PHOTOELECTRON-SPECTROSCOPY FROM THE A1AU STATE OF ACETYLENE - THE BENDING VIBRATIONS OF C2H2+X2-PI-U

Photoelectron spectra are reported for one-photon resonant, two-photon ionization of acetylene via a number of vibronic levels of the A approximately 1A(u) state. Because the A approximately 1A(u) state is trans bent and the X 2-PI-u ground state of the ion is linear, ionization from the A approximately 1A(u) levels produces a long progression in the trans-bending vibration of the ion. The X 2-PI-u state is split by the Renner-Teller interaction along the trans-bending coordinate; the analysis of the photoelectron spectra allows the determination of the Renner-Teller parameters and leads to reassignments of the cis and trans-bending vibrations in earlier photoelectron studies.