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Photoexcitation

About: Photoexcitation is a research topic. Over the lifetime, 5874 publications have been published within this topic receiving 134733 citations.


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TL;DR: In this paper, a modified version of the Mitchell-Makinson time-dependent perturbative calculation of the surface photoelectric effect has been carried out based on a significantly improved treatment of surface-polarization charge-density variations.
Abstract: A modified form of the Mitchell---Makinson time-dependent perturbative calculation of the surface photoelectric effect has been carried out based on a significantly improved treatment of surface-polarization charge-density variations. The approach taken allows calculation of the excitation current back into the metal as well as into vacuum, and is generally applicable to the surface wave (plasmon) or to the direct optical mode of $p$-polarized-light excitation of the surface effect. Numerical results are presented for aluminum, but the general conclusions of the paper should be applicable to all nearly-free-electron metals. The behavior of the surface charge is shown to have a fundamental effect upon the frequency dependence of the surface effect, causing a marked enhancement in the effect at low energies followed by an almost total suppression of the surface effect at energies near the volume plasma energy. Surface photoexcitation at these lower energies is shown to dominate the photoemission from surface-wave decay as well as from direct optical excitation at high angles of light incidence. The surface-wave (plasmon) mode of excitation is shown to be particularly strong, with surface excitation dominating the decay of the high-$k$ plasmons typically excited on real surfaces. Comparisons of the results of this calculation are made with existing experimental data, and the prediction that surface waves (plasmons) should form a uniquely strong mode of surface-effect excitation is shown to be quantitatively consistent with recent experimental studies of photoemission in surface-plasmon decay. The historical failure to observe direct optical excitation of the surface photoelectric effect in the alkalis is explained, and a suggestion for detecting direct-optical excitation of the effect in other nearly-free-electron metals is made based on the results of this calculation.

67 citations

Journal ArticleDOI
TL;DR: In this paper, dipole-bound excited states are reported for the I−⋅CH3CN and I− ⋅ CH3CN2 cluster ions, located just below their vertical electron detachment energies (determined using negative ion photoelectron spectroscopy).
Abstract: Dipole‐bound excited states are reported for the I−⋅CH3CN and I−⋅(CH3CN)2 cluster ions, located just below their vertical electron detachment energies (determined using negative ion photoelectron spectroscopy). The absorption cross sections for excitation to these states are observed to increase with increasing dipole moments of the solvent molecules in the I−⋅M series (M=methyl iodide, acetone, acetonitrile). Photoexcitation at the peak of the transition to the dipole‐bound state results exclusively in the dipole‐bound fragment ion, M−. The photoelectron spectrum of the CH3CN− fragment was also recorded by sequential two‐photon absorption in the I−⋅CH3CN parent, indicating that the excess electron is indeed weakly bound (≤10 meV) with very little intramolecular distortion evident upon electron detachment. The I−⋅(CH3CN)2 cluster displays two absorption bands, one below each of the two features in the photoelectron spectrum. The most intense band correlates with the weaker, lower binding energy photoelectron band. Excitation of this strong absorption band results in production of both CH3CN− and (CH3CN)−2 fragments, while excitation of the weaker absorption band only results in electron detachment. We interpret these results in the context of two structural isomers for I−⋅(CH3CN)2: one with the solvent molecules surrounding the I− and another with both solvent molecules on the same side, asymmetrically solvating I− in a configuration with a large electric dipole moment in the neutral cluster over this anionic geometry.

66 citations

Journal ArticleDOI
TL;DR: Guo et al. as mentioned in this paper developed an open-aperture Gaussian-beam Z-scan theory for evaluating the property of the saturable absorption originating from two-photon absorption (2PA) transition, when a spatial Gaussian beam is used as the excitation source.
Abstract: In our article [B. Gu, Y. X. Fan, J. Wang, J. Chen, J. P. Ding, H. T. Wang, and B. Guo, Phys. Rev. A 73, 065803 (2006)] we have presented the theory of open-aperture Gaussian-beam Z-scan, based on the Adomian decomposition method, which is available only for the saturable absorption caused by single-photon absorption transition. In the present article, using the same technique (Adomian decomposition method, as a common technique), we develop an open-aperture Z-scan theory for evaluating the property of the saturable absorption originating from two-photon absorption (2PA) transition, when a spatial Gaussian beam is used as the excitation source. We find analytic polynomial expressions of the Z-scan traces for a continuous wave laser or a temporal Gaussian pulsed laser. As the experimental evidence, we investigate the saturable 2PA behaviors caused by the interband two-photon transition in the direct-gap II–VI semiconductors CdS, CdSe, ZnSe, and ZnTe, under the excitation condition of a femtosecond laser wi...

66 citations

Journal ArticleDOI
TL;DR: A bimolecular recombination mechanism for both single chain and aggregated chain solutions is distinguished by calculating the analytical dependence of the photoinduced signal on the pump intensity and on the chop frequency.
Abstract: We present a study of the photoexcitation mechanism of poly-3-alkylthienylene and poly-3-alkylthienylenevinylene polymer solutions. We study the photoinduced absorption under steady-state and far from steady-state conditions. By calculating the analytical dependence of the photoinduced signal on the pump intensity and on the chop frequency we distinguish a bimolecular recombination mechanism for both single chain and aggregated chain solutions. The results are discussed assuming that a weak reversible charge transfer between the photoexcited polymer and the solvent takes place.

66 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023249
2022529
2021221
2020204
2019183
2018256