Pump-Probe Spectra Modeled With Inclusion Of A Dipole-Coupled But Not Dipole-Probed F ' State, For The Case Of Rb-85 5s(1/2)(F)<-> 5p(3/2)(F ') Transitions

We have simulated spectra of weak probe absorption from one of two hyperfine structure (hfs) components of an atomic ground state, to a hfs manifold of an upper state. A stronger coupling transition was assumed to bind the other hfs component of the ground state with the same upper hfs manifold. The purpose of this simulation was to study the impact on the spectral features in probe absorption from the presence of a state to which the electric-dipole transition is allowed for coupling, but forbidden for probing. In relation to our other (experimental) work, we considered the D2-line transitions for Rb-85. With coupling from the 5S(1/2)(F=2) state, as in our experiment, the 5P(3/2)(F'=1) state is coupled but not-probed from the 5S(1/2)(F=3) state. In calculations we searched for steady-state solutions of optical Bloch equations assuming a 5-level model and RWA. The collisionless (cold) atoms were considered, and we assumed that decoherence was entirely due to natural decay and exciting lasers' linewidths. We investigated probe absorption spectra as a function of both coupling-field-induced Rabi frequency Omega(c), and coupling field detuning from the atomic resonances. The 5-level model spectra were compared with the corresponding spectra result of 4-level model calculations performed by omission of the 5P(3/2)(F'=1) level. Even for small Omega(c) values close to the natural linewidth, for some detunings a considerable influence of the 5P(3/2)(F'=1) state on the spectra was observed which cannot be ignored in interpretations.