Electromagnetically induced absorption due to transfer of population in degenerate two-level systems

The occurence of electromagnetically induced absorption due to transfer of population (EIA-TOP) in degenerate two-level systems (TLS) where F _e=F_g+1 and F_g>0, was analyzed. EIA-TOP was modeled using a TLS, and the probe absorption spectra for the double TLS was compared with those obtained for the N system, a model of EIA-TOC. It was observed that both model systems gave an EIA peak at line center at low intensity, while double TLS had the same spectrum as a simple TLS and N system had a spectrum with four peaks at a high intensity. It was also observed that the central EIA peaks were narrowed and persisted to higher pump Rabi frequencies than in the absence of collisions.