The rotationally resolved 1.5 μm spectrum of the HCN–HF hydrogen-bonded complex

We have measured the overtone spectrum of the CH stretching mode in HCN–HF. The vibrational predissociation rate is approximately twice that previously determined for fundamental excitation, whereas the complexation induced frequency shift is only marginally larger than that of the fundamental spectrum. These results are discussed in terms of a first-order perturbation theory treatment as set forth by LeRoy, Davies, and Lam [J. Phys. Chem. 95, 2167 (1991)]. We suggest that the frequency shift observed here might not only be due to complexation, but also to a long-range anharmonic interaction.