Journal of Chemical Physics, Vol.100, No.12, 8713-8719, 1994
Strong Resonance Enhancement of the CN-2-Photon Absorption B-2-Sigma(+)(-X(2)Sigma(+)(3,0) by the A(2)Pi(I), V’=4 Level
We have observed a strong two-photon absorption in the B (2) Sigma(+)<--X (2) Sigma(+)(3,0) band of CN by means of a resonant enhancement through the A (2) Pi(i), v’=4 level. Many lines are seen in the two-photon spectrum due to multiple single-photon near resonances in the A (2) Pi(i)<--X (2) Sigma(+)(4,0) band. The detuning of the laser from these resonances varies from less than one to hundreds of wave numbers, producing unusually large 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.
Keywords:DIATOMIC-MOLECULES;MULTIPHOTON TRANSITIONS;2-PHOTON TRANSITIONS;SPECTROSCOPY;SYSTEM;STATE;PERTURBATIONS;POPULATION;EXCITATION;ALIGNMENT