Reinvestigation of the 2 v_1 Band in Trifluoropropyne using a Frequency Stabilized 1.5 μm Color Center Laser in Conjunction with a Laser Field Build-up Cavity

摘要

The highly perturbed spectrum of the first overtone of the acetylenic CH stretch in trifluoropropyne has been reinvestigated with an improved multi-laser, optothermal detection, molecular beam spectrometer. The modifications include installing a build-up cavity to enhance the coupling between a 1.5 μm color center laser and the molecular beam, and stabilizing the laser frequency to improve the spectrometer's resolution. Upon injecting 25 mW into the cavity, a power enhancement of about 600 is measured. The laser frequency is stabilized by locking it to an external, temperature stabilized, etalon and applying the feedback to an intracavity electro-optic crystal. The frequency stability reached is estimated to be less than 4 parts in 10~(10) or 75 kHz (in a 30 Hz bandwidth centered at 300 Hz). Utilizing infrared/infrared double resonance, the K components of this highly perturbed spetrum were assigned. The results indicate that the lifetime of the acetylenic CH stretch is approximately 1.4 ns and does not change as a function of J' for 0 ≤ J' ≤ 4. In agreement with a previous lower resolution study [J. Chem. Phys. 95, 3891 (1991)], the P(1) clump shows an experimental density of states almost equal to the calculated one and the level spacing distribution is similar to that of a Gaussian Orthogonal Ensemble indicating chaotic classical dynamics.