Magnetically assisted Sisyphus effect

This paper presents an experimental and theoretical study of laser cooling in a standing wave in the presence of a small transverse magnetic field (Magnetically Assisted Sisyphus Effect: MASE). The analysis is worked out for a Jg=1 to Je=1 transition corresponding to the experiment performed on the $2^{3}\rm S_{1}\longleftrightarrow 2^{3}\rm P_{1}$ transition of metastable helium. In this situation, MASE has an effect opposed to the usual Doppler cooling effect, i.e. it produces heating for a negative detuning. Depending on the various parameters, the competition between MASE and Doppler cooling, which act on different velocity ranges, leads to interesting new effects, such as a bistable force. The velocity dependence of the total force is calculated, using a semi-classical approach. A second theoretical treatment, where the atomic motion is quantized, is used to study the time evolution of the velocity distribution. The results of these calculations are compared to experimental observations