The development of in situ photon-in/photon-out soft X-ray spectroscopy on beamline 7.0.1 at the ALS

This is a mini-review about the development of various cells built over the years for in situ electronic structure study of gas molecules, molecular liquids, gas/solid and liquid/solid interfaces. In the study of gas molecules, the role of the parity selection rule in the case of homonuclear diatomic molecules (N-2 and O-2) is revealed and illustrated by the resonant X-ray emission spectra, while the occurrence of forbidden transitions in CO2 is explained in terms of dynamical symmetry breaking due to vibronic coupling. X-ray emission spectroscopy has been used to elucidate the molecular structure of liquid water, liquid methanol, methanol-water mixtures, as well as cation-water solutions, and to reveal the influence of the intermolecular interaction on the local electronic structure of water molecules. The in situ soft X-ray spectroscopy experimental studies of electrochemical reactions were also performed under ambient conditions. (C) 2012 Elsevier B.V. All rights reserved.