Key points are not available for this paper at this time.
Σ molecules, the differential shift can be nulled by choice of elliptical polarization. When one component of the polarization vector is ±i2 times the orthogonal component, the light shift for a sublevel of excited rotational states ±approaches that of the ground state at high optical intensity. In this case, fluctuating trap intensity need not limit coherence between ground and excited rotational states.
Rosenband et al. (Tue,) studied this question.