Examination of subnatural spectroscopy using optical pumping

Recent experiments have shown that optical pumping can produce line shapes with subnatural structure, and that this structure could prove to be useful for extracting oscillator strengths. A key question, however, regarding the optical-pumping technique's potential usefulness is how well it allows the determination of resonance line center. In the present paper we address this question theoretically by considering laser optical pumping and probing of an atomic beam. From the analysis (i) we find that depending on laser polarization the optical-pumping subnatural feature is either a dip or a signal enhancement, (ii) we derive the rigorously correct formula relating the dip width to the transition oscillator strength for an alkali-like atom exhibiting a homogeneous line shape, and (iii) we show that, compared to shot-noise-limited laser-induced fluorescence, the optical-pumping technique of signal enhancement is capable of a 15% improvement in the ability to find resonance line center.