MECHANISMS OF ENERGY TRANSFER IN DIELECTRICS.
Abstract
A new method - which avoids making measurements or even applying an external voltage while the X-rays are on - was used in performing experiments on the interaction of low intensity X-rays with organic solid insulators (tetracene and anthracene). The following results were obtained: The X-ray induced current is linear with electric field strength over a large range of electric field strength and saturates at field strengths above 10,000 volt/cm; it is proportional to the intensity of irradiation; its magnitude decreases with the thickness of the sample for the same field strength and X-ray intensity, unlike the behavior of normal conduction; 1,600 eV are required to produce one charge pair in anthracene and 400 eV in tetracene. It was also determined that the saturation field strength is independent of the X-ray intensity (it was varied over a factor of ten). A study was made of the time evolution of the energy distribution of the positrons below the ionization threshold in an external electrostatic field, and found: (1) The field induces diffusion out of the Ore gap, which reduces Ps formation. (2) The overall heating effect of the field on the positrons increases Ps formation. Depending on the magnitude of the relevant cross sections, (1) can outweigh (2) at small fields and cause a significant decline in the Ps formation. At field strengths greater than a characteristic value, (2) becomes the dominant effect. In this way measurements of the field dependence of Ps formation can give access, at the energies of the Ore gap, to the cross sections of Ps formation and of positron energy loss and scattering in matter. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1967
- Accession Number
- AD0662714
Entities
People
- Hartmut P. Kallmann
- Werner Brandt
Organizations
- New York University