Knowledge Bank

A nozzle beam of rubidium is irradiated by the $4765$ {\AA} line of the argon ion laser, and the resulting fluorescence is spectroscopically analyzed. Under these collision-free conditions, the emission consists of molecular fluorescence from the $Rb2C1\Pi u-X1\Sigma g+$ electronic system as well as atomic fluorescence from the Rb $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}P3/2$ fine structure component (the Rb $D2$ line) only. The latter transition is caused by partial predissociation $(\le 25$ of the $Rb2C1\Pi u$ $state.1$ The molecular fluorescence is polarized and has a value $P=0.345\pm 0.009$. This is interpreted to be caused by the superposition of P and $R2$ as well as Q lines, in agreement with studies made by Happer and $Tam.2$ The Rb $52P3/2$ level correlates with the $Rb2A1\Sigma u+$ state or the $B1\Pi u$ state, one or both of which are believed to be responsible for predissociating the $Rb2C1\Pi u$ state.