Knowledge Bank

High flux injection seeded excitation allows vibronic bands in $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2\leftarrow 1A1$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A1\leftarrow 1A1(p\leftarrow n)$ Rydberg transitions of acetone-$h6$ and -$d6$ 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 $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2(3px$) [x=out of plane axis, 2 = parallel to C=O band | Rydberg state. The fundamental and overtone frequencies allow the torsional potential for the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2$ state to be obtained and that for ground state to be refined. The greatly different vibrational sequence structure near the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A1(3py)\leftarrow 1A1$ origin from that of $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2\leftarrow (3px)\leftarrow 1A1$ transition suggests that the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A1(3py)$ Rydberg state methyl torsion protential significantly differs from both the ground state and $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2(3px$) potentials.