Etching of mercuric iodide in cation iodide solutions

The surface properties of mercuric iodide after etching in various cation iodide solutions have been investigated in terms of dissolution rate, morphology, electrical properties and reaction with water vapour. No significant differences have been observed in the etching rates. However, dissolution of HgI₂ in NH₄I, NaI, KI or RbI leaves the surface more or less covered with a residual iodo mercurate compound whose electrical properties and stability with regard to humidity may noticeably influence the behaviour of mercuric iodide devices. The smallest effect has been observed for etching in NaI.     

Magnetic susceptibility of mercuric iodide

The molecular diamagnetic susceptibility of mercuric iodide has been measured at room temperature and was found to be 138.6 × 10^?6$\text{e.m.u.}\text{gm}$ mol for the red tetragonal form. A modified Slater-Angus method gave a satisfactory agreement between the calculated and the experimental results if the bond linking mercury and iodine was assumed to be about 60% covalent.The temperature dependence of the susceptibility of mercuric iodide was also determined.     

Luminescence of mercuric molybdate and tungstate

The compounds HgMoO₄ and HgWO₄ show characteristic molybdate and tungstate luminescence respectively. The emission colour of HgMoO₄ is orange, that of HgWO₄ blue-green. The thermal quenching temperature of their luminescence is relatively high.     

Infrared properties of etched mercuric iodide surfaces

2 samples and on solution-grown KHgI₃,H₂O and NH₄HgI₃,H₂O crystals. A detailed study of the infrared absorption lines confirms that, taking into account small variations in the HgI₂ substrates, the residues on the surface are actually the same complexes. Received: 29 September 1997/Accepted: 31 October 1997     

The kinetics of exciton photoluminescence in mercuric iodide

Time-resolved photoluminescence (TRPL) of red mercuric iodide single crystal is measured at low temperatures and its two-photon luminescence is measured at room temperature. Sharp near band-gap luminescence is observed around 530 nm and was ascribed to radiative annihilation of free and bound excitons; the phonon replica of exciton luminescence are found between 533 and 540 nm at low temperatures. TRPL experiment reveals that near band-gap luminescence comprises fast and slow decay components and shows the different relaxation processes between free and bound exciton annihilation. Luminescence of bound excitons steeply lowers with increasing temperature and disappears about 40 K. A luminescence tail band is observed around 540 nm that is ascribed to defects in the anion sublattice. The temporal behavior of the tail band is described by rate equations very well. A broad luminescent band appears at 630 nm. The decay curves suggest that the luminescence is ascribed to the radiative recombination of donor-acceptor pairs and there are two kinds of mechanisms to control the decay. At room temperature, a luminescent band appears at the band-gap region, which shows the band-gap at room temperature is about 2.125 eV.     

Luminescence properties of calcium-iodide crystals

The effect of the conditions of preparation, temperature, and the action of x rays on the luminescence properties of calcium-iodide scintillation crystals is investigated. On the basis of the results of a study of the spectral characteristics of CaI₂ and CaI₂:H₂ crystals for optical and x-ray excitation in the temperature range 90–400 K, also taking into account the results of a study of the luminescence properties of CaI₂ crystals activated by Cl⁻, Br⁻, OH⁻, and Ca²⁺ impurities, it is suggested that the 236-nm band observed in the excitation spectra of crystals of calcium iodide may be caused by an uncontrollable hydrogen impurity. The luminescence of these crystals with maximum at 395 nm is ascribed to radiative recombination of excitons trapped at H⁻ ions. Zh. Tekh. Fiz. 69, 135–136 (January 1999)     

Optical properties of a polymer host matrix containing mercuric iodide microcrystals

Microcrystals of mercuric iodide have been grown in a polymer matrix with pores 200 nm in diameter. The absorption and luminescence spectra indicate the formation of microcrystals of two (red and orange) modifications in the host matrix. The temperature dependence of the emission spectra and the evolution of absorption and emission spectra in the course of sample ageing have been studied. The evolution of the spectra is governed by the transition from the orange to red modification and the increase in size of microcrystals.     

Luminescence decay in AgCl crystals

The kinetics of luminescence decay of single crystal plates of AgCl was measured at the temperature of liquid nitrogen. Luminescence decay first takes place (fort≦2·5× ×10^?3 sec) according to a hyperbole and then according to an exponential. The constantsa anda of the hyperbolic andt of the exponential dependence were measured for different intensity of the exciting radiation in normal and deformed samples and in samples irradiated withb-particles during measurement.