Zero kinetic energy photoelectron study of SO2+(X2A1) using coherent extreme ultraviolet radiation

Using our newly built extreme ultraviolet (XUV) photoelectron and photoion spectrometer, we have obtained the pulsed field ionization zero kinetic energy (ZEKE) photoelectron spectra of SO2+(X (2)A(1))<--SO2(X (1)A(1)) by coherent XUV radiation in the energy range of 12.29-12.82 eV. The adiabatic ionization potential (IP) of SO2 is 12.3458+/-0.0002 (eV), which was determined by comparing the partially resolved rotational branch contour with the simulated one. Besides the bending vibrational mode (upsilon(2)) which was found to be exclusive in the photoelectron spectra (PE) reported previously, we also observed the other two modes: the symmetric stretching (upsilon(1)) and the antisymmetric stretching (upsilon(3)) vibrations. The fundamental of the symmetric stretching (upsilon(1)) is 1057 cm-1 and the overtone of the antisymmetric stretching (2upsilon(3)) is 2494 cm-1. The new vibrational progressions (upsilon(1)00)(+), (1upsilon(2)0)(+), (2upsilon(2)0)(+), and (0upsilon(2)2)(+) have also been observed, and these new observations suggested that the irregular structure of (0upsilon(2)0)(+) assigned to the previous PE spectra should be reconsidered. The comparison of the intensities of these vibrational bands with the calculated Franck-Condon factors with harmonic approximation was also made. (C) 2004 American Institute of Physics.