Alignment of Cd atoms by photoionization

Abstract

The ${}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}}^{}{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}D_{\frac{5}{2}}^{}{}_{}{}^{}$ excited states of the cadmium ion are produced through photoionization of cadmium atoms by a beam of Hei 584-Å radiation. The presence of alignment in the ions is detected by measuring the degree of linear polarization $P$ of the resulting emission. It is found that $P({}_{}{}^2{}_{}{}^{}D_{\frac{5}{2}}^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{})=-0.052\mathrm{}\pm 0.005$ for the 4416-Å transition, and $P({}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}}^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{})=+0.12\mathrm{}\pm 0.04$ for the 3536-Å transition, demonstrating that both ${}_{}{}^2{}_{}{}^{}D$ fine-structure components are aligned. A simple calculation is presented which ignores anisotropic final-state interactions. This calculation correctly predicts the sign of the degree of polarization, but fails to reproduce the experimental results.