Rydberg states of propyne at 6.8-10.5 eV studied by two-photon resonant ionization spectroscopy and theoretical calculation
Journal
Journal of Chemical Physics
Journal Volume
112
Pages
7384-7393
Date Issued
2000
Author(s)
Abstract
The vibronic spectra of jet-cooled propyne at 6.8-10.5 eV have been observed using 2 + 1 resonance-enhanced multiphoton ionization (REMPI) spectroscopy. The ns (n=4-13), np (n =3-4), and 3dz2 Rydberg states of propyne have been identified, of which seven are newly discovered. The symmetries of the excited vibronic states have been determined directly from polarization-ratio experiments applying linearly and circularly polarized lasers. Under a C3V group, the observed s Rydberg series are of E symmetry and the p Rydberg states belong to A1 or E. Clear doublet splittings in the ns Rydberg states (n=4-9) are observed for the first time. The splittings, 306 cm-1 at 4 s, decrease with increasing n. The doublets of A′ and A″ symmetries, identified from the polarization-ratio measurement, are that due to CS molecular geometry, rather than C3V, for the us Rydberg states. The term values for the ns Rydberg series (n=6-13) converge to an adiabatic ionization energy of 83625±2 cm-1 with a quantum defect of δ=0.95. Comparing with one-photon absorption spectrum of propyne, the absence of π→π*, np (n≥4) and nd (n≥3, except 3dz2) Rydberg states in the REMPI spectra suggests a strong predissociation character for these states. Calculations for the vertical excitation energies of π→π*, ns, np, and nd (n=3,4) Rydberg states of propyne were performed using time-dependent density functional theory and ab initio methods to compare with experimental results and to test the computational accuracy. © 2000 American Institute of Physics.
SDGs
Type
journal article