Level-Crossing spectroscopy in molecules: Application to the OH free radical

We have observed the Hanle effect in the 2(v=0) excited state of the free radical OH in lines which originate from sublevels with rotational quantum numbers K=3,4,5. From the widths of each of these experimental signals we can calculate the g-factor-lifetime product and, since the lifetime of the state has been measured previously, our observations yield the values g[K=3]=0.176(23), g[K=4]=0.141(15), and g[K=5]=0.118(11).