979, result from photon-photon pair production, most likely around an accreting black hole, and that the annihilating, interstellar positrons result from the decay of radionuclei produced by thermonuclear burning in supernovae.

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5

BRODSKY, STANLEY J. "HIGH ENERGY PHOTON–PHOTON COLLISIONS AT A LINEAR COLLIDER". International Journal of Modern Physics A 20, n.º 31 (20 de diciembre de 2005): 7306–32. http://dx.doi.org/10.1142/s0217751x05031137.

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High intensity back-scattered laser beams will allow the efficient conversion of a substantial fraction of the incident lepton energy into high energy photons, thus significantly extending the physics capabilities of an e-e± linear collider. The annihilation of two photons produces C = + final states in virtually all angular momentum states. An important physics measurement is the measurement of the Higgs coupling to two photons. The annihilation of polarized photons into the Higgs boson determines its fundamental H0γγ coupling as well as determining its parity. Other novel two-photon processes include the two-photon production of charged pairs τ+τ-, W+W-, [Formula: see text], and supersymmetric squark and slepton pairs. The one-loop box diagram leads to the production of pairs of neutral particles such as γγ → Z0Z0, γZ0, and γγ. At the next order one can study Higgstrahlung processes, such as γγ → W+W-W-H. Since each photon can be resolved into a W+W- pair, high energy photon-photon collisions can also provide a remarkably background-free laboratory for studying possibly anomalous WW collisions and annihilation. In the case of QCD, each photon can materialize as a quark anti-quark pair which interact via multiple gluon exchange. The diffractive channels in photon-photon collisions allow a novel look at the QCD pomeron and odderon. The C = - odderon exchange contribution can be identified by looking at the heavy quark asymmetry. In the case of eγ → e′ collisions, one can measure the photon structure functions and its various components. Exclusive hadron production processes in photon-photon collisions provide important tests of QCD at the amplitude level, particularly as measures of hadron distribution amplitudes which are also important for the analysis of exclusive semi-leptonic and two-body hadronic B-decays.

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6

Mohammed Ahmed, Elaf, Hadi J. M. Al-Agealy y Nada Farhan Kadhim. "Theoretical Calculation of Photon Emission from Quark-Antiquark Annihilation Using QCD Theory". Ibn AL-Haitham Journal For Pure and Applied Sciences 35, n.º 4 (20 de octubre de 2022): 37–44. http://dx.doi.org/10.30526/35.4.2879.

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In this work, we calculate and analyze the photon emission from quark and anti-quark interaction during annihilation process using simple model depending on phenomenology of quantum chromodynamic theory (QCD). The parameters, which include the running strength coupling, temperature of the system and the critical temperature, carry information regarding photon emission and have a significant impact on the photons yield. The emission of photon from strange interaction with anti-strange is large sensitive to decreases or increases there running strength coupling. The photons emission increases with decreases running strength coupling and vice versa. We introduce the influence of critical temperature on the photon emission rate in order to facilitate its further applied in photon emission spectrum. Photon emission was increased with large critical temperature MeV comparing with photons emission at critical temperature MeV. We analyze and discuss the sensitive of the emission of photon to photons energy . It increases with decreased photons energy and vice versa. However, the photons emission increases with increases thermal energy of system T = 170 MeV to 270 Mev. It is implied that strength coupling, critical temperature and photons energy can be as important as thermal energy of system for emission of photon.

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7

Chiba, M., J. Nakagawa, H. Tsugawa, R. Ogata y T. Nishimura. "A detector with high detection efficiency in 4- and 5-photon-positronium annihilations". Canadian Journal of Physics 80, n.º 11 (1 de noviembre de 2002): 1287–95. http://dx.doi.org/10.1139/p02-107.

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We first measured 4- and 5-photon annihilations in positronium using a multiphoton spectrometer (UNI), which consists of 32 NaI(Tl) scintillators with lead shields, each being located on a surface of an icosidodecahedron. The front face of each scintillator is placed at a distance of L = 262 mm from the center of the UNI. With this setup, the detection efficiency of 4- and 5-photon-annihilation processes are too small to get a sufficient number of events to analyze the physics. To obtain a larger detection efficiency, we must set the NaI(Tl) scintillators closer to the target. The original principle in designing the UNI was to suppress backgrounds (BG) and make them as low as possible allowing modest efficiencies for 4- and 5-photon-annihilation events, i.e., to get the highest signal-to-noise ratio (S/N). The new concept is to get the highest S/σ where σ is an error of one standard deviation of the signal including BG effects. A higher S/σ means a larger number of events with smaller BG taking into account a statistical effect. The detection efficiencies with BG effects are studied with respect to L using a detector simulator based on the EGS4 code in which 2- to 5-photon-annihilation events are generated by quantum-electrodynamic processes based on GRACE and BASES/SPRING codes. As a result, the detection efficiency and S/σ of 5-photon annihilations at L = 136 mm are 529 and 17 times larger than those at L = 262 mm, respectively. PACS Nos.: 36.10Dr, 12.20Fv, 13.10+q

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AKSENOV, A. G., R. RUFFINI, I. A. SIUTSOU y G. V. VERESHCHAGIN. "DYNAMICS AND EMISSION OF MILDLY RELATIVISTIC PLASMA". International Journal of Modern Physics: Conference Series 12 (enero de 2012): 1–9. http://dx.doi.org/10.1142/s2010194512006204.

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Initially optically thick (with τ = 3⋅107) spherically symmetric outflow consisting of electron-positron pairs and photons is considered. We do not assume thermal equilibrium, and include the two-body processes that occur in such plasma: Möller and Bhabha scattering of pairs, Compton scattering, two-photon pair annihilation, two-photon pair production, together with their radiative three-body variants: bremsstrahlung, double Compton scattering, and three-photon pair annihilation, with their inverse processes. We solve numerically the relativistic Boltzmann equations in spherically symmetric case for distribution functions of pairs and photons. Three epochs are considered in details: a) the thermalization, which brings initially nonequilibrium plasma to thermal equilibrium; b) the self-accelerated expansion, which we find in agreement with previous hydrodynamic studies and c) decoupling of photons from the expanding electron-positron plasma. Photon spectra are computed, and appear to be non thermal near the peak of the luminosity. In particular, the low energy part of the spectrum contain more power with respect to the black body one.

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9

Ahmed, Elaf Mohammed, Hadi J. M. Al-Agealy y Nada Farhan Kadhim. "Theoretical Study of Photons Spectra around High Energy of Quark-antiquark Using QCD Theory". NeuroQuantology 20, n.º 4 (6 de abril de 2022): 58–63. http://dx.doi.org/10.14704/nq.2022.20.4.nq22095.

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In this paper, we study and investigate the quark anti-quark interaction mechanism through the annihilation process. The production of photons in association with interaction quark and gluon in the annihilation process. We investigate the effect of critical temperature, strength coupling and photons energy in terms of the quantum chromodynamics model theory framework. We find that the use of large critical temperature Tc =134 allows us to dramatically increase the strength coupling of quarks interaction. Its sensitivity to decreasing in photons rate with respect to strength coupling estimates. We also discuss the effect of photons energy on the rate of the photon , such as energies in range (1.5 to 5 GeV).The photons rate increases association at Tc=116MeV with the more decreased photons energy compared with photos rate association n t Tc=116MeV. This relation of strength coupling a, critical temperature and photons energy are particularly relevant when parametrizing systematic photons emission.

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10

Ye, Chen, Victor Gray, Khushbu Kushwaha, Sandeep Kumar Singh, Paul Erhart y Karl Börjesson. "Optimizing photon upconversion by decoupling excimer formation and triplet triplet annihilation". Physical Chemistry Chemical Physics 22, n.º 3 (2020): 1715–20. http://dx.doi.org/10.1039/c9cp06561j.

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Perylene is a common annihilator in triplet–triplet annihilation photon upconversion schemes. It has however a tendency for excimer formation, which can be reduced by mono-alkylation without severely compromising the TTA-UC efficiency.

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Tesis sobre el tema "Photon annihilation"

1

Deng, Fan. "Photon Upconversion Based on Triplet-Triplet Annihilation". Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1395249331.

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Wilke, Bryn. "UPCONVERTING LOW POWER PHOTONS THROUGH TRIPLET-TRIPLET ANNIHILATION". Bowling Green State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1335378364.

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3

Berkowicz, Sharon, Helena Olsson y Henrik Broberg. "Evaluation of Amyloid Fibrils as Templates for Photon Upconversion by Sensitized Triplet-Triplet Annihilation". Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215658.

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In the face of global warming and shrinking resources of fossil fuels the interest in solar energy has increased in recent years. However, the low energy and cost efficiency of current solar cells has up to this date hindered solar energy from playing a major role on the energy market. Photon upconversion is the process in which light of low energy is converted to high energy photons. Lately, this phenomenon has attracted renewed interest and ongoing research in this field mainly focuses on solar energy applications, solar cells in particular. The aim of this study was to investigate and evaluate amyloid fibrils as nanotemplates for an upconversion system based on the dyes platinum octaetylporphyrin (PtOEP) and 9,10- diphenylanthracene (DPA). This well-known pair of organic dyes upconverts light in the visible spectrum through a mechanism known as sensitized triplet-triplet annihilation. Amyloid fibrils are β-sheet rich protein fibril structures, formed by self-assembly of peptides. Amyloid fibrils were prepared from whey protein isolate using heat and acidic solutions. Dyes were incorporated according to a wellestablished technique, in which dyes are grinded together with the protein in solid state prior to fibrillization. Photophysical properties of pure fibrils and dye-incorporated fibrils were studied using UV-VIS spectroscopy and fluorescence spectroscopy. Atomic force microscopy was further employed to confirm the presence of amyloid fibrils as well as to study fibril structure. Results indicate that amyloid fibrils may not be the optimal host material for the upconversion system PtOEP/DPA. It was found that the absorption and emission spectra of this system overlap to a great deal with that of the fibrils. Though no upconverted emission clearly generated by the dye system was recorded, anti-Stokes emission was indeed observed. Interestingly, this emission appears to be strongly enhanced by the presence of dyes. It is suggested that this emission may be attributed to the protein residues rather than the amyloid structure. Future studies are encouraged to further investigate these remarkable findings.
Intresset för solceller har ökat under de senaste åren, till stor del tillföljd av den globala uppvärmningen och de sinande oljeresurserna. Dagens solceller har dock problem med låg energi- och kostnadseffektivitet, vilket gör att solenergin än så länge har svårt att hävda sig på energimarknaden. Photon upconversion är ett fotofysikaliskt fenomen där fotoner med låg energi omvandlas till fotoner med hög energi. Den senaste tiden har denna process fått förnyat intresse och forskningen inom området har ökat, inte minst med sikte på att integrera processen i solceller och därmed öka dess effektivitet. Målet med denna studie var att undersöka huruvida amyloidfibriller kan användas som stomme för ett photon upconversion-system baserat på platinum-oktaetylporfyrin (PtOEP) och 9,10-difenylantracen (DPA). Dessa två organiska färgämnen är ett välkänt par som konverterar synligt ljus med låg frekvens till mer hög frekvent ljus i det synliga spektrumet, via en mekanism som kallas sensitized triplet-triplet annihilation. Amyloidfibriller är proteinbaserade fiberstrukturer med hög andel β-flak, vilka bildas genom självassociation av peptider. I denna studie skapades amyloidfibriller av vassleprotein genom upphettning i sur lösning. Färgämnena inkorporerades enligt en välbeprövad metod där proteinet mortlas tillsammans med färgämnena i fast tillstånd, innan fibrilleringsprocessen påbörjas. De fotofysikaliska egenskaperna hos fibriller med och utan färgämnen analyserade med UV-VIS samt fluorescensspektroskopi. Atomkraftsmikroskopi användes för att bekräfta att fibriller fanns i proven, samt för att studera dess struktur. De erhållna resultaten antyder att amyloidfibriller inte är ett optimalt material för systemet PtOEP/DPA, delvis på grund av att absorptions- och emissionsspektrumet för systemet överlappar med fibrillernas egna spektrum. Anti-Stokes emission detekterades, men denna är med stor sannolikhet inte orsakad av färgämnena. Dock noterades, intressant nog, att denna emission ökar betydligt i närvaro av färgämnena. En möjlighet är att denna emission är kopplad till monomerer i proteinet snarare än till fibrillstrukturen, eftersom emission observerades hos både nativt och fibrillerat protein. Framtida studier uppmuntras att vidare undersöka dessa effekter.

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4

Aldousari, Hanan. "Study of 2-to-3 photon annihilation using hydrophilic material as hypoxic tumour phantom". Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616952.

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The use of three gamma annihilation as a new PET molecular imaging modality which can predict tumour hypoxia was proposed by Kacperski and Spyrou in 2004. The positronium and its annihilation, could then serve as an oxygen-sensitive marker. The relative magnitude of three photon annihilation is increased in an oxygen deficient environment. The main questions addressed in this thesis are the potential use of the lanthanum bromide LaBr3: Ce (5%) scintillator detector for three-photon positron annihilation measurements. Also, the optimum source-to-detector distance that achieves good efficiency and sensitivity of the measurements. The other question is finding the best method to prepare in vitro three types of hypoxic samples (mineral water, defibrinated horse blood and semm). In addition, the suitability of the hydrophilic material is examined in terms of hydration behaviour, radiation and physical properties, for use as a phantom that represents the hypoxic tumour in the three-photon positron annihilation measurements. The main critical question is which the best method that could be used to measure the three-photon positron annihilation yields. Also, how does the 3y/2y ratio vary with different oxygen concentrations in different hydrophilic materials? Lanthanum bromide LaBr3: Ce (5%) scintillator detectors have good fast timing resolution, good stopping power and large light output. The LaBr3:Ce (5%) has very good scintillator characteristics, combining high effective Z and density, fast decay time, light emission wavelengths matching that of commonly available photon detectors and excellent energy resolution (~3% at 662 keY). However, it is highly hygroscopic in nature, making it difficult to produce, but its commercial availability has been gradually increasing in recent times. LaBr3: Ce (5%) has come to be accepted for the superior energy resolution it offers. Therefore, LaBr3: Ce (5%) detectors can be considered as the scintillators of choice for determining the yield of 2-and3-y positron annihilation. The characterisation of the detector used was can-ied out in terms of energy resolution and efficiency. The effect of amplifier parameters on the energy resolution was also studied. The 'geometrical solid angles subtended by the source-to-detector distances play an important role in the sensitivity and accuracy of the detector efficiency measurements. Therefore, the efficiency measurements were investigated at various distances to optimise the geometrical solid angle for the LaBr3: Ce (5%) detector for the three photon annihilation measurements. The experimental data were compared with the GATE simulated results obtained. The objective to study the factors that affect dissolved oxygen (DO) in three types of samples (mineral water, defibrinated horse blood and semm) was to investigate the 3y/2y ratio in hypoxic, nOlIDoxic and hyperoxic conditions of tissues for future application in oncology in the detection and quantification of tumour hypoxia. This was achieved by measuring the DO, pH and temperature before, during and after treating the samples with nitrogen, carbon dioxide and ascorbic acid (AnaeroGen). Two methods for the preparation of the in vitro hypoxic samples were investigated and evaluated. Carbon dioxide proved to be most effective for the reduction of DO in the samples. Blood tended to resist DO reduction since it decreased at a much slower rate than in water and semm. Together with the fact that the oxygen level in blood remained low after the end of exposure to the gases and ascorbic acid suggests that the solubility of oxygen in blood depends upon the concentration of haemoglobin as well as upon ligands such as CO2 • CO2 combines with haemoglobin affecting oxygen binding and fonns bicarbonate which further decreases the affinity of haemoglobin to oxygen Hydrophilic materials.

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5

RONCHI, ALESSANDRA. "Hybrid and Nanostructured materials for low power photon upconversion based on triplet-triplet annihilation". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/370864.

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Durante il dottorato ho investigato il processo fotofisico di "upconversion" assistito da annichilazione tripletto-tripletto (TTA-UC) tramite studi di spettroscopia in sistemi profondamente differenti gli uni dagli altri. In TTA-UC radiazione ad alta energia è emessa dalla ricombinazione radiativa dello stato di singoletto eccitato di una molecola emettitore, popolato precedentemente dall'annichilazione dei tripletti di due emettitori. Un sensibilizzatore immagazzina la luce incidente a bassa energia e trasferisce l'eccitazione agli emettitori tramite trasferimento di energia alla Dexter. Poiché il suo funzionamento si basa su tripletti mestastabili, TTA-UC può essere altamente efficiente anche in condizioni di luce non coerente e a bassa energia. Come tale, è particolarmente adatto per dispositivi che sfruttano l'energia solare poiché è in grado di aumentarne l'efficienza di conversione limitando le perdite per trasmissione. Mi sono concentrata su due problemi importanti che tuttora limitano l'impiego di materiali che attuano TTA-UC (upconverters), ossia la limitata capacità di immagazzinare energia dei comuni sensibilizzatori organici e le scarse prestazioni di TTA-UC in upconverters a stato solido, i quali sono più adatti per applicazioni tecnologiche rispetto a sistemi liquidi. Per risolvere il primo problema ho investigato sensibilizzatori ibridi, composti da nanostrutture a semiconduttore decorate con molecole organiche, con ampio assorbimento. Nanocristalli di CdSe drogati con cationi d'oro e decorati con acido antracenico carbossilico si sono dimostrati essere sensibilizzatori ibridi efficienti ed innovativi. Il drogante introduce nel gap energetico dei nanocristalli livelli localizzati su cui le lacune si localizzano sulla scala dei picosecondi, più velocemente dell'estrazione di lacune sul livello HOMO dei leganti. Con tale strategia ho raggiunto l'efficienza di UC del 12%, record per sistemi ibridi. Ho poi mostrato come le proprietà superficiali e fotofisiche di nanoplatelets di CdSe le rendano ottimali candidati in sensibilizzatori ibridi. Ho mostrato che il ricoprimento delle superfici non è omogeneo, ma procede ad isole e l'interazione di "π- π stacking" porta alla formazione di aggregati sulle superfici delle nanoplatelets, con il risultato di ridurre l'energia dei tripletti dei leganti con profonde ripercussioni sulle prestazioni di TTA-UC e sulla scelta della specie emettitrice. Riguardo al secondo problema, ho studiato due upconverters a stato solido, polimeri vetrosi nanostrutturati che mostrano proprietà macroscopiche simili ma realizzati con tecniche differenti. Essi presentano domini liquidi di dimensione inferiore a 50 nm dove le specie che attuano TTA-UC si accumulano, racchiuse in una matrice rigida polimerica che fornisce protezione da ossigeno e qualità ottica eccellenti e stabilità a lungo termine. Il confinamento molecolare permette di aumentare la densità locale di eccitoni aumentando l'efficienza di UC a basse potenze grazie alle ridotte distanze intermolecolari e all'attivazione del regime di TTA-UC confinato.Ho inoltre studiato un nuovo emettitore derivato da perilene, realizzato con lo scopo di aumentarne l'efficienza di fluorescenza. Grazie a questo emettitore ho raggiunto l'efficienza record di UC di 42%, dovuta proprio alla struttura molecolare dell'emettitore che permette di limitare la formazione di aggregati, garantendo un'eccellente efficienza di generazione di singoletti tramite TTA. Infine, ho presentato una prospettiva riguardo alle prestazioni che possono essere raggiunte combinando le due tematiche trattate, ossia inserendo sensibilizzatori ad ampio assorbimento in polimeri nanostrutturati. Trovando il giusto compromesso tra taglia dei domini liquidi e distribuzione dell'energia di eccitazione si raggiungerebbe la massima efficienza di UC a potenze minori dell'irradianza solare, promuovendo lo sviluppo di upconverters a stato solido per tecnologie a energia solare
In my PhD project, I investigated the photophysical process of photon upconversion assisted by triplet-triplet annihilation (sTTA-UC) through spectroscopy studies in a variety of systems, profoundly different on many levels. In sTTA-UC high energy radiation is emitted from the fluorescent recombination of the excited singlet of an emitter molecule, previously populated via annihilation of the metastable triplet states of two emitters. This is a sensitized process since a sensitizer is necessary to harvest the low energy incident light and to transfer the stored energy to the emitters via Dexter energy transfer. Because its functioning relies on long-lived metastable triplets, this process can be highly efficient also under low power, noncoherent light. As such, sTTA-UC is particularly suited for solar applications as it can increase the conversion efficiency by reducing transmission losses. During my studies, I focused on addressing two crucial issues that still limit the application of upconverters in solar technologies, i.e. the limited storage ability of common organic sensitizers and the poor sTTA-UC performance in solid-state upconverters, which are intrinsically better suited than liquid solutions for technological applications. To solve the first problem, I investigated hybrid sensitizers, composed of semiconductor nanostructures decorated with conjugated organic ligands characterized by broadband absorption. CdSe nanocrystals (NCs) doped with gold cations and decorated with 9-anthracene carboxylic acid demonstrated to be efficient innovative broadband hybrid sensitizers. The doping strategy inserts into the NCs energy gap localized hole-accepting states where the holes localize on the picosecond timescale, outpacing hole transfer to the ligand HOMO. With this strategy, I achieved the UC efficiency of 12%, the record performance obtained so far for hybrid upconverters. I then discussed how the CdSe nanoplatelets surface and photophysical properties make them potential optimal light harvesters. My studies on the nanoplatelets-to-ligands energy transfer dependency on the surface ligand density revealed that the surface coverage is not homogeneous but proceeds in an island-like way promoted by π- π stacking and results in the formation of ligands aggregates on the nanoplatelets surfaces, which causes a redshift of the ligand triplet energy with critical repercussions on the sTTA-UC performance and on the emitter selection. To address the second issue, I investigated two solid-state upconverters, i.e. nanostructured glassy polymers that show similar macroscopic properties but fabricated via different approaches. They both feature liquid droplets of mean size less than 50 nm where the upconverting dyes accumulate, embedded in a rigid polymer matrix that grants excellent oxygen protection and optical quality and long-term stability. The dyes confinement allows to increase the effective local excitons density resulting in an enhanced UC efficiency at low excitation intensities, thanks to the reduced intermolecular distances and the activation of the confined sTTA-UC regime. I also introduced a new perylene derivative as emitter, specifically designed to prevent molecular aggregation to maximize its fluorescence efficiency. By employing this emitter, I achieved the record UC efficiency of 42%, which directly stems from the emitter molecular structure, as it limits the formation of aggregates, while guaranteeing excellent singlet generation efficiency upon TTA. I finally presented a perspective of the performances that can be achieved by combining the two topics considered, i.e. loading broadband sensitizers in nanostructured polymers. I highlighted that if the best trade-off between nanostructure size and energy distribution is met the maximum UC efficiency can be achieved at excitation powers orders of magnitude lower that the solar irradiance, therefore promoting the development of real-world solid-state upconverters.

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6

Kang, Ji-Hwan. "Energy transfer enhancement of photon upconversion systems for solar energy harvesting". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45846.

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Photon energy upconversion (UC), a process that can convert two or more photons with low energy to a single photon of higher energy, has the potential for overcoming the thermodynamic efficiency limits of sunlight-powered devices and processes. An attractive route to lowering the incident power density for UC lies in harnessing energy transfer through triplet-triplet annihilation (TTA). To maximize energy migration in multicomponent TTA-assisted UC systems, triplet exciton diffusivity of the chromophores within an inert medium is of paramount importance, especially in a solid-state matrix for practical device integration. In this thesis, low-threshold sensitized UC systems were fabricated and demonstrated by a photo-induced interfacial polymerization within a coaxial-flow microfluidic channel and in combination with nanostructured optical semiconductors. Dual-phase structured uniform UC capsules allow for the highly efficient bimolecular interactions required for TTA-based upconversion, as well as mechanical strength for integrity and stability. Through controlled interfacial photopolymerization, diffusive energy transfer-driven photoluminescence in a bi-molecular UC system was explored with concomitant tuning of the capsule properties. We believe that this core-shell structure has significance not only for enabling promising applications in photovoltaic devices and photochromic displays, but also for providing a useful platform for photocatalytic and photosensor units. Furthermore, for improving photon upconverted emission, a photonic crystal was integrated as an optical structure consisting of monodisperse inorganic colloidal nanoparticles and polymer resin. The constructively enhanced reflected light allows for the reuse of solar photons over a broad spectrum, resulting in an increase in the power conversion efficiency of a dye-sensitized solar cell as much as 15-20 %.

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Alkhorayef, Mohammed A. "The potential use of three photon positron annihilation in positron emission tomography for tumour hypoxia imaging". Thesis, University of Surrey, 2010. http://epubs.surrey.ac.uk/843299/.

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Identifying and localising tumor hypoxia in cancer patients is a challenge in oncology imaging. There are many ongoing clinical trials using conventional positron emission tomography (PET) scans and PET agents as cellular markers for detection of tumour hypoxia depending on the concept of the basic physics of 2gamma annihilation. However, Kacperski and Spyrou (2004) proposed, for the first time, to use 3gamma annihilation as a new PET molecular imaging modality, where the positronium and its annihilation, could serve as an oxygen-sensitive marker. The effective yield of 3gamma annihilation depends on the rates of formation and quenching. The formation of positronium is not only sensitive to the physics parameters, but also behaves as an active chemical particle. A hypoxic cell is a microenviromnent which has an inadequate amount of oxygen. Oxygen is known to be a strong positronium quencher where 2gamma annihilation replaces the 3gamma process. It is thus possible for hypoxic cells to be characterised by higher 3gamma rates than those cells which are well oxygenated. The measurement of 3gamma annihilation to differentiate between oxygenated and non-oxygenated biological samples in order to extract useful information in PET for oncology is a challenging project. It opens up very interesting applications in nuclear medicine imaging as the 3gamma yield has not been measured before in biological tissue and in particular hypoxic tumour cells. The project is multidisciplinary involving physics, biology and chemistry. There are many factors which affect the dissolved oxygen in mineral water, defibrinated horse blood and serum samples. These factors and the challenges to prepare in-vitro hypoxic samples have been experimentally measured using polarography with different chemical reactions e.g. carbon dioxide, nitrogen and AnaeroGen(TM). Results have shown that polarography was more suitable than colorimetery in the measurement of dissolved oxygen in blood due to the high absorption characteristic of blood. AnaeroGen(TM) is the method of choice, unlike carbon dioxide or nitrogen treatment, for preparing hypoxic samples due to the good agreement of the behaviour of the oxygen reduction as in the oxyhaemoglobin dissociation curve which is caused by a decrease in pH, an increase in partial pressure of carbon dioxide and an increase in temperature. The 3gamma yield was measured in normoxic and hypoxic environments using the triple coincidence measurement of three high-energy resolution detectors (HPGe). The AnaeroGen(TM) was used to generate a hypoxic environment. The percentage of the coincidence events qualified as 3gamma was 26.5% higher in the hypoxic environment. This reseach work is a step towards the application of the novel modality of 3gamma PET which in conjunction with conventional 2gamma PET could serve as a non-invasive oxygen sensitive marker. The combination of 3gamma and 2gamma coincidences in nuclear medicine imaging systems may contribute important information for the development and validation of appropriate hypoxia markers. The relative 3gamma/2gamma yield was measured for a positron emitter 22Na with the new generation of scintillator LaC13:Ce and LaBr3:Ce detectors, which had been characterised together with NaI(Tl) and HPGe detectors. The experimental focus was on measuring the relative 3gamma/2gamma yield in different samples by applying the peak-to-peak and the peak-to-valley methods. The value of the ratio 3gamma/2gamma depends on the specimen and is of the order of 10-2. The relative 3gamma/2gamma yields obtained for the peak to peak method in the silica sample were, for example, (3.41+/-0.18)x10 -2, (2.98+/-0.13)x10-2, (4.01+/-0.16)x10 -2 and (2.12+/-0.14)x10-2 for LaBr3:Ce, LaCl3:Ce, NaI(Tl) and HPGe detectors, respectively. The results show that the lanthanum based crystals, LaBr3:Ce and LaCl3:Ce, have the potential to replace NaI(Tl) and HPGe due to both good energy resolution and good detection efficiency and can be the scintillator of choice for determining the yield of 3gamma. The peak-to-valley method was applied to measure the relative yield of 3gamma/2gamma positron annihilation using 18F in 11 haematological samples of different oxygenation levels. The relative 3gamma/2gamma yield was found to vary as much as 11% between the components investigated.

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Llewellyn, T. J. "Evaluation of a multi-element ismuth germanate converter for high resolution and efficiency annihilation photon detection". Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377349.

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Abuelhia, Elfatih Ibrahim. "The potential use of three photon positron annihilation processes as a new imaging modality for positron emission tomography (PET)". Thesis, University of Surrey, 2006. http://epubs.surrey.ac.uk/843017/.

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In this thesis the main aspects of three photon positron annihilation processes and their potential use in medical imaging have been investigated as a positron emission tomography technique. The main objectives are focused on: three-photon positron annihilation measurement and imaging, analytical modelling and Monte Carlo simulation and the evaluation of the detection system requirements. A novel method as proof-of-principle of the three photon positron annihilation imaging concept based on a triple coincidence imaging technique using high energy resolution semiconductor detectors has been introduced. It has been shown that a simple system of three high-energy resolution detectors is able to produce images of three photon positron annihilations events. The full energy photopeak detected of the true 3y events can be easily identified in the spectrum. Although the sensitivity is small due to a very small solid angle (~0.05 str) subtended by the detectors and rather poor detection efficiency, it is a first step towards a scanner capable of a new imaging modality. This method has been investigated using Monte Carlo simulation results and experimental data acquired. Further a new three-photon yield measurement method based on three-photon positron annihilation imaging technique with correction for scattered and random events is proposed. The feasibility of this approach has been verified using experiments and compared to existing methods. Results show that this method is more accurate with better scatter correction due to electronic collimation than others but it has also some limitations. In order to obtain quantitative information from the detection system it is necessary to establish mathematical or analytical models, which describe the system. This was achieved for the triple coincidence condition. The count rate of single and triple detected events was investigated. Results have shown differences due to scatter and random events estimation. The effect of semiconductor detectors properties on three-photon image quality and scanner design was also investigated. It was in addition shown that computer simulations can be effectively used to predict the image quality and background noise for a particular scanner design. Important characteristics which affect scanner performance were evaluated. The effect of detector and scanner size on spatial resolution of three photon images was discussed. It was found that by reducing scanner size spatial resolution was improved for three-photon positron annihilation imaging as for conventional two photon-positron annihilation. Variation of scanner size (scanner diameter) affects the point spread function of the three photon positron annihilation image profile and introduces a combination of errors due to photon energy and detection position. To introduce the three-photon technique in a dedicated PET system, high- energy resolution detectors are needed to improve the quality of the image and reduce the noise due to scattered events arising from Compton scattering which do not correspond to 3y events. Semiconductor detectors, particularly CZT which have good energy resolution, significantly better stopping power and can be used at room temperature are proposed as the detectors of choice for the new detection system. Therefore, images of two photon-positron annihilation can be mapped with those of 3- photon events and new valuable information can be extracted. This information will be valuable to treatments involving external beam radiotherapy and may also be of use in brachytherapy.

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Lissau, Jonas Sandby. "Non-Coherent Photon Upconversion on Dye-Sensitized Nanostructured ZrO2 Films for Efficient Solar Light Harvesting". Doctoral thesis, Uppsala universitet, Fysikalisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-229831.

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Photon upconversion by sensitized triplet–triplet annihilation (UC-STTA) is a photophysical process that facilitates the conversion of two low-energy photons into a single high-energy photon. A low-energy photon is absorbed by a sensitizer molecule that produces a triplet excited state which is transferred to an emitter molecule. When two emitter triplet states encounter each other, TTA can take place to produce a singlet excited state which decays by emission of a high-energy (upconverted) photon. While traditional single-threshold dye-sensitized solar cells (DSSCs) have a maximum efficiency limit of ca. 30%, it has been predicted theoretically that implementation of UC-STTA in DSSCs could increase that efficiency to more than 40%. A possible way to implement UC-STTA into DSSCs, would be to replace the standard sensi- tized nanostructured TiO2 photoanodes by upconverting ones loaded with emitter molecules. Following TTA, the excited emitter molecule would be quenched by injection of a high-energy electron into the conduction band of the TiO2. To explore the practical aspects of this strategy for a highly efficient DSSC, in this thesis UC-STTA is studied in model systems based on nanostructured ZrO2 films. These ZrO2 films are a good proxy for the TiO2 films used in DSSCs, and allow for relatively easy optimization and study of UC-STTA by allowing measurements of the upconverted photons without the complications of electron injection into the film. Herein it is experimentally proven that UC-STTA is viable on nanostructured metal oxide films under non-coherent irradiation with intensities comparable to sunlight. Two different system architectures are studied, differing in the position of the molecular components involved in the UC-STTA mechanism. Both architectures have the emitter molecules adsorbed onto the ZrO2 surface, but the sensitizers are positioned either in solution around the nanostructure, or co-adsorbed with the emitters onto the ZrO2 surface. A set of challenges in the study and optimization of the UC-STTA process is identified for each type of system. Proposals are also given for how to further improve the understanding and UC-STTA optimization of these systems toward application in DSSCs to overcome the present solar energy conversion efficiency limit.

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Más fuentes

Libros sobre el tema "Photon annihilation"

1

Grimes, Dale M. Photon creation - annihilation: Continuum electromagnetic theory. Singapore: World Scientific, 2012.

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K, Griest, Fermi National Accelerator Laboratory y United States. National Aeronautics and Space Administration., eds. Rate for annihilation of galactic dark matter into two photons. Batavia, Ill: Fermi National Accelerator Laboratory, 1989.

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National Aeronautics and Space Administration (NASA) Staff. Rate for Annihilation of Galactic Dark Matter into Two Photons. Independently Published, 2018.

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Horing, Norman J. Morgenstern. Interacting Electron–Hole–Phonon System. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198791942.003.0011.

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Chapter 11 employs variational differential techniques and the Schwinger Action Principle to derive coupled-field Green’s function equations for a multi-component system, modeled as an interacting electron-hole-phonon system. The coupled Fermion Green’s function equations involve five interactions (electron-electron, hole-hole, electron-hole, electron-phonon, and hole-phonon). Starting with quantum Hamilton equations of motion for the various electron/hole creation/annihilation operators and their nonequilibrium average/expectation values, variational differentiation with respect to particle sources leads to a chain of coupled Green’s function equations involving differing species of Green’s functions. For example, the 1-electron Green’s function equation is coupled to the 2-electron Green’s function (as earlier), also to the 1-electron/1-hole Green’s function, and to the Green’s function for 1-electron propagation influenced by a nontrivial phonon field. Similar remarks apply to the 1-hole Green’s function equation, and all others. Higher order Green’s function equations are derived by further variational differentiation with respect to sources, yielding additional couplings. Chapter 11 also introduces the 1-phonon Green’s function, emphasizing the role of electron coupling in phonon propagation, leading to dynamic, nonlocal electron screening of the phonon spectrum and hybridization of the ion and electron plasmons, a Bohm-Staver phonon mode, and the Kohn anomaly. Furthermore, the single-electron Green’s function with only phonon coupling can be rewritten, as usual, coupled to the 2-electron Green’s function with an effective time-dependent electron-electron interaction potential mediated by the 1-phonon Green’s function, leading to the polaron as an electron propagating jointly with its induced lattice polarization. An alternative formulation of the coupled Green’s function equations for the electron-hole-phonon model is applied in the development of a generalized shielded potential approximation, analysing its inverse dielectric screening response function and associated hybridized collective modes. A brief discussion of the (theoretical) origin of the exciton-plasmon interaction follows.

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Capítulos de libros sobre el tema "Photon annihilation"

1

Evans, Myron y Jean-Pierre Vigier. "Creation and Annihilation of Photons". En The Enigmatic Photon, 89–102. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-010-9838-0_6.

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Gray, Victor. "Photon upconversion through triplet–triplet annihilation". En Photochemistry, 404–20. Cambridge: Royal Society of Chemistry, 2019. http://dx.doi.org/10.1039/9781788016520-00404.

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Falvard, Alain, Edmond Giraud, Agnieszka Jacholkowska, Karsten Jedamzik, Julien Lavalle, Gilbert Moultaka, Eric Nuss et al. "High Energy Photon Flux Prediction from Neutralino Annihilation in M 31". En ESO ASTROPHYSICS SYMPOSIA, 438–40. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/10857580_45.

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Monguzzi, Angelo. "Photon Upconversion Based on Sensitized Triplet-Triplet Annihilation (sTTA) in Solids". En Emerging Strategies to Reduce Transmission and Thermalization Losses in Solar Cells, 49–70. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70358-5_4.

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Baluschev, Stanislav. "Protective Strategies Toward Long-Term Operation of Annihilation Photon Energy Upconversion". En Emerging Strategies to Reduce Transmission and Thermalization Losses in Solar Cells, 149–67. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70358-5_8.

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Davydov, Andrey V. "Nuclear Resonant Scattering of Annihilation Photons". En Springer Tracts in Modern Physics, 141–71. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-10524-6_5.

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Kleinknecht, Konrad y Ulrich Uwer. "Symmetry Violations and Quark Flavour Physics". En Particle Physics Reference Library, 519–623. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-38207-0_9.

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AbstractOne of the surprising facts in our present understanding of the development of the Universe is the complete absence of “primordial” antimatter from the Big Bang about 13.7 billion years ago. The detection of charged cosmic-ray particles by magnetic spectrometers borne by balloons, satellites, and the space shuttle has shown no evidence for such primordial (high-energy) antibaryons; nor has the search for gamma rays from antimatter–matter annihilation yielded any such observation. In the early phases of the expanding Universe, a hot (1032 K) and dense plasma of quarks, antiquarks, leptons, antileptons and photons coexisted in equilibrium. This plasma expanded and cooled down, and matter and antimatter could recombine and annihilate into photons. If all interactions were symmetric with respect to matter and antimatter, and if baryon and lepton numbers were conserved, then all particles would finally convert to photons, and the expansion of the Universe would shift the wavelength of these photons to the far infrared region.

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Kucherenko, Michael G. "Relaxation of Holographic Record in the System with Annihilating Centers". En Applications of Photonic Technology 2, 157–65. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4757-9250-8_26.

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Hase, Muneaki, Kunie Ishioka, Kiminori Ushida y Masahiro Kitajima. "Annihilation of coherent LO phonon-plasmon coupled modes by lattice defects in n-GaAs". En Springer Proceedings in Physics, 186–87. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-59484-7_81.

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Zhakparov, R. K., A. I. Kozin, S. V. Makarov y S. P. Pivovarov. "Investigation by the Methods of NMR and Angular Correlation of Annihilation Photons (ACAP) of Cyclotron Irradiated Copper". En 25th Congress Ampere on Magnetic Resonance and Related Phenomena, 440. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-76072-3_228.

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Actas de conferencias sobre el tema "Photon annihilation"

1

Rivlin, L. A. "Inducing of Gamma-ray Emission without Overconcentration of Excited Oscillators by High Optical Field". En High Resolution Fourier Transform Spectroscopy. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/hrfts.1994.mc3.

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Two separate self-consistent scenarios inherent in achieving induced emission of gamma-rays will be discussed. (A) The stimulation of annihilation of parapositronium atoms in colliding particle and photon beams by external infra-red radiation. It is known, that soft-photon stimulation of two-photon annihilation requires and inadmissible high particle energy (approx. 50 GeV). The new scenario consists of two positronium beams and two infrared photon beams moving in opposite directions and includes three steps : 1) exciting ls-2p transitions of moving relativistic positronium atoms (approx. 80 MeV) by an infrared beam (approx. 80 micrometer) propagating in the opposite direction ; 2) lasing in the beam of these excited atoms, the inversion being achieved as a result of lower-state cleansing due to spontaneous annihilation; and 3) stimulating the annihilation in the opposite positronium beam by Doppler shifted photons from the moving atomic laser realized in the previous step.

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2

Vogt, C. "Two-photon annihilation into pion pairs". En PHOTON 2000: International Conference on the Structure and Interactions of the Photon. AIP, 2001. http://dx.doi.org/10.1063/1.1402857.

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AMSLER, C. "MESON RESONANCES IN PROTON-ANTIPROTON ANNIHILATION". En Proceedings of the International Conference on the Structure and Interactions of the Photon Including the 14th International Workshop on Photon-Photon Collisions. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812777157_0051.

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AKHMETSHIN, R. R., E. V. ANASHKIN, V. SH. BANZAROV, L. M. BARKOV, N. S. BASHTOVOY, A. E. BONDAR, D. V. BONDAREV et al. "STUDY OF E+E- ANNIHILATION INTO HADRONS AT VEPP-2M". En Proceedings of the International Conference on the Structure and Interactions of the Photon Including the 14th International Workshop on Photon-Photon Collisions. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812777157_0028.

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Toussaint, Maxime, Roger Lecomte y Jean-Pierre Dussault. "Annihilation Photon Acolinearity with Ultra-fast ToF-PET". En 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC). IEEE, 2020. http://dx.doi.org/10.1109/nss/mic42677.2020.9507968.

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Piper, Roland, Megumi Yoshida, Ned Ekins-Daukes, Saif Haque, Yuen Yap Cheng, Burkhard Fuckel, Tony Khoury et al. "Two-photon triplet-triplet annihilation upconversion for photovoltaics". En 2011 37th IEEE Photovoltaic Specialists Conference (PVSC). IEEE, 2011. http://dx.doi.org/10.1109/pvsc.2011.6185936.

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Vyas, Reeta y Surendra Singh. "Photon statistics of a nondegenerate optical parametric oscillator". En OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.tujj3.

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Photon statistics of light produced by a nondegenerate optical parametric oscillator operating below threshold are calculated. Positive-P representation is used to map quantum dynamics onto a set of classical Langevin equations for the complex field amplitudes associated with the annihilation and creation operators for the field produced by the oscillator. Using a Karhunen Loeve expansion of the resulting stochastic processes the moment generating function for photon counting statistics is obtained.

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8

VOGT, C. "THE HANDBAG CONTRIBUTION TO TWO-PHOTON ANNIHILATION INTO MESON PAIRS". En Exclusive Processes at High Momentum Transfer. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812776211_0031.

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Zavatta, A., V. Parigi, M. S. Kim y M. Bellini. "Probing Quantum Rules with Single-Photon Creation and Annihilation Operators". En International Conference on Quantum Information. Washington, D.C.: OSA, 2008. http://dx.doi.org/10.1364/icqi.2008.qwa2.

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Ishii, A., T. Uda y Y. K. Kato. "Room-temperature single photon emission from micron-long air-suspended carbon nanotubes". En JSAP-OSA Joint Symposia. Washington, D.C.: Optica Publishing Group, 2017. http://dx.doi.org/10.1364/jsap.2017.7p_a404_3.

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Carbon nanotubes have great potential for single photon sources as they have stable exciton states even at room temperature and their emission wavelengths cover the telecommunication bands. In recent years, single photon emission from carbon nanotubes has been achieved by creating localized states of excitons [1]. In contrast to such an approach, here we utilize mobile excitons and show that single photons can be generated at room temperature in air-suspended carbon nanotubes with lengths of several microns. We perform photoluminescence microscopy on as-grown air-suspended carbon nanotubes in order to determine their chirality and suspended length. Photon correlation measurements are performed on nanotube emission at room temperature using a Hanbury-Brown-Twiss setup with InGaAs/InP single photon detectors. We observe antibunching with a clear excitation power dependence, where we obtain g(2)(0) value less than 0.5 at low excitation powers (Fig. 1), indicating single photon generation. We show such g(2)(0) data with different chiralities and suspended lengths, and the effects of long exciton diffusion lengths and efficient exciton-exciton annihilation [2] on single photon generation processes are discussed.

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Informes sobre el tema "Photon annihilation"

1

Gold, M. S. Hard photon processes in electron-positron annihilation at 29 GeV. Office of Scientific and Technical Information (OSTI), noviembre de 1986. http://dx.doi.org/10.2172/7059641.

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Davier, M., M. Peskin y A. Snyder. Two-Photon Exchange Model for Production of NeutralMeson Pairs in e+ e- Annihilation. Office of Scientific and Technical Information (OSTI), julio de 2006. http://dx.doi.org/10.2172/886789.

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Higgins, P. D., F. H. Attix, J. H. Hubbell, S. M. Seltzer, M. J. Berger y C. H. Sibata. Mass energy-transfer and mass energy-absorption coefficients, including in-flight positron annihilation for photon energies 1 keV to 100 MeV. Gaithersburg, MD: National Institute of Standards and Technology, 1991. http://dx.doi.org/10.6028/nist.ir.4680.

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Higgens, P. D., F. H. Attix, J. H. Hubbell, S. M. Seltzer, M. J. Berger y C. H. Sibata. Mass energy-transfer and mass energy-absorption coefficients, including in-flight positron annihilation for photon energies 1 keV to 100 MeV. Gaithersburg, MD: National Institute of Standards and Technology, 1992. http://dx.doi.org/10.6028/nist.ir.4812.

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Shen, B. Contribution of the two-photon annihilation process in the measurement of sigma/sub t/ (e/sup +/e/sup /minus//. -->. hadrons at PEP). Office of Scientific and Technical Information (OSTI), enero de 1988. http://dx.doi.org/10.2172/6839454.

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Stancari, Michelle Dawn. Two Photon Decay Widths of Charmonium Resonances Formed in Proton Antiproton Annihilations. Office of Scientific and Technical Information (OSTI), enero de 1999. http://dx.doi.org/10.2172/1421503.

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Fast, James Elliot. Two Photon Decays of Charmonium States Produced in Proton - Anti-proton Annihilations. Office of Scientific and Technical Information (OSTI), enero de 1992. http://dx.doi.org/10.2172/1425849.

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Fast, James Elliot. Two Photon Decays of Charmonium States Produced in Proton - Anti-proton Annihilations. Office of Scientific and Technical Information (OSTI), enero de 1992. http://dx.doi.org/10.2172/1426683.

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Pedlar, Todd Kristofer. A study of Two Photon Decays of Charmonium Resonances Formed in Proton Anti-Proton Annihilations. Office of Scientific and Technical Information (OSTI), junio de 1999. http://dx.doi.org/10.2172/1371869.

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