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1.
Using laser induced fluorescence spectroscopy the hyperfine structure of the even parity levels 4f 146s6d 3 D 1, 4f 14 6s8s 3 S 1 and 4f 13 5d6s6p (7/2, 5/2)J=1,2,3 as well as of the odd parity level 4f 14 6s6p 3 P 2 in neutral ytterbium has been investigated. The isotope shift of the transitions 4f 146s6p 3 P 0 → 4f 14 6s6p 3 D 1 and 4f 14 6s6p 3 P 2 → 4f 14 6s8s 3 S 1, 4f 13 5d6s6p (7/2, 5/2)J=1,2,3 could be measured with high accuracy. The results for the 4f 14 6s6p 3 D 1 level show a considerable influence of second order effects of the hyperfine interaction. The isotope shifts of the 4f 14 6s8s 3 S 1 and 4f 13 5d6s6p (7/2, 5/2)J=1 levels indicate a possible configuration mixing for these levels.  相似文献   

2.
The temperature-dependence of the electrical resistance of Al-Zn 78 wt.% was measured during linear cooling of the samples in the range of eutectoidal decomposition. The resulting resistancevs. temperature curves were analysed by:
  • deriving the temperature-dependence of the volume fractionx(T) of theη precipitate;
  • fitting the theoretical functionx(T)=x h (T)+x c (T) following from numerical integration of the reaction rate equations for the simultaneously occurring homogeneous (H) and cellular (C) precipitation processes.
  • As a result, the activation energiesE h andE c , the JMA exponentsn h andn c , the rate constantsk h andk c , and the critical temperaturesT o of the two processes were estimated.  相似文献   

    3.
    From 17 transitions in the singly ionized Sb II spectrum the hyperfine structure (A andB splitting constants) of the complete excited configurations 5p6s and 5p6p were determined by means of optical interference spectroscopy. In addition, a theoretical analysis both of the fine structure and also of the hyperfine structure was carried out (in the case of 5p6p of the general typenpn′p for the first time in literature). For the 3 levels 5p6p 3 P 1, 5p7p 3 D 2 and 5p6p 1 P 1 a different classification was found and consistent values for the fine structure parameters, mixing coefficients and single electron hyperfine structure splitting parametersa nl ik andb nl ik were obtained. The three new determinations in Sb II of the quadrupole moment (in barn) of121Sb (Q(5p6s)=?0.55(5);Q(5p6p)=?0.57(5) from the 5p-electron andQ(5p6p)=?0.7(2) from the 6p-electron) are well agreeing with each other but differ to former values from SbI. The core polarization and isotope shift of the lines, however, are compatible with our former results in SbI.  相似文献   

    4.
    A simplified model of plane Couette flow is derived by means of a cross-stream (y) Galerkin expansion in terms of trigonometric functions appropriate for idealized stress-free boundary conditions at the plates. A set of partial differential equations is obtained, governing the in-plane (xz) space-dependence of a velocity field taken in the form: u=U0(x,z,t)+[1+U1(x,z,t)]sin(πy/2), v=V1(x,z,t)cos(πy/2), w=W0(x,z,t)+W1(x,z,t)sin(πy/2). Beyond Lorenz-like Waleffe's modeling (Waleffe 1997), this Swift–Hohenberg type of approach is expected to give an access to the microscopic mechanism of spatiotemporal intermittency typical of the transition to turbulence in plane Couette flow (Pomeau 1986, Bergé et al. 1998).  相似文献   

    5.
    An analytic expression for the total energy of metallic clusters composed ofN identical atoms of valencev and with net chargeQ is obtained by means of a variational solution of the Thomas-Fermi-Weizsäcker energy density functional within the spherical jellium model. The minimum energy is given as an expansion in decreasing powers of the cluster radiusR=r s Z 1/3, withZ=vN andr s the radius per electron of the bulk metal. The coefficients are obtained as functions ofr s . Terms of volume (R 3), surface (R 2), curvature (R), constant (R 0), (1/R) and (1/R 2) are clearly separated in the formula, as well as the different contributions (kinetic, coulombic and exchange-correlation) to each of them. The asymptotic values (R→∞) for the work functions,W(r s ), and surface energies σ(r s ), are compared to analogous semiclassical and Kohn-Sham calculations of jellium-like surfaces and to the experimental values. The size dependent behaviour of chemical potentials, μ(R), electron affinities,AF(R), and ionization potentials,IP(R), are easily obtained for any kind of metallic clusters. In particular we discuss the Coulomb and quantum corrections to the coefficients β, δ in the asymptotic formulae:IP?W+β/R andAF?W+δ/R.  相似文献   

    6.
    Homologously pure methyl bacteriopheophorbides-e and f (BPhes-e/fM) were prepared from modification of naturally occurring bacteriochlorophylls-c and d (BChls-c/d), respectively, by transformation of the methyl to formyl group at the 7-position. The absolute configuration of the 1-hydroxyethyl group at the 3-position of (Zn-)BPhes-e/fM was determined from comparison with structurally known BChl-c/d epimers. Visible spectra of synthetic (Zn-)BPhe-c/d/e/fM showed that the 71-oxidation and the 82/121/20-methylation affected Soret, Qx and Qy bands of both the monomeric (in a polar organic solvent) and oligomeric species (in a non-polar solvent).  相似文献   

    7.
    1R,2S,5R,8R; 1R,2S,5R,8S; 1S,2S,5R,8R; and 1S,2S,5R,8S-Iridodials have been prepared in five steps from 4aS,7S,7aR and 4aS,7S,7aS-nepetalactones, major components of catnip oil. 1R,2S,5R,8R-Iridodial has been identified as a male-produced male-aggregation pheromone for Chrysopa oculata, the first pheromone of any kind identified for lacewings.  相似文献   

    8.
    (S,R,S,R,S,R,S)- and (S,R,S,S,S,R,S)-octinaphthalenes were synthesized by oxidative coupling of (S,R,S)-quaternaphthalene, and differences due to axis chirality of (S,R,S,R,S,R,S)-, (S,R,S,S,S,R,S)-, (S,S,S,R,S,S,S)-, and (S,S,S,S,S,S,S)-octinaphthalenes were compared using the Rf values on TLC, specific optical rotations, 1H NMR chemical shifts of the hydroxy groups, and CD spectra. A clear CD additivity was found in the Δ? values of the 1La transition around 290 nm, which are proportional to the difference between the numbers of S and R binaphthalene units.  相似文献   

    9.
    《European Polymer Journal》1987,23(12):955-960
    In order to calculate conversion-time curve in radical polymerization, the termination rate constant for interacting polymer radicals with chain lengths n and s is written as: kt,ns = k(ζn + ζs) where k ∝ exp(−0.40/vf) (vf: free volume), and ζ = 1 at nnc and ζ = (nc/n)1,5 at nnc + 1 (nc: a critical chain length of polymer moving by reptation). The curves are applicable to the experimental data obtained from 20°C to 154°C in the thermal polymerization of styrene. Further, it is shown that the curves can be applied to the experimental data for polymerization in the presence of initiator.  相似文献   

    10.
    《Thermochimica Acta》1987,112(2):215-220
    The Law-Lielmezs (L-L) modification of the Van der Waals equation of state: P = RT/(V-b)-a(T)/V2 where: a(T) = a(Tca(Tc·a(T1) and: a(T1) = 1 + pT1q has been extended to include unsaturated states in terms of a correcting function Cf(such that the α(T1) term becomes: a(T1) = 1 + pCfT1q The proposed extension has been compared with the results obtained by the use of the original Van der Waals equation of state.  相似文献   

    11.
    The high resolution laser-atomic-beam technique was used to investigate the hyperfine structure in Nd I 4f 46s 2 5 I,5 F,5 S and 4f 45d6s 7 L,7 K,7 I,7 H. The metastable states were populated by an arc discharge burning in the atomic beam. The measured hyperfine constantsA andB of the levels of 4f 46s 2 and 4f 45d6s allow a parametric analysis to be performed using the effective tensor operator formalism. The experimental radial integrals of the 4f and 5d electrons fit with those of the other lanthanides. The 4f radial integrals are in agreement with values of optimized Hartree-Fock-Slater calculations. The spectroscopic quadrupole moments of143Nd and145Nd are deduced from the 4f parameters:Q I =?0.610(21) b and ?0.314(12) b, respectively. TheQ I resulting from the 5d parameter are in satisfactory agreement with these values. The hyperfine anomaly due to thes electron in 4f 45d 6s amounts to about 1%.  相似文献   

    12.
    A vibrating-tube densimeter (DMA 512P, Anton Paar, Austria) was used to investigate the densities and volumetric properties of aqueous potassium hydrogen phthalate (KHP) and potassium sodium phthalate (KNaP). Measurements were made at molalities m from (0.006 to 0.66)mol · kg  1, at temperatures from 278.15 K to 368.15 K and at the pressure 0.35 MPa. The densimeter was calibrated through measurements on pure water and on 1.0 mol · kg  1NaCl(aq). We also used a twin fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter (NanoDSC 6100, Calorimetry Sciences Corporation, Spanish Fork, UT, U.S.A.) to measure solution heat capacities. This was accomplished by scanning temperature and comparing the heat capacities of the unknown solutions to the heat capacity of water. Apparent molar volumes Vφand apparent molar heat capacities Cp, φof the solutions were calculated and fit by regression to equations that describe the surfaces (Vφ, T, m) and (Cp, φ, T, m). Standard state partial molar volumesV2o and heat capacities Cp,2owere estimated by extrapolation to the m =  0 plane of the fitted surfaces. Previously determinedCp, φ for HCl(aq) and NaCl(aq) were used to obtain (ΔrCp, m, T, m) for the proton dissociation reaction of aqueous hydrogen phthalate. This (ΔrCp,m, T, m) surface was created by subtracting Cp,φfor KHP(aq) and for NaCl(aq) from the sum of Cp,φfor KNaP(aq) and for HCl(aq). Surfaces representing (ΔrHm, T, m) and (pQa, T, m), where pQadenotes the molality equilibrium quotient, were created by integration of our (ΔrCp,m, T, m) surface using values for (ΔrHm, m) and (pKa, m) at T =  308.15 K from the literature as integration constants.  相似文献   

    13.
    《Polyhedron》1986,5(10):1607-1613
    Three types of vibronic coupling in hexacoordinate complexes are compared: the Tig−(a1g + eg) type in the group Oh, the Eg−(α1g + eg) type in the group D3d, and the Eg−(α1g + b1g) type in the group D4h. It is shown that the group with the highest symmetry (Oh) does not imply the best model of vibronic coupling. Numerical applications were obtained for 29 complexes of the MXq6 type having a triply degenerate electronic state in an octahedral geometry on the CNDO-UHF level of the MO-LCAO-SCF method. Characteristics of these Jahn-Teller active systems are calculated and discussed.  相似文献   

    14.
    High-resolution laser atomic beam spectroscopy has been applied to studyJ and term dependences in the isotope shift of the levels 4f 75d6s a 10 D J ,a 8 D J of Eu I. A parametric analysis of the isotope shift has been performed. TheJ dependence is interpreted through two term-dependent parametersz 5d , and the term dependence through one parameterΔT:z 5d (a 10 D)=44.1 (2.6) MHz,z 5d (a 8 D)=55.9 (2.3) MHz,ΔT=408.5 (3.2) MHz. Ab initio Hartree-Fock and Dirac-Fock calculations have been made to interpret these parameters. Within the accuracy of the calculations the parameters can be attributed to field shift effects.  相似文献   

    15.
    The kinetic model of the physical process of evaporation of plasticizer from plasticized PVC foils was developed from the results of isothermal thermogravimetric investigation of evaporation of benzyl-butyl phthalate in the temperature range 120-150 °C under nitrogen flow. The kinetic parameters were estimated by integral method of analysis. Mathematical modeling of the kinetic of plasticizers evaporation was performed on the basis of function c=f(T,t) and kinetic equation of evaporation −dc/dt=f(T,c0,c(t)). The developed mathematical model was described by the general kinetic equation . The differential quotients δ(−dc/dt)/δT=f(T,c0,c(t))=f(T,c0,t) and δ(−dc/dt)/δc0=f(T,c(t))=f(T,c0,t) were performed, and mathematical definition of the changes of the evaporation rate constant with the change of temperature and the change of the initial plasticized concentration were discussed.  相似文献   

    16.
    《Tetrahedron: Asymmetry》1998,9(6):1043-1049
    A technical scale preparation of optically active (1R,cisS)-cypermethrine 4 from racemic m-phenoxybenzaldehyde cyanohydrin acetate (RS)-1 and (1R,cis)-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid chloride (1R,cis)-3 is described. Key steps of the new procedure are a lipase catalyzed enantioselective transesterification of (RS)-1 with n-butanol and direct acylation of the mixture of (R)-1 and (S)-cyanohydrin (S)-2 with (1R,cis)-3 to give enantiomerically pure (1R,cisS)-4. The unchanged (R)-1 is removed from (1R,cisS)-4 by distillation, and is racemized with triethylamine to give (RS)-1 which is returned to the process. The total yield of (1R,cisS)-4 referred to (RS)-1 is 80%.  相似文献   

    17.
    Molar excess volumes VEijk of methylenebromide i + pyridine j + β-picoline (k, cyclohexane (i) + pyridine (j) + β-picoline(K), benzene(i)+toluene(j)+1,2-dichloroethane(k), benzene(i) + 0-xylene(j) + 1,2-dichloroethane(k) and benzene(i) + p-xylene(j) + 1,2-dichloroethane(k) mixtures have been determined dilatometrically at 298.15 K. The data have been examined in terms of Sanchez and Lacombe theory and the graph-theoretical approach, and it is found that they are described well by the latter. Self- and cross-volume interaction coefficients Vjk, Vjjk and Vjkk, etc., have also been evaluated and the values utilised to study molecular interactions between the jth and kth molecular species in the presence of the ith in these i + j + k mixtures.  相似文献   

    18.
    The hyperfine spectra of the 5s4d 3 D 1-5s20f, 5s4d 3 D 2-5s23f, and 5s 4d 3 D 3-5s32f transitions of87Sr (I=9/2) have been measured by collinear fast beam laser spectroscopy. The structure in the upper configurations is highly perturbed by fine structure splitting that is of comparable size to the hyperfine interaction energy. These perturbations can be adequately treated with conventional matrix diagonalization methods, using the 5s-electron magnetic dipole interaction terma 5s and the unperturbed fine structure splittings as input parameters. Additionally, hyperfine constants for the lower 5s4d 3 D configurations, including theA- andB-factors and a separation of the individuals- andd-electron contributions to these factors, are derived.  相似文献   

    19.
    O,O″- and O,O′-bis(2-aminoethyl)-p-tert-butylthiacalix[4]arenes of anti conformation have been prepared by the reduction of the corresponding O,O″- and O,O′-bis(cyanomethyl) ethers. Their syn-O,O″- and O,O′-counterparts have been prepared by alternative routes via the Mitsunobu reaction of thiacalix[4]arene with N-(2-hydroxyethyl)phthalimide and the reduction of a O,O′-disiloxanediyl-bridged O″,O?-bis(cyanomethyl) ether of 1,2-alternate conformation, respectively. These products are expected to serve as useful precursors of highly elaborated synthetic receptors, including biscalixarenes.  相似文献   

    20.
    《Tetrahedron: Asymmetry》2000,11(23):4737-4752
    The synthesis of enantiomerically pure (S)-4-phenylsulfinyl- and 4-phenylsulfonyl-(5S)-5-(l-menthyloxy)furan-2(5H)-ones 5a and 6 and (5R)-5-(l-menthyloxy)-4-phenylsulfonylfuran-2(5H)-one 8 and the study of their reactions with cyclopentadiene are described. The sulfur substituents at C-4 modify (sulfone 8, anti/syn=78/22) and invert (sulfoxide 5a and sulfone 6, anti/syn≈27/73) the trend imposed by C-5 on the π-facial selectivity and the syn-adducts become the favoured ones. The endo or exo approach mode is favoured for anti (endo/exo ratio ranging between 26 and 5) or syn (exo/endo ratio ranging between 4.5 and 2.3) attack, respectively.  相似文献   

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