Alignment of the2Pstate of 2-MeV/amu heliumlike sulfur

The $2{}_{}{}^1{}_{}{}^{}P$ and $2{}_{}{}^3{}_{}{}^{}P$ levels of two-electron S xv have been aligned by collision at 2 MeV/amu with carbon atoms in a foil. The degree of alignment is obtained by analysis of the normalized angular distribution of $K$ x-ray radiation measured in high resolution with a pivoted plane-crystal Bragg spectrometer. The mean cross-section ratio $\frac{{\sigma }_0}{{\sigma }_1}$ for population of the $m=0\mathrm{}$ sublevel relative to the $m=\pm 1$ sublevels of the $2P$ parent state is obtained by analysis of the $1{}_{}{}^1{}_{}{}^{}S-2\mathrm{}{}_{}{}^1{}_{}{}^{}P$ and $1{}_{}{}^1{}_{}{}^{}S-2\mathrm{}{}_{}{}^3{}_{}{}^{}P$ transition intensities. The result $\frac{{\sigma }_0}{{\sigma }_1}=1.79\mathrm{}\pm 0.1$ leads to the polarization fractions $P\left({}_{}{}^1{}_{}{}^{}P\right)=0.28\mathrm{}\pm 0.05$, and $P\left({}_{}{}^3{}_{}{}^{}P\right)=-0.16\mathrm{}\pm 0.03$, in good agreement with results obtained by an independent analysis, and in excellent agreement with coupled-states calculations of Reading et al. Comparison with other theories is also made.