Knowledge Bank

Ground state $X2\Sigma +CO+$ molecular ions have been produced in a thermal He bath by Penning ionization of CO by He metastables. Specific rovibronic levels of the $A2\Pi$ state of $CO+$ have been excited by a tunable dye laser. Observation of the time-resolved laser-induced fluorescence allows the determination of the upper level lifetime as a function of He pressure. Radiative lifetimes and cross-sections for radiationless relaxation via He-$CO+$ collisions are deduced for the v = 0-3 levels. The cross-sections are surprisingly large. Observations of laser-induced fluorescence from levels other than that initially excited indicates that relaxation between adjacent vibrational levels of the $A2\Pi$ state is not direct. It is postulated that it may involve high vibrational levels of the ground $X2\Sigma +$ state.