The radiative lifetime of metastable CO ($a^3\Pi, v=0$)

TL;DR

This study combines experimental measurements and theoretical calculations to determine the radiative lifetime of metastable CO molecules, revealing the influence of spin-orbit coupling and other states on their decay rates.

Contribution

It provides the first combined experimental and theoretical analysis of the radiative lifetime of metastable CO in the $a^3\Pi$ state, including the effects of spin-orbit coupling.

Findings

Measured radiative lifetime of 2.63 ms for $a^3\Pi_1, v=0, J=1$

Calculated a 20% longer lifetime of 3.16 ms considering spin-orbit coupling

Identified coupling to other $^1\Pi$ states affects phosphorescence rate

Abstract

We present a combined experimental and theoretical study on the radiative lifetime of CO in the $a^3\Pi_{1,2}, v=0$ state. CO molecules in a beam are prepared in selected rotational levels of this metastable state, Stark-decelerated and electrostatically trapped. From the phosphorescence decay in the trap, the radiative lifetime is measured to be $2.63\pm0.03$ ms for the $a^3\Pi_1, v=0, J=1$ level. From spin-orbit coupling between the $a^3\Pi$ and the $A^1\Pi$ state a 20% longer radiative lifetime of 3.16 ms is calculated for this level. It is concluded that coupling to other $^1\Pi$ states contributes to the observed phosphorescence rate of metastable CO.