Mid-infrared spectra of He-HN + 2 and He2-HN + 2
Abstract
Mid-infrared vibrational spectra of He-HN+2 and He2-HN+2 have been recorded by monitoring their photofragmentation in a tandem mass spectrometer. For He-HN+2 three rotationally resolved bands are seen: the fundamental ν1 transition (N-H stretch) at 3158.419±0.009 cm-1, the ν1+νb combination band (N-H stretch plus intermolecular bend) at 3254.671±0.050 cm-1, and the ν1+νs combination band (N-H stretch plus intermolecular stretch) at 3321.466±0.050 cm-1. The spectroscopic data facilitate the development of approximate one-dimensional radial intermolecular potentials relevant to the collinear bonding of He to HN+2 in its (000) and (100) vibrational states. These consist of a short range potential derived from an RKR inversion of the spectroscopic data, together with a long range polarization potential generated by considering the interaction between the He atom and a set of multipoles distributed on the HN+2 nuclei. The following estimates for binding energies are obtained: D0″=378 cm-1 [He+HN+2(000)], and D0'=431 cm-1 [He+HN+2(100)]. While the ν1 band of He2-HN+2 is not rotationally resolved, the fact that it is barely shifted from the corresponding band of He-HN+2 suggests that the trimer possesses a structure in which one of the He atoms occupies a linear proton-bound position forming a He-HN+2 core, to which a second less strongly bound He is attached.
- Publication:
-
Journal of Chemical Physics
- Pub Date:
- March 1996
- DOI:
- 10.1063/1.471244
- Bibcode:
- 1996JChPh.104.3876M