Anomalous Frequency Shift in the Photoassociation Spectrum of a Bose-Einstein Condensate

We theoretically investigate the effect of anomalous quantum correlations on the light-induced frequency shift in the photoassociation spectrum of a Bose-Einstein condensate. Anomalous quantum correlations arise because, although formed from a pair of zero-momentum condensate atoms, a condensate molecule need not dissociate back to the atomic condensate, but may just as well form a noncondensate atom pair with equal and opposite momentum, i.e., due to rogue photodissociation. The uncorrelated frequency shift of the photoassociation spectrum is to the red and linearly dependent on the laser intensity $I$. In contrast, anomalous correlations due to rogue dissociation lead to a blueshifted photoassociation spectrum. For sufficiently low light intensities, the rogue blueshift is dominant and proportional to $\sqrt{I}$.