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Journal articles on the topic 'Exciton g-Factor'

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Author: Grafiati

Published: 24 June 2023

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1

SCHMIDT, T., L. WORSCHECH, M. SCHEIBNER, T. SLOBODSKYY, L. W. MOLENKAMP, and A. FORCHEL. "SPIN POLARIZATION IN SEMIMAGNETIC CdMnSe/ZnSe QUANTUM DOTS WITH ZERO EXCITON g FACTOR." International Journal of Modern Physics B 21, no. 08n09 (April 10, 2007): 1626–31. http://dx.doi.org/10.1142/s0217979207043324.

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We have investigated the degree of circular polarization (ρ) in the emission of semimagnetic CdMnSe/ZnSe quantum dots (QDs) with Mn contents of nominally 0, 1 and 2 %. Circularly polarized excitation was used to control the polarization of the excited carriers. The g factors were determined from the dependence of ρ on the magnetic field strength. We demonstrate that in QDs with 1 % Mn the exciton g factor is vanishingly small. We also present measurements on the excitation power dependent changes of the polarization. A direct heating mechanism is identified as origin of the drastic enhancement of the g factor by ramping up the excitation power. For high laser powers the exciton g factor increases by a factor of 30. In addition, by comparing the luminescence polarization of QDs with 2 % Mn and without Mn a sign reversal of the g factor was observed.

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2

Lalitha, D., A. John Peter, and Chang Woo Lee. "Magneto-trions in a GaMnAs/Ga0.6Al0.4As Quantum Dot." International Journal of Nanoscience 14, no. 05n06 (October 2015): 1550023. http://dx.doi.org/10.1142/s0219581x15500234.

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Magneto bound exciton and the charged exciton in a GaMn 0.02 As / Ga 0.6 Al 0.4 As quantum dot are reported with the spatial confinement effect. The numerical calculations are carried out with the inclusion of exchange interaction between the carrier and the magnetic impurities. The binding energies of exciton and the trions and the optical transition energy are obtained as a function of dot radius. Numerical computations are followed using exact diagonalization method. The spin polaronic energy of the exciton and the charged excitons are obtained using a mean field theory in the presence of magnetic field strength. The magnetization of Mn ion impurities as a function of dot radius is investigated. The effective g-factor of conduction (valence) band electron (hole) is obtained in the GaMnAs quantum dot. The magnetic field induced size dependence of effective Landé g-factor is computed. The result shows that (i) the geometrical dependence on sp-d exchange interaction in the GaMn 0.02 As / Ga 0.6 Al 0.4 As quantum dot has great influence with the geometrical confinement, (ii) the monotonic behavior of effective g-factor with the reduction of dot radius is observed, (iii) the Landé factor is more sensitive if the geometrical confinement effect is included and (iv) the value of effective g-factor increases when the spatial confinement is enhanced for all the dot radii. Our results show that the effective Landé g-factor can be manipulated negative to positive values in the GaMn 0.02 As / Ga 0.4 Al 0.6 As quantum dot.

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3

N. R. Senthil Kumar, N. R. Senthil Kumar, A. John Peter A. John Peter, and Chang Woo Lee Chang Woo Lee. "Optical properties of excitons in strained Gax In1-xAs/GaAs quantum dot: ef fect of geometrical conf inement on exciton g-factor." Chinese Optics Letters 11, no. 8 (2013): 082501–82507. http://dx.doi.org/10.3788/col201311.082501.

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4

Ju, Long, Lei Wang, Ting Cao, Takashi Taniguchi, Kenji Watanabe, Steven G. Louie, Farhan Rana, et al. "Tunable excitons in bilayer graphene." Science 358, no. 6365 (November 16, 2017): 907–10. http://dx.doi.org/10.1126/science.aam9175.

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Excitons, the bound states of an electron and a hole in a solid material, play a key role in the optical properties of insulators and semiconductors. Here, we report the observation of excitons in bilayer graphene (BLG) using photocurrent spectroscopy of high-quality BLG encapsulated in hexagonal boron nitride. We observed two prominent excitonic resonances with narrow line widths that are tunable from the mid-infrared to the terahertz range. These excitons obey optical selection rules distinct from those in conventional semiconductors and feature an electron pseudospin winding number of 2. An external magnetic field induces a large splitting of the valley excitons, corresponding to a g-factor of about 20. These findings open up opportunities to explore exciton physics with pseudospin texture in electrically tunable graphene systems.

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5

Faria Junior, Paulo E., Klaus Zollner, Tomasz Woźniak, Marcin Kurpas, Martin Gmitra, and Jaroslav Fabian. "First-principles insights into the spin-valley physics of strained transition metal dichalcogenides monolayers." New Journal of Physics 24, no. 8 (August 1, 2022): 083004. http://dx.doi.org/10.1088/1367-2630/ac7e21.

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Abstract Transition metal dichalcogenides (TMDCs) are ideal candidates to explore the manifestation of spin-valley physics under external stimuli. In this study, we investigate the influence of strain on the spin and orbital angular momenta, effective g-factors, and Berry curvatures of several monolayer TMDCs (Mo and W based) using a full ab initio approach. At the K-valleys, we find a surprising decrease of the conduction band spin expectation value for compressive strain, consequently increasing the dipole strength of the dark exciton by more than one order of magnitude (for ∼ 1 % – 2 % strain variation). We also predict the behavior of direct excitons g-factors under strain: tensile (compressive) strain increases (decreases) the absolute value of g-factors. Strain variations of ∼1% modify the bright (A and B) excitons g-factors by ∼0.3 (0.2) for W (Mo) based compounds and the dark exciton g-factors by ∼0.5 (0.3) for W (Mo) compounds. Our predictions could be directly visualized in magneto-optical experiments in strained samples at low temperature. Additionally, our calculations strongly suggest that strain effects are one of the possible causes of g-factor fluctuations observed experimentally. By comparing the different TMDC compounds, we reveal the role of spin–orbit coupling (SOC): the stronger the SOC, the more sensitive are the spin-valley features under applied strain. Consequently, monolayer WSe2 is a formidable candidate to explore the role of strain on the spin-valley physics. We complete our analysis by considering the side valleys, Γ and Q points, and by investigating the influence of strain in the Berry curvature. In the broader context of valley- and strain-tronics, our study provides fundamental microscopic insights into the role of strain in the spin-valley physics of TMDCs, which are relevant to interpret experimental data in monolayer TMDCs as well as TMDC-based van der Waals heterostructures.

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6

Burakowski, M., P. Mrowiński, M. Gawełczyk, J. P. Reithmaier, S. Höfling, and G. Sęk. "Diamagnetic coefficients and g-factors of InAs/InGaAlAs quantum dashes emitting at telecom wavelengths." Journal of Applied Physics 132, no. 14 (October 14, 2022): 144301. http://dx.doi.org/10.1063/5.0101345.

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Semiconductor nanostructures of various material systems are heavily researched for information processing applications as single-photon sources for communication and as a spin memory for storage. Here, exciton, electron, and hole properties in single InAs/InP asymmetric quantum dots (quantum dashes) emitting in a broad spectral range from 0.8 to above 1 eV are studied experimentally and theoretically. Experiments using magneto-microphotoluminescence allowed us to determine g-factor tensor components and diamagnetic coefficients. The growth-axis exciton g-factor is in a 0.0–2.9 range with a constant hole g-factor of 4.5 and variation governed by electron contribution. The in-plane g-factor is more stable with the size of the nanostructure exhibiting values of around −0.7 and −1.6 for holes and electrons, respectively. The diamagnetic coefficients are [Formula: see text] and [Formula: see text] in the growth and in-plane directions, respectively. Simulations based on the eight-band k⋅p model qualitatively reproduce the key experimental features, including the vanishing of the inverse fine-structure splitting of bright exciton at around 3 T, making these structures prospective for the generation of entangled photons.

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7

Turyanska, L., R. J. A. Hill, O. Makarovsky, F. Moro, A. N. Knott, O. J. Larkin, A. Patanè, et al. "Tuneable paramagnetic susceptibility and exciton g-factor in Mn-doped PbS colloidal nanocrystals." Nanoscale 6, no. 15 (2014): 8919–25. http://dx.doi.org/10.1039/c4nr02336f.

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We report on PbS colloidal nanocrystals that combine within one structure solubility in physiological solvents with near-infrared photoluminescence, and magnetic (magnetic susceptibility) and optical (exciton g-factor) properties tuneable by the controlled incorporation of magnetic impurities (Mn).

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8

Lacroix, Y., C. A. Tran, S. P. Watkins, and M. L. W. Thewalt. "Optical identification of the exciton–polariton in epitaxial InAs." Canadian Journal of Physics 74, S1 (December 1, 1996): 212–15. http://dx.doi.org/10.1139/p96-861.

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We report optical identification of the exciton–polariton in epitaxial InAs by combined photoluminescence, reflectance, and transmittance spectroscopy. The photoluminescence of these samples showed identifiable spectral lines a thousand times narrower than previously published results from other groups. The measurements were made at 1.4 K and at magnetic fields up to 7 T. Contrary to what is observed in other III–V semiconductors such as GaAs or InP, the free exciton (polariton) is nearly invisible in the photoluminescence spectrum without the application of a magnetic field. We believe that the relatively large residual donor concentration coupled with the large spatial extent of the exciton wave function in this material inhibit the existence of unbound excitonic recombination. Reflectance and transmittance spectroscopy provide very strong evidence that our identification is correct, and the magnetic field dependence yielded values of the electron effective mass and g-factor of (0.026 + 0.002)m0 and −15.3 ± 0.2, respectively, based on this assignment.

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9

Klotz, F., V. Jovanov, J. Kierig, E. C. Clark, D. Rudolph, D. Heiss, M. Bichler, G. Abstreiter, M. S. Brandt, and J. J. Finley. "Observation of an electrically tunable exciton g factor in InGaAs/GaAs quantum dots." Applied Physics Letters 96, no. 5 (February 2010): 053113. http://dx.doi.org/10.1063/1.3309684.

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10

Quax, G. W. W., T. E. J. Campbell Ricketts, A. M. Yakunin, T. van Lippen, R. Nötzel, P. M. Koenraad, C. A. C. Bosco, J. H. H. Rietjens, B. Koopmans, and A. Yu Silov. "All-optical control of the exciton g-factor in InAs/GaAs quantum dots." Physica E: Low-dimensional Systems and Nanostructures 40, no. 6 (April 2008): 1832–35. http://dx.doi.org/10.1016/j.physe.2007.10.089.

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11

Li, Shulun, Xiangjun Shang, Yao Chen, Xiangbin Su, Huiming Hao, Hanqing Liu, Yu Zhang, Haiqiao Ni, and Zhichuan Niu. "Wet-Etched Microlens Array for 200 nm Spatial Isolation of Epitaxial Single QDs and 80 nm Broadband Enhancement of Their Quantum Light Extraction." Nanomaterials 11, no. 5 (April 27, 2021): 1136. http://dx.doi.org/10.3390/nano11051136.

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Uniform arrays of three shapes (gauss, hat, and peak) of GaAs microlenses (MLs) by wet-etching are demonstrated, ∼200 nm spatial isolation of epitaxial single QDs embedded (λ: 890–990 nm) and broadband (Δλ∼80 nm) enhancement of their quantum light extraction are obtained, which is also suitable for telecom-band epitaxial QDs. Combined with the bottom distributed Bragg reflector, the hat-shaped ML forms a cavity and achieves the best enhancement: extraction efficiency of 26%, Purcell factor of 2 and single-photon count rate of 7×106 counts per second at the first lens; while the gauss-shaped ML shows a broader band (e.g., longer λ) enhancement. In the MLs, single QDs with featured exciton emissions are observed, whose time correlations prove single-photon emission with multi-photon probability g(2)(0)=0.02; some QDs show both biexciton XX and exciton X emissions and exhibit a perfect cascade feature. This work could pave a step towards a scalable array of QD single-photon sources and the application of QD photon-pair emission for entanglement experiments.

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12

Kumar, N. R. Senthil, and A. John Peter. "Pressure Induced Effective Exciton g-Factor in a Strained Ga_0.2In_0.8As/GaAs Quantum Dot." Journal of Advanced Physics 4, no. 3 (September 1, 2015): 191–98. http://dx.doi.org/10.1166/jap.2015.1190.

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13

Lalitha, D., A. John Peter, and Chang Kyoo Yoo. "Effects of sp-d exchange on a bound polaron and the g-factor of the exciton in a GaMnAs quantum dot." Superlattices and Microstructures 60 (August 2013): 453–61. http://dx.doi.org/10.1016/j.spmi.2013.05.031.

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14

FUKUOKA, DAISUKE, KOUSHIRO ARAHARA, TAKAAKI KOYAMA, NAOKI TANAKA, KENICHI OTO, KIYOFUMI MURO, SHOJIRO TAKEYAMA, GREGOSZ KARCZEWSKI, THOMASZ WOJTOWICZ, and JACEK KOSSUT. "COMPREHENSIVE STUDY OF SPIN-FLIP EXCITATIONS IN CdZnTe/CdZnMnTe QUANTUM WELLS." International Journal of Modern Physics B 21, no. 08n09 (April 10, 2007): 1610–14. http://dx.doi.org/10.1142/s0217979207043294.

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Spin-flip excitations in non-doped Cd 0.93 Zn 0.07 Te/Cd 0.48 Zn 0.04 Mn 0.48 Te quantum wells have been comprehensively studied by spin-flip Raman scattering (SFRS) spectroscopy and time-resolved Kerr rotation (TRKR) spectroscopy. In 4 nm quantum well, two spin-flip Raman peaks were observed in addition to the multiple Mn 2+ spin-flip scatterings. The spin-flip energies are isotropic against the magnetic field direction and well described by modified Brillouin functions. Based on the circumstantial analysis, they are assigned to the spin-flip of residual electrons and the electron spin-flip in the localized exciton, respectively, even though the large energy difference between the two electron spin-flip processes is a puzzle. While, in 9 nm quantum well a strange spin-flip excitation was observed together with a very weak Mn 2+ spin-flip scattering. The spin-flip energy changed strangely up to the magnetic field 4T, and then linearly increased with field (| g *|=1.15). A high-resolution TRKR spectroscopy revealed an unusual temperature dependence, which resembled "softening mode" of spin resonance observed in p-doped ferromagnetic CdMnTe quantum wells. However, these behaviors are well understood by an "inverted spin configuration", which results from a negative g*-factor and a very weak s-d interaction between the electrons and the manganese ions in the barrier.

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15

Chen, Zhi, Valentina Robbiano, Giuseppe M. Paternò, Giseppe Carnicella, Aline Debrassi, Antonino A. La Mattina, Stefano Mariani, et al. "Nanoscale Photoluminescence Manipulation in Monolithic Porous Silicon Oxide Microcavity Coated with Fluorescent Polyelectrolytes Via Electrostatic Nanoassembling." ECS Meeting Abstracts MA2022-01, no. 47 (July 7, 2022): 1986. http://dx.doi.org/10.1149/ma2022-01471986mtgabs.

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Porous silicon (PSi) is a promising material for future integrated nanophotonics when coupled with guest emitters [1,2], still facing challenges in terms of homogenous distribution and nanometric thickness of the emitter coating within the silicon nanostructure. Herein, it is shown that the nanopore surface of a porous silicon oxide (PSiO2) microcavity (MC) can be conformally coated with a uniform nm-thick layer of a cationic light-emitting polyelectrolyte, e.g., poly(allylamine hydrochloride) labeled with Rhodamine B (PAH-RhoB), leveraging the self-tuned electrostatic interaction of the positively-charged PAH-RhoB polymer and negatively-charged PSiO2 surface. It is found that the emission of PAH-RhoB in the PSiO2 MC is enhanced (≈2.5×) and narrowed (≈30×) at the resonant wavelength, compared with that of PAH-RhoB in a non-resonant PSiO2 reference structure [3]. The time-resolved photoluminescence analysis highlights a shortening (≈20%) of the PAH-RhoB emission lifetime in the PSiO2 MC at the resonance versus off-resonance wavelengths, and with respect to the reference structure, thereby proving a significant variation of the radiative decay rate. Remarkably, an experimental Purcell factor Fp = 2.82 is achieved. This is further confirmed by the enhance- ment of the photoluminescence quantum yield of the PAH-RhoB in the PSiO2 MC with respect to the reference structure. By building on these results, we envisage many emerging photonic applications of the electrostatic nanoassembly coating technology for introduction of foreign emitters into PSi-based photonic nano-/mesostructures, though not lim- ited to, including ultrasensitive fluorescence-enhanced optical nanosensors, nanolasers, exciton-polaritonic devices, spintronic devices, and quantum optical devices. References [1] V. Robbiano, G. M. Paterno, A. A. La Mattina, S. G. Motti, G. Lanzani, F. Scotognella, G. Barillaro, ACS Nano 2018, 12, 4536. [2] V. Robbiano, S. Surdo, A. Minotto, G. Canazza, G. M. Lazzerini, S. M. Mian, D. Comoretto, G. Barillaro, F. Cacialli, Nanomater. Nanotechnol. 2018, 8, 184798041878840. [3] Z. Chen, V. Robbiano, G. M. Paternò, G. Carnicella, A. Debrassi, A. A. La Mattina, S. Mariani, A. Minotto, G. Egri, L. Dähne, F. Cacialli, G. Barillaro, Adv. Optical Mater. 2021, 2100036 Acknowledgements Z.C. and V.R. contributed equally to this work. G.B. and Z.C. acknowledges the European Community and the Tuscany Region for their funding within the framework of the SAFE WATER project (European Union’s Horizon 2020 Research & Innovation program and the ERA-NET “PhotonicSensing” cofund – G.A. No 688735). G.M.P. thanks Fondazione Cariplo by (grant n° 2018-0979) for financial support. F.C. and A.M. acknowledge funding by EPSRC (grant EP/P006280/1, MARVEL), and G.C. and V.R. the European Community’s H2020 ETN MSCA action under grant agreement 643238 (SYNCHRONICS). F.C. acknowledges the Royal Society and the Wolfson Foundation for a Royal Society Wolfson Foundation Research Merit Award.

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16

Chen, Zhanghai, L. H. Bai, S. H. Huang, H. Xiong, S. C. Shen, I. Souma, K. Hyomi, A. Murayama, and Y. Oka. "SPIN-RESOLVED MAGNETO-OPTICAL STUDY OF CdSe SINGLE QUANTUM DOT." International Journal of Modern Physics B 21, no. 08n09 (April 10, 2007): 1549–54. http://dx.doi.org/10.1142/s0217979207043178.

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We report on the magneto-optical study of spin polarized energetic fine structures for exciton complex in single CdSe quantum dot (QD) by using micro- photoluminescence (micro-PL) spectroscopy. The zero-field splitting of exciton luminescence peak arisen from the anisotropic exchange interaction of carriers in the QDs was observed. The g-factors for exciton and negatively-charged exciton, i.e. trion in a single QD were determined by fitting the magnetic field dependence of the corresponding PL peaks. By exciting the single QD with circularly polarized light of σ- and σ+ polarization, the spin-up and spin-down trions were selectively generated. The ratio, τ/τsf, of the exciton lifetime and the time constants for the spin-flipping process of trion in a single QD was estimated to be 0.13, which implies a long spin-lifetime in single CdSe QD.

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17

Kono, Junichiro. "(Invited, Digital Presentation) Macroscopically Aligned Carbon Nanotubes for Photonics, Electronics, and Thermoelectrics." ECS Meeting Abstracts MA2022-01, no. 10 (July 7, 2022): 775. http://dx.doi.org/10.1149/ma2022-0110775mtgabs.

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The remarkable flexibility, stable chemical structure, and extraordinary thermal, electrical, and optical properties of carbon nanotubes (CNTs) are promising for a variety of applications in flexible and/or high-temperature electronics, optoelectronics, and thermoelectrics, including wearables, refractory photonics, and waste heat harvesting [1]. However, the long-standing goal in the preparation of CNT ensembles is how to maintain the extraordinary properties of individual CNTs on a macroscopic scale. The polydispersity and randomness remain two main challenges. Here, we will discuss different methods for creating macroscopically aligned CNTs, including spontaneous formation of wafer-scale aligned CNT films via controlled vacuum filtration [2-4] and production of ultrahigh-conductivity CNT fibers and films through solution spinning and coating [5,6]. We will then describe the optical [2,7-11], dc and ac electrical [2,12-17], thermal [18], and thermoelectric [19-21] properties of these materials. These results are promising for device applications in various fields such as flexible CNT broadband detectors [22-26], spectrally selective thermal emitters [11], and thermoelectric devices [20,21]. W. Gao et al., “Macroscopically Aligned Carbon Nanotubes for Flexible and High-Temperature Electronics, Optoelectronics, and Thermoelectrics,” Journal of Physics D: Applied Physics 53, 063001 (2020). X. He et al., “Wafer-Scale Monodomain Films of Spontaneously Aligned Single-Walled Carbon Nanotubes,” Nature Nanotechnology 11, 633 (2016). W. Gao and J. Kono, “Science and Applications of Wafer-Scale Crystalline Carbon Nanotube Films Prepared through Controlled Vacuum Filtration,” Royal Society Open Science 6, 181605 (2019). N. Komatsu et al., “Groove-Assisted Global Spontaneous Alignment of Carbon Nanotubes in Vacuum Filtration,” Nano Letters 20, 2332 (2020). N. Behabtu et al., “Strong, Light, Multifunctional Fibers of Carbon Nanotubes with Ultrahigh Conductivity,” Science 339, 182 (2013). L. W. Taylor et al., “Improved Properties, Increased Production, and the Path to Broad Adoption of Carbon Nanotube Fibers,” Carbon 171, 689 (2021). K. Yanagi et al., “Intersubband Plasmons in the Quantum Limit in Gated and Aligned Carbon Nanotubes,” Nature Communications 9, 1121 (2018). W. Gao et al., “Continuous Transition between Weak and Ultrastrong Coupling through Exceptional Points in Carbon Nanotube Microcavity Exciton–Polaritons,” Nature Photonics 12, 362 (2018). M. E. Green et al., “Bright and Ultrafast Photoelectron Emission from Aligned Single-Wall Carbon Nanotubes through Multiphoton Exciton Resonance,” Nano Letters 19, 158 (2019). F. Katsutani et al., “Direct Observation of Cross-Polarized Excitons in Aligned Single-Chirality Single-Wall Carbon Nanotubes,” Physical Review B 99, 035426 (2019). W. Gao et al., “Macroscopically Aligned Carbon Nanotubes as a Refractory Platform for Hyperbolic Thermal Emitters,” ACS Photonics 6, 1602 (2019). X. Wang et al., “High-Ampacity Power Cables of Tightly-Packed and Aligned Carbon Nanotubes,” Advanced Functional Materials 24, 3241 (2014). A. Zubair et al., “Carbon Nanotube Fiber Terahertz Polarizer,” Applied Physics Letters 108, 141107 (2016). D. Tristant et al., “Enlightening the Ultrahigh Electrical Conductivities of Doped Double-Wall Carbon Nanotube Fibers by Raman Spectroscopy and First-Principles Calculations,” Nanoscale 18, 19668 (2016). N. Komatsu et al., “Modulation-Doped Multiple Quantum Wells of Aligned Single-Wall Carbon Nanotubes,” Advanced Functional Materials 27, 1606022 (2017). F. R. G. Bagsican et al., “Terahertz Excitonics in Carbon Nanotubes: Exciton Autoionization and Multiplication,” Nano Letters 20, 3098 (2020). A. Baydin et al., “Giant Terahertz Polarization Rotation in Ultrathin Films of Aligned Carbon Nanotubes,” Optica 8, 760 (2021). S. Yamaguchi et al., “One-Directional Thermal Transport in Densely Aligned Single-Wall Carbon Nanotube Films,” Applied Physics Letters 115, 223104 (2019). K. Fukuhara et al., “Isotropic Seebeck Coefficient of Aligned Single-Wall Carbon Nanotube Films,” Applied Physics Letters 113, 243105 (2018). Y. Ichinose et al., “Solving the Thermoelectric Trade-Off Problem with Metallic Carbon Nanotubes,” Nano Letters 19, 7370 (2019). N. Komatsu et al., “Macroscopic Weavable Fibers of Carbon Nanotubes with Giant Thermoelectric Power Factor,” Nature Communications 12, 4931 (2021). S. Nanot et al., “Broadband, Polarization-Sensitive Photodetector Based on Optically-Thick Films of Macroscopically Long, Dense, and Aligned Carbon Nanotubes,” Scientific Reports 3, 1335 (2013). X. He et al., “Photothermoelectric p-n Junction Photodetector with Intrinsic Broadband Polarimetry Based on Macroscopic Carbon Nanotube Films,” ACS Nano 7, 7271 (2013). X. He et al., “Carbon Nanotube Terahertz Detector,” Nano Letters 14, 3953 (2014). X. He, F. Léonard, and J. Kono, “Uncooled Carbon Nanotube Photodetectors,” Advanced Optical Materials 3, 989 (2015). A. Zubair et al., “Carbon Nanotube Woven Textile Photodetector,” Physical Review Materials 2, 015201 (2018).

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Occhiuto, Ilaria Giuseppina, Maria Angela Castriciano, Mariachiara Trapani, Roberto Zagami, Andrea Romeo, Robert F. Pasternack, and Luigi Monsù Scolaro. "Controlling J-Aggregates Formation and Chirality Induction through Demetallation of a Zinc(II) Water Soluble Porphyrin." International Journal of Molecular Sciences 21, no. 11 (June 3, 2020): 4001. http://dx.doi.org/10.3390/ijms21114001.

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Under acidic conditions and at high ionic strength, the zinc cation is removed from its metal complex with 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) thus leading to the diacid free porphyrin, that subsequently self-organize into J-aggregates. The kinetics of the demetallation step and the successive supramolecular assembly formation have been investigated as a function of pH and ionic strength (controlled by adding ZnSO4). The demetallation kinetics obey to a rate law that is first order in [ZnTPPS4] and second order in [H+], according to literature, with k2 = 5.5 ± 0.4 M−2 s−1 at 298 K (IS = 0.6 M, ZnSO4). The aggregation process has been modeled according to an autocatalytic growth, where after the formation of a starting seed containing m porphyrin units, the rate evolves as a power of time. A complete analysis of the extinction time traces at various wavelengths allows extraction of the relevant kinetic parameters, showing that a trimer or tetramer should be involved in the rate-determining step of the aggregation. The extinction spectra of the J-aggregates evidence quite broad bands, suggesting an electronic coupling mechanism different to the usual Frenkel exciton coupling. Resonance light scattering intensity in the aggregated samples increases with increasing both [H+] and [ZnSO4]. Symmetry breaking occurs in these samples and the J-aggregates show circular dichroism spectra with unusual bands. The asymmetry g-factor decreases in its absolute value with increasing the catalytic rate kc, nulling and eventually switching the Cotton effect from negative to positive. Some inferences on the role exerted by zinc cations on the kinetics and structural features of these nanostructures have been discussed.

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Faria Junior, Paulo E., and Jaroslav Fabian. "Signatures of Electric Field and Layer Separation Effects on the Spin-Valley Physics of MoSe2/WSe2 Heterobilayers: From Energy Bands to Dipolar Excitons." Nanomaterials 13, no. 7 (March 27, 2023): 1187. http://dx.doi.org/10.3390/nano13071187.

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Multilayered van der Waals heterostructures based on transition metal dichalcogenides are suitable platforms on which to study interlayer (dipolar) excitons, in which electrons and holes are localized in different layers. Interestingly, these excitonic complexes exhibit pronounced valley Zeeman signatures, but how their spin-valley physics can be further altered due to external parameters—such as electric field and interlayer separation—remains largely unexplored. Here, we perform a systematic analysis of the spin-valley physics in MoSe2/WSe2 heterobilayers under the influence of an external electric field and changes of the interlayer separation. In particular, we analyze the spin (Sz) and orbital (Lz) degrees of freedom, and the symmetry properties of the relevant band edges (at K, Q, and Γ points) of high-symmetry stackings at 0° (R-type) and 60° (H-type) angles—the important building blocks present in moiré or atomically reconstructed structures. We reveal distinct hybridization signatures on the spin and the orbital degrees of freedom of low-energy bands, due to the wave function mixing between the layers, which are stacking-dependent, and can be further modified by electric field and interlayer distance variation. We find that H-type stackings favor large changes in the g-factors as a function of the electric field, e.g., from −5 to 3 in the valence bands of the Hhh stacking, because of the opposite orientation of Sz and Lz of the individual monolayers. For the low-energy dipolar excitons (direct and indirect in k-space), we quantify the electric dipole moments and polarizabilities, reflecting the layer delocalization of the constituent bands. Furthermore, our results show that direct dipolar excitons carry a robust valley Zeeman effect nearly independent of the electric field, but tunable by the interlayer distance, which can be rendered experimentally accessible via applied external pressure. For the momentum-indirect dipolar excitons, our symmetry analysis indicates that phonon-mediated optical processes can easily take place. In particular, for the indirect excitons with conduction bands at the Q point for H-type stackings, we find marked variations of the valley Zeeman (∼4) as a function of the electric field, which notably stands out from the other dipolar exciton species. Our analysis suggests that stronger signatures of the coupled spin-valley physics are favored in H-type stackings, which can be experimentally investigated in samples with twist angle close to 60°. In summary, our study provides fundamental microscopic insights into the spin-valley physics of van der Waals heterostructures, which are relevant to understanding the valley Zeeman splitting of dipolar excitonic complexes, and also intralayer excitons.

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McCormick, B. P., A. E. Stuchbery, A. Goasduff, A. Kusoglu, and G. Georgiev. "Modelling hyperfine interactions for nuclear g-factor measurements." EPJ Web of Conferences 232 (2020): 04009. http://dx.doi.org/10.1051/epjconf/202023204009.

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A promising technique for g-factor measurements on short-lived nuclear states utilises the hyperfine fields of free ions in vacuum. To fully utilise this technique the hyperfine interaction must be modelled based on atomic structure calculations. Atomic structure calculations were performed using the most recent release of the General Relativistic Atomic Structure Package, and Monte-Carlo simulations of atomic-decay cascades in highly charged ions were developed. The simulations were used to fit experimental data on excited 56Fe ions recoiling in vacuum with a view to determining the first-excited state g factor, g(21+), of 56Fe.

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21

Hara, Ryujiro, and Aziz Sancar. "The SWI/SNF Chromatin-Remodeling Factor Stimulates Repair by Human Excision Nuclease in the Mononucleosome Core Particle." Molecular and Cellular Biology 22, no. 19 (October 1, 2002): 6779–87. http://dx.doi.org/10.1128/mcb.22.19.6779-6787.2002.

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ABSTRACT To investigate the role of chromatin remodeling in nucleotide excision repair, we prepared mononucleosomes with a 200-bp duplex containing an acetylaminofluorene-guanine (AAF-G) adduct at a single site. DNase I footprinting revealed a well-phased nucleosome structure with the AAF-G adduct near the center of twofold symmetry of the nucleosome core. This mononucleosome substrate was used to examine the effect of the SWI/SNF remodeling complex on the activity of human excision nuclease reconstituted from six purified excision repair factors. We found that the three repair factors implicated in damage recognition, RPA, XPA, and XPC, stimulate the remodeling activity of SWI/SNF, which in turn stimulates the removal of the AAF-G adduct from the nucleosome core by the excision nuclease. This is the first demonstration of the stimulation of nucleotide excision repair of a lesion in the nucleosome core by a chromatin-remodeling factor and contrasts with the ACF remodeling factor, which stimulates the removal of lesions from internucleosomal linker regions but not from the nucleosome core.

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22

Stuchbery, Andrew E., Brendan P. McCormick, Timothy J. Gray, and Ben J. Coombes. "Pushing the limits of excited-state g-factor measurements." EPJ Web of Conferences 178 (2018): 02005. http://dx.doi.org/10.1051/epjconf/201817802005.

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Current developments in excited-state g-factor measurements are discussed with an emphasis on cases where the experimental methodology is being extended into new regimes. The transient-field technique, the recoil in vacuum method, and moment measurements with LaBr3 detectors are discussed.

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Pakou, A. A., J. Billowes, A. W. Mountford, C. Tenreiro, and D. D. Warner. "g-factors of some excited states in 49,50Cr." HNPS Proceedings 3 (December 5, 2019): 205. http://dx.doi.org/10.12681/hnps.2388.

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Magnetic moments of the first excited states in 50Cr and of the 7/2" and 19/2' states in 49Cr, have been measured by the transient field technique. The states were excited by the inverse reaction 40Ca + 12C and the recoil nuclei traversed a thick gadolinium foil. The observed rotations, of the 2+, 4+, 6+, 8+ states of the ground-state band in 50Cr, were found into the experimental error to be the same, suggesting similar g-factors for these states and thus supporting a high collectivity for the ground-state band, g-factors of the 7/2' and 19/2 states in 49Cr, were deduced by adopting both an overall parametrization of the transient magnetic field in Gd and by comparing the 49Cr rotations with rotations of states with known magnetic moments, as the 2+ ones of 50Cr and of 46Ti which was also populated in the same reaction. Both methods gave similar results and the g-factors adopted for the 19/2" and 7/2" states were + 0.78(17) and +0.35(7) respectively. These results are discussed in terms of cranked shell model calculations and are found to support a proton alignment in the f7/2 shell.

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24

Glazov, D. A., A. V. Volotka, A. A. Schepetnov, M. M. Sokolov, V. M. Shabaev, I. I. Tupitsyn, and G. Plunien. "g factor of boron-like ions: ground and excited states." Physica Scripta T156 (September 1, 2013): 014014. http://dx.doi.org/10.1088/0031-8949/2013/t156/014014.

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25

Bazzacco, D., F. Brandolini, K. Löwenich, P. Pavan, C. Rossi Alvarez, M. De Poli, and A. M. I. Haque. "g-factor of the first excited 4+ states in156Gd and158Gd." Hyperfine Interactions 59, no. 1-4 (August 1990): 125–28. http://dx.doi.org/10.1007/bf02401205.

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26

Pakou, A., F. Brandolini, D. Bazzacco, P. Pavan, C. Rossi-Alvarez, E. Maglione, M. Depoli, and R. Ribas. "THE 19/2- g-FACTOR IN 39K USING A TRANSIENT FIELD-FUSION REACTION TECHNIQUE." HNPS Proceedings 2 (February 18, 2020): 333. http://dx.doi.org/10.12681/hnps.2860.

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The magnetic moment of the 19/2- state in 39K has been measured by the transient field technique. The state was excited by the inverse reaction 12C(32S,pa)39K and the recoil nucleus traversed a thin Gd foil. Its absolute g-factor, g= 0.35(3), was obtained by an internal calibration, which makes use of the magnetic moment of the 15/2+ state in 41Ca also excited in the same reaction. The experimental result agrees well within shell model predictions.

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27

Xiong, Wen. "The effective excitonic g factors of Mn-doped InAs nanowires." Superlattices and Microstructures 104 (April 2017): 205–14. http://dx.doi.org/10.1016/j.spmi.2017.02.031.

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28

Sheng, Weidong. "Electrical tuning of exciton g factors in quantum dot molecules: Effect of hole localization." Applied Physics Letters 95, no. 11 (September 14, 2009): 113105. http://dx.doi.org/10.1063/1.3227653.

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29

Kadushkin, V. I. "Spin splitting and electron g-factor of an excited quantum confinement subband." Semiconductors 40, no. 4 (April 2006): 433–39. http://dx.doi.org/10.1134/s1063782606040117.

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30

Kenn, O., K. H. Speidel, R. Ernst, J. Gerber, P. Maier-Komor, N. Benczer-Koller, G. Kumbartzki, and F. Becker. "Particle detection for future g factor measurements of Coulomb excited radioactive beams." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 171, no. 4 (December 2000): 589–96. http://dx.doi.org/10.1016/s0168-583x(00)00304-9.

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31

Covre, F. S., P. E. Faria, V. O. Gordo, C. Serati de Brito, Y. V. Zhumagulov, M. D. Teodoro, O. D. D. Couto, et al. "Revealing the impact of strain in the optical properties of bubbles in monolayer MoSe₂." Nanoscale 14, no. 15 (2022): 5758–68. http://dx.doi.org/10.1039/d2nr00315e.

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We have investigated the optical properties of strained MoSe2 monolayer bubbles at low temperature. We have observed a red-shift of the exciton and trion emissions, a reduction of the trion binding energy and an enhancement of the valley g-factors.

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32

Pomerantz, Andrew E., Florian Ausfelder, Richard N. Zare, and Winifred M. Huo. "Line strength factors for E,F1Σ+g(v′ = 0, J′ = J′′) X1Σ+g (v′′, J′′) (2 + 1) REMPI transitions in molecular hydrogen." Canadian Journal of Chemistry 82, no. 6 (June 1, 2004): 723–29. http://dx.doi.org/10.1139/v04-074.

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Experimentally and theoretically determined line strengths are presented for E,F1Σ+g(v′ = 0, J′ = J′′) X1Σ+g (v′′, J′′) (2 + 1) REMPI transitions in H2, HD, and D2. The experimental technique employs a hot filament source of internally excited hydrogen that allows experimental determination of line strengths for the low rotational states of highly excited vibrational manifolds (v′′ ≤ 4). The line strengths are found to depend only weakly on J′′ for the states measured here, and theoretical results indicate that the line strengths depend strongly on v′′. These values are combined with previously measured and calculated line strengths for these transitions (K.-D. Rinnen, M.A. Buntine, D.A.V. Kliner, R.N. Zare, and W.M. Huo. J. Chem. Phys. 95, 214 (1991)), resulting in a more complete compilation of REMPI line strengths for molecular hydrogen. Key words: hydrogen, spectroscopy, REMPI, line strength, multiphoton.

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33

WU, S. Y., H. M. ZHANG, G. D. LU, and J. S. YAO. "THEORETICAL STUDIES OF THE ZERO-FIELD SPLITTING AND g FACTOR FOR Gd3+ IN La2-xSrxCuO4." International Journal of Modern Physics B 21, no. 18n19 (July 30, 2007): 3254–57. http://dx.doi.org/10.1142/s0217979207044317.

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The zero-field splitting D of the 8 S 7/2 ground singlet for the tetragonal Gd 3+ center in La 2-x Sr x CuO 4 is theoretically studied from the superposition model. Meanwhile, the g factor is also quantitatively investigated from the approximation formula including admixture of the ground 8 S 7/2 and the excited 6 L 7/2 ( L=P , D, F, G) states via the spin-orbit coupling interactions. The calculated zero-field splitting and g factor are in reasonable agreement with the experimental data. It is found that the significant zero-field splitting can be ascribed to the average impurity-ligand bonding angles [≈ (θ1 + θ2)/2 ≈ 62°] related to the four-fold axis larger than that (≈ 54.74°) of the cubic case. Nevertheless, the experimental g factor close to 2 may be largely due to the very slight admixture of the ground 8 S 7/2 and the excited 6 L 7/2 states via the spin-orbit coupling interactions.

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34

Steffan, A. G., and R. T. Phillips. "Exciton g-Factors, Diamagnetic Shifts, and Exchange Splittings in Quantum Dots in GaAs Quantum Wells." physica status solidi (a) 190, no. 2 (April 2002): 541–45. http://dx.doi.org/10.1002/1521-396x(200204)190:2<541::aid-pssa541>3.0.co;2-w.

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35

Zheng, Wen-Chen, Hui-Ning Dong, Shao-Yi Wu, and Sheng Tang. "Defect Model of a Tetragonal Sm3+ Center Found from EPR Measurements in CaF2 and SrF2 Crystals." Zeitschrift für Naturforschung A 58, no. 5-6 (June 1, 2003): 373–75. http://dx.doi.org/10.1515/zna-2003-5-621.

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The EPR parameters (g factors g∥, g⊥ and hyperfine structure constants A∥, A⊥) of a tetragonal(C4v) Sm3+ center in CaF2 and SrF2 crystals are calculated by considering the crystal-field Jmixingamong the ground 6H5/2, the first excited 6H7/2 and second excited 6H9/2 state multiplets.In the calculations the free-ion and crystal-field parameters of the tetragonal Sm3+-F− centerobtained from polarized laser-selective excitation spectroscopy are used. The calculated resultssuggest that the tetragonal Sm3+-F− center is the Sm3+ center found by later EPR measurements.The g factors g∥, g⊥ and hyperfine structure constants A∥, A⊥ of this EPR center are satisfactorilyexplained.

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36

Dong, Hui-Ning, Shao-Yi Wu, Wei-Dong Chen, and Deng-Feng Li. "The g Factors and Defect Structure of Orthorhombic Dy3+ Ions in CdF2 Crystals." Zeitschrift für Naturforschung A 61, no. 1-2 (February 1, 2006): 87–90. http://dx.doi.org/10.1515/zna-2006-1-214.

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The electronic paramagnetic resonance g factors gx, gy and gz of an orthorhombic Dy3+ center in CdF2 are studied by the perturbation formulae of the g factors for a 4f9 ion in orthorhombic symmetry. In these formulae, the contributions to g factors due to J-mixing among the ground 6H15/2, the first excited 6H13/2 and the second excited 6H11/2 states via crystal-field interaction, lead to admixtures among the states with the same J-value via spin-orbit coupling. In addition, the admixtures between the lowest Kramers doublet Γγ and other 20 Kramers doublets Γ x within the states 6HJ (J = 15/2, 13/2 and 11/2) via crystal-field and orbital angular momentum interactions are considered. In the above orthorhombic center, the impurity Dy3+ is associated with co-doped crystals with alkali metal ions in the [110] axis. By analyzing the g factors, we find that the impurity Dy3+ ion does not reside in the ideal Cd2+ site but moves towards the co-doped alkali metal ion along the [110] direction by a displacement Δ Z ≈ 0.272 Å.

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37

Bylicki, F., H. G. Weber, G. Persch, and W. Demtröder. "On g factors and hyperfine structure in electronically excited states of NO2." Journal of Chemical Physics 88, no. 6 (March 15, 1988): 3532–38. http://dx.doi.org/10.1063/1.453901.

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38

Garcia-Arellano, Guadalupe, Gaëlle Trippé-Allard, Thomas Campos, Frédérick Bernardot, Laurent Legrand, Damien Garrot, Emmanuelle Deleporte, Christophe Testelin, and Maria Chamarro. "Unexpected Anisotropy of the Electron and Hole Landé g-Factors in Perovskite CH3NH3PbI3 Polycrystalline Films." Nanomaterials 12, no. 9 (April 19, 2022): 1399. http://dx.doi.org/10.3390/nano12091399.

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In this work, we studied, at low temperature, the coherent evolution of the localized electron and hole spins in a polycrystalline film of CH3NH3PbI3 (MAPI) by using a picosecond-photo-induced Faraday rotation technique in an oblique magnetic field. We observed an unexpected anisotropy for the electron and hole spin. We determined the electron and hole Landé factors when the magnetic field was applied in the plane of the film and perpendicular to the exciting light, denoted as transverse ⊥ factors, and when the magnetic field was applied perpendicular to the film and parallel to the exciting light, denoted as parallel ∥ factors. We obtained |ge,⊥|=2.600 ± 0.004, |ge,∥|=1.604 ± 0.033 for the electron and |gh,⊥|=0.406 ± 0.002, |gh,∥|=0.299 ± 0.007 for the hole. Possible origins of this anisotropy are discussed herein.

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39

Zamick, L., S. Yeager, Y. Y. Sharon, and S. J. Q. Robinson. "Lawson method for obtaining wave functions and g factors of Ar isotopes." International Journal of Modern Physics E 28, no. 01n02 (February 2019): 1950002. http://dx.doi.org/10.1142/s0218301319500022.

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Lawson has shown that one can obtain sensible wave functions even in the weak deformation limit of the Nilsson model as long as one projects out states of good total angular momentum. We apply this method to obtain wave functions and magnetic [Formula: see text] factors of excited states of select even–even Ar isotopes with emphasis on the comparison of [Formula: see text]Ar and [Formula: see text]Ar. These [Formula: see text] factors are compared with the values that are obtained by matrix diagonalization in the same space using the WBT residual interaction.

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40

Kutrowski, M., T. Wojtowicz, P. Kossacki, V. Ciulin, and J. Kossut. "Neutral and Charged Exciton Photoluminescence in a Magnetic Field Studied for Different Electron Concentrations and g-Factors." physica status solidi (b) 229, no. 2 (January 2002): 791–95. http://dx.doi.org/10.1002/1521-3951(200201)229:2<791::aid-pssb791>3.0.co;2-3.

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41

CHRISTIANEN, PETER C. M. "SEMICONDUCTOR NANOSTRUCTURES IN HIGH MAGNETIC FIELDS: RECENT RESULTS AT HFML NIJMEGEN." International Journal of Modern Physics B 23, no. 12n13 (May 20, 2009): 2573–74. http://dx.doi.org/10.1142/s0217979209062001.

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A short overview of the current experimental facilities at the HFML Nijmegen, including an update on the planned development of a 45 T Hybrid magnet in conjunction with a Free Electron Laser, was presented. That was followed by a brief highlight of recent results on the high field physical properties of semiconductor nanostructures, such as quantum rings1 and dots,2 graphene3,4 and organic nanostructures.5 The majority of the talk was devoted to the investigation of negatively charged excitons (negative trions, two electrons bound to one hole) in semiconductor quantum wells in high magnetic fields. A comprehensive overview of photoluminescence (PL) experiments on GaAs and CdTe quantum wells (QWs) of variable well widths, containing a low density electron gas (2DEG) was presented. Particular interest was given to the magnetic field range where the ground state of negative trions is changing from a singlet (both electrons having opposite spin) to a triplet (parallel electron spins) state. Using polarized magneto-PL (excitation) and reflectivity spectroscopy we have identified (for both GaAs and CdTe QWs) the four typical excitonic peaks, usually denoted as the singlet, dark triplet and bright triplet trion peaks, as well as the neutral exciton peak. All peaks exhibit a pronounced dependence on polarization, 2DEG density and temperature. CdTe QWs exhibit all four peaks at the entire field range used (< 44 T), whereas the dark triplet emission disappears at high fields for GaAs QWs. We have determined the field strength at which the singlet-triplet crossover occurs for all QWs, which allows us to critically compare our experimental results with theoretical predictions. Remarkably, the actual singlet-triplet transition is hidden in GaAs QWs and a narrow (12 nm) CdTe QW. Since the PL emission energy equals the energy difference between the initial (trion) and final (electron) states, the PL lines themselves do not cross at the singlet-triplet crossover as a result of the different Zeeman energies of the final electron states.6 In contrast the cross-over is directly visible in the PL lines of a wide (20 nm) CdTe QW. This behaviour can be readily understood by the dependence of the electron- and hole g -factors on well width and host material. Note from Publisher: This article contains the abstract only.

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42

Stuchbery, A. E., and P. F. Mantica. "Nuclear structure of neutron-rich nuclei near closed shells from excited-state g-factor measurements." European Physical Journal Special Topics 150, no. 1 (November 2007): 177–82. http://dx.doi.org/10.1140/epjst/e2007-00297-1.

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43

DONG, HUI-NING, SHAO-YI WU, and JUE WANG. "THEORETICAL STUDIES ON THE EPR g FACTORS FOR Dy3+ IN YBa2Cu3O6." International Journal of Modern Physics B 21, no. 18n19 (July 30, 2007): 3171–73. http://dx.doi.org/10.1142/s0217979207044111.

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In the past years, the typical high Tc superconductor YBa 2 Cu 3 O 6 has been extensively studied by many authors. And electron paramagnetic resonance (EPR) studies of rare-earth ( Re 3+) ions in high- Tc oxide superconductors have attracted much interest because they can provide valuable information on spin-lattice relaxation, exchange interactions and the ground state properties of Re 3+ ions, which are further employed as sensitive probes of spin dynamics in high- Tc superconductor. The EPR anisotropic g factors of Dy 3+ in YBa 2 Cu 3 O 6 crystal has been measured by M.R. Gafurov et al., and there is no theoretical explanations related to the crystal structural data. In this paper, parameters g factors for Dy 3+ in YBa 2 Cu 3 O 6 are theoretically studied from the perturbation formulas of these parameters for a 4f9 ion in tetragonal symmetry. In these formulas, the contributions to the EPR parameters from the second-order perturbation terms and the admixtures of various excited states are taken into account. The related crystal-field parameters are determined from the superposition model and crystal structural data. The theoretical results show reasonable agreement with the experimental values.

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44

Arora, Ashish, Nirupam Hatui, Arnab Bhattacharya, and Sandip Ghosh. "Large exciton g-factors in anisotropically strained A-plane GaN film measured using magneto-optical Kerr effect spectroscopy." Applied Physics Letters 103, no. 5 (July 29, 2013): 052109. http://dx.doi.org/10.1063/1.4817399.

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45

Xiong, Wen, and Jianglong Huang. "Giant effective excitonic g factors of Mn-doped ZnO/MgxZn1−xO core–shell nanowires." Superlattices and Microstructures 70 (June 2014): 91–97. http://dx.doi.org/10.1016/j.spmi.2014.02.020.

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46

Li, Dong-Xiao, and Wen Xiong. "The electronic structure and effective excitonic g factors of GaAs/GaMnAs core-shell nanowires." Superlattices and Microstructures 112 (December 2017): 584–95. http://dx.doi.org/10.1016/j.spmi.2017.10.016.

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47

Barnett, Gene H., John R. Little, Zeyd Y. Ebrahim, Stephen C. Jones, and Harry T. Friel. "Cerebral Circulation during Arteriovenous Malformation Operation." Neurosurgery 20, no. 6 (June 1, 1987): 836–42. http://dx.doi.org/10.1227/00006123-198706000-00003.

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Abstract The circulatory changes in the cortex around a cerebral arteriovenous malformation (AVM) were studied in 18 patients. The AVMs had rapid circulation times with early draining veins on angiography. Local cortical blood flow (ICoBF) was measured with cortically applied thermister/Peltier stack arrays. The AVMs had a more pronounced effect on ICoBF at a 2- to 4-cm distance from the AVM margin than in the adjacent cortex. Mean preexcision ICoBF was 62.9 ± 6.7 (SE) ml/100 g/minute (i.e., similar to normal controls) near the AVM margin and 43.0 ± 4.2 ml/100 g/minute far (i.e., >2 cm) from the AVM. CO2 reactivity (COR) before excision was 1.1 ± 0.3 ml/100 g/minute/torr of CO2 (i.e., similar to normal controls) at near sites and 0.6 ± 0.3 ml/100 g/minute/torr of CO2 at far sites. The mean postexcision near ICoBF remained stable at 55.8 ± 5.1 ml/100 g/minute at near sites, but the far ICoBF significantly increased (P < 0.05) to 57.2 ± 6.8 ml/100 g/minute. The cortical feeding artery pressure was substantially below the normal cortical artery pressure in 50% of the cases studied. Pressure in these arteries normalized after occlusion and AVM excision, resulting in a rapid increase in cortical artery perfusion pressure. Draining red vein pressure, which was elevated before AVM excision, also dropped after excision, contributing to the increase in perfusion pressure. Two patients who developed the normal perfusion pressure breakthrough syndrome (PBS) after operation had low ICoBF and disturbed COR before AVM excision and marked increase of ICoBF after excision. Factors that contribute to the development of PBS include: (a) low ICoBF around an AVM; (b) impaired COR; (c) low cortical artery pressure before AVM excision; (d) normalization in cortical artery pressure after AVM removal; and (e) substantial increase in ICoBF after AVM removal. Maintenance of a low systemic arterial blood pressure during the early postoperative period is essential in reducing the risk of severe cerebral edema.

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48

Coin, Frédéric, Philippe Frit, Benoit Viollet, Bernard Salles, and Jean-Marc Egly. "TATA Binding Protein Discriminates between Different Lesions on DNA, Resulting in a Transcription Decrease." Molecular and Cellular Biology 18, no. 7 (July 1, 1998): 3907–14. http://dx.doi.org/10.1128/mcb.18.7.3907.

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ABSTRACT DNA damage recognition by basal transcription factors follows different mechanisms. Using transcription-competition, nitrocellulose filter binding, and DNase I footprinting assays, we show that, although the general transcription factor TFIIH is able to target any kind of lesion which can be repaired by the nucleotide excision repair pathway, TATA binding protein (TBP)-TFIID is more selective in damage recognition. Only genotoxic agents which are able to induce kinked DNA structures similar to the one for the TATA box in its TBP complex are recognized. Indeed, DNase I footprinting patterns reveal that TBP protects equally 4 nucleotides upstream and 6 nucleotides downstream from the A-T (at position −29 of the noncoding strand) of the adenovirus major late promoter and from the G-G of a cisplatin-induced 1,2-d(GpG) cross-link. Together, our results may partially explain differences in transcription inhibition rates following DNA damage.

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Chen, Y. H., X. L. Ye, B. Xu, Z. G. Wang, and Z. Yang. "Large g factors of higher-lying excitons detected with reflectance difference spectroscopy in GaAs-based quantum wells." Applied Physics Letters 89, no. 5 (July 31, 2006): 051903. http://dx.doi.org/10.1063/1.2245213.

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50

Schmidt, Falko, Agnieszka L. Kozub, Uwe Gerstmann, Wolf Gero Schmidt, and Arno Schindlmayr. "A Density-Functional Theory Study of Hole and Defect-Bound Exciton Polarons in Lithium Niobate." Crystals 12, no. 11 (November 7, 2022): 1586. http://dx.doi.org/10.3390/cryst12111586.

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Hole polarons and defect-bound exciton polarons in lithium niobate are investigated by means of density-functional theory, where the localization of the holes is achieved by applying the +U approach to the oxygen 2p orbitals. We find three principal configurations of hole polarons: (i) self-trapped holes localized at displaced regular oxygen atoms and (ii) two other configurations bound to a lithium vacancy either at a threefold coordinated oxygen atom above or at a two-fold coordinated oxygen atom below the defect. The latter is the most stable and is in excellent quantitative agreement with measured g factors from electron paramagnetic resonance. Due to the absence of mid-gap states, none of these hole polarons can explain the broad optical absorption centered between 2.5 and 2.8 eV that is observed in transient absorption spectroscopy, but such states appear if a free electron polaron is trapped at the same lithium vacancy as the bound hole polaron, resulting in an exciton polaron. The dielectric function calculated by solving the Bethe–Salpeter equation indeed yields an optical peak at 2.6 eV in agreement with the two-photon experiments. The coexistence of hole and exciton polarons, which are simultaneously created in optical excitations, thus satisfactorily explains the reported experimental data.

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