Zero ac Stark frequency shift of an atom trapped in pulsed laser light

We report a theoretical analysis of the spectral properties of atoms localised in an optical pulsed trap. It is shown that this analysis can be carried out using the correlation coefficient calculated from the averaged dynamics of atomic excitation by resonant probe laser light in the presence of a nonresonant pulsed field. It follows from calculations that at a laser pulse duration of 8 ps, atoms can be trapped at a zero shift in the D₂ line transition frequency of the Rb atom, caused by the ac Stark effect. This configuration can be used to build optical frequency standards without the need for localising laser radiation at the 'magic' wavelength.