Collision induced transitions between the A 2Πi(v=0) and X 2Σ+(v=10) states of CO+

Abstract

We report on a laser double resonance study of collisional electronic transfer between the A 2∏i(v=0) and X 2Σ+(v=10) states of CO+. In particular, we have selectively populated individual rotational levels of the A 2∏i(v=0) manifold of CO+ with a pump laser and probed the adjacent X 2Σ+(v=10) manifold with a second pulsed laser. The only other molecules studied by this technique, N+2 and CN, are isoelectronic to CO+ and have efficient collisional transfer between their analogous A and X states even though perturbations are nonexistent or negligible. The pair of vibronic levels selected for CO+ has a zero energy gap and a much smaller Franck–Condon factor (FCF) than those studied for the A and X states of N+2 and CN. Previous works have indicated that the FCF is not important in these electronic transfer processes. We find, however, that unlike N+2 and CN, rapid collisional transfer between unperturbed rotational levels of the A 2∏i(v=0) and X 2∑+(v=10) electronic states of CO+ is not observed. Efficient electronic transfer occurred only through the perturbed levels of these two manifolds. In addition, we find that of the two spin components that make up the A 2∏i(v=0) rotational manifold, the propensity for collisional e↔f rotational transfer is more favorable for the 2∏3/2 member in agreement with theoretical considerations.