Vibrational assignments in the 3p Rydberg states of acetone

The 2 and 3 photon resonantly enhanced multiphoton ionization spectra of the 3p Rydberg ←X̃ transitions of acetone and acetone-d6 were remeasured and reanalyzed. Seven of the eight a1 and one b1 vibrational modes were assigned. On the basis of these assigned fundamental frequencies the anomalous isotope shift of the origin of the A1 transition was rationalized, the contribution of the nonbonding electrons to the scissors force constant was demonstrated, and a location for the A1 ππ* valence excited transition was proposed.