Selective reflection spectroscopy on the UV third-resonance line of Cs: Simultaneous probing of a van der Waals atom-surface interaction sensitive to far IR couplings and interatomic collisions (original) (raw)

We report on the analysis of FM selective reflection experiments on the 6S 1/2 → 8P 3/2 transition of Cs at 388 nm, and on the measurement of the surface van der Waals interaction exerted by a sapphire interface on Cs(8P 3/2). Various improvements in the systematic fitting of the experiments have permitted us to supersede the major difficulty of a severe overlap of the hyperfine components, originating, on the one hand, in a relatively small natural structure, and, on the other hand, on a large pressure broadening imposed by the high atomic density needed for the observation of selective reflection on a weak transition. The strength of the van der Waals surface interaction is evaluated to be 73 ± 10 kHz µm3. An evaluation of the pressure shift of the transition is also provided as a by-product of the measurement. Finally, we discuss the significance of an apparent disagreement between the experimental measurement of the surface interaction, and the theoretical value calculated for an electromagnetic vacuum at a null temperature. The possible influence of the thermal excitation of the surface is evoked, because the dominant contributions to the van der Waals interaction for Cs(8P 3/2) lie in the far-infrared range.