THE TRANS-BENDING AND F-F STRETCHING VIBRATIONS OF HF DIMER IN NU-HF=1 - THE INFLUENCE OF INTERMOLECULAR VIBRATIONAL-EXCITATION ON THE PREDISSOCIATION DYNAMICS

The optothermal detection method has been used to obtain near infrared spectra for combination bands of HF dimer associated with the F-F stretching (v4) and trans-bending (v5) vibrations, built upon the HF fundamental stretches (v1 and v2). These spectroscopic results are used to estimate the intermolecular trans-bend and F-F stretch frequencies, as well as the associated tunneling frequencies, all corresponding to the excited HF stretch vibrational states. Photofragment angular distributions have also been obtained for these excited states. These provide new insights into the effects of intermolecular vibrational excitation on the vibrational predissociation dynamics of this dimer. The initial state dependence of the final rotational state distributions suggests that the intermolecular stretch and bend are decoupled, with the energy in the F-F stretch evolving directly into relative translation of the photofragments, while excitation of the bend has no effect on the average kinetic energy release.