Open AccessPump and probe X‐ray absorption fine structure using high‐brilliance photon sources
Author(s) -
Oyanagi H.,
Kolobov A.,
Tanaka K.
Publication year - 1998
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049597014301
Subject(s) - x ray absorption fine structure , excitation , excited state , photodarkening , lone pair , chemistry , picosecond , amorphous solid , absorption (acoustics) , materials science , atomic physics , molecular physics , laser , optics , spectroscopy , optoelectronics , crystallography , molecule , physics , wavelength , fiber laser , organic chemistry , quantum mechanics , composite material
Pump and probe X‐ray absorption fine structure (XAFS) is used as a local probe of excited atoms, which can provide direct information on lattice distortion, relaxation and atomic rearrangements associated with electronic excitations. In situ XAFS experiments during optical excitation are reported. Utilizing a grazing‐incidence fluorescence excitation, which minimizes the mismatch between the probing depths of X‐ray excitation and optical pumping, it is found that the dominant photoinduced defect state in amorphous selenium at low temperature is a pair of threefold neutral states: , where denotes the twofold excited lone‐pair state. The results indicate that optical pumping of chalcogen atoms at low temperature leads to locally over‐coordinated defect pairs similar to those in the liquid state. The origin of reversible photostructural changes, such as photodarkening or photoinduced fluidity, is attributed to the structural disorder caused by the formation and annihilation of dynamical interchain bonds during optical melting.