Photoexcitation

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

Electronic determinants of photoacidity in cyanonaphthols.

Abstract: We present semiempirical AM1 calculations for the ground and excited state of 2-naphthol and some of its cyano derivatives in the gas phase. Following photoexcitation, the Mulliken electron density...

Photoinduced possible superconducting state with long-lived disproportionate band filling in FeSe

Abstract: Photoexcitation is a very powerful way to instantaneously drive a material into a novel quantum state without any fabrication, and variable ultrafast techniques have been developed to observe how electron, lattice, and spin degrees of freedom change. One of the most spectacular phenomena is photoinduced superconductivity, and it has been suggested in cuprates that the transition temperature Tc can be enhanced from the original Tc with significant lattice modulations. Here, we show a possibility for another photoinduced high-Tc superconducting state in the iron-based superconductor FeSe. The transient electronic state over the entire Brillouin zone is directly observed by time- and angle-resolved photoemission spectroscopy using extreme ultraviolet pulses obtained from high harmonic generation. Our results of dynamical behaviors from 50 fs to 800 ps consistently support the favourable superconducting state after photoexcitation well above Tc. This finding demonstrates that multiband iron-based superconductors emerge as an alternative candidate for photoinduced superconductors. Light-matter interactions can be used to induce a superconducting-like state in some cuprate superconductors at temperatures above the expected transition temperature. Here, the authors provide time and angle resolved spectroscopic evidence to suggest that photo induced superconductivity can also be achieved in Fe-based superconductors

Monte Carlo studies of nonequilibrium phonon effects in polar semiconductors and quantum wells. I. Laser photoexcitation.

Abstract: The present paper illustrates a series of theoretical results on nonequilibrium phonon effects based on a novel Monte Carlo algorithm. The details of the numerical procedure are given. No assumptions on the form of the phonon or the electron distributions are required. The main emphasis is given to the study of LO-phonon perturbations as a result of the relaxation of photoexcited carriers in polar semiconductors. Bulk GaAs and InP, as well as GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As heterostructures are analyzed. Good agreement is found with available experimental results from time-resolved luminescence and Raman measurements. The strong phonon emission by the high-energy photoexcited electrons in the first stage of their relaxation (within a few tenths of a picosecond) is found to drive the phonon distribution strongly out of equilibrium. After the excitation, reabsorption of the emitted phonons by the carriers and nonelectronic phonon-decay processes bring the distribution back to its equilibrium value.

Excitation mechanism in the photoisomerization of a surface-bound azobenzene derivative: Role of the metallic substrate.

Abstract: Two-photon photoemission spectroscopy is employed to elucidate the electronic structure and the excitation mechanism in the photoinduced isomerization of the molecular switch tetra-tert-butyl-azobenzene (TBA) adsorbed on Au(111). Our results demonstrate that the optical excitation and the mechanism of molecular switching at a metal surface is completely different compared to the corresponding process for the free molecule. In contrast to direct (intramolecular) excitation operative in the isomerization in the liquid phase, the conformational change in the surface-bound TBA is driven by a substrate-mediated charge transfer process. We find that photoexcitation above a threshold hν≈2.2 eV leads to hole formation in the Au d-band followed by a hole transfer to the highest occupied molecular orbital of TBA. This transiently formed positive ion resonance subsequently results in a conformational change. The photon energy dependent photoisomerization cross section exhibit an unusual shape for a photochemical rea...

Efficient visible light sensitization of TiO2 by surface complexation with Fe(CN)64

Abstract: A coloured charge-transfer complex formed by adsorption of Fe(CN)64– at the surface of TiO2 particles and electrodes upon photoexcitation injects electrons into the conduction band of this semiconductor with a quantum yield of at least 37%.