Radiative Transitions and Coherent Scattering of Light in Helium and Helium-Like Atoms.

Yvan R. P. Sortais

John Lawall, Mara Goff Prentiss

We have demonstrated a coherent beam splitter for metastable helium based on adiabatic passage. Light from a homemade LNA laser at 1.083 {mu} is used to excite the {sup 3}S{sub 1}-{sup 3}P{sub 0} transition in a highly collimated beam of metastable helium. The atoms are first optically pumped into the m=0 and m=-1 sublevels. These sublevels are two independent {open_quotes}dark{close_quotes} states from which no further absorption is possible. Population is transferred adiabatically from the m = -1 level to the m =+1 level by means of two partially overlapping laser beams. As well as absorbing 2{h_bar} of angular momentum from the radiation field, the atoms initially in the m = -1 sublevel acquire 2{h_bar}k of linear momentum via an absorption/stimulated emission process. The process can be repeated back to m = -1, and we have demonstrated 4{h_bar}k and 6{h_bar}k coherent momentum transfer using successive interactions regions. The population initially in the m = 0 sublevel is undeflected by the light.

A. I. Magunov, С. И. Страхова

Coherent effects in the interference of overlapping laser-induced resonances in helium atoms are considered. The simultaneous action of single-mode radiation of the 294-nm second harmonic of a cw dye laser and a 1064-nm Nd:YAG laser on helium atoms provides the overlap of two resonances induced by transitions from the 1 s 2 s 1 S and 1 s 4 s 1 S helium levels. The shape of the overlapping laser-induced resonances in the rotating-wave approximation is described by analytic expressions, which depend on the laser radiation intensities and the ratio of laser frequencies.

V. A. Grinchuk, A. P. Kazantsev, Gregory I. Surdutovich +4 more

A theoretical and experimental study is presented of the effect of stimulated radiation pressure (SRP) under the conditions of strong saturation of the resonance transition when the interaction times between the atom and the field are short (shorter than the radiative lifetime). An experimental method for studying the scattering of an atomic beam by the field of a standing light wave is described. The measured dependence of the scattering efficiency on the electric field and the detuning from resonance are reported. Experimental relationships are compared with theoretical calculations based on the quasi-classical description of the motion of atoms in the field of a light wave, using an effective potential. It is shown that the efficiency of scattering of atoms by SRP forces is of the order of unity in relatively weak (100–1000-V/cm) laser fields.

A. P. Kazantsev, G. A. Ryabenko, Gregory I. Surdutovich +1 more