Far-Infrared Rotational and Fine-Structure Transition Frequencies and Molecular Constants of 14NO and 15NO in the X2Π (v = 0) State

Abstract

We have made highly accurate measurements of the absorption spectrum of the 14NO and 15NO isotopomers of nitric oxide in the far-infrared. Pure rotational transitions up to J″ = 3712 within the 2Π1/2 and 2Π3/2 spin components and several 2Π3/2 ← 2Π1/2 fine-structure transitions were recorded within the ground vibrational state. A least-squares fit to these data combined with some lambda-doubling and rotational transitions measured by previous workers has resulted in accurate values for the rotational, fine, and hyperfine parameters of these two isotopomers. Most of the far-infrared transitions reported here have an experimental uncertainty of about 20 kHz and will be useful for astronomers and atmospheric scientists studying this important molecule. The more accurate calculated frequencies will also be useful as spectroscopic calibration standards.