Experimental dipole moment function and calculated radiative lifetimes for vibrational transitions in carbon monoxide a 3Π

We have used precision Stark effect data from a previously reported molecular beam electric resonance study of CO a 3Π to determine the dipole moment operator as a function of the internuclear coordinate R for this state. The resulting experimental dipole moment function is well determined in the range 1.10 Å⩽R⩽1.35 Å, corresponding to the region sampled by the v=0–3 vibrational levels used for this analysis. With this dipole moment function we then calculate the spontaneous vibrational transition probabilities for the lower vibrational levels within CO a 3Π. We obtain a lifetime for CO a 3Π v=1→v=0 transition of 17 msec, approximately half the corresponding v=1→v=0 lifetime observed for ground state CO X 1Σ+. It is shown that vibrational radiative lifetimes are quite comparable to electronic radiative lifetimes in CO a 3Π.