Using the multipole expansion we analyze photo induced reactions in an ultra-cold atomic gas
composed of neutral bosons.
While the Frank-Condon factor dominates the photo induced spin flip reactions,
we have found that for frozen-spin process the reaction rate is governed by the r^2 and quadrupole terms
for identical particles, and by the dipole term for non-identical particles.

Comparing the relative strength of the r² and quadrupole modes in dimer photoassociation, we predict that the mutual importance of these
two modes changes with temperature and scattering length.