The dipole moment and infrared transition strengths of nitric oxide

The electric dipole moment function for NO(X 2Π) is determined by nonlinear least-squares analysis of experimental data, including previously reported (Δv=2)/(Δv=1) transition branching ratios for v′⩽13. Polynomial fits to the dipole moment function are determined over the range of internuclear separation from 0.97 to 1.50 Å. The fitted dipole moment functions agree well with previous ab initio predictions, but differ somewhat at the larger internuclear separations. The observed dipole moment functions are used to compute rotationless Einstein coefficients for Δv=1–4 vibrational transitions with v′⩽20. The absolute Δv=1 and Δv=2 Einstein coefficients are well determined by this analysis, especially for v′⩽12. The results provide a firm basis for determinations of vibration-rotation emission intensities of NO(X 2Π) in high-temperature or nonequilibrium chemiexcitation systems.