Pure Rotational Spectrum of Nitric Oxide

Abstract

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 $$\begin{array}{ccc}{B}_0& {\mathrm{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}D}}_0& H_0\\ {}^2{\Pi }_{\frac{1}{2}}\text{\hspace{0.17em}\hspace{0.17em}1.671854±0.000081\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}& {\text{(3.4±3.0)×10}}^{\text{−7}}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}& {\text{(−1.42±0.29)×10}}^{\text{−9}}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}\\ {}^2{\Pi }_{\frac{3}{2}}\text{\hspace{0.17em}\hspace{0.17em}1.720178±0.000062\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}& {\text{(10.24±0.23)×10}}^{\text{−6}}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}& {\text{(+1.00±0.23)×10}}^{\text{−9}}\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}.\end{array}$$ 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.