Electromagnetically induced transparency and absorption in warm Rb vapor via the Hanle effect: Analysis of observed spectra*

We have observed electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) in room temperature Rubidium vapor, by coherent population trapping on the Zeeman substates formed by a magnetic field co-linear with a laser beam passing through the vapor. We have observed EIA on $F_{g} = 3 \rightarrow F'$ transitions in ${}^{85}$Rb and on $F_{g} = 2 \rightarrow F'$ transitions in ${}^{87}$ Rb. We have observed with good signal-to-noise ratio EIT on $F_{g} = 2 \rightarrow F'$ transitions in ${}^{85}$Rb and, for the first time, on $F_{g} = 1 \rightarrow F'$ transitions in ${}^{87}$ Rb. However, certain unexpected features are revealed in the observed spectra, the origins for which remain unclear. We report on our progress toward modelling and understanding the observed EIT and EIA spectra.