15min:

SHEUNN-JIUN TANG, JIM JER-MIN LIN AND YEN-CHU HSU, Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 107, Taiwan, Republic of China, and Department of Chemistry, National Taiwan University, Taipei, Taiwan, R.O.C..

The 1+1' two-color pulsed-field induced zero-kinetic-energy (PFI-ZEKE) photoelectron spectra of C₂H₂ via a single rovibronic level of the A¹A_u state of acetylene were previously reported by Pratt et al . In this work, with similar approach the effects of the pulsed-field strengths and the rovibronic symmetries of the intermediate states of C₂H ₂ and C₂D₂ on the PFI-ZEKE photoelectron spectra near the ionization threshold were investigated and will be reported. Although the number of observed transitions was limited, the spectroscopic constants of the zero-point energy levels of C₂H₂⁺ obtained from the best fit are in good agreement with those reported by Jagod et al : B=1.098\pm 0.002 cm ^-1, A_so(spin-orbit constant)=-30.84\pm 0.05 cm^-1, and IP₀ =91967.06\pm 0.03 cm^-1. Those of C₂D₂⁺ are B=0.82\pm 0.03 cm^-1, A_so=-31.1\pm 0.3 cm^-1, and IP₀=92004.7\pm 0.3 cm ^-1. IP₀ is defined as the energy difference between the zero-point levels of the ground states of the neutral and its cation. We propose to use IP₀ to denote the ionization potential of the molecule, of which the cation belongs to the Hund's case (b) coupling.