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1.
Using the re-equilibration kinetic method the chemical diffusion coefficient in nonstoichiometric chromium sesquisulfide, Cr2+yS3, has been determined as a function of temperature (1073–1373 K) and sulphur vapour pressure (10?104 Pa). It has been found that this coefficient is independent of sulphur pressure and can be described by the following empirical equation: D?Cr2+yS3=50.86 exp(-39070 cal/mole/RT) (cm2s?1). It has been shown that the mobility of the point defects inCr2+yS3 is independent of their concentration and that the self-diffusion coefficient of chromium in this sulfide has the following function of temperature and sulphur pressure: DCr=2.706×102P?14.85S2exp(-56070 cal/mole/RT). (cm2s?1).  相似文献   

2.
The transverse spin pair correlation function pxn=<SxmSxm+n>=<SxmSxm+n> is calculated exactly in the thermodynamic limit of the system described by the one-dimensional, isotropic, spin-12, XY Hamiltonian
H=?2Jl=1N(SxlSxl+1+SylSyl+1)
. It is found that at absolute zero temperature (T = 0), the correlation function ρxn for n ≥ 0 is given by
ρx2p=142π2pΠj=1p?14j24j2?12p?2jif n=2p
,
ρx2p+1142π2p+1Πj=1p4j24j2?12p+2jif n=2p+1
, where the plus sign applies when J is positive and the minus sign applies when J is negative. From these the asymptotic behavior as n → ∞ of |?xn| at T = 0 is derived to be xn| ~ an with a = 0.147088?. For finite temperatures, ρxn is calculated numerically. By using the results for ?xn, the transverse inverse correlation length and the wavenumber dependent transverse spin pair correlation function are also calculated exactly.  相似文献   

3.
The X-band EPR spectrum of SrCl2:V has been measured at liquid nitrogen temperature. A signal associated with V2+ in a site of trigonal symmetry is observed. The EPR data have been explained using the spin hamiltonian = μβHg?S + D[S2z ? 13S(SH)] + SA?I, with D ? hv, g = 1.957 ± 0.004, g6 = 1.954 ± 0.004, A = 230 ± 5 MHz, A6 = 235 ± 5 MHz. This V2+ defect is similar to those previously reported in fluoride crystals with the fluorite structure.  相似文献   

4.
The complex polar Kerr effect (rotation and ellipticity) of magnetite single crystals has been measured at room temperature between 0.5 and 4.3 eV. From the magneto-optical data and the optical constants, the off-diagonal elements (?xy) of the dielectric tensor has been derived. Three well separated magneto-optical transitions have been indentified. At about 0.75 eV one strong magneto-optical structure with a diamagnetic line shape is assigned to a 3d6→3d5(6A1g) 4s transition from Fe2+ in octahedral sites. Two other structures with paramagnetic line shapes near 1.85 and 2.90 eV are assigned to the orbital promotion processes 3d6(Fe2+oct)→3d5(4T1g) 4s and 3d5(Fe3+tet)→3d4(5T2) 4s, respectively, which take into account Fe 3dn?1 final state effects.  相似文献   

5.
Mössbauer spectra were obtained of the paramagnetic spinels Zn2+|Zn2+(1?x)2Ti4+(1+x)2Fe3+(1?x)Fe2+x|O4 and susceptibilities were measured. The strong difference between the paramagnetic Fe2+ and Fe3+ spectrum, due to the different quadrupole splitting, is used for the distinction between the two species. At 300 K a superposition of the Fe3+ and the Fe2+ spectra is found for most of the iron and, in addition, some continuous absorption. The latter is strongest for equal Fe3+ and Fe2+ concentration (x = 12) while it disappears towards the end members (Fe3+ only or Fe2+ only) as well as with decreasing temperature (between 78 and 200 K). From this it is concluded that it arises from thermally activated electron exchange, the frequency of which passes a “critical” value of ~108 sec?1 for increasing temperature. Paramagnetic susceptibilities are found to obey a Curie-Weiss law down to low temperatures. From the dependence of the asymptotic Curie temperature on the composition the magnetic interaction parameters J11 = ?1.4 K, J22 = ?3.3 K and J12 = + 1.6 K for the Fe3+Fe3+, Fe2+Fe2+ and Fe3+Fe2+ interactions are derived. The experimental results are discussed in terms of a hopping model with an activation energy q ~- 0.12eV and a non-equivalence of the octahedral sites expressed by a varying potential energy difference U0 between neighbouring sites. The continuous absorption at 300 K for x = 12 is attributed to about 17% of the iron on sites with U0 running from 0 to ??0.06 eV. The ferromagnetic Fe3+, Fe2+ interaction (J12) is attributed to electron transfer from localized Fe2+ ions to Fe3+ neighbours via a transfer integral b of the order of 0.05 eV. The magnitudes of J12 and b are tentatively explained.  相似文献   

6.
The first observation of the ESR spectra of Mn2+, entering substitutionally for Fe2+ in the Van Vleck paramagnet FeS2 (polycrystals), is reported. The data from 5 to 295 K fits the spin-Hamiltonian hs = gβH·S + [S2z?13 S(S + 1)] + AS·I, with g = 2.000 ± 0.001, A/β = ?95.0 ± 0.5 Oe and D/β varying from 50 Oe (5K) to 59 Oe (295 K). The temperature dependence of D can be described in terms of a single phonon-mode with frequency ? 145 cm?1.  相似文献   

7.
The fine structures of the (ν1 + ν2) and (ν2 + ν3) combination bands of ozone in the 5.7-μm region have been recorded and analyzed. The two vibrational states are coupled through Coriolis and second-order distortion terms. The interaction has been treated by the numerical diagonalization of the secular determinant for the two coupled states. With the centrifugal distortion parameters fixed to the ground state values, the following constants have been obtained: ν1 + ν2 = 1796.266, A110 = 3.6104, B110 = 0.44145, C1110 = 0.39029, ν2 + ν3 = 1726.526, A011 = 3.5537, B011 = 0.43982, C1011 = 0.38844, Y13 = ?0.466, and X13 = ?0.010 cm?1. In addition, the following anharmonic constants have been obtained: x12 = ?7.821 and x23 = ?16.494 cm?1. The value of the dipole moment ratio, R = 〈011|μz|0〉〈110|μx|0〉, is 1.30 ± 0.10.  相似文献   

8.
The differential cross sections dσdx and dσdpt2 of inclusive J/ψ production by 43 GeV/c π? off Be, Cu and W nuclei have been measured. Fitting dσdpt2 ~ Aα(pt2) we observed the increase of α with pt2.  相似文献   

9.
The electronic absorption spectra of thioformaldehyde and thioformaldehyde-d2 have been obtained. A vibrational analysis of the discrete band system in the 6100-4400-Å region is reported. The type A origin bands are at 16 39416 484cm?1 for CH2SCD2S, and are magnetic dipole allowed. The electronic transition is A?1A2-X?1A1 under the C2v point group. Most of the intensity of the system is in type B bands, and is due to vibronic mixing with higher 1B2 states when the inversion mode ν4 is excited. The molecule in the excited 1A2 state is “floppy-planar,” having a broad potential function with a barrier of the order of 20 cm?1 to the inversion motion.  相似文献   

10.
On the basis of the known group theoretical structure of the conformal invariant four point functions in the case of identical scalar fields ?(x) of scale dimension d,
<0|?(x1)?(x2)?(x3)?(x4)|0〉 = [(x1?x4)2(x2?x3)2] -dg(A,B),
the analytical properties of g(A, B) as a function of the harmonic ratios A and B are investigated. By imposing the conditions of spectrality and locality, and using invariance under complex dilatations, it is shown that the function g(A, B) must be homomorphic in the whole complex A-plane and B-plane with exception of the values A=0 and A=∞, B arbitrary, and B=0 and B=∞, A arbitrary.  相似文献   

11.
Two electrochemical methods - involving the application of a long-time galvanostatic current pulse and a small potentiostatic voltage step to a M/MxSSE cell - are presented. From the overvoltage, respectively current response the chemical diffusion coefficient (DM+) and the thermodynamic factor (? ln a/? ln c) are obtained. The methods have been applied to the cells: Li/1M·LiClO4 in propylenecarbonate/LixTi1.03S2 0.05 < x < 0.95, T = 20°C; and LixCoO2 0.10 < × < 1, T = 20°C. From the application of the current pulse/voltage decay method it followed: DLi+(LixTi1.03S2) = 1?4 × 10?8cm2s?1, with a slight tendency to increase with decreasing x; DLiC(LixCoO2) = 2?40 × 10?9cm2s?1, decreasing with decreasing x. These values are among the highest found for solid state Li+-ion diffusion, and will be closely evaluated and compared with data reported by other workers. The x-dependence of the thermodynamic factor, determined from kinetic data, for LixTi1.03S2 (x = 0.05-0.95) and LixCoO2 (x = 0.60-1.00) is in accordance with a simple thermodynamic model. Unlike for LixTi1.03S2, the thermodynamic factor for LixCoO2, determined from the EMF-x relation, cannot be accounted for by this model. Furthermore, a fast, but crude method to determine the average chemical diffusion coefficient in LixTi1.03S2 and LixCoO2 is discussed.  相似文献   

12.
The solid electrolyte Ce1?xCaxO2-?x with the fluorite-type structure (Ca-doped CeO2) is a mixed conductor. Conduction occurs predominantly by migration of O2? ions via oxygen vacancies or by electrons, depending on the departure from stoichiometry. The ionic transference number σi/σi + σe was determined as a function of dopant concentration (0.07?x?0.15), temperature (400–800°C), and oxygen pressure by emf measurements with oxygen concentration cells. It is described by
ti1 + PO2?14exp ? 5.42 ? S1(x)T4kT?1
The entropy term S1(x) changes from 38.7k for x = 0.07 to 31.7k for x = 0.15; the enthalpy term, 5.42 eV, is independent of x and in excellent accord with semi-empirical calculations.  相似文献   

13.
The diffusion constant (D) and the spin depolarisation rate (λS) of the positive muon in the ferromagnetic b.c.c. lattices such as Fe have been calculated on the basis of the small polaron (SP) model with particular attention to the hopping and the coherent motions. They have been obtained in the forms: D=d2wD6 and λS=2μH2d3wS, where d is a jump length, and Hd is a magnitude of internal dipolar field. At high temperatures, the activated-type hopping motion gives a dominant contribution to wD, and wS coincides with wD. With decreasing temperature, wD turns to be increasing owing to the coherent motion. Whereas wS deviates from wD, after passing the minimum, to have a maximum, and then decreases in inverse proportion to a lifetime (B) of the SP band states. Because of the cell periodicity of the internal fields, the spin in an SP band state feels a definite magnetic field corresponding to the state, and sees various fields if scattered to other states. These scattering processes succeeding in a time shorter than (γμHd)-1 result in the motional narrowing of the spectra, with λS ? γ2μHdB.  相似文献   

14.
With the use of the similarity of interatomic potentials relations concerning vacancy and diffusion characteristics in disordered regular solid solutions have been derived. It has been shown that the vacancy concentration is constant along ifTc(x) = TA + (TB ? TA)x + 2ΔTx(1?x), (TA and TB are the melting points of pure components A and B respectively, and ΔT is proportional to the excess enthalpy of mixing, x is the concentration of the atoms B) which is proportional to the binding energy of the crystal. The validity conditions of several empirical rules known in the literature are also analyzed. It has been found that the generalization of the well-known rule for self- and impurity diffusion in pure metals has the following form In D0z(x) ~ pQz(x)Tc(x) (Z = AorB) where p is a constant for alloys having identical structures (D0z(x) and Qz(x) denote the preexponential factors and the activation energies respectively). The results calculated from the relations derived were compared with experimental data for tracer diffusion in the systems AgAu, CuNi (having slight deviation from regularity), Pb-Tl (showing ordering phenomena) and AlZn (clustering effects) and a good agreement was found.  相似文献   

15.
The (1-0), (2-0), and (3-0) transitions of 15N16O and 15N18O are investigated. The wavenumbers of the rotation-vibration lines are reported for the overtone bands and the 2Π32-2Π12 (1-0) subband. It is shown that in the data reduction it is advantageous to calculate first merged spectroscopic constants ignoring the Λ-type doubling. The vibrational constants ωe, ωexe, ωeye and the vibrational dependence of the rotational constants are determined. The study of 15N18O allows the determination of the equilibrium values of the centrifugal distortion correction ADe to the spin-orbit constant and of the spin-rotation constant γe from the isotopic invariance of the ratios ADeBe and γeBe. It is found that ADeBe = (?3.9 ± 1.3) × 10?6 and γeBe = (?4.00 ± 0.05) × 10?3.  相似文献   

16.
The E-B (0g+-0u+) band system of Br2 has been investigated at Doppler-limited resolution using polarization labeling spectroscopy. Merged E state data for the three naturally occurring isotopes in the range vE = 0–16, expressed in terms of the constants for 79Br2, are (in cm?1) Y0,0 = 49 777.962(54), Y1,0 = 150.834(22), Y2,0 = ?0.4182(28), Y3,0 = 6.6(11) × 10?4, Y0,1 = 4.1876(28) × 10?2, Y1,1 = ?1.607(16) × 10?4, and Y0,2 = 1.39(39) × 10?8. The bond distance is re = 3.194 A?, and the diabatic dissociation energy to Br+(3P2) + Br?(1S0) is 34 700 cm?1.  相似文献   

17.
The wavenumbers of the rotation-vibration lines of 14N16O are reported for the (2-0) and (3-0) bands. The full set of spectroscopic constants for the three bands (1-0), (2-0), and (3-0) has been determined with the method developed by Albritton, Schmeltekopf, and Zare for merging the results of separate least-squares fits. The vibrational constants ωe, ωexe, ωeye, and the vibrational dependence of the rotational constants have been deduced. The apparent spin-orbit constant A?v and its centrifugal correction A?D (including the spin-rotation constant) have a vibrational dependence of the following form: A?v = A?e ? αA(v + 12) + γA(v + 12)2 and A?Dv = A?De ? βA(v + 12) + δA(v + built+12)2; the values of the constants in these two equations have been determined.  相似文献   

18.
The Casimir energy is evaluated for a free scalar field that has a mass term m2(x1), depending on one space coordinate x1. The formalism for evaluating the Casimir energy is developed for the case of m2(x1) finite everywhere in d-dimensional space-time. The case with m2(x1) = m02θ(12L-|x1|) + m2θ (|x1| - 12L) is explicity evaaluated for any value of 1197 1568 V m0 and m without any approximation. The result consists of valume energy terms, a surface term, and a non-leading term. Most of the UV divergences are in the volume energy terms and renormalize the coupling constants of the underlying theory. The surface energy term is finite for d ? 4 and divergent for d ? 5 due to the boundaries being sharp. A closed finite expression is obtained for the non-leading term. Our results are shown to reproduce the known Casimir energies for the limiting cases, 1197 15 m0 → ∞ andm → ∞.  相似文献   

19.
A rotational assignment of approximately 80 lines with Ka′ = 0, 1, 2, 3, and 4 has been made of the 593 nm 2A12B2 band of NO2 using cw dye laser excitation and microwave optical double-resonance spectroscopy. Rotational constants for the 2B2 state were obtained as A = 8.52 cm?1, B = 0.458 cm?1, and C = 0.388 cm?1. Spin splittings for the Ka′ = 0 excited state levels fit a simple symmetric top formula and give (?bb + ?cc)2 = ?0.0483 cm?1. Spin splittings for Ka′ = 1 (N′ even) are irregular and are shown to change sign between N′ = 6 and 8. Assuming that the large inertial defect of 4.66 amu Å2 arises solely from A, a structure for the 2B2 state is obtained which gives r (NO) = 1.35 A? and an ONO angle of 105°. Alternatively, weighting the three rotational constants equally gives r = 1.29 A? and θ = 118°.  相似文献   

20.
The threshold behaviour of pion production presented in our earlier work is successfully compared with the new SPEAR data. By using duality and sum rules we derive FT(π+)(x) ≈ FL(π+)(x) ≈ FT(π0)(x) ? FL(π0)(x) for x near 1. An accompanying results is σπA2(s) ≈ 2σπω(s) ≈ 4σππ(s) ≈ 9(m?2/s)3σμμ for large s.  相似文献   

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