Vibrational frequency shifts caused by weak intermolecular interactions

Vibrational frequency shifts of HF monomers and hydrogen-bonded aggregates of HF and H2O are analyzed in terms of their correlation with the square root of the critical temperature of the matrix material. This empirical correlation, justified by simple model considerations, may prove useful in establishing proper assignments of vibrational bands in the spectra of van der Waals and hydrogen-bonded species trapped in cryogenic matrices, in host clusters, and even in the gas phase.