  X-ray absorption near edge structure (XANES) spectroscopy technique is used
to better understand the charging and decharging processes of the persistent
luminescence in the Cr$^{3+}$ doped AB$_2$O$_4$ spinels (A = Zn, Mg and B = Ga
and Al) with low photon energy excitation by visible light. Cr K edge XANES
spectra have been simulated for different near neighbour environments around
the Cr$^{3+}$ recombination centres and compared with the experimental curve.
In Cr$^{3+}$:ZnGa$_2$O$_4$ compound, the Cr$^{3+}$ local structure corresponds
mostly to that of a normal spinel ($\sim$70\%), while the rest comprises of
distorted octahedral environment arising from cationic site inversion and a
contribution from chromium clustering. This local structure is strongly
different in Cr$^{3+}$:MgGa$_2$O$_4$ and Cr$^{3+}$:ZnAl$_2$O$_4$ where, for
both cases, chromium clustering represents the main contribution. The strong
correlation between the intensity of persistent luminescence and \% of Cr in
clusters leads us to infer that presence of Cr clusters is responsible for
decrease of the intensity of the visible light induced persistent luminescence
in the Cr$^{3+}$ doped AB$_2$O$_4$ spinels.
