Spectroscopic study of red-light-emitting centers in K2Al 2B2O7: Fe single crystals

We report on spectroscopic study of red-light-emitting centers in K 2Al2B2O7 (KABO) single crystals containing ca. 2 ppm of Fe3+. Owing to the low Fe3+- concentration, KABO does not show noticeable absorption due to Fe3+ d-d-transitions in the visible spectral region, but it exhibits the charge-transfer (CT) UV-absorption bands O-Fe at 4.7, 5.7 and 6.5 eV. The red photoluminescence at 1.675 eV (FWHM = 0.173 eV) is due to intracenter 4T1 (4G) → 6A1 (6S) transitions in Fe3+ ions. Because of partial overlapping of the fundamental absorption edge of the crystal, where mobile excitons are created, and a broad CT absorption band at 6.5 eV, the most intensive red emission occurs at 7 K upon excitation in the excitonic energy region. The presence of two nonequivalent Al2O7 clusters in KABO lattice provides two different types of red-light-emitting centers in the form of Fe3+ ion occupied the Al3+ tetrahedral site. Superposition of their luminescence bands determines both the spectrum and temperature dependence of red emission in KABO at T = 7-80 K: two bands with the ratio of intensities of ca. 2:1 are 20 meV-shifted relative to each other; two-stage thermal quenching obeys the Mott law with ET = 9 and 20 meV. © 2013 Elsevier B.V. All rights reserved

Optical and photoelectron spectroscopy studies of KPb2Cl 5 and RbPb2Cl5 laser crystals

The paper presents the results of experimental study of electronic structure of RbPb2Cl5 and KPb2Cl5 laser crystals performed by the optical and photoelectron spectroscopy methods. On the basis of the optical absorption and low-temperature reflection spectra of these crystals we have determined the energy positions of the edges of the low-energy tail of the host absorption, the positions of the first excitonic absorption peaks, and exciton binding energies. The bandgap widths of these crystals at 8 K were estimated as Eg = 4.83 and 4.79 eV, respectively. Qualitative and quantitative analysis of RbPb2Cl 5 and KPb2Cl5 crystals were made on the basis of the core states photoelectron spectra. The elemental composition of the (0 0 1) surfaces of the crystals, the chemical state of the host atoms, the electronic structure of the valence band of the crystals were discussed on the basis on the spectroscopic data. © 2012 Elsevier B.V. All rights reserved

Radiation-stimulated processes in SrMgF4 single crystals irradiated with fast electrons

Large single crystals of SrMgF4 (SMF), grown by the Bridgman method, were studied (T = 7–350 K, E = 1.2–6.2 eV) for both the pristine unirradiated and irradiated by an electron-beam (Ee = 10 MeV, D = 100–160 kGy, Φmax = 5 × 1015 electrons/cm2) SMF-crystals. The optical absorption spectra at different radiation doses were determined. The luminescence spectra were studied upon excitation with visible/ultraviolet light (PL), or X-ray radiation (XRL). The PL excitation (PLE) spectra under UV-radiation, the temperature dependence curves for the luminescence intensity of steady-state XRL and PL recorded monitoring emission at different energies, as well as low-temperature thermoluminescence were studied. The paper discusses the effect of electron-beam irradiation on the optical and luminescence properties of SMF crystals, the temperature dependence of the luminescence intensity and low-temperature thermoluminescence of irradiated SMF crystals. © 2021 Elsevier B.V.Nuclear Physics, NPSiberian Branch, Russian Academy of Sciences, SB RAS, (RFMEFI62119X0022)Ministry of Education and Science of the Russian Federation, Minobrnauka, (FEUZ-2020-0060)Ministry of Education and Science of the Republic of Kazakhstan, (AP08855672)Ural Federal University, UrFUFunding text 1: The work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (through the basic part of the government mandate, project № FEUZ-2020-0060 ), the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant № AP08855672 ). All the crystals examined were grown in framework of the state assignment of IGM SB RAS. The X-ray excited measurements were performed at the shared research center SSTRC based on the VEPP-4—VEPP-2000 complex at Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences (Novosibirsk, Russia) using equipment supported by project RFMEFI62119X0022 . The authors are grateful to A.Yu. Sofronova and M.N. Sarychev (UrFU) for assistance with low-temperature measurements.Funding text 2: The work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (through the basic part of the government mandate, project № FEUZ-2020-0060), the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant № AP08855672). All the crystals examined were grown in framework of the state assignment of IGM SB RAS. The X-ray excited measurements were performed at the shared research center SSTRC based on the VEPP-4—VEPP-2000 complex at Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences (Novosibirsk, Russia) using equipment supported by project RFMEFI62119X0022. The authors are grateful to A.Yu. Sofronova and M.N. Sarychev (UrFU) for assistance with low-temperature measurements

Optical pump-probe processes in Nd 3+ doped KPb2Br5, RbPb2Br5, and KPb2CI5

Recently, laser activity has been achieved in the low phonon energy, moisture-resistant bromide host crystals, neodymium-doped potassium lead bromide (Nd{sup 3+}:KPb{sub 2}Br{sub 5}) and rubidium lead bromide (Nd{sup 3+}:RbPb{sub 2}Br{sub 5}). Laser activity at 1.07 {micro}m was observed for both crystalline materials. Laser operation at the new wavelengths 1.18 {micro}m and 0.97 {micro}m resulting from the {sup 4}F{sub 5/2}+{sup 2}H{sub 9/2} {yields} {sup 4}I{sub J} transitions (J=13/2 and 11/2) in Nd:RPB was achieved for the first time in a solid state laser material. In this paper we present cw pump-probe spectra in order to discuss excited state absorption, reabsorption processes due to the long lived lower laser levels as well as possible depopulation mechanisms feasible for more efficient laser operation in these crystals. The bromides will be compared with potassium lead chloride (Nd{sup 3+}:KPb{sub 2}Cl{sub 5})

Time-Resolved Luminescence Spectroscopy of Pure and Doped with Ce3+ ions SrAlF5 Crystals

The results of a study of time-resolved photoluminescence (PL) and energy transfer in both pure and doped with Ce3+ ions SrAlF5 (SAF) single crystals are presented. The time-resolved and steady-state PL spectra in the energy range of 1.5-6.0 eV, the PL excitation spectra and the reflectivity in the energy range of 3.7-21 eV, as well as the PL decay kinetics were measured at 8.8 and 295 K. The lattice defects were revealed in the low temperature PL spectra (emission bands at 2.9 and 4.5 eV) in the undoped SAF crystals. The luminescence spectra of the doped Ce3+:SAF crystals demonstrate a new selective emission bands in the range of 3.7-4.5 eV with the exponential decay kinetics (τ ≈ 60 ns at X-ray excitation). These bands correspond to the d-f transitions in Ce3+ ions, which occupy nonequivalent sites in the crystal lattice. © 2010 Pleiades Publishing, Ltd.This work was supported by the RFBR (grants Nos. 07-02-00442; 07-02-12015; 09-02-00493)