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Near-Resonant Two-Photon Excitation of CN.
Final rept. Jan 91-Dec 96,
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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Development of sensitive detection methods for CN is important because of applications to propellant flames. This radical plays a critical role in propellant combustion chemistry. We have observed a strong two photon absorption in the 3,0 band of CN by means of a resonant enhancement. Many lines are seen in the two photon spectrum due to multiple single photon near resonances in the 4,0 band. The detuning of the laser from these resonances varies from less than one to hundreds of wavenumbers, producing unusually large peak intensity variations in the two photon spectrum. This effect is not observed in two photon transitions far from resonance. Resonant enhancement is observed over a range from N 5 to 20. We know of no other molecular two photon transition in which a near resonance produces such dramatically varying intensities over a short range of rotational levels. A calculation of the line strengths for these transitions reproduces the major features of the spectrum.
APPROVED FOR PUBLIC RELEASE