Hyperfine spectra of KBr and KI

The molecular beam electric resonance technique has been used to conduct a high precision examination of the hyperfine spectra of ³⁹K⁷⁹Br, ³⁹K⁸¹Br and ³⁹K¹²⁷I. Coupling constants for the nuclear electric quadrupole interactions, the spin–rotation interactions, the tensor and scalar spin–spin interactions, as well as the electric dipole moment of KI, and their dependence on vibrational and rotational state have been determined. A few transitions observed for ⁴¹K¹²⁷I show a small shift in the iodine nuclear electric quadrupole interaction, and the fit improves somewhat with the inclusion of an iodine nuclear electric hexadecapole interaction term.     

Absorption spectra and oscillator strength of KBr:Pb

Absorption measurements on hydroxide-free KBr crystals containing various amounts of Pb²⁺ were made. The spectra were corrected for scattering and reflection losses and the B-, C- and D-bands were deconvoluted as three Gaussian bands. Band maxima were found: A -band at 4.15 ± 0.05 eV, 5-band at 5.1 ± 0.1 eV, C-band at 5.52 ± 0.07 eV, D¹-band at 5.79 ± 0.05 eV. The oscillator strengths for the A -, B- and C-bands were 0.12 ± 0.01, 0.04 ± 0.01 and 0.77 ± 0.02, respectively. The ƒ-sum for the three bands is 0.93. The nearness of the ƒ-sum to unity indicates that very little interaction between the impurity s² electrons and the host and supports the usual assumption that these bands originate from the same ground state.     

Luminescence studies of thallium co-doped KBr:Eu2+ powder phosphors

In this study, photoluminescence (PL) and photostimulated luminescence (PSL) properties in KBr:Eu²⁺, Tl⁺ powder phosphors are reported. PL emission spectra of these Tl⁺ co-doped KBr:Eu²⁺ phosphors show four overlapping bands around 310, 325, 360 and 375 nm in addition to the characteristic of Eu²⁺ ions at 420 nm. These additional short wavelength bands were attributed to centres involving Tl⁺ ions. The decrease in PSL intensity of γ-irradiated KBr:Eu²⁺, Tl⁺ powder phosphors with Tl⁺ concentration and the absence of thallium emission bands in PSL were attributed to the efficient electron trapping by Tl⁺ ions during irradiation.     

Emission and decay time studies on Pb2+ centers in KBr,RbBr, and RbCl

The emission spectra and the luminescence decay times of KBr, RbBr, and RbCl crystals doped with Pb²⁺ and excited in the A-absorption band have been studied in the temperature range 5–300 K. The emission-lineshape spectra have been analysed in terms of skew-Gaussian bands. New bands have been observed in RbCl and RbBr at very low temperatures. While the luminescence decay of KBr:Pb²⁺ and RbBr:Pb²⁺ show only a single component with a decay time τ ～ 20 ns, RbCl:Pb²⁺ shows a short and a long component. The reason for the missing long component in KBr:Pb²⁺ and RbBr:Pb²⁺ is tentatively attributed to an anomaly in the structure of the adiabatic potential energy surface (APES) of the excited states.     

Emission spectra of excitons created in a single crystal of KBr by irradiation of heavy ions at 4.2 K

An intensity ratio of the σ- to π-emission higher than that in X-irradiation was observed for a heavy-ion irradiated single crystal of KBr at 4.2 K. The result was interpreted in terms of the interaction of free excitons at higher energy states.     

Luminescence spectra of lead-doped NaCl,KCl and KBr

The luminescence spectra of lead-doped NaCl, KCl and KBr have been systematically investigated. Special attention has been paid to the effects of concentration and thermal history of the crystals. In the three systems, the emission spectra for A and C band excitation consists mainly of two well-defined emission bands whose energy separation is ～0.7 eV. It has been concluded that none of the bands can be attributed to a single type of lead center but are both typical of Pb²⁺ luminescence. In fact, their behavior can be correlated with that found for most monovalent ions and interpreted in a similar way. The excitation spectra for the two emissions have shown that the A-band is complex. One of the components appearing in very low doped and quenched samples is ascribed to dipoles, whereas additional side bands are attributed to complexes or small aggregates involving Pb²⁺ ions.     

Influence of europium nanostructure size on the emission of KBr:Eu^{2 + }

The shape and size of nanostructures formed by the precipitation of europium ions in KBr single crystal has been analyzed using optical absorption (OA), luminescence (LM) and atomic force microscopy (AFM). This work reports a relationship between the emission band peak (EBP) and the nanostructure size. The shift of the t_2g absorption band towards longer wavelengths and a larger 10 Dq value reveals the growth of the nanostructures (NS). The AFM images show that the precipitates have circular shape and ～ 20 to 400 nm diameter according to the position of EBP at around 428–433 nm. The AFM technique allowed us to relate the shape and size of the nanostructures with our previous research by OA and LM. To our knowledge, the topography of europium ions forming NS of different diameter is observed for first time.     

Low-temperature photoluminescence of ion-implanted SiO2:Sn+ films and glasses

Low-temperature photoluminescence spectroscopy with pulsed synchrotron excitation is applied to study the regularities of excitation and relaxation of both point defects and nanoparticles formed by tin implantation into SiO₂ films and glasses. It has been found that tin implantation followed by air and nitrogen annealing yields the formation of α-Sn nanoclusters and nonstoichiometric SnO _x nanoparticles, while a stable phase of SnO₂ does not appear. Alternative channels of luminescence excitation are revealed for nanoclusters, including energy transfer from excitons and electron-hole pairs of the host SiO₂ matrix.     

KMgF3:Eu2+晶体中Eu2+的受激发射研究

二价铕离子(Eu2 )在KMgF3晶体中产生窄带线状发射,峰值位于360 nm.依据自身建立的激发态能量损耗模型,预测了4f7(6P7/2)→4f7(8S7/2)跃迁实现受激发射的可能性.采用ASE技术测得了KMgF3:Eu2 晶体360 nm发射的光学增益,得到净光学增益系数g=(11.4±3.2)cm-1,实验证实了理论预测.晶体退火或掺杂敏化离子Gd3 或Ce3 可以改善Eu2 的增益效果.     

Radiation induced defects in KBr:Tl+ crystals

The defects produced in KBr:Tl⁺ crystals during x-irradiation at 77 K were studied using thermoluminescence (TL), thermally stimulated currents (TSC), and absorption and emission spectra. Three main glow peaks at 165, 193 and 258 K were observed both in the TL and in the TSC curves. A variety of irradiation induced absorption bands were observed in the UV, visible and infrared up to about 2 microns. The 165 K TL peak was found to emit only the 440 nm band assigned to thallium dimers, while the peaks at 193 and 258 K exhibited the UV bands at 310 and 365 nm as well as the 440 nm band.The defects produced during the irradiation were the V_k hole center, the Tl° and the Tl⁺₂ electron centers. Smaller concentrations of Tl²⁺ and (Tl⁺)⁺₂ centers were also produced.An analysis of the results including measurements on lightly and heavily doped crystals enabled to draw conclusions on the nature of the defects and on the recombination processes involved. A close correlation has been found between the temperatures at which changes in the various absorption bands take place and the temperatures of the TL peaks. The analysis enabled also a full classification of the absorption bands.     

Emission spectra and cross-section spectra of neodymium laser glasses

Amplified spontaneous emission spectra and light amplification spectra of some Nd³⁺:glass rods (silicate glass Schott LG680, phosphate glasses Schott LG760 and Hoya LHG5) are measured by pulsed flashlamp excitation. The spontaneous emission distribution, the stimulated emission cross-section spectra and the excited state absorption cross-section spectra are extracted. Excited state absorption prevents laser action around 1320 nm for the⁴F_3/2-⁴L_13/2 transition of Nd³⁺ in the investigated glasses.     

Radiative energy transfer from Pb2+ to Eu2+ ions in NaCl,Kcl, and KBr single crystals

In the present work, the emission and excitation spectra of NaCl, KCl, and KBr doubly doped with europium and lead ions were investigated. In all cases, excitation with light lying in the A-band of the Pb²⁺ ions produces in addition to the ³P₁ → ³S_o Pb²⁺ emission, the 4f⁶ 5d (^t2g) → 4f⁷ europium emission. This fact indicates that energy transfer occurs from Pb²⁺ to Eu²⁺ ions. From the data obtained, it was determined that the energy transfer process is of a radiative nature and that it is more efficient in KCl than in either of NaCl or KBr. A possible explanation for this fact is given.     

Electronic and vibrational spectra of MnO2−4 in KBr crystals

Two new features have been observed in the electronic spectrum of KBr crystals doped heavily with MnO^2?₄ ions. The band at 870 nm is assigned to the crystal field transition e → t₂. The band at 600 nm shows a series of vibrational sub-bands at an interval of 740cm^?1 and is ascribed to the coupling between electronic transition and totally symmetric mode of the ion.A line at 830cm^?1, ascribed to totally symmetric mode v₁(A₁), has been observed for the first time in the Raman spectrum. I.R. spectrum of KBr: MnO^2?₄ shows four lines—one due to MnO^2?₄ in Td symmetry and the other three to the split components of v₃(T₂) for MnO^2?₄ in Cs symmetry. I.R. spectrum of KBr: MnO^2?₄: Ca²⁺ shows another s of four lines—one due to MnO^2?₄ in Td symmetry and the other three to the v₃(T₂) mode of the ion in C_2v symmetry. The v₁(A₁) line could not be observed in the i.r. spectra.