Microwave Spectrum and Molecular Constants of Nitrosyl Bromide

The microwave spectrum of NOBr has been studied in the region 20 000 to 40 000 Mc/sec and an analysis made of the J = 2→3 transition. The following molecular constants were obtained. $$\begin{array}{ccc}& {\mathrm{NOBr}}^{79}& {\mathrm{NOBr}}^{81}\\ \mathrm{Rotational\; constants\; (Mc/sec)}& & \\ \mathrm{A}& \text{83\hspace{0.17em}340}& \text{83\hspace{0.17em}340}\\ \mathrm{B}& \text{3747.24}& \text{3722.49}\\ \mathrm{C}& \text{3586.00}& \text{3563.34}\\ \mathrm{Asymmetry\; parameter}& & \\ \mathrm{b}& \text{−0.001012}& \text{−0.000998}\\ \mathrm{Quadrupole\; coupling\; components\; (Mc/sec)}& & \\ {\chi }_{\mathrm{aa}}& \text{\hspace{0.17em}\hspace{0.17em}388.3}& \text{\hspace{0.17em}\hspace{0.17em}325.5}\\ {\chi }_{\mathrm{bb}}& \text{−239.5}& \text{−200.2}\\ {\chi }_{\mathrm{cc}}& \text{−148.8}& \text{−125.3}\end{array}$$ The structural parameters obtained from these are d(N–O) = 1.15 A, d(N–Br) = 2.14 A, d(O–Br) = 2.81 A, and ∠Br–N–O = 114°. The interatomic distances are compared with electron diffraction results, and a brief interpretation of the quadrupole coupling in terms of chemical bonds is given.