  We consider dynamics of a slowly time-dependent Dicke model, which represents
a many-body generalization of the Landau-Zener model. In particular, the model
describes narrow Feshbach resonance passage in an ultracold gas of Fermi atoms.
Adiabaticity is destroyed when a parameter crosses a critical value, even at
very slow sweeping rates of a parameter. The dynamics crucially depends on
direction of the sweep. We apply our recent analysis [A.P. Itin, P. Torma,
arXiv:0901.4778v1] to the "inverse" sweep through the resonance, corresponding
(in a context of Feshbach resonance passage) to dissociation of molecules. On a
level of the mean-field approximation, the dynamics is equivalent to a
molecular condensate formation from Bose atoms within a two-mode model. Mapping
the system to a Painlev\'e equation allows us to calculate deviation from
adiabaticity at very slow sweeps analytically.
