Variations of intensity in Rb D<inf>2</inf> line at weak/intermediate fields

Zeeman splitting in the D2 line of rubidium atoms ( 87Rb and 85Rb) has been studied using 'Doppler broadened' as well as 'saturation absorption spectroscopy'. While a linearly polarized beam was used for the former experiment, in the latter case a (π, σ±) polarization configuration was employed for both pump and probe beams. Zeeman lines have been observed by applying a field up to 5 mT. The field variation of relative line intensities in Doppler-broadened spectrum was determined following Tremblay et al and Nakayama's four-level model. For the saturation spectrum, a four-level model was used. Because the enhancement of absorption at the field is as low as 1 mT, the Fg ≤ 2 to Fe ≤ 3 transition for 87Rb can be used as the reference for laser locking. Level crossing is observed in 85Rb at fields less than 5 mT. © 2007 IOP Publishing Ltd.