Kr with the JANUS Setup*

The JANUS setup [1] has been used for sub-barrier projectile Coulomb excitation measurements with rare and stable isotopes [1-8] at Michigan State University since its commissioning with ⁷⁸Kr beam Coulomb-excited on a ²⁰⁸Pb target [1]. In the same experiment, JANUS was also used to explore the population of excited states in the inelastic scattering of ⁷⁸Kr beam on ⁴⁸Ti target at an energy that is 150% of the Coulomb barrier. In this regime of “unsafe” Coulomb excitation, higher-energy and higher-spin states were shown to be excited [9]. The angular coverage and particle-gamma detection scheme of JANUS allowed to track how the population patterns change for the excited states of ⁷⁸Kr when entering such a highly “unsafe” regime. The results for ⁷⁸Kr will be presented and the potential for using JANUS for spectroscopy following unsafe Coulomb excitation will be discussed.

[1] E. M. Lunderberg et al., Nucl. Inst. and Meth. in Phys. Res. A 885, 30 (2018)

[2] J. Henderson et al., Phys. Rev. Lett. 121, 8 (2018)

[3] J. Henderson et al., Phys. Rev. C. 99, 5 (2019)

[4] D. Rhodes et al., Phys. Rev. C. 103, 5 (2021)

[5] D. Rhodes et al., Phys. Rev. C. 105, 2 (2022)

[6] S. Kisyov et al., Phys. Rev. C. 106, 3 (2022)

[7] R. Russell et al., Phys. Rev. C. 108, 6 (2023)

[8] J. Heery et al., Phys. Rev. C. 109, 1 (2024)

[9] D. Ward et al., Nucl. Phys. A 600 (1996)