On damping of Rabi oscillations in two-photon Raman excitation in cold ${}^{87}$Rb atoms

Two-photon Raman excitation between the ground hyperfine states $\mathrm{\mid }5{}^2{S}_{1\mathrm{/}2},F=2⟩$ and $\mathrm{\mid }5{}^2{S}_{1\mathrm{/}2},F=1⟩$ of ${}^{87}$Rb atom has been experimentally studied. The Rabi coupling strengths of various transition involved have been calculated in presence of a weak magnetic field. A density matrix formalism has been developed to understand the experimentally observed damping of Rabi oscillations of population in a hyperfine state of ${}^{87}$Rb atom during interaction with the Raman laser beams. The observed damping of Rabi oscillations has been attributed to the dephasing during the light atom interaction.