Rotational structure and vibrational predissociation in the HF stretching bands of the HF dimer

摘要

The rotational structure in the HF stretching bands of the HF dimer has been recorded with nearly Dopplerhyphen;limited resolution using a tunable differencehyphen;frequency laser spectrometer and a longhyphen;path cell held at low temperatures and pressures. Two bands are observed; the higher frequency band, corresponding principally to the lsquo;lsquo;freersquo;rsquo; hydrogen stretch, has the appearance of aBhyphen;type or perpendicular band with two prominentQsubbranchesRQ0andPQ1; the lower band is anAhyphen;type or parallel band arising primarily from the lsquo;lsquo;bondedrsquo;rsquo; hydrogen vibration. TheK=0 subbands of both vibrations have been fully assigned and fit with polynomial expansions inJ(J+1) to yield ground state constants in excellent agreement with a previous microwave resonance molecular beam study of the HF dimer. The subbands exhibit doubling and 10:6 intensity ratios for alternateJindicative of the internal rotation tunneling motion proposed in the microwave study. A pressurehyphen;independent broadening of the lines to about twice the Doppler width, attributed to vibrational predissociation, is observed for the bonded hydrogen stretching band.