Coupling between the internal rotation of the methyl group and proton/deuteron transfer in jet-cooled 5-methyl-9-hydroxyphenalenone(OH) and 5-methyl-9-hydroxyphenalenone(OD): Tunneling rate dependence of coupling potential

The energy levels and the potentials arising from coupling between the two large amplitude motions, the internal rotation of the methyl group, and the proton/deuteron transfer have been investigated by measuring the fluorescence excitation, dispersed fluorescence, and hole-burning spectra in the S1-S0 region of jet-cooled 5-methyl-9-hydroxyphenalenone(OH)/5-methyl9-hydroxyphenalenone(OD) and 5-methyl-9-hydroxyphenalenone(OD)–water 1:1 complex. The symmetry of the potential functions for the internal rotation of the methyl group have been analyzed by a one-dimensional periodic potential V=V3/2(1−cos 3φ)+V6/2(1−cos 6φ), where Vn is the barrier height for n-fold symmetry and φ is the rotational angle. The internal rotation of the methyl group in the S0 and S1 states of the 5-methyl-9-hydroxyphenalenone(OD)–water complex has been described well by three-fold potentials. The potential for the S0 state of 5-methyl9-hydroxyphenalenone(OD) is three-fold, whereas that for the S1 state of 5-methyl9-hydroxyphenaleno...