MOLECULAR-BEAM INFRARED-SPECTROSCOPY OF THE HCCCN-HCCH AND HCN-HCCCCHVAN-DER-WAALS COMPLEXES

High resolution IR spectra of the linear HCCCN-HCCH and HCN-HCCCCH hyd rogen bonded complexes have been obtained using optothermal detection molecular beam techniques. Two vibrational bands have been observed fo r each complex, which correspond to the terminal ''free'' C-H stretch vibrations (nu(2)) Of the cyano units and the hydrogen bonded vibratio ns (nu(3)) Of the acetylenic CH stretches. For both complexes, accurat e molecular constants have been Obtained. Furthermore, predissociation lifetimes for the nu(3)=1 states of the both complexes have been dete rmined. The results are compared with those of the linear HCN-HCCH com plex obtained by Block et al. [Chem; Phys. 139, 15 (1989)]. 1996 Ameri can Institute of Physics.