Collisional quenching of CO B 1Σ+(v′=0) probed by two-photon laser-induced fluorescence using a picosecond laser

We report measurements of room-temperature, species-specific quenching cross sections of CO B 1Σ+ (v′=0) in collisions with He, Ne, H2, N2, Ar, CO, Kr, CH4, O2, Xe, CO2, C3H8, and H2O. The measured quenching cross sections (in Å2) were 0.25±0.02, 0.54±0.04, 11.0±0.4, 24.6±0.5, 27.7±0.5, 37±2, 42±2, 81±4, 85±5, 99±6, 133±5, 144±7, and 170±8, respectively. Two-photon excitation of the CO molecules via the Hopfield–Birge system (X 1Σ+→→B 1Σ+) was performed using the frequency-tripled 690 nm emission of a custom-built picosecond dye laser. Blue-to-green fluorescence in the Angström bands (B 1Σ+→A 1Π) was detected using a microchannel-plate photomultiplier tube and recorded with a digital storage oscilloscope. The quenching cross sections were directly obtained by time resolving the temporal decay of the fluorescence signal and observing its variation as a function of the quencher pressure. The effect of radiative trapping on the observed fluorescence was also quantitatively modeled.