			15min:

SPECTRAL ANALYSIS OF THE BENDING LEVELS OF ACETYLENE CATION.

YUNG-CHING CHOU AND YEN-CHU HSU, INSTITUTE OF ATOMIC AND MOLECULAR SCIENCES, ACADEMIA SINICA, P.O. BOX 23-166, TAIPEI 107, TAIWAN, R. O. C..

Twenty-seven vibronic levels (v₄=0-6, v₅=0-2, K=0-3) of the ground electronic state of acetylene cation have been previously studied by 1+1' two-color pulsed-electric field induced zero-kinetic energy (PFI-ZEKE) photoelectron spectroscopy. These levels, rotationally resolved, are about 0-3520 cm^-1 above the zero-point energy level. Previously, only the Renner-Teller effects of the trans- and cis-bending vibration and the vibrational anharmonicity were included in the effective Hamiltonian; one standard deviation of the fit was 4.1 cm^-1, about six times of the measurement uncertainties. Large discrepancies between the observed and calculated frequencies were identified at combination levels. In this fit, effects such as vibrational \ell -type doubling and second-order anharmonic interaction were also considered due to the near degeneracy of the trans- and cis-bending vibration. The results of the fit are satisfactory; most of the vibronic bands can be fitted within one standard deviation of 1.0 cm^-1, except the lower component of (v₄=0, v₅=1, K=0). The results of the fit will be presented and few observed vibronic levels, yet unassigned, will be discussed.