Vibrational and electronic excitation of nitric oxide in optical pumping experiments

• Published in: Chemical physics 1993-08, Vol.174 (2), p.219-228
• Main Authors: Saupe, Stephan, Adamovich, Igor, Grassi, Michael J., William Rich, J., Bergman, Richard C.
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Exact sciences and technology; Molecular properties and interactions with photons; Optical activity and dichroism; magnetooptical and electrooptical spectra; Physics
• ISSN: 0301-0104
• DOI: 10.1016/0301-0104(93)87006-9

Nitric oxide is vibrationally excited in a flowing gas mixture of NOAr using resonance absorption of single-line CO laser radiation. The fluorescence in the infrared and in the ultraviolet is analyzed under steady-state pumping conditions. Quantitative analysis of the NO IR overtone spectrum, Δ v=2, allows inference of the vibrational distribution function of the X 2Π ground state up to vibrational level v=15. It is shown that the mechanism of vibrational excitation is anharmonic vibration-vibration pumping. In particular, the higher vibrational levels, v⩾8, are populated by near-resonant vibration-to-vibration exchange processes. It is suggested that the electronically excited NO molecules in A 2Σ and B 2Π states, which are observed, can be produced both by resonant vibration-to-electronic energy transfer processes and in energy pooling reactions. Previous rate measurement experiments in NO are analyzed and discussed in light of the present data, and further state-resolved measurements are proposed.