VUV optical parameters of LiF and color-center formation mechanisms

Aleksandrov, Yu.M.; Glagolev, K. V.; Makhov, V.N.; Mirov, Sergey; Syreishchikova, T. I.; Yakimenko, M.N.

doi:10.1007/bf00660256

Cited by 9 publications

(12 citation statements)

References 6 publications

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“…The fast (τ∼0.92 ns [5]) cross-luminescence (CL) is caused by the recombination of electrons in the valence band (VB) with holes in the Ba 5p outermost core band (symbols Fig. 2a), as was shown in [13]. The CL bands have the strongest intensity at wavelengths shorter than 250 nm that is mostly outside of transmission range of the used filter set.…”

Section: Resultsmentioning

confidence: 95%

Influence of excitation density on luminescence decay in Y ₃ Al ₅ O ₁₂ :Ce and BaF ₂ crystals excited by free electron laser radiation in VUV

Kirm

Andrejczuk

Krzywiński

et al. 2005

phys. stat. sol. (c)

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The influence of excitation density on luminescence decay in Y 3 Al 5 O 12 :Ce and BaF 2 crystals at room temperature was investigated for the first time using pulsed free electron laser radiation in vacuum ultraviolet. Increased excitation density led to the remarkable shortening of luminescence decays with nonexponential behaviour in both crystals. The possible reasons for dramatic changes in the dynamics of electronic excitations in insulators excited by free electron laser radiation will be discussed. IntroductionThe investigation of decay kinetics of luminescence is a very sensitive technique to learn about nature of electronic excitations in solids. Using weak and moderate excitation densities (ED) the processes due to elementary excitations can be monitored. Further increase of ED leads to their mutual interactions and other cooperative effects. In theVUV energy range such investigations of wide-gap solids have been carried mostly out using weak tuneable sources, such as pulsed discharge lamps and synchrotron radiation (SR). High-power, but non-selective excitation by "white" hard X-rays [1], by particles like ion beams [2,3], and by pulsed electrons [3,4] has been used for such purposes in the past. The XUV radiation from storage ring [5] and generated by a plasma laser [6] was applied as well. However, excitation provided by above-mentioned sources populates many of the available relaxation channels thereby enormously complicating the analysis of processes. In order to investigate the dynamics of relaxation processes in solids, a pulsed excitation with variable energy and intensity in a large dynamic range would be an ideal source. In the VUV range, only free electron laser (FEL) radiation is suitable for this purpose practically fulfilling these requirements. We reporting here the first results of the luminescence investigation of crystals excited by VUV radiation from the unique FEL source [7] that was constructed by an international consortium at the HASYLAB at DESY (Hamburg, Germany).

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Section: Resultsmentioning

confidence: 95%

Influence of excitation density on luminescence decay in Y ₃ Al ₅ O ₁₂ :Ce and BaF ₂ crystals excited by free electron laser radiation in VUV

Kirm

Andrejczuk

Krzywiński

et al. 2005

phys. stat. sol. (c)

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“…The structure of the excitation spectra for fast emissions is determined by the parameters of the medium valence subband. The minimum ionization energies for the outermost shell of cations equal 20.5 eV for 3pK + [12], 14 eV for 5pCs + [4] and 18 eV for 5pBa 2+ [3]. According to Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The IBL is a fast, continuous and temperature-independent emission in a wide region with a structureless spectrum. The crossluminescence is connected with the radiative transitions of the holes, formed by irradiation in a cation outermost-core band, to the upper anion valence band [3,4]. This emission is also known as Auger-free or core-valence luminescence.…”

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confidence: 99%

Fast intrinsic emission with the participation of oxyanion and cation excitations in metal sulphates

Savikhin

Kerikmäe

Feldbach

et al. 2005

phys. stat. sol. (c)

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Several bands of fast emission (τ < 2 ns) have been observed in the spectral region of 1.6-6.0 eV in K 2 SO 4 , Rb 2 SO 4 , Cs 2 SO 4 , CaSO 4 , SrSO 4 and BaSO 4 under irradiation by single electron pulses (300 keV, 3 ns, 80 A/cm 2 ) at 80 K. In K 2 SO 4 , Cs 2 SO 4 and BaSO 4 , the photoexcitation of fast emission starts at 14-15 eV. At a crystal heating the intensity of fast emission bands decreases, while the intensity of a structureless intraband luminescence increases (especially at hν > 6 eV). On the basis of our experimental data and band structure calculations, we interpret the observed fast emissions as elecron transitions between the subbands of a split valence band. There are manifestations of the cationic states, superimposed on the states from an oxygen-sulphur medium subband, in the excitation spectra of fast emissions.1 Introduction In addition to impurity luminescence and the luminescence of free or self-trapped excitons, data on two new types of intrinsic emission in several wide-gap crystals was accumulated in the last decades. These two emissions are the so-called intraband luminescence (IBL) and crossluminescence. The IBL arises under irradiation due to the transitions of hot electrons (electron IBL) and hot holes (hole IBL) between the levels of the conduction band or the valence band of a crystal, respectively [1, 2]. The IBL is a fast, continuous and temperature-independent emission in a wide region with a structureless spectrum. The crossluminescence is connected with the radiative transitions of the holes, formed by irradiation in a cation outermost-core band, to the upper anion valence band [3,4]. This emission is also known as Auger-free or core-valence luminescence. The present study is devoted to the fast emissions that can be detected in metal sulphates in addition to IBL and crossluminescence.Several bands of fast (τ < 2 ns) emission have been observed in K 2 SO 4 under irradiation by single nanosecond electron pulses [5]. The threshold exciting photon energy of 15 eV has been detected in the excitation spectra for the most intense emission bands at 5.8 and 3.8 eV. Taking into account the band structure calculations of K 2 SO 4 [6], these fast emissions have been ascribed to the electron transitions between subbands of a splitted valence band [5]. The investigation of the nature of fast emissions and the conditions of their excitation in various metal sulphates has much potential for yielding important information about the structure of a valence band. Therefore, our efforts are aimed at the search for fast emissions and the measuring of the excitation spectra for these emissions in Me 2 SO 4 (Me: Na, K, KLi, Rb, NH 4 ) and MeSO 4 (Me: Ca, Sr, Ba) systems.

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“…In accordance with simple model [1], CL in BaF 2 is due to radiative transitions of the holes from the uppermost core Ba 5p band into the valence F 2p band. It is observed after complete electronic and lattice relaxation occurring near the long-lived (τ ~ 10 -9 s) core hole.…”

Section: Introductionmentioning

confidence: 89%

A comparative study of photoemission and cross luminescence from BaF2

Makhov¹,

Terekhin²,

Kirm³

et al. 2005

Nuclear Instruments and Methods in Physics Research Section A:

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The photoelectron spectra of the well known fast scintillator material BaF 2 have been recorded and compared with luminescence spectra measured earlier. A comparison of cross luminescence and photoelectron spectra for BaF 2 has allowed to estimate the relaxation energy of the core (Ba 5p 3/2 ) hole during its radiative lifetime with respect to cross luminescence transition being equal to ~1.3 eV. The photoelectron spectra obtained at low temperature favors the model of the F 2p -Ba 5p 1/2 electron transition for the recently found emission band of BaF 2 at 7.6 eV.

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VUV optical parameters of LiF and color-center formation mechanisms

Cited by 9 publications

References 6 publications

Influence of excitation density on luminescence decay in Y ₃ Al ₅ O ₁₂ :Ce and BaF ₂ crystals excited by free electron laser radiation in VUV

Influence of excitation density on luminescence decay in Y ₃ Al ₅ O ₁₂ :Ce and BaF ₂ crystals excited by free electron laser radiation in VUV

Fast intrinsic emission with the participation of oxyanion and cation excitations in metal sulphates

A comparative study of photoemission and cross luminescence from BaF2

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VUV optical parameters of LiF and color-center formation mechanisms

Cited by 9 publications

References 6 publications

Influence of excitation density on luminescence decay in Y 3 Al 5 O 12 :Ce and BaF 2 crystals excited by free electron laser radiation in VUV

Influence of excitation density on luminescence decay in Y 3 Al 5 O 12 :Ce and BaF 2 crystals excited by free electron laser radiation in VUV

Fast intrinsic emission with the participation of oxyanion and cation excitations in metal sulphates

A comparative study of photoemission and cross luminescence from BaF2

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Influence of excitation density on luminescence decay in Y ₃ Al ₅ O ₁₂ :Ce and BaF ₂ crystals excited by free electron laser radiation in VUV

Influence of excitation density on luminescence decay in Y ₃ Al ₅ O ₁₂ :Ce and BaF ₂ crystals excited by free electron laser radiation in VUV