Structure, harmonic force field and hyperfine coupling constants of nitrosyl chloride

Abstract

The pure rotational spectra of five isotopic species of nitrosyl chloride were measured using a cavity pulsed microwave Fourier-transform spectrometer. Some a-type transitions of all five isotopomers, and some weak b-type transitions of four of these isotopomers were measured in the 4–26 GHz frequency range. Precise values for the rotational constants and the quartic centrifugal distortion constants were obtained. The rotational constants were used in structure determinations and the centrifugal distortion constants were used in a refinement of the harmonic general valence force field. A harmonic central valence force field was also calculated.

Hyperfine structure in these transitions arising from quadrupole and spin–rotation coupling interactions was also observed. Diagonal and off-diagonal quadrupole coupling constants and diagonal spin–rotation coupling constants of both the chlorine and nitrogen nuclei were determined. The principal quadrupole coupling constants were evaluated and used to calculate the approximate ionic character of the N—Cl bond. The spin–rotational coupling constants were used to calculate the diamagnetic shielding factor for the nitrogen nucleus; the magnitude of this value indicates a fairly ionic N—Cl bond.