doped glasses in the LiF–MgF2–Ba(PO3)2 system are investigated. The intensities of the doublet signals from
and 
centers in regions with different contents of the fluoride component are determined as func-tions of the terbium concentration. It is shown that fluorophosphate glasses can be characterized by two values
of the capture volume parameter, which differ by a factor of 5.0–6.6 depending on the dopant concentration. In
the range of minimum dopant concentrations at which the capture volume is maximum, the dopant ions have a
hypothetically phosphate environment. It is suggested that the capture volume parameter defined by the expres-
sion ln c/c0 = –VC3 can be treated as a characteristic of the distribution of dopant ions in fluorophosphate
glasses.