Excitation Dependence of Dipole–Dipole Broadening in Selective Reflection Spectroscopy

We investigate the dipole–dipole broadened selective reflection spectrum with the Cs atomic density of 10^14–10^15 cm^-3. The dipole–dipole broadening is reduced and the hyperfine splitting is well resolved when the ground state atoms are excited by a detuned pump beam. The dependences of dipole–dipole broadening of Cs atoms in the 6S_1/2(F=3)\rightarrow6P_3/2(F'=4) hyperfine transition line on atomic density and the excitation factor are studied. It is found that the reduction of the dipole–dipole broadening is dependent on the pump beam power and is independent of the atomic density in this density range. These results are useful for understanding of the dynamical process in this range of atomic density.