Eur. Phys. J. D 46, 9-14 (2008)
https://doi.org/10.1140/epjd/e2007-00275-5

Lifetime of the Cs 6P_1/2 state in bcc and hcp solid ⁴He

¹ Département de Physique, Université de Fribourg (), Chemin du Musée 3, 1700 Fribourg, Switzerland
² EPFL, Lausanne, Switzerland

Corresponding author: ^a adrian.hofer@unifr.ch

Received: 16 May 2007
Revised: 4 September 2007
Published online: 26 September 2007

Abstract

We present the first experimental study of time-resolved fluorescence from laser-excited Cs(6P_1/2) atoms isolated in a solid ⁴He matrix. The results are compared to the predictions of the bubble model including the interaction of the atomic dipole with its radiation reflected at the bubble interface. Our results show that in liquid He as well as in the body-centered cubic (bcc) crystalline phase of He the lifetime of excited Cs atoms does not depend on He pressure, in agreement with our theory. When going from the bcc to the hexagonally close-packed (hcp) phase of ⁴He the lifetime is reduced by ≈10% and decreases further with increasing He pressure. We assign this effect to the formation of Cs^*He_n exciplexes, and determine the pressure dependence of the probability that the 6P_1/2 state decays via this nonradiative channel.