X-RAY INDUCED CURRENTS IN ANTHRACENE AND TETRACENE

A new method which avoids making measurements or applying an external voltage while the X-rays are on, was used in investigating the ionization process by X-rays in organic crystals (tetracene and anthracene). The following results were obtained: The X-ray induced current is linear with electric field strength over a large range of field strengths and saturates at field strengths above 104 V/cm; it is proportional to the intensity of irradiation and to the thicknes of the sample for the same field strength; about 1500 eV are required to produce one charge pair in anthracene and 400 eV in tetracene. It was also found that the saturation field strength is independent of the X-ray intensity (the intensity was varied by a factor of ten). From these results it was concluded that recombination occurs mostly between the electron and the hole from which it was separated. It was also found that a large X-ray irradiation (8 x 105 ergs absorbed) produces trapping sites in the bulk of the crystal which trap charges and thus produce some bimolecular recombination. © 1969, Walter de Gruyter. All rights reserved.