Index of content:
Volume 83, Issue 6, 15 March 1998
- GENERAL PHYSICS: NUCLEAR, ATOMIC, AND MOLECULAR (PACS 01-39)
83(1998); http://dx.doi.org/10.1063/1.367074View Description Hide Description
Currently there is much interest in stabilized amorphous selenium (-Se alloyed with 0.2–0.3% As and doped with 5–20 ppm Cl) as an x-rayphotoconductor in various x-ray imaging systems. Although optical photogeneration in -Se is well characterized, experiments on its x-ray sensitivity have been limited and, further, have resulted in widely differing conclusions especially for the electron hole pair (EHP) creation energy In this work, we first introduce absolute and incremental sensitivity ( and respectively) concepts within the electrostatic readout mode of operation and then establish models linking these two sensitivities to the energy absorbed to create a free EHP. X-rayirradiation induced xerographic discharge experiments have been carried out on vacuum deposited stabilized -Se x-rayphotoconductor films to examine how the sensitivity depends on the charge carrier schubwegs ( where μ is the drift mobility, τ is the lifetime, and is the electric field), the mean photon energy, and the detector thickness Experiments indicate that unless both electron and hole schubwegs are much longer than the photoconductor thickness, the sensitivity is reduced. The efficiency of EHP generation per absorbed x-rayphoton, i.e., the apparent energy absorbed per free electron hole pair has been determined as a function of electric field and mean photon energy. decreases with increasing applied field and energy. By examining vs and extrapolating to a saturation value for is predicted and estimated (4 to 6 eV) which, within experimental errors, is close to the theoretical expectation of and substantially smaller than previously reported values for (18–29 eV).
83(1998); http://dx.doi.org/10.1063/1.367075View Description Hide Description
We have developed an experimental setup for the measurement of the polarizability anisotropy of push–pull molecules in solution. We have used this technique to investigate prototype push–pull molecules that have been incorporated as doping chromophores in low glass transition temperature photorefractive polymers. Results obtained evidence for these compounds that the refractive index modulation is dominated by the orientational birefringence contribution while the electro-optic contribution remains small.