Multiphoton induced fluorescence and ionization of carbon monoxide (B 1Σ+)

Abstract

The B 1Σ+ state of carbon monoxide was created by a two-photon absorption of 230 nm laser radiation. The B 1Σ+ state was identified by the positions of the Q branch 0–0 absorption band and the vibrational bands of B 1Σ+ → A 1Π fluorescence occurring after excitation. Collision-induced b 3Σ+ → a 3Π emission in the 350 nm region was also observed. The lifetimes of the B 1Σ+ → A 1Π and the b 3Σ+ → a 3Π emission were obtained as well as the self-quenching rate constants and the CO (B 1Σ)) quenching rate by N2. In addition to the two-photon laser induced fluorescence of B 1Σ+ carbon monoxide, a three-photon resonant (2+1) ionization was observed. Laser power dependence studies indicate that ionization of the B 1Σ+ state was nearly saturated at the laser fluence used, implying that most CO (B 1Σ+) was ionized rather than fluorescing. The measured polarization ratios for circularly to linearly polarized excitation of fluorescence and ionization was much larger than the expected values suggesting that other three-photon processes are occurring and occur more efficiently for linear polarization.