Accession Number : AD0705195

Title :   PHOTOCHROMIC MATERIALS RESEARCH.

Descriptive Note : Final rept. 1 Oct 67-30 Sep 69,

Corporate Author : RCA LABS PRINCETON N J

Personal Author(s) : Heyman,Philip M. ; Staebler,David L.

Report Date : DEC 1969

Pagination or Media Count : 136

Abstract : The photoconductive properties of CaF2 and SrTiO3 and the optical properties of CaF2 were investigated in order to better characterize photochromic behavior. It has been found that there is charge transfer during switching that is detectable as a photocurrent in both systems; however, the photoconductive sensitivity is quite low due to the large density of photochromic trapping centers. Room temperature photo-Hall measurements on CaF2:Tb show that charge transfer is via the conduction band with a Hall mobility of 30 sq cm/V.sec. The thermal depth of the metastable centers has been found to be between 1.10 and 1.20 eV for CaF2:Ce, CaF2:Tb, and CaF2:Gd. The emission cross section (the product of the photogeneration efficiency and the absorption cross section) for the metastable center at the peak of its absorption band appears to be about a decade smaller than that of the stable center in the 30,000/cm region. Photoconductive models for the metastable and stable centers are discussed. The effect of an externally applied magnetic field upon the absorption of circularly polarized light (circular dichroism) has been used to study the physical nature of the thermally stable photochromic center in rare earth doped CaF2. The results are discussed in terms of the orbital and paramagnetic states of the center. The principal result is that the center involves a rare earth ion. (Author)

Descriptors :   (*PHOTOCHROMISM, *CALCIUM FLUORIDES), DOPING, PHOTOCONDUCTIVITY, CESIUM, TERBIUM, GADOLINIUM, COLOR CENTERS, TITANATES, STRONTIUM COMPOUNDS

Subject Categories : Optics
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE