The Hyperfine Structure of Cs Atoms in the b.c.c. Phase of Solid 4 He

Abstract

We have detected the ground state F = 4 → F = 3 hyperfine transition of cesium atoms implanted in a b.c.c. matrix of solid ⁴He using a microwave-optical double-resonance technique. The transition frequency is blue-shifted by ~ 197 MHz (2.1%) with respect to the free atomic transition and grows with increasing pressure at a rate of ~ 1.4 MHz/bar.