EXPERIMENTAL AND THEORETICAL STUDIES OF THE RADIATIVE LIFETIME AND PREDISSOCIATION RATES OF THE $A^{2} \triangle$ STATE OF $PH^{+}$

Abstract

The High Frequency Deflection technique has been applied to obtain the radiative lifetime of the $A^{2} \triangle$ state of $PH^{+}$. The predissociation is known to occur for $N^{\prime}> 12$ for $v^{\prime} = 0$ and weakly for all $N^{\prime}$ values of $v^{\prime} = 1$, and the measured lifetime of the stable rotational levels of $v^{\prime} =0 (1.5\pm 0.2 \mu s)$. In order to deduce the predissociation rates for $v^{\prime}=1$ we have also carried out ab-initio CASSCF calculations of the electronic transition moment for the $A^{2} \triangle-X^{2}\Pi$ transition. The calculated radiative lifetime of $v^{\prime} =0$ was in good agreement with experiment $(1.4 \mu s)$. For further potential curves were improved by multireference CI calculations and corresponding calculations were carried out for the $^{2}\sigma^{-}$ and $^{4}\Pi$ states. Weyl's theory for second order differential equations were used to analyse the predissociation mechanism. The exact mechanism is at this moment not quite clear, although it appears that one state alone can not cause the observed predissociation pattern.