首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The magnetic susceptibility of the garnet-type single crystal Tm3Al5O12 exhibits the typical Van Vleck temperature independent paramagnetism below ≈8 K. The temperature dependence of the susceptibility over the range 2.0-300 K has been analyzed on the assumption that the cubic crystal-electric-field dominates the energy level on 3H6 (J=6) ground multiplet for Tm3+ ion having 12-electrons in 4f shell. The ground state of the 3H6 is nonmagnetic with Γ2 singlet, avoiding the Kramers doublet. The energy separation between Γ2 and the first excited state Γ(2)5 triplet is evaluated to be 68.0 K. The whole energy interval Δ between Γ2 and the highest state Γ1 in 3H6 is estimated to be 339.5 K.  相似文献   

2.
Dy3+: Ca3(BO3)2 crystal was grown successfully by the Czochraski technique. The absorption spectrum was measured and its absorption peaks were assigned. The Judd-Ofelt intensity parameters were found to be Ω2=5.216×10−20, Ω4=1.858×10−20, Ω6=0.623×10−20 cm2. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetime as well as the branching ratios were calculated. Also, room temperature luminescence decay curve in correspondence with the emission line 4F9/26H13/2 centered at 575 nm was measured.  相似文献   

3.
The photoconductivity spectrum of a AgInS2 single crystal grown both by chemical transport and by the Bridgman method has been studied at 300 K. Splitting of the valance band was clearly observed in both the chaleopyrite and pseudo-wurtzite structures. The observed splitting is in reasonable agreement with the values reported by the electroreflection technique.  相似文献   

4.
Good quality crystals ZnWO4 activated with Er3+ have been grown by means of Czochralski method and characterized using optical spectroscopy techniques. XRD, absorption spectra, fluorescence spectrum are presented and the Judd-Ofelt intensity parameters Ω2, Ω4, and Ω6 are obtained to be 6.76×10-20, 0.37×10-20, and 0.50×10-20 cm2, respectively. Along crystallographic axes, refractive indices are presented. The fluorescence decay time of the 4I13/2 level has also been investigated and shows an exponential behavior with a lifetime value of 5.52 ms. The crystal is potentially used for green and infrared eye-safe lasers.  相似文献   

5.
Impurity photoconductivity spectra in the range 0.5–1.5 eV are studied in epitaxial layers of n-GaAs grown on substrates of semiconductive GaAs withρ > 106 Ω·cm in the system Ga-AsCl3 -H2. The effect of uncontrolled acceptor impurities on the impurity photoconductivity spectrum is evaluated.  相似文献   

6.
In this paper, results of photoconductivity measurements on four EuO samples are given. Low frequency photoconductivity versus temperature (10°K < T < 300°K) and magnetic field H is investigated for two wavelengths: 6600 Å and 9000 Å. The photoconductivity kinetic is also described, and is characterized by a distribution in decay times. Temperature, magnetic field and carrier concentration have small effects on this kinetic. Quenching effect is obtained by adding a continuous illumination (λ2) to the weak modulated light (λ1). The kinetic is strongly affected by quenching and becomes more simple. Quenching effect is maximum for the wavelength associated to the 4?7–4?6 5d, transition. In contrast to the Penney-Kasuya[1] model we propose another one in which the conduction of equilibrium carriers as photo-excited carriers takes place in a broad band. The variation of low frequency photoconductivity versus temperature is attributed to the mobility variation. This variation agrees well with the model of mobility controlled by spin-disorder. The photoconductivity kinetic is interpreted by a three levels recombination model: the conduction band, the 4f levels and a distribution of trap levels. The lack of variation of photoconductivity decay in the range of metal-semiconductor transition is discussed.  相似文献   

7.
Er3+:Li3Ba2Gd3(MoO4)8 crystal has been grown from a melt of Li2MoO4 by the top seeded solution growth method (TSSG). The polarized spectral properties of Er3+:Li3Ba2Gd3(MoO4)8 crystal were investigated and the spectroscopic parameters were calculated and analyzed based on the Judd-Ofelt (J-O) theory. The emission cross-sections were calculated by the Fuchtbauer-Ladenburg (F-L) equation and the peak values of the emission band at 1535 nm were 9.7×10−21, 7.9×10−21 and 8.4×10−21 cm2 for Eb, E∥D1 and ED2, respectively. Under 977 nm excitation five up-conversion fluorescence bands around 490, 530, 550, 660 and 800 nm were observed, and the possible up-conversion mechanisms were proposed.  相似文献   

8.
Sodium acid phthalate (SAP), an efficient semi-organic crystal having dimensions 17×8×2 mm3 has been grown from aqueous solution by slow evaporation technique at room temperature within the period of 2 weeks. The lattice parameters of the grown crystals were determined using single-crystal X-ray diffraction analysis. The presence of functional groups was estimated qualitatively by Fourier transform infrared (FTIR) analysis. The band gap energy was determined using optical absorption studies. The TG/DTA analysis reveals that the SAP crystal is thermally stable up to 141.6 °C. The dielectric constant and dielectric loss was studied as a function of frequency and the corresponding activation energy (Ea) has been calculated for the grown crystal. Scanning electron microscope studies enunciate the ferroelectric domain patterns of the SAP crystal. Ferroelectric property of the grown crystal was confirmed by hysteresis loop studies.  相似文献   

9.
In this work, an α-Al2O3:C crystal was directly grown by the temperature gradient technique (TGT) using Al2O3 and graphite powders as the raw materials. The optical, optically stimulated luminescence (OSL) properties and dosimetric characteristics of as-grown crystal were investigated. As-grown α-Al2O3:C crystal shows strong absorption band at 205, 230 and 256 nm. Three-dimensional thermoluminescence (TL) emission spectrum of the crystal shows a single emission peak at ∼415 nm. The OSL decay curve can be fitted to two exponentials, the faster component and the slower component. The OSL response of the crystal shows a linear-sublinear-saturation characteristic. As-grown α-Al2O3:C crystal shows excellent linearity in the dose range from 5×10−6 to 50 Gy. For doses higher than the saturation dose (100 Gy), the OSL sensitivity decreases as the dose increases.  相似文献   

10.
Electron paramagnetic resonance (EPR) studies of V O2+ ions in L-asparagine monohydrate single crystals are reported at room temperature. It is found that the V O2+ ion takes up an interstitial site. The angular variations of the EPR spectra in three mutually perpendicular planes are used to determine the principal g and A values and their direction cosines. The values of g and A parameters are: gx=1.9011, gy=2.1008, gz=1.9891 and Ax=100, Ay=78, Az=126 (×10−4) cm−1. The optical absorption spectrum of V O2+ ions in L-asparagine monohydrate is also studied at room temperature. The band positions are calculated using the energy expressions and compared with the observed band positions to confirm the transitions. The best-fit values of the crystal field (Dq) and tetragonal (Ds and Dt) parameters are evaluated from the observed band positions.  相似文献   

11.
In this paper, the Czochralski growth, absorption spectra, and photoluminescence spectra of Nd:GdVO4 crystals are studied. From its absorption spectra, Nd:GdVO4 is found to exhibit an anisotropic optical absorption effect, and its effective Judd-Ofelt parameters are calculated: Ω2=10.281×10−20 cm2, Ω4=5.426×10−20 cm2 and Ω6=9.943×10−20 cm2. By these parameters, the absorption oscillator strengths, emission oscillator strengths, transition probabilities, fluorescence branch ratios, energy lifetimes, and integrated emission cross-sections are also derived. The photoluminescence spectra of Nd:GdVO4 crystal consist of a wide emission band of host and the characteristic emission bands of Nd3+. Based on the excitation spectrum, both the two evident peaks locating at 345 and 371 nm are ascribed to the characteristic excitation of Nd3+, and an energy transfer from the host to its doping Nd3+ ions is indicated.  相似文献   

12.
13.
Raman spectra of Cs2NaTmCl6 have been recorded using a diamond anvil cell at ambient temperature. The vibrational energy of each of the Raman-active TmCl6−3 moiety modes increases linearly with pressure. The integrated band areas of the ν1(a1g) and ν2(eg) modes are independent of applied pressure. However, the band area of the ν5(t2g) mode shows an anomalous behaviour, which has been qualitatively interpreted as due to electron-phonon coupling of the aΓ5 electronic state with the Γ15(t2g) vibronic state. This interaction between the coupled states is strongest between ca. 10 and 13 GPa at ambient temperature. The results serve to emphasize the specificity of the occurrence of strong electron-phonon coupling for particular transitions of a given rare earth ion.  相似文献   

14.
    
Interaction of host magnons with impurity magnetic excitations in antiferromagnetic crystals CoCO3 and CoF2 containing substitutional impurity amounting to 10–4 and (4±2)×10–3 (by weight) Mn2+ respectively, has been investigated in the wavelength range 0.35–0.8 mm in a magnetic field of up to 20 T. In the CoCO3+10–4 Mn2+ crystal the impurity line was observed to merge with the AFMR line, which is peculiar to incoherent spectrum rearrangement. In the CoF2+4×10–3 Mn2+ crystal the cross splitting of spectrum was revealed as the impurity lower lying Zeeman level approached the AFMR low frequency mode, peculiar to coherent spectrum rearrangement. In both cases the impurity line intensity increases very much as it approaches the spin-wave band of the crystal. The constant of resonance interaction of the impurity excitation with magnons is determined for CoF2+Mn2+ to be m=18 cm–1.  相似文献   

15.
crystal with the size up to Φ 13 mm×44 mm was grown successfully by the Czochralski technique and its optical properties were presented. The absorption cross-section and emission cross-section were presented. Also, the potential laser gain near 1.9 μm was investigated. In the framework of the Judd-Ofelt (J-O) theory, the intensity parameters were calculated to be: Ω2=11.375×10−20 cm2, Ω4=5.077×10−20 cm2 and Ω6=6.524×10−20 cm2. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetime as well as the branching ratios were calculated, too. This crystal is promising as a tunable infrared laser crystal.  相似文献   

16.
Er:YSGG single crystals with good optical quality were grown by Czochralski method. X-ray diffraction (XRD) measurements show that the crystal lattice parameters of the 30 at.% Er3+-doped YSGG crystal were a=b=c=12.4640±0.0065 Å, α=β=γ=90°. The doping concentration of Er3+ in YSGG was calculated. The absorption spectrum and photoluminescence spectra of Er:YSGG crystal were studied at room temperature. Based on Judd-Ofelt (J-O) theory, the J-O intensity parameters Ωt (t=2, 4, 6), the experimental and theoretical oscillator strengths were calculated using the absorption spectrum. The intensity parameters Ωt (t=2,4,6) obtained to be Ω2=0.23×10−20 cm2, Ω4=0.86×10−20 cm2, Ω6=0.37×10−20 cm2, respectively. With these intensity parameters, the line strengths, oscillator strengths, transition probabilities, fluorescence branching ratios and radiation lifetimes were calculated. The photoluminescence spectra and excitation spectrum of Er:YSGG were measured and studied.  相似文献   

17.
Recently, we have discovered a new type of first order phase transition around 120 K for (n-C3H7)4N[FeIIFeIII(dto)3] (dto=C2O2S2), where the charge transfer transition between FeII and FeIII occurs reversibly. In order to elucidate the origin of this peculiar first order phase transition. Detailed information about the crystal structure is indispensable. We have synthesized the single crystal of (n-C3H7)4N[CoIIFeIII(dto)3] whose crystal structure is isomorphous to that of (n-C3H7)4N[FeIIFeIII(dto)3], and determined its detailed crystal structure. Crystal data: space group P63, a=b=10.044(2) Å, c=15.960(6) Å, α=β=90°, γ=120°, Z=2 (C18H28NS6O6FeCo). In this complex, we found a ferromagnetic transition at Tc=3.5 K. Moreover, on the basis of the crystal data of (n-C3H7)4N[CoIIFeIII(dto)3], we determined the crystal structure of (n-C3H7)4N[FeIIFeIII(dto)3] by simulation of powder X-ray diffraction results.  相似文献   

18.
GaN have sphalerite structure (Cubic-GaN) and wurtzite structure (hexagonal GaN). We report the H-GaN epilayer with a LT-AlN buffer layer has been grown on Si(1 1 1) substrate by metal-organic chemical vapor deposition (MOCVD). According to the FWHM values of 0.166° and 14.01 cm−1 of HDXRD curve and E2 (high) phonon of Raman spectrum respectively, we found that the crystal quality is perfect. And based on the XRD spectrum, the crystal lattice constants of Si (a = 5.3354 ?) and H-GaN (aepi = 3.214 ?, cepi = 5.119 ?) have been calculated for researching the tetragonal distortion of the sample. These results indicate that the GaN epilayer is in tensile strain and Si substrate is in compressive strain which were good agreement with the analysis of Raman peaks shift. Comparing with typical values of screw-type (Dscrew = 7 × 108 cm−2) and edge-type (Dedge = 2.9 × 109 cm−2) dislocation density, which is larger than that in GaN epilayers growth on SiC or sapphire substrates. But our finding is important for the understanding and application of nitride semiconductors.  相似文献   

19.
The linestrengths and self-broadening coefficients are determined from high-resolution measurements for P(1)-P(10) and R(0)-R(15) lines in the fundamental vibration-rotation band of hydrogen iodide at different gas pressures in the range of 2-280 Torr. Dipole matrix elements are calculated from the linestrength data. New values of the Herman-Wallis coefficients obtained, C10=0.1319, D10=4.41×10-3, are in a better agreement with theory than previously reported. A significant influence of the hyperfine splitting on the spectral line profiles is demonstrated.  相似文献   

20.
The Γ8(4A2g) →Γ7(2T2g), Γ8(2T2g) electronic transitions for the 5d3 hexafluororhenate(IV) ion have been observed at liquid hydrogen temperature in a single Cs2GeF6 crystal and in a mixed crystal where the ReF?26 ion is doped in the cubic Cs2GeF6 lattice. The electronic transitions have been assigned with a crystal field model to give information about the parameters B, C, Dq, and spin-orbit coupling. The vibrational structure in the mixed crystal system may be assigned to the ungerade modes of the ReF?26 moiety. Comparison of the mixed and pure crystal vibrational structure shows that the pure crystal vibrational structure can be interpreted on the basis of K ≠ 0 lattice effects and a small distortion in the pure crystal.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号