SLOW PHOTOELECTRON VELOCITY-MAP IMAGING SPECTROSCOPY
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Date
2007
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Ohio State University
Abstract
A new technique recently developed in our lab, slow photoelectron velocity-map imaging (SEVI) spectroscopy, is presented. A tunable laser is used to photodetach anions slightly above the threshold and the resulting low kinetic energy electrons are collected using velocity-map imaging. The technique yields greatly improved resolution (up to 1 cm$^{-1}$) over conventional photoelectron spectroscopy, and the data-acquisition time is considerably shorter than anion-ZEKE. The ability of SEVI is demonstrated with the studies of carbon monohydrides (C$_{2n}$H with n=1-3) where several new vibronic transitions on the two low-lying electronic states are resolved. SEVI has also been applied to high-resolution transition-state spectroscopy in the investigation of ClH$_2$$^-$ and ClD$_2$$^-$, probing the shallow well at the entrance of the Cl+H$_2$ (D$_2$) reactive surface. The SEVI spectra showed clearly resolved features corresponding to the hindered-rotor motion of D$_2$ and the low frequency stretching vibration of the pre-reactive van der Waals cluster. Excellent agreement is found between the experimental result and the Franck-Condon simulations calculated from ab initio reactive potential energy surfaces.
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Author Institution: Department of chemistry, University of California, Berkeley, 94720