Long-wavelength Spectral Region Research Articles

Recombination processes during excitation of AgCl:Me2+ crystals by ionizing radiation

Spectra and temperature vs. intensity plot of radioluminescence of AgCl single crystals both, pure and doped with Cd2+, Pb2+, Mn2+ ions, are studied. Introduction of bivalent activators not only creates new emission bands in the long-wavelength spectral region, but also strongly affects the position and configuration of the only band present in the emission spectrum of nominally pure AgCl (cationic impurities < 10−7): the band maximum shifts from 498 to 480 nm, its halfwidth changes from 0.39 to 0.29 to 0.35 eV and the activation energy of thermal quenching, from 0.05 to 0.18 to 0.21 eV. The experimental data give reasons to ascribe the short-wavelength luminescence to a [Ag++Cl−6Ag11Vk]Me2+ complex and that of long-wavelength luminescence to the Me2+ activator ion. In the first case free electrons radiatively recombine with trapped holes, while in the second case a recombination of holes with localized electrons takes place. [Russian text Ignored.]

The Radiant Transmittance of Tandem Arrays of Filters

The spectral transmittance of tandem arrays of multilayer filters is measured and compared with theory. The theory assumes that the irradiances of the multiply reflected beams can be added incoherently. Various arrangements of tandem arrays are examined in order to optimize the attenuation in the long-wavelength spectral region of an ultra-violet bandpass filter.

Improvement in use of photometric methods for measurement of birefringence

Visual or graphical determination of isochromatic order in photoelastic models is not sufficiently accurate for many photoelastic observations. This is especially true in the long-wavelength spectral region where fringe orders are low and photometric devices must be used for observation. In such cases, some method of fractional-fringe measurement is required. The Tardy and Senarmont methods are often chosen for convenience, with preference given to the Senarmont method because of smaller system error. These methods are based on detection of the analyzer angle at which the light transmitted through the given point in the model is minimum. The experimental problem is poorly conditioned, and the procedure is incompatible with nonideal light-sensing apparatus. The equations of the Senarmont technique show that the intensity of radiation is an even function of the rotation of the analyzer from the position which produces minimum intensity. The indeterminacy in the measurement of minimum-intensity angle may be reduced by observing the angles at which the intensity reaches arbitrary values greater than minimum. The average of two such readings on both sides of the minimum-intensity angle provides an improved measurement of this angle. Best results are obtained if observations are made where the intensity reaches half its maximum value. For a signal-to-noise ratio of 1000, this procedure improves results by a factor of 16. Improvement is greater asS/N is increased.