Differential two-photon spectroscopy for nondestructive temperature measurements of cold light atoms in a magneto-optical trap
A differential two-photon spectroscopic technique for measurement of atomic temperatures in a working magneto-optical trap was demonstrated. We performed experimental and theoretical studies of two-photon resonances on Rydberg transitions 2S_1/2−2P_3/2−58S in cold Li7 atoms by using counter- and co-propagating laser beams. By analyzing the spectral shapes, a dependence of Rabi broadening and Doppler broadening on total intensity of cooling laser beams was obtained. We measured the temperature of Li7 atoms in the range from 0.25 to 0.75 mK. Our theoretical and experimental results are in reasonably good agreement. The developed approach for temperature measurements can be applied to cold atoms in different traps, including confined hydrogen and antihydrogen atoms.