Laser-induced fluorescence measurements of a3Π metastable carbon monoxide in a high enthalpy flow

Excitation of carbon monoxide molecules has been carried out in a cold cell and in a low-pressure plasma jet using an ArF narrow-band excimer laser. The different excitation models are discussed and the relevance of atomic carbon absorption into the laser cavities is pointed out. Excitation spectra of Cameron bands have been obtained in a room-temperature cell and compared with calculated spectra. A value of the constant sigma related to the interaction strength between a 3 Pi(nu = 2) state and its neighbouring singlet states is derived: 0 less than or equal to sigma less than or equal to 0.05. The fluorescence spectrum following broad band excitation of CO has been observed both in UV and visible. Similar experiments carried out in a high enthalpy flow have allowed to point out the presence of a 3 Pi metastable carbon monoxide. A method for relative measurements of this species concentration is proposed.