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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: An induced absorption on the high-energy side of spectral hole burning in band-to-band transitions in GaAs is observed in the early stage of photoexcitation by an intense femtosecond pump pulse.
Abstract: We report the observation of an induced absorption on the high-energy side of spectral hole burning in band-to-band transitions in GaAs. This effect appears in the early stage of photoexcitation by an intense femtosecond pump pulse. This feature can be explained by edge singularities in the presence of a «nonequilibrium Fermi sea»
51 citations
TL;DR: In this paper, an experimental apparatus for surface reaction research has been designed as an end-station of a soft x-ray beamline, BL23SU, in the SPring-8.
Abstract: An experimental apparatus for surface reaction research has been designed as an end-station of a soft x-ray beamline, BL23SU, in the SPring-8. The soft x-ray with intense flux density is provided by a variable-polarizing undulator and is monochromized by using a varied line-spacing plane grating with grazing-incidence. A supersonic molecular beam technique is applied to obtain translational-energy control of incident molecules. Owing to keeping low pressure in the surface reaction chamber during molecular beam operation, the analysis of translational-energy-induced surface reactions is achieved by simultaneous application of the photoelectron spectroscopy. The end-station will promote research activities on new atomic layer reactions induced by the kinetic energy of incident molecules as well as new photofragmentation of monolayer due to the inner-shell selective photoexcitation.
51 citations
TL;DR: The results indicate that if the S(1) state of the amino compound is sufficiently stabilized, other rapid decay channels like internal conversion to the ground state will minimize the transfer of population to the triplet manifold.
Abstract: We present a study of the dynamics following photoexcitation in the first electronic band of NO2-para-substituted nitronaphthalenes. Our main goal was to determine the interplay between the nitro group, electron-donating substituents, and the solvent in defining the relative excited-state energies and their photoinduced pathways. We studied 4-nitro-1-naphthylamine and 1-methoxy-4-nitronaphthalene in solution samples through femtosecond fluorescence up-conversion and transient absorption techniques. In all solvents, both compounds have ultrafast fluorescence decays, showing that, similarly to the parent compound 1-nitronaphthalene, these molecules have highly efficient S1 decay channels. The evolution of the transient absorption signals in the visible region reveals that for the methoxy-substituted compound, independently of solvent polarity, the photophysical pathways are the same as in 1-nitronaphthalene, namely, ultrafast intersystem crossing to an upper triplet state (receiver Tn state) followed by rel...
51 citations
TL;DR: In this article, the onset of chaos in the electrical avalanche breakdown caused by weak photoexcitation at 4.2 K in n-GaAs has been described as the first example of a new type of phase transition in semiconductors.
Abstract: Periodic oscillations and turbulence in the electrical avalanche breakdown caused by the weak photoexcitation at 4.2 K in n-GaAs have been presented as a first example of the onset of chaos which originates in a new type of phase transition in semiconductors.
50 citations
TL;DR: The photophysical and photochromic properties of 2,2-diphenyl-2H-naphtho[1, 2-b]pyran and substituted derivatives were investigated by steady state and time-resolved optical absorption and emission spectroscopy in solution at room temperature and in a frozen matrix at 77 K as discussed by the authors.
Abstract: The photophysical and photochromic properties of 2,2-diphenyl-2H-naphtho[1,2-b]pyran and substituted derivatives were investigated by steady state and time-resolved optical absorption and emission spectroscopy in solution at room temperature and in a frozen matrix at 77 K. Fluorescence quantum yields, fluorescence lifetimes, and singlet energies depend strongly on the substitution patterns. Photoexcitation of the naphthopyrans (A) leads to efficient ring opening to produce the merocyanines (B) and (C). The optical absorption of the merocyanines can be tuned by the substituents and can cover most of the visible spectrum (400−700 nm). The decoloration kinetics of the open forms (merocyanines) B and C to produce naphthopyrans (A) depends strongly on the substituents. The ring closure rate constants (kB→A) range from 0.0009 to 0.04 s-1.
50 citations