Hyperfine Resolved Spectroscopy of Thulium in Solid Argon : Selection Rules and Zeeman Effect

Atomic defects in solid noble gases are a localized quantum system with uses in sensing and tests of fundamental physics. When implanted in solid argon, the ²F_7/2 ↔ ²F_5/2 ground state transition of atomic thulium is split into multiple narrow components [1]. High resolution fluorescence spectroscopy reveals the splittings are due to the crystal field, hyperfine interactions, and presence of multiple trapping sites. The matrix environment introduces alternate transition mechanisms with strong selection rules, and we propose that these transitions are caused by dielectric effects in the host. Finally, we utilize the narrow (120 MHz) homogeneous optical linewidths to observe the isolated thulium's sensitivity to magnetic fields, measurable by all-optical laser excitation.

[1] Gaire, V., Do, M. Y., Pei, Y., Semenova, A., & Parker, C. V. (2023). High resolution spectroscopy of thulium atoms implanted in solid noble gas crystals. Physical Review B, 108(21), 214101.