Vibrational predissociation spectroscopy of (HF)3

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Abstract
The vibrational predissociation spectra of (HF)3, (HF)2DF, and HF(DF)2 in the HF stretching region, and (DF)3 in the DF stretching region have been measured using a molecular beam apparatus equipped with a mass spectrometer and a LiNbO3 optical parametric oscillator. The structure of (HF)3 has been found to be cyclic with C3h symmetry. No evidence for a noncyclic complex was found. Following vibrational excitation of the HF stretch, there was direct evidence for the trimer vibrational predissociation to the dimer plus monomer and indirect evidence for complete predissociation to three monomers. The total translational energy in the dimer plus monomer channel was 30 cm−1. The inability to resolve rotational features in the vibrational band, combined with negligible broadening of the rotational band contour bracketed the upper state lifetime between 2.5 and 21 ps. The largest ion fragment of the trimer produced by electron impact ionization was the protonated monomer.