Halide Phosphors Research Articles

Spectral studies on single crystal BaBr2?Sn phosphor

The absorption spectra at 300 K, the emission and excitation spectra at 77 K and 300 K of BaBr2−Sn phosphor have been studied. The complicated structure observed in the absorption and excitation spectra was connected with transitions to the components of the1P1,3P1 and3P2 excited states in tin centers which preserve the symmetry of the basic lattice. There has also been observed a complicated structure of the emission spectrum at 77 K which unlike all alkali earth halide phosphors observed so far, manifests itself also in the visible region of the spectrum.

Optical absorption of s2-configuration ions in alkali halide crystals—IV : Line shape of the C band in Sn 2+-doped crystals

The line shape of the C band in the alkali halide phosphors KBr:Sn 2+, RbBr:Sn 2+, and RbCl:Sn 2+ has been measured as a function of temperature between about 15 K and room temperature. In contrast to earlier measurements on In +-doped phosphors, the C band shows a well-marked triplet structure over the whole temperature range. This triplet structure cannot be accounted for solely in terms of the dynamical Jahn-Teller effect without assuming a very large temperature-dependence for the coupling constant to vibrational modes of trigonal symmetry. The temperature-dependence both of the second moment of the line shape and of the separation between the components of the C band, suggests that there is a contribution to the splitting of the C state from a lowering in the symmetry of the static crystal field and a model which includes such a static splitting in addition to the dynamical Jahn-Teller effect provides a good representation of the experimental line shapes.

Analyse de l'interaction electron-reseau dans KBr dope au thallium

By a computerized best fit of the magnetic circular dichroism spectrum the A, B and C bands, the electron-lattice interaction in KBr : Tl has been analyzed. The a 2, b 2 and c 2 coupling constants describing this kind of interaction have been quantitatively determined by comparison with theoretical curves. The obtained results are consistent with the conclusions of a general analysis of this interaction in alkali halide phosphors containing Tl +-like impurity centres. The Jahn-Teller effect in the excited states of these defects has also been discussed.

Luminescence of Alkali Halide Phosphors Excited with XUV Radiation

Photoluminescence of alkali halide phosphors activated with Ag + or Tl + ions is studied in the XUV region from 10 eV to 40 eV. Excitation spectrum of the luminescence is found to be very rugged and two prominent peaks are observed in the photon energy region studied. The appearance of these peaks is attributed to the slowing down of the conduction electrons caused by excitation of the valence electrons. Some fine structures are also found on the gross structure of excitation spectra at the same energies with the core exciton bands.

Investigation of the persistence of photostimulated luminescence of alkali halide phosphors

Investigation of the persistence of photostimulated luminescence of alkali halide phosphors

Line Shape of C Bands in Alkali Halide Phosphors by the Method of Moments

We have derived the optical absorption line shape for C bands in alkali halide phosphors by the method of moments. The dynamic Jahn–Teller interaction is considered in the excited T1u electronic states. This interaction is taken to be linear in the lattice displacements. The obtained line shape exhibits asymmetric triplet structure even in the linear electron–lattice interaction. The use of the quasi-classical approach (i.e. the use of the adiabatic approximation and Franck–Condon principle) for electronic transition to orbitally degenerate states is discussed by comparing the line shapes obtained in this approach with those obtained by the method of moments.

Dynamic Jahn‐Teller effect in the excited states of SeCl62−, SeBr62−, TeCl62− and TeBr62−: Interpretation of electronic absorption and Raman spectra

AbstractAlthough the complex‐ions SeCl62−, SeBr62−, TeCl62− and TeBr62− are regular octahedral, the infrared spectra show that some evidence is present for vibronic coupling between ground state and first excited state (dynamic second order Jahn‐Teller effect).The electronic absorption spectra are reported and assignments given. The splittings of the absorption bands closely resemble those found in the spectra of the alkali halide phosphors (KCl: Tl+ etc.). As for the phosphors, an explanation is given in terms of a dynamic Jahn‐Teller effect in the excited states.In connection with this, attention is paid to the unusual intensities of the Jahn‐Teller active modes (eg and t2g) in the Raman spectra of these complex‐ions.

On the Monomolecular Recombination Luminescence and Its “Blowing‐up” by the Electric Field

AbstractOn the basis of the diffusional theory of luminescence the fraction of the monomolecular luminescence and the effect of not very strong electric fields on recombination processes in uniformly excited phosphors are estimated taking into account the smallness of the free carrier mean path. The fraction of the luminescence of short duration caused by a recombination before the localization and that one of long duration caused by the recombination after localization are also estimated. A formula which determines the probability of the recombination of electron‐hole pair components is derived. Some calculations for alkali halide phosphors are carried out.

Theory of Stress and Magnetic Circular Dichroism in Alkali Halide Phosphors

Magnetic circular dichroism (MCD) and stress dichroism (SD) in the absorption spectrum due to ( s ) 2 →( s ) 1 ( p ) 1 transition with electron lattice interaction have been theoretically studied in order to investigate the further consequence of the Jahn-Teller effect in the excited state. In the framework of the classical Frank-Condon approximation, dichroic absorption spectra have bee numerically calculated by means of the Monte Carlo integration over the five-dimensional “interaction-mode” coordinate space. Calculated dichroic spectra are consistent with the existing data for the line shapes of MCD and SD in the Tl + -like centers in alkali halides.

Method of Moments for Optical Absorption Bands of Impurities in Solids

An attempt to reformulate and extend the method given by HSS (C. H. Henry, S. E. Schnattely, and C. P. Slichter: Phys. Rev. 137 (1965) A583) is made. The unperturbed electronic Hamiltonian H 0 responsible for the absorption lines is chosen only under the condition that its solution has many degenerate levels. Using the perturbation theory, the moments are calculated up to the third order in the perturbing Hamiltonian H 1 , in contrast to the first order in the HSS's theory. Since the spin-orbit interaction H S O may be contained in H 0 or H 1 , the obtained formulae of moments are applicable to many kinds of systems, although the HSS's treatment is restricted to the systems in which H S O is regarded as the perturbation. The results are applied to the absorption bands of the alkali halide phosphors containing heavy-metal ions with ( s ) 2 configuration, and the method to determine the values of energy parameters for these ions is discussed.

The Temperature Dependence of Radioluminescence Yield in Alkali Halide Crystal Phosphors

AbstractEmission spektra, thermal luminescence, and temperature dependence of luminescence yield of thallium and indium activated alkali halide phosphors are measured in the temperature range 80 to 600°K. The decrease of luminescence yield at low temperatures is explained as being due to localisation of electrons at activator centres.

The nature of capture center ?interaction? in silver halide phosphors

It is shown that luminescence flashes in silver chloride stimulated by long-wave light were due to the photoemission of electrons from precolloidal and colloidal silver centers. The effect of electron redistribution over localization levels in AgCl phosphors was investigated.

Effect of Pressure on Emission and Absorption Spectra of Alkali Halide Phosphors

Absorption and emission energies of certain alkali halide phosphors under pressure have been measured. The systems involved were KCl:Tl, NaCl:Tl, KCl:Pb, NaCl:Pb, CsI:Tl, and NaI:Tl, and pressures in excess of 40 kbar were employed. Data for NaCl:Tl and the low- and high-pressure forms of KCl:Tl could be fitted by a configuration coordinate model, but the behavior of the other systems could not be described in this way.

Electroluminescent ( Zn , Mg ) S : Cu , Halide Phosphors

Electroluminescent , halide phosphors can be prepared with up to substituting for . substitutions above 5% in the cubic Cl or Br coactivated phosphor result in a shift of the emission to shorter wavelengths, a change to the hexagonal modification, a decrease in brightness and an expansion of the unit cell. The iodine coactivated phosphors show similar but more complex changes. An unexpected effect of specific structural variations, i.e., variations of the unit cell dimensions, on the EL characteristics of the phosphors was found in the iodine coactivated samples.

336. The luminescence centers of alkali halide phosphors doped with divalent metals: N. I. Ivanova and A. P. Zhukovskii, Optics & Spectrosc., 12 (1), Jan. 1962, 56–57

336. The luminescence centers of alkali halide phosphors doped with divalent metals: N. I. Ivanova and A. P. Zhukovskii, Optics & Spectrosc., 12 (1), Jan. 1962, 56–57

Narrow bands of the luminescence of CuBr and of alkali halide phosphors activated by CuBr

We have examined the luminescence of alkali halide phosphors activated with CuBr at room and low temperature. The phosphors contained a large amount of activator. The results demonstrated that in these cases the narrow bands in the luminescent spectra belong to the surface centres. We have also examined the luminescence of CuBr at 77°K and 20°K. In the 4175–4315 A range a series of the narrow bands appear. The effect of gases on the luminescence of CuBr has been observed. The experimental results show that in this case there are several kinds of centres and the luminescence of CuBr is connected with surface phenomena.

Molecular-Orbital Model for Alkali Halide Phosphors Activated by Heavy Metals

It is pointed out that the Seitz model may be interpreted as a molecular-orbital model. This enables us to avoid some difficulties encountered in the interpretation within a Heitler-London framework. It is demonstrated that the observed positions of the A, B, and C absorption bands and the observed ratio of the dipole strength of the C band to that of the A band are consistent with each other in the molecular orbital model for KCl:Tl, KI:Tl, and also for KCl:In with some reservation.

Some Optical Properties of Lead Activated Potassium Halide Phosphors

Absorption, emission and excitation spectra of KCl:Pb and KBr:Pb have been measured at various temperatures. These observed spectra are similar to those of KCl:Tl, and the absorption bands seemed to be due to transitions in Pb ++ ions which occupies the normal positive ion sites. The two principal excited states are 1 P 1 and 3 P 1 of Pb ++ ion. 273 mµ absorption, 345 mµ emission in KCl:Pb and 302 mµ absorption, 365 mµ emission in KBr:Pb are attributed to 3 P 1 – 1 S 0 transitions perturbed by surrounding host lattice ions. The excitation to 1 P 1 state does not manifest any dstinct emission which is different from the case of Tl activated phosphors. The near ultra-violet emission suffers violent thermal quenching at room temperature, and the activation energies of these nonradiative process are found to be 0.28 eV and 0.18 eV for KCl:Pb and KBr:Pb, respectively. Several discussions using a single configuration coordinate model are given.

Effect of Pressure and Temperature on the Absorption Spectra of Four Alkali Halide Phosphors

The effect of pressure and temperature has been measured on the ``A''. bands in KI:Tl and in three alkali halides containing Pb++ impurity. The effect of temperature is to impose a red shift on the observed room-temperature pressure shift. The most remarkable result is the appearance of a new band in the high-pressure phase of KCl:Pb and KBr:Pb upon heating under pressure. The band remains after cooling, but disappears upon lowering the pressure into or through the region of the transformation back to the fcc phase. Repressuring and reheating reintroduces the band. It seems most probably that the band is associated with the ionic configuration near the Pb++ ion; especially with the location of the accompanying K+ vacancy.

The effect of pressure on the absorption spectra of alkali halide phosphors

The effect of pressure (over 150,000 atm) has been measured on the spectra of twenty-six alkali halide phosphors, including nine doped with Tl +, two doped with In +, twelve doped with Pb ++, two doped with Cu ++ and one doped with Bi +++. v max for the T1 + doped phosphors depends very strongly on the crystal structure and very little, if any, on the halide ion involved, which is consistent with the Seitz model. The In + doped phosphors behave like the Tl + analogs. For the Pb ++ phosphors, the shift of v max depends very strongly on the halide ion, and only incidentally on the lattice structure. This is consistent with the complex model.