Magnetic dipole transitions in the far infra-red spectrum of nitric oxide

Rotational lines in the far infra-red spectrum of nitric oxide corresponding to direct transitions between the two spin components of the ground 2II state have been observed. Intensity calculations show that these lines arise from magnetic dipole transitions between the two spin components. Analysis of the spectrum leads to a direct determination of the value for the spin-orbit coupling parameter A 0 of 123·16±0·02 cm-1. In addition, the pure rotational spectrum of nitric oxide has been extended to higher J values.