CONTAMINATED TORSIONAL TUNNELING SPLITTINGS IN 5 NORMAL-MODE VIBRATIONS OF PROPENE

Sub-Doppler infrared spectra of five normal-mode vibrations of propene between 900-1100 cm-1 reveal strongly perturbed torsional tunneling s plittings due to nonresonant anharmonic couplings to vibrational state s in which the torsional mode is excited. The present results suggest that perturbed tunneling splittings will be a general feature for vibr ationally excited states. Consequently, care should be taken when usin g tunneling splittings to obtain the vibrational dependence of a tunne ling barrier. Instead, tunneling splittings in excited states can be u sed as a probe of long-range vibrational-torsional state mixing in mol ecules.