VIBRATIONAL PREDISSOCIATION IN D2HF

Calculations are presented of linewidths for the vibrational predissociation of D2 HF induced by excitation of the HF stretching vibration in the weakly bound molecule. A potential energy surface based on ab initio computations with the correct leading multipole terms has been used. The vibrational predissociation linewidths are obtained from accurate close-coupling computations of scattering resonances for the D2 + HF collision. The calculated linewidths are in excellent agreement with those obtained from infrared absorption experiments and confirm that the mechanism for vibrational predissociation is D2 HF(upsilon = 1) --> D2 (upsilon-1 = 1) + HF(upsilon-2 = 0). It is found that the vibrational predissociation linewidths associated with the SIGMA vibration in para-D2 HF are about five times narrower than those for the PI-vibration. This implies that it should be possible to observe the D2 HF(upsilon = 0, PI --> upsilon = 1,SIGMA) transition in infrared spectroscopy measurements. The rotational distributions of the D2 + HF products of the vibrational predissociation process are predicted and should be observable.