Abstract

The γ-system (A²Σ⁺ X²Π) of nitric oxide (NO) is observed in many environments including combustion and atmospheric applications. Molecular properties of the A²Σ⁺ state are thus important in collision theories used to predict A-X radiative efficiencies. These theories often involve electric-multipole expansions,^1,2 in which the permanent electric dipole moment of A²Σ⁺ (µ_A) is the leading term for long-range interactions. Moreover, µ_A is a basic property of the molecular charge distribution and has often been used to gauge the accuracy of ab initio quantum chemistry calculations.^3-6 Here we describe measurements of Stark quantum beats in the fluorescence of NO from which we derive a precise value for µ_A in v'=0. This is the vibrational level most often excited in laser-based methods for detecting NO. Bergeman and Zare,⁷ using a radio frequency-optical double-resonance technique, provide the only other measurement of µ_A in a different vibrational level (v'=3). We thus also determine the change in µ_A with v', which provides a sensitive test of computed dipole moment functions.

© 1993 Optical Society of America