Quasistable extreme motion vibrational states of HFCO above its dissociation threshold

摘要

The anharmonic mixing of highly excited vibrational states of HFCO above its dissociation threshold is studied by stimulated emission pumping spectroscopy. At 0.05hyphen;cmminus;1resolution, individual molecular eigenstates were resolved and state mixings observed by the distribution of oscillator strength to nearby dark states of the background. Most of the zerohyphen;order vibrational levels observed in the energy range between 13thinsp;000 and 23thinsp;000 cmminus;1are assigned to long Franckndash;Condonhyphen;allowed progressions of extremely high overtones of the Cndash;H outhyphen;ofhyphen;plane bending mode (ngr;6) in combination with the Csquflg;O stretching mode (ngr;2). The extent of state mixing of highly excited vibrational states is strongly mode dependent. For vibrational states with almost the same total vibrational energy, states with the most quanta in ngr;6show the least coupling with other states. More strikingly, as the total energy is increased by adding ngr;6quanta, the state mixing becomes weaker. For the vibrational states observed above 18thinsp;000 cmminus;1, those that have all of the energy in ngr;6or at most one quantum of excitation in ngr;2are extremely stable against state mixing. These appear to be the regular states or quasiperiodic trajectories predicted in some theoretical studies of twohyphen;dimensional systems. Extreme motion of the Cndash;H outhyphen;ofhyphen;plane bending mode seems to localize and prevent coupling with other modes.