The shifts of the $1s3p{}^1{P}_1\to 1s^2{}^1{S}_0$ He-$\beta$ transition of ${\mathrm{Cl}}^{15+}$ were measured in hot ($\ge 600$ eV), dense (1–2 g/${\mathrm{cm}}^3$) plasmas generated by a (66–151)-J short-pulse laser beam at the Orion laser facility. The subpicosecond laser beam irradiated optically thin, KCl microdot targets buried in layers of plastic. The measured red shifts ranged from $4.8\pm 1.1$ eV for unshocked to $5.9\pm 1.2$ eV for shocked targets. These values are significantly smaller than recent predictions from a self-consistent-field ion-sphere model.

• Received 6 August 2018
• Revised 7 May 2019

DOI:https://doi.org/10.1103/PhysRevA.100.012511