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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.
I. N. Ogorodnikov V. A. Pustovarov S. A. Yakovlev L. I. Isaenko S. A. Zhurkov 《Physics of the Solid State》2012,54(1):111-116
This paper reports on the results of the comprehensive study of the dynamics of electronic excitations in K2Al2B2O7 (KABO) crystals, obtained by low-temperature luminescence vacuum ultraviolet spectroscopy with nanosecond time resolution
upon photoexcitation by synchrotron radiation. For the first time, the data have been obtained on the photoluminescence (PL)
decay kinetics, PL spectra with time resolution, PL excitation spectra with time resolution, and reflection spectra at 7 K;
the intrinsic nature of PL at 3.28 eV has been established; luminescence bands of defects have been separated in the visible
and ultraviolet spectral regions; an intense long-wavelength PL band has been detected at 1.72 eV; channels of the formation
and decay of electronic excitations in K2Al2B2O7 crystals have been discussed. 相似文献
3.
P. A. Rodnyĭ I. V. Berezovskaya A. S. Voloshinovskii G. B. Stryganyuk A. S. Potapov 《Optics and Spectroscopy》2003,94(4):550-555
Spectral and kinetic characteristics of the luminescence and luminescence excitation spectra of polycrystalline SrB4O7:Pr (1%) and SrB6O10:Pr (1%) samples are studied at 150–170 K. The samples show an intense luminescence band in the vicinity of 405 nm (1 S 0→1 I 6 transitions of Pr3+) and shorter wavelength bands also assigned to transitions from the 1 S 0 level. The main luminescence decay constant is ~2×10?7 s. The excitation spectra of the 1 S 0 luminescence in these crystals are significantly different. The SrB4O7:Pr crystal shows three well-resolved bands at 6.14, 6.55, and 6.91 eV in the region of the 4f 2→4f 15d transitions and a complex structure in the region of interband transitions (7.1–20 eV), whereas the SrB6O10:Pr crystal shows a weakly structured band at 6.31 eV and no excitation in the region of the interband transitions. The physical mechanisms that may be responsible for the observed features of the spectra are discussed. 相似文献
4.
I. N. Ogorodnikov M. Kirm V. A. Pustovarov V. S. Cheremnykh 《Optics and Spectroscopy》2003,95(3):385-389
A complex investigation of the dynamics of electronic excitations in potassium dihydrophosphate (KDP) crystals is performed by low-temperature time-resolved vacuum ultraviolet optical luminescence spectroscopy with subnanosecond time resolution and with selective photoexcitation by synchrotron radiation. For KDP crystals, data on the kinetics of the photoluminescence (PL) decay, time-resolved PL spectra (2–6.2 eV), and time-resolved excitation PL spectra (4–24 eV) at 10 K were obtained for the first time. The intrinsic character of the PL of KDP in the vicinity of 5.2 eV, which is caused by the radiative annihilation of self-trapped excitons (STEs), is ascertained; σ and π bands in the luminescence spectra of the STEs, which are due to singlet and triplet radiative transitions, are resolved; and the shift of the σ band with respect to the π band in the spectra of the STEs is explained. 相似文献
5.
I. N. Ogorodnikov V. A. Pustovarov S. A. Yakovlev L. I. Isaenko S. A. Zhurkov 《Physics of the Solid State》2012,54(4):735-740
This paper reports on a study of the dynamics of electronic excitations in KBe2BO3F2 (KBBF) crystals by low-temperature luminescent vacuum ultraviolet spectroscopy with nanosecond time resolution under photoexcitation
by synchrotron radiation. The first data have been obtained on the kinetics of photoluminescence (PL) decay, time-resolved
PL spectra, time-resolved PL excitation spectra, and reflection spectra at 7 K; the estimation has been performed for the
band gap E
g = 10.6−11.0 eV; the predominantly excitonic mechanism for PL excitation at 3.88 eV has been identified; and defect luminescence
bands at 3.03 and 4.30 eV have been revealed. The channels of generation and decay of electronic excitations in KBBF crystals
have been discussed. 相似文献
6.
S. V. Gorbunov A. F. Zatsepin V. A. Pustovarov S. O. Cholakh V. Yu. Yakovlev 《Physics of the Solid State》2005,47(4):733-737
A time-resolved cathodo-and photoluminescence study of nanostructural modifications of Al2O3 (powders and ceramics) excited by heavy-current electron beams, as well as by pulsed synchrotron radiation, is reported. It was found that Al2O3 nanopowders probed before and after Fe+ ion irradiation have the same phase composition (the γ-phase/δ-phase ratio is equal to 1), an average grain size equal to ~17 nm, and practically the same set of broad cathodoluminescence (CL) bands peaking at 2.4, 3.2, and 3.8 eV. It was established that Al2O3 nanopowders exhibit fast photoluminescence (PL) (a band at 3.2 eV), whose decay kinetics is described by two exponential stages (τ1 = 0.5 ns, τ2 = 5.5 ns). Three bands, at 5.24, 6.13, and 7.44 eV, were isolated in the excitation spectrum of the fast PL. Two alternate models of PL centers were considered, according to which the 3.2-eV luminescence either originates from radiative relaxation of the P? centers (anion-cation vacancy pairs) or is due to the formation of surface analogs of the F+ center (F S + -type centers). In addition to the fast luminescence, nano-Al2O3 was found to produce slow luminescence in the form of a broad band peaking at 3.5 eV. The excitation spectrum of the 3.5-eV luminescence obtained at T = 13 K exhibits two doublet bands with maxima at 7.8 and 8.3 eV. An analysis of the luminescent properties of nanostructural and single-crystal Al2O3 suggests that the slow luminescence of nanopowders at 3.5 eV is due to radiative annihilation of excitons localized near structural defects. 相似文献
7.
M. Niemietz M. Engelke Y.D. Kim G. Ganteför 《Applied Physics A: Materials Science & Processing》2007,87(4):615-619
We present time-resolved photoelectron spectra of mass-selected Ag2O2 anions. The anions are photoexcited by photons with an energy of 3.1 eV, and photoelectron spectra of the excited species
Ag2O2
-
* and the subsequently appearing fragments are recorded using a probe laser pulse with a photon energy of 1.5 eV. The excited
state of Ag2O2
- has a short lifetime of 130 fs±70 fs only and decays by direct photodesorption of O2. The data demonstrate the ability of time-resolved photoelectron spectroscopy (TR-PES) to observe the breaking of chemical
bonds if the decay process of the excited state is direct (non-thermal desorption). The data are compared to recent results
of a NeNePo experiment [1] on the same system.
PACS 68.43.Tj; 78.47.+p; 33.80.Eh; 36.40.-c 相似文献
8.
G. M. Shapochkin V. V. Mikhailin S. P. Chernov D. N. Karimov 《Moscow University Physics Bulletin》2009,64(2):141-145
The short-wave transmission spectrum of Na0.4Lu0.6F2.2 with the visible/ultraviolet transmission edge of 8 eV was studied. Absorption spectra of the 4f—5d transitions of the Ce3+ ion in the region of 4–8 eV were studied in Ce3+-doped Na0.4Lu0.6F2.2 single crystals. Luminescence spectra in the ultraviolet and visible spectral regions, luminescence decay kinetics and reflection and luminescence excitation spectra in the visible/ultraviolet and ultraviolet regions (4–20 eV) were investigated at helium and room temperatures. 相似文献
9.
V. A. Pustovarov V. Sh. Aliev T. V. Perevalov V. A. Gritsenko A. P. Eliseev 《Journal of Experimental and Theoretical Physics》2010,111(6):989-995
The electronic structure of an oxygen vacancy in α-Al2O3 and γ-Al2O3 is calculated. The calculation predicts an absorption peak at an energy of 6.4 and 6.3 eV in α-Al2O3 and γ-Al2O3, respectively. The luminescence and luminescence excitation spectra of amorphous Al2O3 are measured using synchrotron radiation. The presence of a luminescence band at 2.9 eV and a peak at 6.2 eV in the luminescence
excitation spectrum indicates the presence of oxygen vacancies in amorphous Al2O3. 相似文献
10.
It is discovered that the electron paramagnetic resonance (EPR) spectrum of the doubly charged copper centers occurs in single crystals of Pb5Ge3O11 doped with gadolinium or iron after annealing in an atmosphere containing chlorine and bromine. Similar annealing of the crystals doped with copper in a chlorine and fluorine atmosphere leads to redistribution of the intensities of the EPR spectra of two types of Cu2+ centers. The influence of annealing on the ongoing intensity of spectra of the dimeric triclinic centers Fe3+–A, Gd3+–A (where A represent Cl?, Br?, O2?, F?) was the subject of this research. Consideration is given to the mechanisms for changing the charge state and association of copper center with defects. 相似文献
11.
A. A. Smirnov I. N. Ogorodnikov V. A. Pustovarov L. I. Isaenko V. Yu. Yakovlev 《Optics and Spectroscopy》2008,105(3):377-379
The efficiency of formation and time evolution of radiation-induced structural defects and pulsed luminescence in KPb2Cl5 crystals under the action of a single electron pulse (E = 250 keV, τ = 20 ns) have been investigated. The spectra (1.1–3.8 eV) and relaxation kinetics (time interval 5 × 10?8?5 s) of transient optical absorption and the pulsed cathodoluminescence spectra and decay kinetics (1.4–3.1 eV) have been measured in the temperature range 80–300 K. It is revealed that the induced optical density and its time evolution depend strongly on temperature, and the absorption relaxation time contains several components and reaches several seconds at T = 300 K. The decay kinetics of transient absorption and pulsed cathodoluminescence kinetics have different orders and are controlled by different relaxation processes. 相似文献
12.
K.?Koyasu M.?Niemietz W.?Westh?user G.?Gantef?r 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):59-62
The decay path of an Ag8(O2)- cluster photoexcited by a 3.1 eV photon is elucidated using time-resolved photoelectron spectroscopy. Photoabsorption results
in the formation of an excited state giving rise to a peak in the photoelectron spectra with well-resolved vibrational finestructure.
With a lifetime of about 100 fs this bound state decays into an anti-bonding state which dissociates into O2 and Ag8- on a timescale of 10 ps. In the photoelectron spectra, this corresponds to a broad maximum shifting gradually towards higher
binding energy while the O2 and Ag8- separate. Finally, the spectrum of bare Ag8- appears. This process is unique to small clusters, because on metal surfaces excited state lifetimes are too short to allow
for direct dissociation. 相似文献
13.
V. N. Kolobanov V. V. Mikhailin N. N. Petrovnin D. A. Spasskii Yu. V. Zorenko 《Moscow University Physics Bulletin》2007,62(1):34-36
The luminescence spectra of single-crystal films and bulk crystals of yttrium-aluminum garnet Y3Al5O12 and Ce3+-activated Y3Al5O12 were investigated. It was shown that the room-temperature luminescence intensity of the Ce3+-free single-crystal Y3Al5O12 film was considerably lower than that of the bulk crystals, while the luminescence intensity of the Ce3+ ions in the Y3Al5O12:Ce films was considerably higher than that one for the corresponding bulk crystal. 相似文献
14.
A. A. Makhnev A. V. Lukoyanov L. V. Nomerovannaya A. A. Shirokov S. N. Barilo G. L. Bychkov S. V. Shiryaev 《Journal of Experimental and Theoretical Physics》2018,126(6):779-783
The anisotropy of the components of the complex permittivity of vanadate Co3V2O8 and Co3V2O8 single crystals in the paramagnetic phase are studied by optical ellipsometry in the spectral region 0.5–5.0 eV. Our experimental results support the weak anisotropy of the optical response detected earlier for axes a and c. The optical properties are also investigated along axis b. The properties of both compounds are compared. The optical spectra of both compounds along axis b are shifted toward low energies as compared to axes a and c. The maximum of the main interband absorption band of Co3V2O8 is shifted toward low energies by 0.25–0.3 eV as compared to Co3V2O8. The electronic structure parameters of both compounds are determined. Optical function spectra are analyzed using the results of ab initio band calculations. 相似文献
15.
A. G. Burachenko D. V. Beloplotov I. A. Prudaev D. A. Sorokin V. F. Tarasenko O. P. Tolbanov 《Optics and Spectroscopy》2017,123(6):867-870
The spectra and amplitude–time characteristics of the radiation of studied Sn and Fe-doped Ga2O3 crystals excited with a runaway electron beam and an excilamp with a wavelength of 222 nm were investigated. The main contribution to the luminescence of samples in the region of 280–900 nm under excitation with a beam was shown to be made by cathodoluminescence. In the Fe-doped crystal, a new cathodeand photoluminescence band was detected within a wavelength range of 650–850 nm. In the Sn-doped crystal, Vavilov–Cherenkov radiation was detected in the region of 280–300 nm using a monochromator and a photomultiplier. 相似文献
16.
The optical absorption and luminescence properties of potassium-holmium and potassium-erbium double tungstates have been studied. It is established that the potassium-holmium double tungstate belongs to a group of biaxial and pleochromic crystals. The emission and excitation spectra of the KHo(WO4)2 and KEr(WO4)2 single crystals were measured at room temperature.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, pp. 810–814, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date. 相似文献
17.
Zhaoxia Bi Rong Zhang Weiping Li Xusheng Wang Shulin Gu Bo Shen Yi Shi Zhiguo Liu Youdou Zheng 《中国科学G辑(英文版)》2003,46(1):41-46
With the solid phase reaction between pulsed-laser-deposited (PLD) ZnO film and α-Al2O3 substrate, ZnAl2O4/α-Al2O3 complex substrates were synthesized. X-ray diffraction (XRD) spectra show that as the reaction proceeds, ZnAl2O4 changes from the initial (111)-oriented single crystal to poly-crystal, and then to inadequate (111) orientation. Corresponding
scanning electron microscope (SEM) images indicate that the surface morphology of ZnAl2O4 transforms from uniform islands to stick structures, and then to bulgy-line structures. In addition, XRD spectra present
that ZnAl2O4 prepared at low temperature is unstable at the environment of higher temperature. On the as-obtained ZnAl2O4/α-Al2O3 substrates, GaN films were grown without any nitride buffer using light-radiation heating low-pressure MOCVD (LRH-LP-MOCVD).
XRD spectra indicate that GaN film on this kind of complex substrate changes fromc-axis single crystal to poly-crystal as ZnAl2O4 layer is thickened. For the single crystal GaN, its full width at half maximum (FWHM) of X-ray rocking curve is 0.4°. Results
indicate that islands on thin ZnAl2O4 layer can promote nucleation at initial stage of GaN growth, which leads to the (0001)-oriented GaN film. 相似文献
18.
Na0.4Y0.6F2.2:Er3+ (NYF:Er) crystals with an erbium concentration as high as 100 at. % (Na0.4Er0.6F2.2) were grown by the Bridgman-Stockbarger method. The optical spectra were investigated at low (6 K) and room temperatures. It is shown that the absorption spectrum of NYF:Er crystals contains wide bands (790–801 and 965–980 nm) corresponding to the emission range of laser diodes. The peak absorption cross section σa for the band peaked at λ=970.4 nm is 0.15×10?20 cm2. On the basis of the analysis of the absorption and luminescence spectra at low (6 and 12 K) temperatures, the structure of the Stark splitting of erbium levels was determined as a structure of quasi-centers for which Stark components are inhomogeneously broadened. The oscillator strengths of the transitions from the ground state of erbium to excited multiplets were calculated from the absorption spectra measured at T=300 K, and the intensity parameters Ωt were determined by the Judd-Ofelt method: Ω2=1.65×10?20 cm2, Ω4=0.56× 10?20 cm2, and Ω6=1.01×10?20 cm2. These values of the intensity parameters were used to calculate the probabilities of radiative transitions and the branching ratios. The rates of multiphonon nonradiative transitions in NYF: Er were estimated. The luminescence decay kinetics for radiative levels of erbium ions upon their selective excitation by nanosecond laser pulses was studied. The intracenter lifetimes of radiative levels of erbium ions were determined from the luminescence kinetics upon selective ion excitation by low-intensity light in a sample with a low erbium concentration (0.5%). It is demonstrated that, with an increase in temperature from 6 to 300 K, luminescence from the 4 G 11/2, 2 G(H)9/2, and 4 F 9/2 levels is quenched as a result of multiphonon nonradiative transitions. Luminescence from the 4 I 9/2 level is quenched only insignificantly with increasing temperature, and no quenching of luminescence from the 4 I 11/2 and 4 I 13/2 levels is observed. The spectra of steady-state luminescence of NYF:Er(0.5–15%) crystals were investigated upon broadband excitation by UV and UV-visible lamp light and selective time-resolved laser excitation. It is shown that low-lying levels of erbium ions separated by an energy gap smaller than 2500 cm?1 are populated via cascade mechanisms. On the basis of the results obtained, it is concluded that NYF:Er 3+ crystals are promising candidates for active media of tunable diode-pumped lasers. 相似文献
19.
This paper reports on a study of the kinetics of electron tunneling transport between electron and hole centers in Li2B4O7 and LiB3O5 lithium borate crystals under the conditions where the mobility of one of the partners in the recombination process is thermally
stimulated. A mathematical model has been proposed to describe all specific features in the relaxation kinetics of the induced
optical density observed in Li2B4O7 (LTB) and LiB3O5 (LBO) nonlinear optical crystals within a broad time interval of 10−8−1 s after a radiation pulse. The results of calculations have been compared with experimental data on transient optical absorption
(TOA) of LTB and LBO crystals in the visible and ultraviolet spectral regions. The nature of the radiation defects responsible
for TOA and the dependence of the TOA decay kinetics on temperature, excitation power, and other experimental conditions have
been discussed. 相似文献
20.
Yu. V. Zorenko V. P. Savchin V. I. Gorbenko T. I. Voznyak T. E. Zorenko V. M. Puzikov A. Ya. Dan’ko S. V. Nizhankovskii 《Physics of the Solid State》2011,53(8):1620-1625
Luminescence and scintillation properties of Y3Al5O12:Ce single crystals grown from the melt by the Czochralski and horizontal directed crystallization methods in various gas
media and Y3Al5O12:Ce single-crystal films grown by liquid-phase epitaxy from a melt solution based on a PbO-B2O3 flux have been comparatively analyzed. The strong dependence of scintillation properties of Y3Al5O12:Ce single crystals on their growth conditions and concentrations of YAl antisite defects and vacancy defects has been established. Vacancy defects are involved in Ce3+ ion emission excitation as the centers of intrinsic UV luminescence and trapping centers. It has been shown that Y3Al5O12:Ce single-crystal films are characterized by faster scintillation decay kinetics than single crystals and a lower content
of slow components in Ce3+ ion luminescence decay during high-energy excitation due to the absence of YAl antisite defects in them and low concentration of vacancy defects. At the same time, the light yield of Y3Al5O12:Ce single-crystal films is comparable to that of single crystals grown by directed crystallization due to the quenching effect
of the Pb2+ ion impurity as a flux component and is slightly lower (∼25%) than the light yield of single crystals grown by the Czochralski
method. 相似文献