METHYL ROTOR EFFECTS ON ACETONE RYDBERG $SPECTRA^{\dagger}$

$^{\dagger}$ Supported by the petroleum Research Fund of the American Chemical Society, National Science Foundation and Rutgers University Research Council.Author Institution: Chemistry Department, Rutgers UniversityHigh flux injection seeded excitation allows vibronic bands in $^{1}A_{2} \leftarrow ^{1}A_{1}$ and $^{1}A_{1} \leftarrow ^{1}A_{1}(p \leftarrow n)$ Rydberg transitions of acetone-$h_{6}$ and -$d_{6}$ through three quanta of the methyl torsional modes to be recorded in two-photon resonant MPI jet spectra at rotational co lour resolution. The torsional energy splitting is found to substantially increase over that in the ground state for the $^{1}A_{2} (3p_{x}$) [x=out of plane axis, 2 = parallel to C=O band | Rydberg state. The fundamental and overtone frequencies allow the torsional potential for the $^{1}A_{2}$ state to be obtained and that for ground state to be refined. The greatly different vibrational sequence structure near the $^{1}A_{1} (3p_{y}) \leftarrow ^{1}A_{1}$ origin from that of $^{1}A_{2} \leftarrow (3p_{x}) \leftarrow ^{1}A_{1}$ transition suggests that the $^{1}A_{1} (3p_{y})$ Rydberg state methyl torsion protential significantly differs from both the ground state and $^{1}A_{2}(3p_{x}$) potentials