Parity-Violation Studies with Partially Stripped Ions

A theoretical study of photoexcitation of highly charged ions from their ground states, a process which can be realized at the Gamma Factory at CERN, is presented. Special attention is paid to the question of how the excitation rates are affected by the mixing of opposite-parity ionic levels, which is induced both by an external electric field and the weak interaction between electrons and the nucleus. In order to reinvestigate this Stark-plus-weak-interaction mixing, well-known in neutral atomic systems, we employ relativistic Dirac theory. Based on the developed approach, detailed calculations are performed for the 1s1/2 ->$_{1/2} \rightarrow$ 2s(1/2) and 1s22s1/2 -> 1s23s1/2${\rm 1s}<^>2 \; {\rm 2s}_{1/2} \rightarrow {\rm 1s}<^>2 \; {\rm 3s}_{1/2}$ (M1 + parity-violating-E1) transitions in hydrogen- and lithium-like ions, respectively. In particular, we focus on the difference between the excitation rates obtained for the right- and left-circularly polarized incident light. This difference arises due to the parity violating mixing of ionic levels and is usually characterized in terms of the circular-dichroism parameter. We argue that future measurements of circular dichroism, performed with highly charged ions in the SPS or LHC rings, may provide valuable information on the electron-nucleus weak-interaction coupling.

Automated summary

In this theoretical study, the process of photoexcitation of highly charged ions from their ground states is investigated, with a focus on the effects of mixing of opposite-parity ionic levels induced by external electric fields and weak electron-nucleus interactions. Relativistic Dirac theory is employed to study the Stark-plus-weak-interaction mixing, and detailed calculations are performed for specific transitions in hydrogen-like and lithium-like ions. The importance of circular dichroism measurements with highly charged ions in understanding the electron-nucleus weak-interaction coupling is highlighted.