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Abstract
A new one-photon process for latent image formation in silver halides is proposed. The model is an extension of the theoretical concepts of Gurney-Mott, Hamilton and Lowe. Hamilton proposed a four-photon mechanism for the photochemical formation of Ag4 latent image centres. Subsequently, Lowe developed a two-photon mechanism, which includes hole trapping by Ag2 reduction centres. Mitchell proposed a two-photon mechanism based on the presence of electron trapping Ag2 centres that act as sublatent image centres. One-photon latent image formation was proposed which relied on gold-containing electron-trapping centres; however, these mechanisms were considered to be fogging mechanisms. From the concepts of the previous mechanisms, a one-photon latent image mechanism is proposed that does not result in fog. This one-photon process is based on the presence of both electron and hole-trapping Ag2 centres on the same crystal before exposure. Both photoelectron and photohole, which arc formed by light absorption, participate in this mechanism. The required electron-hole energy separation is estimated to be about 1.4 eV and is thus well above the thermal energy at room temperature (about 0.03 eV). Experimental evidence for one-photon processes in silver halide systems supports the proposed one-photon mechanism for Ag4 latent image formation.
Notes
This paper was presented at the PICS ’99 Conference of the Society for Imaging Science and Technology held in Savannah, Georgia on 25-28 April 1999 and later published in Proceedings of the IS&T PICS ’99 Conference, 1999, p. 4.