Département de Physique, Université de Fribourg (Suisse)
Ulzega Simone
Theoretical and experimental study of the
Stark effect in the ground state of alkali
atoms in helium crystals
The quadratic Stark effect in the ground state of alkali atoms, treated in the frame of a
perturbation theory approach, can be parameterized in terms of a strongly suppressed
tensor polarizability 2 which arises only as a third order effect when the hyperfine
interaction is included in the perturbation. The first theoretical model describing the Stark
effect in the nS1/2 ground state of alkali atoms was published in 1968 by Sandars. The
tensor polarizability of cesium was measured in a few experiments in the 1960s and about
40 years later in Fribourg by our group. Although all these experiments yielded
compatible results, they showed a large discrepancy with respect to the theoretical value
of the tensor polarizability derived from Sandars' model. The third order Stark interaction
also leads to a shift of the hyperfine clock transition frequency. A precise knowledge of
this effect is of great importance for the calibration of atomic clocks and for the definition
of the second. At present, the atomic-clock community is involved in an important open
debate due to the existence of contradicting values of the Stark shift of the hyperfine
transition frequency. This thesis work gives a relevant contribution to both the points
mentioned above.
Prof. Dr. Dionys Baeriswyl, Université de Fribourg (Président de Jury)
Prof. Dr. Antoine Weis, Université de Fribourg (Directeur de thèse)
Prof. Dr. Jean-Claude Dousse, Université de Fribourg (Corapporteur)
Prof. Dr. Majed Chergui, EPFL, Lausanne (Corapporteur)