Infrared spectra of N_2O-hydrogen complexes

摘要

The infrared spectra of five distinct species of N_2O-hydrogen van der Waals complex (N_2O-paraH_2, -orthoH_2, -orthoD_2, -paraD_2, and -HD) were studied in the region of the v_1 fundamental band of N_2O (approx=2224 cm~(-1)) by tunable diode laser spectroscopy in a pulsed supersonic jet expansion. The spectra corresponded to those of T-shaped asymmetric rotors with mainly a-type transitions (#DELTA#K_a = 0), plus weaker b-type transitions (#DELTA#K_a = +-1) in the case of N_2O-D_2. They were analyzed using a conventional Hamiltonian with quadratic centrifugal distortion parameters. The fitted rotational parameters were consistent with structures having intermolecular separations between 3.25-3.4 A and angles of about 80 deg between the N_2O axis and the hydrogen center-of-mass. These intermolecular distances are abut 0.3 A shorter than those observed previously for the related system. OCS-hydrogen. The band origins were blue shifted relative to the free N_2O molecule by from +0.25 to +0.79 cm~(-1). These vibrational shifts showed regularities among the different spin and isotopic forms of hydrogen that were analogous to those in OCS-hydrogen.