Radio-frequency control of spontaneous emission from a coherently driven multilevel atom

The spontaneous emission properties of radio-frequency(RF)-driven multilevel atomic systems with three different configurations are investigated in details. It is demonstrated that, due to the presence of the RF-induced coherence in the multilevel system, a few interesting phenomena such as spectral-line narrowing, spectral-line enhancement, spectral-line suppression, and fluorescence-quenching can be realized under realistic experimental conditions. By inspecting single-RF-driven, double-RF-driven, and triple-RF-driven atomic systems, we find that (i) when only one RF-driven field is applied, there are two fluorescence-quenching points and four spectral lines; (ii) in the case of applying two RF-driven fields, there are three fluorescence-quenching points and five spectral lines; (iii) when applying three RF-driven fields, there are four fluorescence-quenching points and six spectral lines; and (iv) as expected, when the atomic system coupled by N RF-driven fields, there will be N + 1 fluorescence-quenching points and N + 3 spectral lines. Interestingly enough, the spectral-line enhancement, the spectral-line suppression, and the selective cancellation of fluorescence-quenching can be well controlled just by appropriately modulating the intensities and frequencies of the applied RF fields, respectively. The proposed schemes can be achieved by use of RF-driven fields into hyperfine levels in rubidium atomic systems. These investigations may find applications in high-precision spectroscopy.