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Magneto-optical resonances in fluorescence from sodium D2 manifold

We report on magneto-optical resonances observed in sodium fluorescence from D2 manifold with an intensity modulated light. Fluorescence resonances are measured in the perpendicular and backward directions to the light propagation, in laboratory experiments using a sodium cell containing neon buffer gas. Properties of these resonances are studied by varying the magnetic field at fixed light modulation frequency, and vice-versa. Modulation with low-duty cycle shows higher-harmonic resonances of the modulation frequency and sub-harmonic resonances of the Larmor frequency. A dark resonance with maximum amplitude for laser wavelength closer to the crossover peak is observed. The origin of this dark resonance observed in Na D2 line is discussed using a theoretical model. Present study is aimed towards improving the understanding of magneto-optical resonances for remote magnetometry applications with mesospheric sodium.