Esther W. Claffy

Thermoluminescence and Color Centers in LiF:Mg

A variety of optical absorption, emission and luminescence excitation spectra have been measured in an attempt to identify the centers involved in the thermoluminescence of commercial LiF:Mg. It is concluded that the principal trapping centers consist of a hole trapped near various groupings of Mg2+ ions and vacancies. The optical absorption bands of these centers occur in the 3100–3800 A region which contains several absorption bands corresponding to different geometries of the centers. It is suggested that the 2200‐A band arises from Mg2+ ion‐vacancy complexes which have captured two holes. During thermoluminescence, holes are transported from traps to emitting centers. The luminescent center appears to be the F center both in an isolated position and when adjacent to a complex involving Mg2+ ions.

Laser‐Stimulated Thermoluminescence in Glass

Thermoluminescence has been investigated as a tool for the detection of damage precursors in laser glass samples exposed to 1.06‐μ laser radiation. Exposure which did not produce visible damage gave very small thermoluminescence yields. Damaged glasses produced stronger thermoluminescence, but in even those the effect is not large enough to provide a convenient materials test. A quenching action due to neodymium was noted. The emitting centers are believed to be impurities in the glass.

Diffuse Reflectance and Fluorescence Measuring Apparatus

An apparatus is described for measuring the diffuse reflectance and/or fluorescence of small (15–30 mg) granulated or powdered samples of solid materials. The sample rests in the horizontal plane, thus requiring no special mounting procedure. Input light is provided by a quartz‐iodine lamp through a monochromator having a range of wavelengths from 350 to 800 nm. A photomultiplier measures the light scattered from the diffusely reflecting walls of the sample chamber. The optical absorption spectrum of γ‐irradiated lithium fluoride powder is shown as an example of performance, obtained in a study of the possible applicability of LiF M‐,R2‐, and N2‐band absorption for radiation dosimetry purposes.