Absorption intensity measurements of the second overtone band of NO

The absolute intensity A3–0 of the second overtone band of NO has been measured using helium and argon as pressure broadening gases at mixture densities up to 360 amagat. The absolute intensity, obtained from the integrated absorption coefficients of NO–He and NO–Ar gaseous mixtures at high pressures, is found to be (4.08 ± 0.21) × 10−2 cm−2 amagat−1. From the line intensity measurement data of Meyer, Haeusler, and Barchewitz and the absolute intensity obtained with the NO–He gaseous mixtures, the rotationless matrix element R3–0 (0) of the 3–0 band of NO is calculated and its value is 7.75 × 10−4 D. This value of R3–0 (0) is combined with previous results on the NO 1-0 and 2-0 bands to obtain a dipole moment expression accurate to M3. The following expansion for the dipole moment function in the ground state of NO is determined: M (x) = −0.166 + 2.56x−1.94x−1.20x3 D, where x is the relative internuclear separation (r−re)/re.