P-TYPE DOUBLING IN THE INFRARED-SPECTRUM OF NO-HF

The HF stretching band of the NO-HF open-shell complex has been recorded using a molecular-beam optothermal spectrometer. The spectrum exhibits P-type doubling indicative of an unpaired electron spin coupled to the rotational angular momentum of a bent complex with substantially quenched electron orbital angular momentum. From B̄″ = 0.111 320( 17) cm-1, and an off-axis angle for the NO of 30°, the zero-point center-of-mass separation is estimated to be 3.4396(3) Å. The HF frequency shift of 84 cm -1 indicates that the complex is hydrogen bonded, and the spectral intensities imply that the HF axis is aligned closely to the center-of-mass axis and the NO is off axis by 30 ± 15°. The Renner-Teller-like orbital quenching parameter is somewhat larger than the spin-orbit constant in the free NO molecule and increases substantially upon vibrational excitation. The transitions in this band exhibit vibrational predissociation broadening of 200 ± 40 MHz (FWHM), similar to that observed for a number of closed-shell hydrogen-bonded HF complexes. © 1990 American Institute of Physics.