Pure Rotational Spectrum of Nitric Oxide

The pure rotational spectrum of nitric oxide was measured over the frequency range 18–94 cm−1. The values of the effective rotational constants, B0, are in close agreement with microwave values. The values of the effective rotational constants, derived by least-squares analyses, are B0 D0H0Π122 1.671854±0.000081 cm−1(3.4±3.0)×10−7 cm−1(−1.42±0.29)×10−9 cm−1Π322 1.720178±0.000062 cm−1(10.24±0.23)×10−6 cm−1(+1.00±0.23)×10−9 cm−1.These constants reproduce the observed spectrum to an average deviation of approximately ±0.0012 cm−1. The unperturbed ground-state constants are also given. The spin—orbit coupling constant A0 is discussed.