Inverted crossover resonances with ΔF=0 or 1 inverted crossover resonances with the intercombination line of 171 Yb

We demonstrate the presence of inverted crossover resonances (ICRs) in the intercombination line of 171 Yb (I=1/2) with the use of saturated fluorescence spectroscopy on an atomic beam. The principal lines involved in the crossover are symmetrically separated Zeeman transitions. The signals are observed for both the hyperfine lines of the 171 Yb 1 S 0 - 3 P 1 line. We use a four-level rate equation model to help validate the nature of the resonance. In the case of F'=3/2 (upper state) the resonance can be used to frequency stabilize laser light for laser cooling of 171 Yb. While that of the F'=1/2 ICR acts as a rather robust frequency reference with an overall fractional frequency uncertainty in the low 10 −11 range.