Hyperfine interaction in the Autler-Townes effect: Control of two-photon selection rules in the Morris-Shore basis

Earlier research highlighted the absence of certain bright peaks in Autler-Townes laser excitation spectra of alkali-metal atoms and attributed this phenomenon to a specific architecture of adiabatic (or ``laser-dressed'') states in hyperfine (HF) components. Here we have studied the dressed states' properties in several two-photon excitation schemes where constructive and destructive interferences between HF excitation pathways limit the available two-photon transitions. The analysis reveals a mechanism by which this interference reduces the conventional two-photon selection rule for the total angular momentum F, from ΔF=0,±1 to ΔF≡0. Our discovery presents a practical method for selectively controlling the populations of unresolvable HF F components of ns1/2 Rydberg states in alkali-metal atoms. Using numerical simulations with sodium and rubidium atoms, we demonstrate that by blocking the effects of HF interaction with a specially tuned auxiliary control-laser field, the deviations from the ideal selectivity of the HF components population can be lower than $0.01%$ for Na and $0.001%$ for Rb atoms.