Nonstatistical population of magnetic substates of the(1s−12p−1)P11state in Al

We have measured the polarization of the $K{\alpha }^{\prime }$ [$\left(1\mathrm{}{s}^{-1\mathrm{}}2p^{-1\mathrm{}}\right){}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$] to [$\left(2\mathrm{}{p}^{-2\mathrm{}}\right){}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$] x ray from an Al target following bombardment by various ion beams at several different incident energies. The polarization of the $K{\alpha }^{\prime }$ x ray is a measure of the ratio of the $2p$ substate populations ${\sigma }_1(M_L=\pm 1)$ and ${\sigma }_0(M_L=0)$ of the ${}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ state. We compare our results with recent collision-theory calculations which predict nonstatistical substate populations for simultaneous $K$- and $L$-shell ionization.