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1.
I. N. Ogorodnikov V. A. Pustovarov M. Kirm V. S. Cheremnykh 《Optics and Spectroscopy》2004,97(2):244-250
A complex investigation of the dynamics of electronic excitations in nonlinear optical crystals of ammonium dihydrophosphate NH4H2PO4 was performed using low-temperature vacuum UV luminescence spectroscopy with time resolution upon selective photoexcitation by synchrotron radiation. Data on the photoluminescence decay kinetics, time-resolved photoluminescence spectra (2–6.2 eV), and time-resolved photoluminescence excitation spectra (4–24 eV) were obtained for the first time for NH4H2PO4 crystals at 8 K. It is ascertained that the photoluminescence of NH4H2PO4 crystals in the vicinity of 4.7 eV has intrinsic character due to the radiative annihilation of self-trapped excitons. Possible channels of generation and decay of relaxed and unrelaxed electronic excitations in NH4H2PO4 crystals are discussed. 相似文献
2.
K.?V.?IvanovskikhEmail author V.?A.?Pustovarov M.?Kirm B.?V.?Shul'gin 《Journal of Applied Spectroscopy》2005,72(4):564-568
The photoluminescence and photoexcitation spectra as well as the luminescence decay kinetics of Er3+ ions in the visible ultraviolet and vacuum ultraviolet (VUV) regions have been studied by the method of low-temperature,
time-resolved VUV-spectroscopy on excitation by synchrotron radiation. In the VUV spectral region of the luminescence of SrF2:1% Er3+, the 146.5-nm band with a time of decay of less than 0.6 nsec was revealed together with the well-known emission band at
164.3 nm (decay constant in the microsecond range). Its possible nature is discussed. The specific features of the formation
of photoexcitation spectra of the f-f and f-d transitions in the Er3+ ion are considered. Competition between the processes of excitation of f-f and d-f luminescence has been revealed. It manifests
itself in the inverse relationship of their photoexcitation spectra in a range of energies of incident photons that are close
to the position of the 4fn−15d configuration levels.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 519–523, July–August, 2005. 相似文献
3.
M. Kodu M. AintsT. Avarmaa V. DenksE. Feldbach R. JaanisoM. Kirm A. MaaroosJ. Raud 《Applied Surface Science》2011,257(12):5328-5331
Hydrogen doped MgO films were grown by pulsed laser deposition method. Gaseous hydrogen stored in cavities of milky MgO single crystal targets provided doping in film deposition process. Clear MgO targets without hydrogen were used in the preparation of reference films. The influence of hydrogen doping on firing voltage (FV) of gas discharge and its AC frequency dependence was investigated. According to thermoluminescence experiments, the films grown from milky targets contained two kinds of electron traps with the activation energies of 0.051 and 0.31 eV, while latter traps were absent in reference samples. The 0.31 eV trap was assigned to the hydride ion H− occupying an oxygen vacancy site in MgO crystal structure. Using standard gas mixture (Ne-10% Xe), FVs of hydrogen doped sample showed considerable frequency dependence and were up to 55 V lower in comparison to the reference sample. The FVs of reference sample were shifted 14-28 V to higher values when N2 gas was added to the mixture. The N2 addition lowered the FVs of hydrogen doped sample up to 38 V and almost eliminated the FV frequency dependence. 相似文献
4.
V. Nagirnyi S. Chernov L. Grigorjeva L. Jönsson M. Kirm A. Kotlov 《辐射效应与固体损伤》2013,168(6-12):1123-1126
A systematic spectroscopic study of single ZnWO 4 :Fe crystals with different iron concentrations has been performed under excitation by ultraviolet light, by synchrotron radiation or under photostimulation by near-infrared light. The luminescence of Fe 3+ -related centres has been studied. It is shown that iron centres of different types efficiently promote the formation of crystal defects at low temperatures. Electrons and holes can be trapped near Fe 2+ or Fe 3+ ions, which is further revealed in phosphorescence, thermostimulated or photostimulated luminescence. At room temperature the main effect of iron impurity is to reduce the light yield of a ZnWO 4 scintillator. 相似文献
5.
I. N. Ogorodnikov V. A. Pustovarov M. Kirm A. V. Kruzhalov L. I. Isaenko 《Optics and Spectroscopy》2002,92(5):702-709
For the first time, subnanosecond time resolution is attained in the low-temperature (at 7 K) measurements of the photoluminescence (PL) spectra (2–6 eV), the PL excitation spectra (4–32 eV), the PL kinetics, and the reflection spectra (4–21 eV) of undoped potassium pentaborate KB5O8·4H2O (KB5) crystals under selective photoexcitation by synchrotron radiation. The PL peaks associated with the intrinsic defects of the KB5 lattice are detected. The PL bands resulting from radiative annihilation of the localized and self-localized electron excitations are singled out; these excitations are most efficiently photogenerated at the fundamental absorption edge in the region where the free exciton formation is expected. The difference between the PL spectra of the fast and slow components is revealed. An effective low-temperature energy transport over the KB5 hydrogen sublattice is deduced from a drop in efficiency of PL excitation in the interband-transition region as a result of nonradiative energy loss. Long-term vacuum UV irradiation of a KB5 crystal at 7 K gives rise to defects in the hydrogen sublattice, which facilitate localization of the electron excitations and reduce the effective length of their diffusion. This leads to a decrease in the nonradiative energy loss, thus enhancing the efficiency of the PL photoexcitation in the band-to-band transition region. 相似文献
6.
S. Omelkov V. Pustovarov M. Kirm I. Ogorodnikov L. Isaenko 《Radiation measurements》2010,45(3-6):292-294
This paper reports the results of a time-resolved photoluminescence and energy transfer processes study in Ce3+ doped SrAlF5 single crystals. Several Ce3+ centers emitting near 4 eV due to 5d-4f transitions of Ce3+ ions substituting for Sr2+ in non-equivalent lattice sites were identified. The lifetime of these transitions is in the range of 25–35 ns under intra-center excitation in the energy region of 4–7 eV at T = 10 K. An effective energy transfer from lattice defects to dopant ions was revealed in the – 7–11 eV energy range. Both direct and indirect excitation channels are efficient at room temperature. Excitons bound to dopants are revealed at T = 10 K under excitation in the fundamental absorption region above 11 eV, as well as radiative decay of self-trapped excitons resulting in luminescence near 3 eV. 相似文献
7.
Tanner PA Ning L Makhov VN Khaidukov NM Kirm M 《The journal of physical chemistry. B》2006,110(24):12113-12118
Excitation of the 4f3 ion Nd3+ in hexafluoroelpasolite lattices by synchrotron radiation of wavelength approximately 185 nm leads to fast 4f(2)5d --> 4f3 emission below 52,630 cm(-1) and slower 4f3 --> 4f3 emission from the luminescent states (4)F(3/2) gamma8u (11 524 cm(-1)) and 2G2(9/2) gamma8u (approximately 47,500 cm(-1)). The near-infrared emission is well-resolved, and a clear interpretation of the 4I(9/2) crystal field levels and of the one-phonon vibronic sideband is given. The excitation spectrum of the 2G2(9/2) emission enables clarification of the structure of the 4f(2)5d configuration (which extends from approximately 52,000 to 128,000 cm(-1)). Detailed energy level and intensity calculations have been performed, which provide simulations of the d-f emission and the f-d excitation spectra in good agreement with experiment. It is interesting that although the 4f3 2G2(9/2) gamma8u --> 4f3 4I(J) transitions are very weak in intensity compared with transitions terminating upon higher multiplet terms, most of the 4f(2)5d (3H) 4I(9/2) gamma8g --> 4f3 emission intensity resides in the transitions to 4I(J). 相似文献
8.
9.
V. A. Pustovarov V. L. Petrov É. I. Zinin M. Kirm G. Tsimmerer B. V. Shul’gin 《Physics of the Solid State》2000,42(2):253-256
Electronic excitations and the processes of their radiative relaxation are studied in pure and Ce3+ ion-doped crystals of lanthanum beryllate excited by synchrotron radiation in the x-ray and VUV ranges by methods of optical and luminescent vacuum ultraviolet time-resolved spectroscopy. Manifestations of excitons of the valence band are absent in the reflection spectra. However, a fast (τ=1.7 ns) and a slow (microsecond range) channel corresponding to two possible types of self-trapped excitons (STE) are found in radiative relaxation of intrinsic electronic excitations at T=10 K. The slow channel corresponds to emission of STE formed through recombination, the fast channel corresponds to emission of relaxed metastable excitons from the STE state. In the energy region higher than 14 eV (E>2E g), the effect of multiplication of electronic excitations due to generation of secondary electron-hole pairs resulting from inelastic scattering of both hot photoelectrons and hot photoholes is exhibited. 相似文献
10.
Daniel Schiffbauer Claudia Wickleder Gerd Meyer Marco Kirm Michael Stephan Peter C. Schmidt 《无机化学与普通化学杂志》2005,631(15):3046-3052
The crystal structure, electronic states and VUV spectroscopic behaviour of Cs2KYF6 doped with Pr3+ ions have been investigated both by experimental and theoretical methods. Cs2KYF6 ( , Z = 4, a = 945.5(3) pm, R1all = 0.0297) crystallizes with the cubic elpasolite type of structure. The local relaxation of the activator ions in the host lattices has been calculated by the projector augmented wave method (computer code VASP). The electronic states have been calculated using a spin density functional procedure based on the atomic sphere approximation (computer code ASW). VUV spectroscopic measurements show fast 4f15d1 → 4f2 emission of nanosecond duration as well as slow 4f2 → 4f2 emission depending on the excitation energy which indicates the occupation of different sites in the host lattice. This assumption was verified by a recently developed quantum mechanical method. The combination of the experimental and the theoretical results show that the Pr3+ ions are occupying three different sites, namely the Y3+ and the Cs+ site as well as the K+ site. 相似文献