Emission spectra following radiation trapping switching off: coherent effects detected up to resonance and signal enhancement

This paper reports strong-field modified emission spectra of a dipole allowed transition to the ground state, detected in an optically thick vapour subject to radiation trapping. The strong field coupled the higher level of the atomic transition to an upper level of the same atomic species (strontium). The coherence effects were outlined up to resonance in rather dilute vapour conditions. Enhancement of the fluorescent signal after radiation trapping switching off depends on the overlapping of the coupling laser beam with the radiation trapping region.