Two-photon spectroscopy of Rydberg states of jet-cooled C2H4 and C2D4

Publisher Website
Google Scholar
Abstract
Spectroscopic studies of two-photon resonant vibronic bands of the (π,3s), (π,3p), and (π,nf ) (n=4–18) Rydberg states of jet-cooled C2H4 and C2D4 are reported. New vibronic bands are resolved by these low temperature (<10 K) observations and previous vibronic assignments of two-photon 3s and 3p transitions are confirmed. A new vibronic progression is observed in the 3s spectrum, tentatively assigned to two-photon allowed 1B2g←1Ag transitions, vibronically induced via excitation of the b1u ν6 CH2 antisymmetric scissors mode. Polarization ratio measurements and identification of the previously unreported 3pσ origin band show that the energies of the 3p levels are in good agreement with theoretical predictions. Higher-lying members of the s- and p-Rydberg series are not observed, suggestive of the onset of strong predissociation. These first observations of the two-photon allowed nf-Rydberg series yield ionization potential estimates of 84 799±5 cm−1 for C2H4 and 84 918±5 cm−1 for C2D4 that compare favorably with previous measurements.