共查询到20条相似文献,搜索用时 515 毫秒
1.
本文对NaCl型结构的稀土化合物RX(X=N,P,As,Sb,Bi)的晶场参数B 40的实验值进行了分析。在此基础上我们提出一个新的利用简单点电荷模型计算RX晶场参数B 40值的关系式:B 40=k 3(B 40) p+c 3。用此关系式我们确定了一系列RX的晶场参数B 40值,结果与实验值符合很好。对关系式的含义本文也作了充分讨论。
关键词: 相似文献
2.
Lithium niobate (LiNbO 3) crystals doped with chromium ions show a clear green colouring reflecting the absorption profile of the dominating [Cr] Li defect centres. A significant change in its colouration takes place when it is co-doped with other valency impurities such as Mg 2+, Sc 3+ and W 6+, above a certain threshold concentration. This concentration singularity has been attributed to the formation of [Cr] Nb centres coexisting with the [Cr] Li centres.In this work, we extended the investigation on the effect of co-dopant ions in Cr:LiNbO 3 to tetravalent cation such as GeO 2. A singularity in the relative intensity of the 4A 2→ 4T 1 and 4A 2→ 4T 2 absorption band was observed for a concentration of ~1.5 mol%, compared with 4.5 mol% for Mg 2+. The photoluminescence emission spectra also reveal a new emission band, at a lower energy than the [Cr] Li centre, corresponding to this threshold concentration. A charge compensation model is proposed to explain the role of cation impurities and results are compared with those of other valence impurities. 相似文献
3.
With a Fourier-transform spectrometer, especially developed for nuclei with weak NMR signals, the lines of 89Y have been investigated in aqueous solutions of Y(NO 3) 3, YCl 3, and Y(ClO 4) 3. The concentration dependence of the chemical shifts of the 89Y resonance frequencies in these solutions were measured. Using this dependence, the Larmor frequency of the 89Y 3+ ion solely surrounded by water was determined by extrapolation. The Larmor frequency of 89Y was referred to those of 2H, 39K, and 73Ge with high accuracy. The magnetic moment of the 89Y 3+ ion purely surrounded by H 2O molecules is μ( 89Y 3+) = ?0.1368523(4) μ N. The concentration dependence of Y(NO 3) 3 solutions in D 2O yields the solvent isotope effect δ( 89Y 3+ in D 2O)?δ( 89Y 3+ in H 2O)= ?(4.3±0.5)ppm. The 89Y relaxation times T 1 and T 2 of a 3 molal aqueous Y(NO 3) 3 solution were determined in the pH range ?0.5...+1.25. T 1 190...90 s is nearly constant in this range, whereas the transverse relaxation rate T 2 ?1 increases strongly with increasing pH; this effect seems to be due to the chemical exchange of the hydrated Y 3+ ion between a monomer and a polymer site. 相似文献
4.
In this work, we investigated the bombardment of polymer surfaces (PC, PMMA) with very low energy (250 eV) Cs + ions.In the positive mode, we observed many cations combining a molecular fragment of the polymer (M) with two Cs atoms, similar to the well-known MCs 2+ clusters commonly observed in inorganic depth profiling with Cs. For example, Cs 2COOH + or Cs 2C 6H 5O + were measured on PC and Cs 2CH 3O + or Cs 2C 4H 5O 2+ were measured on PMMA. In fact, most of the polymer characteristic fragments measured in negative spectra also appear in the positive spectra, combined with two Cs atoms. It is remarkable that stable negative ions tend to combine not with one Cs, but with two Cs atoms to create the MCs 2+ cluster.This effect is, to some extent, similar to the well-known cationisation of polymers (with Ag or Au) although here few clusters with only one Cs atom are detected (MCs + clusters), like in classical cationisation. The most abundant clusters are the MCs 2+ clusters, but heavier clusters (MCs 3+, MCs 4+ and above) are also measured with high yields in the spectrum.Surprisingly, some of those MCs 2+ clusters were still detected even after a very long sputtering fluence (above 10 17 ions/cm 2), proving that some molecular depth profiling is also possible in this “Cs 2-cationisation” mode. In other words, this work could open the way to an extension of the MCs n+ cluster analysis, commonly used in inorganic depth profiling, to the in-depth molecular analysis of organic layers. 相似文献
5.
Gd 2MoB 2O 9 doped with Sm 3+ and Dy 3+ were used for this study. The photoluminescence behaviors of Sm 3+ and Dy 3+ in this phosphor material were investigated by the excitation and emission spectra. The Sm 3+-doped Gd 2MoB 2O 9 phosphor powders show a red luminescence, whereas the Dy 3+-doped Gd 2MoB 2O 9 phosphor powders show a yellow luminescence. In addition, the optimum doping concentration and the time-resolved luminescence spectroscopy were also investigated. 相似文献
6.
We present an estimate of the cross-section for the exclusive production of a ρ L
0-meson pair in e +e - scattering, which will be studied in the future high-energy International Linear Collider. For this aim, we complete calculations
of the Born order approximation of the amplitudes γ *
L,T(Q 1
2)γ *
L,T(Q 2
2)→ρ L
0ρ L
0, for arbitrary polarization of virtual photons and longitudinally polarized mesons, in the kinematical region s≫-t,Q 1
2,Q 2
2. These processes are completely calculable in the hard region Q 1
2,Q 2
2≫Λ 2
QCD, and we perform most of the calculations in an analytical way. The resulting cross-section turns out to be large enough for
this process to be measurable with foreseen luminosity and energy, for Q 1
2 and Q 2
2 in the range of a few GeV 2. 相似文献
7.
In this study, SnO 2 and ZnO were co-doped in In 2O 3, and the phase development and electrical characteristics were examined. When Zn 2+ was added to 20 at.% Sn 4+ contained In 2O 3, in which a large amount of In 4Sn 3O 12 second phase exists, the amount of the second phase decreased as the content of Zn 2+ increased, which promoted grain growth and increased carrier mobility. In the case of a simultaneous substitution of Sn 4+ and Zn 2+ into In 2O 3 with almost the same atomic ratio, a large grain size without second phase was observed, while small grain sizes with many second phases were developed when Sn 4+ and Zn 2+ were added with different atomic ratios. The electrical characteristics analyzed by Hall effect measurement showed that the electron mobility and conductivity showed a close relationship with the microstructure, while the carrier concentration was almost constant regardless of the Zn 2+ content. 相似文献
8.
利用微观sdIBM-2+2q.p.方案,成功地计算出 124Te核的低自旋态和部分高自旋态,特别是较成功地再现了1 +1,1 +2,3 +1,3 +2和5 +1态.基于该方案推出的能量关系指认:6 +1,8 +关键词:
能谱特征
拆对与顺排
微观sdIBM-2+2q.p.方案
124Te核')" href="#">124Te核 相似文献
9.
The purpose of this study is to investigate the feasibility for quantitative measurement of singlet oxygen ( 1O 2) generation by using a newly developed 1O 2-specific fluorescence probe Singlet Oxygen Sensor Green reagent (SOSG). 1O 2 generation from photoirradiation of a model photosensitizer Rose Bengal (RB), in initially air-statured phosphate buffered saline (PBS) was indirectly monitored with SOSG. In the presence of 1O 2, SOSG can react with 1O 2 to produce SOSG endoperoxides (SOSG-EP) that emit strong green fluorescence with the maximum at 531 nm. The green fluorescence of SOSG-EP is mainly dependent on the initial concentrations of RB and SOSG, and the photoirradiation time for 1O 2 generation. Furthermore, kinetic analysis of the RB-sensitized photooxidation of SOSG is performed that, for the first time, allows quantitative measurement of 1O 2 generation directly from the determination of reaction rate. In addition, the obtained 1O 2 quantum yield of porphyrin-based photosensitizer hematoporphyrin monomethyl ether (HMME) in PBS by using SOSG is in good agreement with the value that independently determined by using direct measurement of 1O 2 luminescence. The results of this study clearly demonstrate that the quantitative measurement of 1O 2 generation using SOSG can be achieved by determining the reaction rate with an appropriate measurement protocol. 相似文献
10.
We have examined the fluorescence characteristics of the garnet-type crystal Yb 3Al 5O 12 : Er 3+ (YbAlG : Er 3+) and studied the energy transfer process between the two rare earth ions over a temperature range 78–297 K. Certain data were compared with those of YAlG : Er 3+. In YbAlG : Er 3+, Yb fluorescence is observed at ?1.03 μm (corresponding to the 2F 5/2 → 2F 7/2 transition); Er fluorescence occurs at ?8500 Å ( 4S 3/2 → 4I 13/2 transition) and ?1.6 μm ( 4I 13/2 → 4I 15/2 transition). In YAlG : Er 3+, the same Er lines are observed with the addition of a band at ?1 μ ( 4I 11/2→ 4I 15/2 transition). In YbAlG : Er 3+, the decay pattern of the Yb emission is purely exponential at all the temperatures examined; the fluorescence lifetime ranges from 36 μ s (at 78 K) to 74 μs(at 269 K). The lifetime of the Er 4I 13/2 level in the same sample increases from 5.4 ms (at 78 K) to 6.85 ms (at 294 K). The lifetime of this Er level in YAlG : Er 3+ is weakly temperature dependent over the same range with a value of ?12 ms. Excitation spectra were obtained for the Er 1.53 μm fluorescence in YbAlG : Er 3+ in order to verify the presence of Yb → Er energy transfer in this sample. The presence of the Yb absorption band (?1 μm) in these spectra provides direct evidence of this energy transfer. The relative enhancement of this Yb band with respect to the Er bands in going from 78 K to 175 K is an indication of a more efficient transfer at the higher temperature. Excitation spectra obtained for the Yb 1.03 μm fluorescence in YbAlG : Er 3+ revealed the presence of Er → Yb energy transfer as well in this sample. The existence of both Yb → Er and Er → Yb transfer is expected, due to the resonance between the 4I 11/2 → 4I 15/2 transition of Er and the 2F 5/2 → 2F 7/2 transition of Yb. The above results are explained in terms of a rate equation model in which transfer in both directions is treated in the following manner: Yb → Er transfer is considered to be much more probable than decay processes originating at the Yb 2F 5/2 level; Er → Yb transfer is treated as much more probable than decay processes originating at the Er 4I 11/2 level. 相似文献
11.
The differences in the optical spectra of CdF 2:In semiconductors with bistable DX centers (concentrated (CdF 2) 0.9(InF 3) 0.1 solid solutions) and “standard” samples with a lower impurity concentration used to record holograms are discussed. In contrast to the standard samples, in which complete decay of two-electron DX states and transfer of electrons to shallow donor levels may occur at low temperatures, long-term irradiation of a (CdF 2) 0.9(InF 3) 0.1 solid solution by UV or visible light leads to decay of no more than 20% deep centers. The experimental data and estimates of the statistical distribution of electrons over energy levels in this crystal give the total electron concentration, neutral donor concentration, and concentration of deep two-electron centers to be ~5 × 10 18 cm ?3, ~9 × 10 17 cm ?3, and more than 1 × 10 20 cm ?3, respectively. These estimates show that the majority of impurity ions are located in clusters and can form only deep two-electron states in CdF 2 crystals with a high indium content. In this case, In 3+ ions in a limited concentration (In 3+ (~9 × 10 17 cm ?3) are statistically distributed in the “unperturbed” CdF 2 lattice and, as in low-concentrated samples, form DX centers, which possess both shallow hydrogen-like and deep two-electron states. 相似文献
12.
The absorption spectra of C 6H 6 and C 6D 6 in the liquid phase have been studied near 340 nm. The absorption spectrophotometric mounting was a sequential double-beam attachment with linear response to energy on scanning of the spectrum before the exit slit and an electronic device which gives directly either the absorbance or the integrated absorbance of a transition and, consequently, its oscillator strength.The oscillator strength measured for the band of C 6H 6 is 8×10 ?8, which corresponds to a dipole moment of 2.4×10 ?3 Debye; this value is of the same order as a theoretical value calculated by Tsubomura and Mulliken (3.8×10 ?3 Debye) for a transition between states 3F and 3A of an oxygen-benzene pair. This agreement corroborates the hypothetical existence of such a transition.The first vibrational band is at 28553 cm ?1 for C 6H 6; this band is not observed in the vapor or solid phase. It corresponds probably to the transition 0-0, which is considered in the literature to be near 29500 cm ?1. The isotopic shift measured for this first band is 164 cm ?1. The vibrational frequencies are, respectively, 910 cm ?1 for C 6H 6 and 889 cm ?1 for C 6D 6. 相似文献
13.
The paper presents the EPR evidence for the occurrence of phase transitions in (NH 4) 4ThF 8 and (NH 4) 3ThF 7. In both cases the Cu 2+ probe occupies a NH 4+ site and predominantly experiences a dynamic coordination, either due to dynamic Jahn-Teller effect, or due to fluxional behaviour of surrounding (ThF 8) 4- units in (NH 4) 4ThF 8. It is proposed that the structural phase transition in this compound at 214 K is associated with the transition of the dynamic coordination of Cu 2- into a static one, probably due to freezing of motion of (ThF 8) 4- units below this temperature. In (NH 4) 3ThF 7 the dynamic features of the Cu 2+ EPR spectrum are absent and characteristics of a local orthorhombic symmetry are seen down to 77 K. However, in the high temperature range a change from orthorhombic to axial symmetry is observed at 524 K, possibly due to a phase transition. 相似文献
14.
Diazirine is one of the seven possible isomers of diazomethane. The medium-resolution infrared spectrum of this cyclic compound, which seems to be very stable in the gas phase, was reported by Ettinger. The mid-infrared spectra of diazirine and of the substituted isotopic species D 2CN 2, H 213CN 2, and H 2C 15N 2 were recorded with a resolution of 0.08 cm ?1. The overall assignment of these spectra is reported here. The ν3 fundamental of the main species at 1459.15 cm ?1 (CH 2 deformation) is an A-type parallel band but presents a complicated band structure since diazirine is an asymmetric rotor with κ = ?0.427. The rovibrational assignment and the analysis of this band, together with the determination of the molecular constants, is given. 相似文献
15.
We report low temperature Electron Spin Resonance experiments on diluted Er, Dy and Yb in YPd 3. The host cubic crystal field leaves a Γ 6 ground state for Er 3+, and a Γ 7 excited state could be observed at 18 ± 4 K for this system. A lower lying Γ 7 was measured for Yb 3+ in YPd 3, and a broad undefined resonance for Dy 3+ in this host. A comparison of our data with those obtained by Inelastic Neutrons Scattering is given. 相似文献
16.
A new baryonic state Λ c(2940) + has recently been discovered by the Babar collaboration in the D 0p channel. Later Belle collaboration also observed this state in the Σ c(2455) 0,++π ±→Λ c
+π +π - channel. The mass of Λ c(2940) + is just a few MeV below the sum of D *0 and p masses suggesting a possibility that this state may be a D *0p molecular state. In this paper we study whether such a molecular state can be consistent with data. We find that the molecular
structure can explain data and that if Λ c(2940) + is a D *0p molecular state it is likely a 1/2 - state. Several other decays modes are also suggested to further test the molecular structure of Λ c
+(2940).
PACS 13.30.Eg; 14.20.Lg; 12.39.Pn 相似文献
17.
The [H 2, C, N, 0] + potential energy surface (PES) has been explored by means of high-level ab initio calculations, carried out in the framework of the G2 theory. From this survey we concluded that the predominant products of the CN + + H 2O reaction are the result of the dissociation of HNCOH + species and to a much lesser extent of the CNHOH + cation to yield CNH + + OH. According to our results HCN + should not be a product of this reaction because all pathways leading to its formation are unfavourable with regards to other competitive processes. Other reactive channels lead to the formation of the H 2ONC + structure which dissociates into CN + H 2O +. The loss of NH(3σ) and O( 3P) seems to take place following spin-forbidden reaction paths through an intersystem crossing between the singlet and the triplet PESs. The global minimum of the PES, H 2NCO + is easily accessible and should lead to the loss of carbon monoxide which has not been experimentally observed in CN + + H 2O reactions. We cannot offer a clear explanation for this disagreement between theory and experiment. 相似文献
18.
Infrared and Raman spectra of CaFeSn(PO 4) 3 have been recorded and discussed with the aid of a site-symmetry analysis. The Mössbauer ( 57119Fe and 119Sn) spectra of this compound as well as the Sn-spectra of KSn 2(PO 4) 3 and TlSn 2(PO 4) 3 were also reported. The obtained spectroscopic information allows a deeper insight into the structural and electronic properties of this type of solids. 相似文献
19.
For the first time, direct experimental evidence of a new mechanism for the quenching of fluorescence of organic ligands (L) in complex compounds with lanthanide ions (Ln3+) is obtained. By analogy with the mechanism of luminescence quenching upon pair interactions of Ln3+ ions in inorganic systems, this mechanism is called the cross-relaxation mechanism. The experiments are performed with complexes of Tb3+ with dianions of halogen-substituted fluoresceins (HSFs): 4,5-dibromo-and 4,5-diiodofluorescein, eosin B, eosin, erythrosin, and Rose Bengal in dimethyl sulfoxide. In accordance with this mechanism—exchange energy transfer, L2?(*S
1), Tb3+(7
F
6)→L2?(T
1), Tb3+(7
F
5, 4), allowed by the spin selection rules—an increase in the quantum yield of formation of the triplet state (ΦT) of a ligand L2? and a decrease in the quantum yield of fluorescence (Φfl) are found to take place upon complexation. The efficiency of this process amounts to ~1 in accordance with the equality Φfl+ΦT=1, valid for solutions of HSFs. The possibility of other processes leading to a similar effect, specifically, recharging of the system (as for complexes of HSFs with Eu3+ and 3+) is considered. An example of inductive resonance interactions in complexes of HSFs with Pr3+ is given. The manifestation of equilibrium between outer-sphere and inner-sphere complexes in the photophysics of complexes of metals with HSFs is discussed. 相似文献
20.
The kinetics of the reaction of CH 3 + ions with N 2O and NH 3 has been investigated in He and Ar buffers using Selected Ion Flow Drift Tube technique (SIFDT). Both studied reactions proceed with nearly collisional rate at near thermal energies. The rate coefficient of the reaction of CH 3 + with N 2O is decreasing more than one order of magnitude (from 1.2×10 ?9cm 3s ?1 up to 8×10 ?11cm 3s ?1) with reactant ion/reactant neutral average centre-of-mass kinetic energy ( E r) increasing from near thermal up to 2 eV. The dominant product of this reaction is the isomer HCO + (≥94%) and the minor product is CH 3O +. The reaction of CH 3 + with NH 3 has two binary channels with the dominant product ion CH 2NH 2 + (>70%) and the minor product ion NH 4 + (≈10%) and three body association channel with product CH 3NH 3 + (≈20% at 0.32 Torr). The rate coefficient of this reaction is decreasing nearly by one order of magnitude with increasing E r from near thermal up to 0.8eV, for E r>0.8 eV the rate coefficient increases with increasing E r. The experimental results are interpreted in terms of a simple model assuming the reactions to proceed via the formation of long-lived collision complexes. 相似文献
|