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1.
S. Urabe K. Hayasaka M. Watanabe H. Imajo R. Ohmukai R. Hayashi 《Applied physics. B, Lasers and optics》1993,57(5):367-371
This paper describes trapping and laser cooling of a Ca+ ion in an rf quadrupole ion trap. A single Ca+ ion is laser cooled to below 130 mK and quantum jumps are observed by exciting the ion into the metastable D
5/2 state via the P
3/2 state. The lifetime of the metastable D
5/2 state is estimated from the distribution of the dark periods of the quantum-jump signal. Collision-induced jumps between the metastable D
3/2 state and the D
5/2 state in a background gas are also directly observed. 相似文献
2.
N. F. Fatkullin G. A. Yatsenko R. Kimmich E. Fischer 《Journal of Experimental and Theoretical Physics》1998,87(2):294-302
A general theory of spin diffusion in condensed media is constructed by the method of Zwanzig-Mori projection operators using
the superpositional approximation to decouple the many-particle correlation functions. The spin diffusion coefficient is expressed
in the form D
sp=D
tr+D
f
, where D
tr is the contribution associated with translational displacements of the molecules and D
f
is the contribution caused by intermolecular flip-flop processes. The expression for D
tr differs from the well-known Kubo-Green formula for the self-diffusion coefficient D
sd in that the integrand contains an additional factor P
f
(t), which is the probability of the molecular spins not participating in intermolecular flip-flop transitions over the time
t. A microscopic expression is obtained for D
f
in the form of a time integral of the intermolecular dipole-dipole dynamic correlation functions. For liquid-phase polymer
system with fairly high molecular mass the condition D
sp≫D
sd is satisfied.
Zh. éksp. Teor. Fiz. 114, 538–554 (August 1998) 相似文献
3.
The bubble model of ortho—positronium annihilation rates customarily employs the value of the planar-surface tension in the estimation of the (surface) energy required to expand a normal interstitial cavity to form the bubble. However, bubble radii are estimated to be only about 0.4 nm; the surface of such a small bubble is expected to have a tension different from that of the planar surface. We have replaced the surface tension parameter by the isothermal compressibility, which is thought not to have a nanostructure limitation. The model has been further improved by introducing the polarization ratio (n 2 D ? 1)/(n 2 D + 2) as a parameter, n D being the refractive index of the organic liquid. Calculations are presented for 20 liquids. 相似文献
4.
The notions of D-computable state and D-concurrence are generalized to the C
M
⊗ C
N
system. A class of D-computable state on C
M
⊗ C
N
is given and the calculating method of the lower bound of D-concurrence is provided. The obvious expression of the lower bound of D-concurrence for the state mixed by two D-pure states is derived.
Supported by the National Natural Science Foundation of China (Grant No. 60433050) and the Key Project of the Science Foundation
of Xuzhou Normal University (Grant No. 06XLA05) 相似文献
5.
S. I. Masharov 《Russian Physics Journal》1996,39(9):839-842
A general expression is obtained for the thermodiffusion coefficientD
T of a film, also for its dependence on temperature, film thickness and type of concentration distribution of the interstitials,
according to its profile. In neglecting interaction of interstitials with each other in a model of a film with single-plane
boundaries with the vacuum and the substrate, it is shown thatD
T>D
T
(∞) is possible, whereD
T
(∞) is the thermodiffusion coefficient of a bulk specimen.
Ural State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 43–46, September,
1996. 相似文献
6.
Jimmy Y. H. Liao Cordelia Selomulya Graeme Bushell Gtz Bickert Rose Amal 《Particle & Particle Systems Characterization》2005,22(5):299-309
Several methods to measure the structures of coal aggregates are compared. Loose and compact coal aggregates were generated through flocculation of ultrafine coal particles (mean volume diameter of 12 μm) under specific shearing conditions. Aggregate structure in terms of mass fractal dimension, Df, was determined using various methods; namely 2D and 3D image analysis, interpretation of intensity patterns from small angle light scattering, changes in aggregation state through light obscuration, and settling behavior. In this study, the measured values of Df ranged from 1.84–2.19 for coal aggregates with more open structures, and around 2.27–2.66 for the compact ones. All of these approaches could distinguish structural differences between aggregates, albeit with variation in Df values estimated by the different techniques. The discrepancy in the absolute values for fractal dimension is due to the different physical properties measured by each approach, depending on the assumptions used to infer Df from measurable parameters. In addition, image analysis and settling techniques are based on the examination of individual aggregates, such that a large number of data points are required to yield statistically representative estimations. Light scattering and obscuration measure the aggregates collectively to give average Df values of the particulate systems; consequently ignoring any structural variation between the aggregates, and leaving possible small contaminations undetected (e.g. by dust particles or air bubbles). Appropriate utilization of a particular method is thus largely determined by system properties and required data quality. 相似文献
7.
A. N. Yakunin 《Central European Journal of Physics》2003,1(2):355-362
Based on a solution of the polymer excluded volume problem, a technique is proposed to estimate some parameters at the isotropic-nematic
liquid crystal phase transition (the product of the volume fraction of hard sticks and the ratio of the stick length, L, to its diameter, D; the maximum value of this ratio at which one cannot regard the stick as hard). The critical exponents are estimated. The
transition of a swelling polymer coil to ideal is revealed as the polymerization degree of a macromolecule increases. The
entanglement concentration obtained agrees with experimental data for polymers with flexible chains. The number of monomers
between neighbor entanglements is assumed to be the ratio L/D. A comparison of the theory with other ones and recent experimental data is made. 相似文献
8.
9.
We investigated using transmission electron microscopy (TEM) the state of a long-period superstructure (LPS) composed of a metastable D03 phase, which emerged during crystallisation of Fe89Nd7B4 amorphous alloys [Konno, Uehara, Hirosawa, et al., Phil. Mag. A 79 2413 (1999)]. Diffraction studies showed that it is a two-dimensional (2D) LPS characterized by 1/4a 0?111? antiphase boundaries (APBs) perpendicular to ?100? directions and 1/2a 0?100? APBs perpendicular to ?110? directions, where a 0 is the unit cell parameter of the D03 cell. Dark field images and high-resolution TEM showed that superperiods estimated from diffraction patterns, 3.2 and 2.4?nm, respectively, represent an average structure; and real arrangements of APBs are rather diverse in terms of both periodicity and APB planes. These observations indicate that the 2D LPS emerged in the following reaction sequence: amorphous?→?A2?→?D03 with 2D LPS?→?D03, where all the phases are metastable. 相似文献
10.
S. E. Burkov 《Journal of statistical physics》1988,52(1-2):453-461
Hamiltonians for nonperiodic tilings are considered. It is shown that the quasicrystalline tiling obtained by the cut-and-strip method from aD-dimensional cubic lattice may bs a ground state only if the tiling possesses a high orientational symmetry: the (2,D)-quasicrystal should haveD-fold symmetry ifD is even and 2D-fold symmetry ifD is odd. For interactions of a finite range the restrictions are stronger: only a (2, 5)-quasicrystal (Penrose tiling) may be a stable ground state. 相似文献
11.
H. Vogler 《Molecular physics》2013,111(5):1179-1193
The lower excited singlet and triplet states and the zero-field splitting parameters D of [2.2]paracyclophane are studied within a semiempirical π theory which takes into account overlap effects between the two benzene rings, transanular and through-bond interaction via the methylene bridges. Whereas the singlet energies depend strongly on the through-bond interaction and the mutual polarization of σ core and π system this is not the case for the energies and zero-field splitting parameters D of the two lowest triplet states. The deformations of the benzene rings in [2.2]paracyclophane lead only to a small decrease of the excitation energies of about 0·2 eV. The D parameter can be written as a sum D = DA + DB + DAB with the intrasubunit contributions DA and DB of the conjugated subunits A and B of the phane and an intersubunit term DAB . We demonstrate that the deformations reduce the intrasubunit terms DA and DB and that they are crucial for the decrease of the D values of [2.2]paracyclophane with respect to p-xylene. The difference between the D values of the first and second triplet states is governed by the intersubunit term DAB which has a different sign in the two states. However, this difference does not depend markedly on the transanular interaction. A further reduction of DA and DB in the first triplet state only is caused by transanular interaction by means of symmetrical charge-transfer terms in the wavefunction. 相似文献
12.
Karl Kummerer 《Zeitschrift für Physik A Hadrons and Nuclei》1962,169(1):166-177
For the evaluation of float measurements all individual steps of the calculations are comprised under the expression of “precise float formula”. From this simplified approximations can be deduced. Their errors are estimated under little restraining conditions. The rather simple “difference formula” in the range of high D2O-concentration together with a density scale for pure D2O gained by interpolation suffice for most practical purposes. This is proved by numerical comparing with the precise formula. 相似文献
13.
Aycan Özkan 《Phase Transitions》2016,89(1):94-105
The mixed spin 3–spin 3/2 ferrimagnetic Ising model was simulated using cooling algorithm on cellular automaton (CA). The simulations were carried out in the intervals ?4 ≤ DA/J ≤ 8 and ?4 ≤ DB/J ≤ 8 for the square lattices with periodic boundary conditions. The ground-state phase diagram of the model has different types of ferrimagnetic phases. Although only the antiferromagnetic nearest-neighbor interaction was contained in the Hamiltonian, the compensation points emerged through DA/J = 2 at kT/J = 0. The values of the critical exponents (ν, α , β and γ) were estimated within the framework of the finite-size scaling theory and power-law relations for the selected DA/J values (?2, 0, 1, 2, and 4). The estimated critical exponent values were in good agreement with the universal values of the two-dimensional Ising model (ν = 1, α = α′ = 0, β = 0.125, β′ = 0.875 and γ = γ′ = 1.75). 相似文献
14.
Dipl.-Phys. Ottfried Thümmel 《Annalen der Physik》1987,499(8):601-611
To describe the degree of chaos of a strange attractor created by a nonlinear map, GRASSBERGER [1] revived Renyi Dimension Dq which is a common generalization of both metric capacity D0 and information dimension D1. But often, the numerical determination of Dq is complicated by an oscillating effect first investigated by BADII and PUOLITI [5] for a dimension similar to D0. This effect is studied in the present paper. We consider the conditions for the appearance of oscillations and the dependence on q, and we give some numerical examples. 相似文献
15.
The Laplace operator acting on antisymmetric tensor fields in a D-dimensional Euclidean ball is studied. Gauge-invariant local boundary conditions (absolute and relative ones, in the language
of Gilkey) are considered. The eigenfuctions of the operator are found explicitly for all values of D. Using in a row a number of basic techniques, as Mellin transforms, deformation and shifting of the complex integration contour
and pole compensation, the zeta function of the operator is obtained. From its expression, in particular, ζ(0) and ζ'(0)
are evaluated exactly. A table is given in the paper for D=3,4,...,8. The functional determinants and Casimir energies are obtained for D=3,4,...,6.
Received: 2 May 1996 / Accepted: 20 July 1996 相似文献
16.
The electromagnetic mass splittings of heavier hadrons are estimated in the framework of gauge theory model where ligher quarks
are taken to behave relativistically and the spatial wave functions are described by the spin-spin interaction affected relative
distances between quarks. The predictions for (Ξ−-Ξ0), (Σ*0−Σ*+), (Ξ*−-Ξ*0), (D
c
+−D
c
0) and (D
c
*+
−D
c
*0
) are in fair agreement with the experimental data available whereas those for (D
b
−
−D
b
0
) and (D
b
*−
−D
b
*0
) are in qualitative agreement with other theoretical estimates. 相似文献
17.
D. Schulze-Hagenest H. Harde W. Brand W. Demtröder 《Zeitschrift für Physik A Hadrons and Nuclei》1977,282(2):149-156
The fast-beam-spectroscopy is used for cascade-free high-precision lifetime measurements of highly excited atomic states, which are populated by a two-stage excitation as resulting from gas cell and laser interactions. An experimental extension of the method is presented demonstrating the selective population of high lying levels even from shorter-living intermediate states by an intracavity dye-laser excitation. A first example for this type of experiments is given for the lifetime of the Li 3d 2 D level, which was determined to be τ(32 D)=14.60±0.13 ns. The appropriate experimental set-up is described in detail and an approximate expression for signal calculation is presented, by which the applicability of this method to other levels can be estimated. 相似文献
18.
New calculations have been made of the self-diffusion coefficient D, the shear viscosity ηs, the bulk viscosity ηb and thermal conductivity λ of the hard sphere fluid, using molecular dynamics (MD) computer simulation. A newly developed hard sphere MD scheme was used to model the hard sphere fluid over a wide range up to the glass transition (~0.57 packing fraction). System sizes of up to 32 000 hard spheres were considered. This set of transport coefficient data was combined with others taken from the literature to test a number of previously proposed analytical formulae for these quantities together with some new ones given here. Only the self-diffusion coefficient showed any substantial N dependence for N < 500 at equilibrium fluid densities (ε 0.494). D increased with N, especially at intermediate densities in the range ε ~ 0.3–0.35. The expression for the packing fraction dependence of D proposed by Speedy, R. J., 1987, Molec. Phys., 62, 509 was shown to fit these data well for N ~ 500 particle systems. We found that the packing fraction ε dependence of the two viscosities and thermal conductivity, generically denoted by X, were represented well by the simple formula X/X 0 = 1/[1 ? (ε/ε1)]m within the equilibrium fluid range 0 > ε > 0.493. This formula has two disposable parameters, ε and m, and X 0 is the value of the property X in the limit of zero density. This expression has the same form as the Krieger-Dougherty formula (Kreiger, I. M., 1972, Adv. Colloid. Interface Sci., 3, 111) which is used widely in the colloid literature to represent the packing fraction dependence of the Newtonian shear viscosity of monodisperse colloidal near-hard spheres. Of course, in the present case, X o was the dilute gas transport coefficient of the pure liquid rather than the solvent viscosity. It was not possible to fit the transport coefficient normalized by their Enskog values with such a simple expression because these ratios are typically of order unity until quite high packing fractions and then diverge rapidly at higher values over a relatively narrow density range. At the maximum equilibrium fluid packing fraction ε = 0.494 for both the hard sphere fluid and the corresponding colloidal case a very similar value was found for ηs/ηo ?30–40, suggesting that the ‘crowding’ effects and their consequences for the dynamics in this region of the phase diagram in the two types of liquid have much in common. For the hard sphere by MD, Do/D ~ 11 at the same packing fraction, possibly indicating the contribution from ‘hydrodynamic enhancement’ of this transport coefficient, which is largely absent for the shear viscosity. Interestingly the comparable ratio for hard sphere colloids is the same. 相似文献
19.
S. Stoyanov 《Applied Physics A: Materials Science & Processing》1990,50(3):349-352
A quantitative treatment of the crystallization kinetics in MBE growth of vicinal surfaces results the relation l
2=2D
sK between the surface diffusion coefficient D
s, the time for a monolayer deposition and the interstep distance l at which the RHEED intensity oscillations disappear. The correction factor K depends on the size and the energy of the two-dimensional critical nucleus and it is estimated to be smaller than 10–2. The currently used interpretation of the RHEED intensity oscillations ignores the correction factor K and, therefore, the calculated values of D
s are several orders of magnitude smaller than its real values. The surface transport during the time of growth interruption is discussed in connection with the tendency to three dimensional growth at every second interface (where a deposition of the material with strong intermolecular bonds starts) of a small period superlattice. 相似文献
20.
Shimon Ochi Osamu Kamishima Junichiro Mizusaki Junichi Kawamura 《Solid State Ionics》2009,180(6-8):580-584
The proton dynamics in Nafion ®117 is investigated by comparison of the diffusion coefficient DNMR estimated from PFG-NMR with that of Dσ estimated from electrical conductivity. At high water content region, Dσ is about two times higher than DNMR as a result of Grotthuss mechanism. At low water content region, Dσ and DNMR are in good agreement with each other. Both of the diffusion coefficients decrease steeply at low water content region. It can be explained as a result of the percolation transition due to the isolation of ion clusters, which is suggested by the recent small angle X-ray scattering data. 相似文献