Vibrational Fluorescence of Carbon Monoxide

Abstract

Carbon monoxide gas (1 atm pressure) has been vibrationally excited by absorption of infrared light emitted by rich CH4–O2 flames. The CO issued from a 286°K porous plate with a laminar flow velocity of 10 cm/sec. It was contained in an annular flow of argon of matched velocity. Resonance fluorescence was observed in the fundamental vibration—rotation band of CO at 2143 cm—1 when impurities were reduced below the ppm level. Intensity measurements showed that a vibrational temperature of 993°K had been reached by light absorption. Under the same conditions the rotational temperature remained at 286°K as shown by the intensity distribution of the rotational lines. Trapping of the resonance radiation permitted observation of the vibrational excitation for 0.2 sec after removal of the exciting light. The rate of the quenching reaction CO (v=1)+M→CO (v=0)+M has been determined from Stern—Volmer quenching curves for the collision partners H2, HD, D2, He, Ne, and O2. An extreme dependence of collisional vibrational relaxation time upon collision mass has been observed, as predicted by theory. Oxygen is anomalously efficient as a collision partner by several orders of magnitude.