High signal-to-noise detection of rotational Raman scattering through refluorescent and dispersive atomic filters

We introduce new methods for capturing rotational Raman scattering that sim ultaneously suppress background scattering and have exceedingly high spectr al dispersion at low wavenumbers, These methods are based on resonant absor ption and refractive index dispersion of atomic vapor, and take advantage o f the availability of tunable lasers, Three different configurations are pr esented. The first is an atomic notch transmission filter which is based on refluorescence from an optically thick atomic vapor cell. This configurati on is demonstrated in air using mercury vapor at 254 mn, The second configu ration is an atomic resonance prism cell which is demonstrated in CO2 using mercury vapor, again at 254 nm, The third configuration is a density gradi ent atomic vapor cell which uses rubidium vapor at 780 nn, In the last two configurations, the atomic cell simultaneously blocks the elastic scatterin g while spatially dispersing the rotational Raman lines. In each case, a tu nable Ti:sapphire laser was employed as an illuminating source. Copyright ( C) 2000 John Wiley & Sons, Ltd.