HIGH-LYING RYDBERG STATES AND IONIZATION POTENTIAL OF VINYL CHLORIDE STUDIED BY TWO-PHOTON RESONANT IONIZATION SPECTROSCOPY

$^{a}$B. A. Williams and T. A. Cool. J. Phys. Chem., 97, 1270 (1993). $^{b}$A. M. Mebel, Y. -T. Chen and S. H. Lin. J. Chem. Phys., 105, 9007 (1996).Author Institution: Department of Chemistry, National Taiwan University, Institute of Atomic and Molecular SciencesHigh-lying Rydberg states of jet-cooled vinyl chloride $(C_{2}H_{3}Cl)$ at 7.5-10 eV have been observed using 2+1 resonance- enhanced multiphoton ionization (REMPI) spectroscopy. The vibronic transitions in the ranges of $62500-65000 cm^{-1} 67000-70000 cm^{-1}$ and $70000-72500 cm^{-1}$ are attributed to $\pi \rightarrow 3p, \pi \rightarrow 3d/n_{Cl} \rightarrow 3s$ and $\pi \rightarrow 4p$ excitations according to the previous assignment by $Williams and Cool.^{a}$ Comprehensive analysis for the vibronic transitions is facilitated with the calculation of Franck-Condon factors based on our recently developed theoretical $method.^{b}$ Four Rydberg series at 9.5-10 eV are newly observed and tentatively assigned as due to the promotion of a $\pi$-electron to the ns (n = 8-13, 20), np (n = 7-11, 18). $np^{\prime} (n = 6, 7, 10-18, 21)$ and nf (n = 6-16) Rydberg orbitals. All the four Rydberg series converge to the same limit, i.e. the ground state of vinyl chloride cation. The term values of the nf Rydberg series, fitted to Rydberg formula, provide a very accurate adiabatic ionization energy, $80718 \pm 2 cm^{-1}$, for vinyl chloride with a quantum defect of $\delta = 0.02$