OPTICAL AND PHYSICAL-PROPERTIES OF SILVER COLOR-CENTERS IN MICROCRYSTALS IN SILVER BROMIDE FILMS

Results are presented of investigations of silver colour centres of mo lecular and colloidal types arising from the deep photolysis of AgBr m icrocrystals in ultra-fine-grain emulsions. Using experimental data co nnecting the position of the absorption maximum of first, secondary an d ''limited'' colour centres, their dimensions and the size of the AgB r crystals, values of solubility, partial degree of solubility and sur face tension of Ag in AgBr are calculated. Dependence of these values on the dimensions of the AgBr crystals are studied. It is shown that t he surface tension increases with the number of atoms in the colioidal particles. The solubility of Ag changes by 6 orders of magnitude as t he colloidal particles decrease from massive to atomic size. Good agre ement is shown between the experimental results and the predictions of thermodynamic theory for the nucleation and growth of a new phase. Th e possibility of a photostimulated phase transition from molecular cen ters to colloidal ones is considered.