The (n, 3s) Rydberg State in Deuterated Aldehydes: Jet-Cooled MPI Spectra of the Propanal Isotopomeric Series

We report here the results of our investigation into the vibrational structure in the (n, 3s) Rydberg state of various isotopomers of propanal via 2 + 1 multiphoton ionization (MPI) spectroscopy in both a static cell and a supersonic expansion. A vibronic analysis of the 3s ← n transition has resulted in an assignment for a number of excited state vibrational frequencies. Most structure is due to the cis conformer with three features identified as belonging to the higher energy skew, conformer. The d1-methyl- and d2-methyl-deuterated propanal isotopomers exhibit ≍ 18 cm−1 splitting of all peaks due to the occurrence of symmetric and asymmetric methyl rotamers.