COLORATION OF PURE AND DOPED CALCIUM FLUORIDE CRYSTALS AT 20C AND -190C

Journal Article · Tue Nov 15 04:00:00 EST 1960 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.120.1154· OSTI ID:4145932

Scouler, W J; Smakula, A

S>Coloration of pure CaF/sub 2/ crystals with 2.5 Mev electrons at room temperature results in bands at 580, 400, 335 and 225 m mu . In YF/sub 3/-doped crystals the bands are in the same spectral positions as in pure crystals. They are, however, enhanced and their intensity ratios are significantly changed the 400-m mu band being predominant. NaF-doped crystals show an even more drastic change. Coloration at room temperature produces bands at 605, 385, and 330 m mu and is deeper than in either pure or YF/sub 3/-doped crystals. Since the 400-m mu band is strongly enhanced by YF/sub 3/ addition, which forms F/sup -/ interstitials, it is correlated to neutral fluorine atoms in interstitial positions. Similarly the 605-m mu band in crystals doped with NaF, which creates F/sup -/ vacancies, is correlated to electrons trapped in F/sup -/ ion vacancies (F centers), The enhancement of the 385-m mu band by NaF is explained by the reduction of the activation energy required for formation of interstitials and vacancies. Of several possible correlations the 330-m mu band is probably connected with a hole trapped in a Ca/sup 2+/ vacancy and that at 225 m mu with an electron trapped by a Ca/sup 2+/ interstitial. The bands at 440 and 200 m mu that appear in NaF-doped crystals only must be connected with Na ions. Coloration at - 190 deg C produces strong changes in the absorption spectrum. In pure and YF/sub 3/-doped crystals, bands appear at 550, 320, and 270 m mu whereas, in NaF-doped crystals, bands are formed at 440, 390, 315, and 200 m mu in addition to the 550-m mu band. The primary process of coloration at low temperature cannot differ from that at room temperature, but the secondary processes are strongly influenced by temperature. (auth)

• Research Organization: Massachusetts Inst. of Tech., Cambridge
• NSA Number: NSA-15-003172
• OSTI ID: 4145932
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 120; ISSN PHRVA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ABSORPTION
ACTIVATION
CALCIUM FLUORIDES
COLOR
CRYSTALS
DEFECTS
ELECTRON BEAMS
ENERGY
F CENTERS
IMPURITIES
INTERSTITIALS
IONS
LATTICES
LOW TEMPERATURE
METALS, CERAMICS, AND OTHER MATERIALS
RADIATION EFFECTS
SODIUM FLUORIDES
SPECTRA
TRAPS
VACANCIES
VARIATIONS
YTTRIUM FLUORIDES