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

Jet-Cooled Multiphoton Ionization Spectroscopy of the iso-Butanal 3s←n Rydberg Transition

“…Second, the ab initio predictions of the relative conformer energies in the excited state may be inaccurate. We have shown previously that the origin of the higher energy (skew) conformer in the 3s ← n transition of propanal actually appears to the blue of the lower energy (cis) conformer (10). This indicates that the energy separation has increased in the excited state relative to the ground state in propanal.…”

“…The multiphoton ionization time-of-flight mass spectrometer (MPI-TOFMS) has been described elsewhere (9,10). Briefly, a Lumonics excimer laser (TE861S-2) operating at 308 nm pumps a tunable dye laser (Lambda-Physik FL2002) using the dye DMQ (Exciton).…”

“…4. Unlike the spectra of the straight chain alkyl aldehydes (10,11), this spectrum is quite congested. This difference may be explained in terms of the molecular symmetry being reduced from C s to C 1 symmetry and the accompanying relaxation of the spectroscopic selection rules.…”

“…The molecules acetaldehyde (9), propanal (propionaldehyde) (10), and n-butanal (nbutyraldehyde) (11) have been studied to examine the effect of increasing the alkyl chain length. In this paper, we examine the effect that a branched alkyl chain has on the 3s ← n transition in alkyl aldehydes.…”

The lowest-lying excited singlet and triplet electronic states of propanal: an ab initio molecular orbital investigation of the potential energy surfaces

“…It has been experimentally and computationally shown that propanal exists as two conformers in its ground electronic state. [3][4][5][6][7][8][9][10][11][12] Rotation of the formyl group with respect to the ethyl group results in energetic minima at CCCO dihedral angles of 0 and $131 , corresponding to the cis (or synperiplanar in IUPAC nomenclature), and skew (or anticlinal) conformers, respectively. The relative energetics of these two minima, as well as barriers to rotation, have been well established by various spectroscopies and ab initio calculations.…”