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1.
First-principles investigation of diffusion behaviours of H isotopes:From W(110) surface into bulk and in bulk W 下载免费PDF全文
<正>The diffusion behaviours of hydrogen(H),deuterium(D),and tritium(T) from W(110) surface into bulk and in bulk W are investigated using first-principles calculations combined with simplified models.The diffusion energy barrier is shown to be 1.87 eV from W(110) surface to the subsurface,along with a much reduced barrier of 0.06 eV for the reverse diffusion process.After H enters into the bulk,its diffusion energy barrier with quantum correction is 0.19 eV. In terms of the diffusion theory presented by Wert and Zener,the diffusion pre-exponential factor of H is calculated to be 1.57×10-7 m2·s-1,and it is quantitatively in agreement with the experimental value of 4.1×10-7 m2·s-1. Subsequently,according to mass dependence((1/m)1/2) of H isotope effect,the diffusion pre-exponential factors of D and T are estimated to be 1.11×10-7 m2·s-1 and 0.91×10-7 m2·s-1,respectively. 相似文献
2.
The chirality-asymmetry macroscopic force mediated by light
pseudoscalar particles between α -quartz and some achiral
matter is studied. If this force between achiral source mass and
α -quartz with some chirality is attractive, it will become
repulsive when the chirality of the α -quartz crystal is
changed. According to the tested limits of the coupling constant
gs gp /\hbar c< 1.5× 10-24 at the
Compton wavelength λ = 10-3 m, the force (F) between
a 0.08× 0.08× 0.002 m3 block of α -quartz
and a 0.08× 0.08× 0.01 m3 copper block with a
separation being 0.5× 10-3 \mbox{m} in between, is
estimated from the published data at less than 4.64× 10-24 N, i.e. F < 4.64× 10-24 N. 相似文献
3.
An interaction potential for an N2(X1σg+) molecule is constructed by using the highly accurate
valence internally contracted multireference configuration
interaction method and the largest basis set, aug-cc-pV6Z, in the
valence range. The potential is used to investigate the elastic
scattering of two N atoms at energies from 1.0× 10-11
to 1.0× 10-4 a.u. The derived total elastic cross
sections are very large and almost constant at ultralow
temperatures, and the shape of total elastic cross section curve is
mainly dominated by the s-partial wave at very low collision
energies. Three shape resonances are found in the total elastic
cross sections. Concretely, the first one is very sharp and strong.
It results from the g-partial-wave contribution and the resonant
energy is 3.645× 10-6 a.u. The second one is contributed
by the h-partial wave and the resonant energy is 1.752× 10-5 a.u. This resonance is broadened by those from the d- and
f-partial waves. The third one comes from the l = 6 partial wave
contribution and the resonant energy is 3.522× 10-5 a.u.
This resonance is broadened by those from the g- and h-partial
waves. The N2(X1σg+) molecular
parameters, which are determined at the current theoretical level,
achieve very high accuracy due to the employment of the largest
correlation-consistent basis set in the valence range. 相似文献
4.
We have established a caesium double magneto-optical trap (MOT) system for
cavity-QED experiment, and demonstrated the continuous transfer of cold caesium
atoms from the vapour-cell MOT with a pressure of ~ 1×10-6 Pa to
the ultra-high-vacuum (UHV) MOT with a pressure of ~ 8×10-8 Pa via a
focused continuous-wave transfer laser beam. The effect of frequency detuning as
well as the intensity of the transfer beam is systematically investigated, which
makes the transverse cooling adequate before the atoms leak out of the vapour-cell
MOT to reduce divergence of the cold atomic beam. The typical cold atomic flux got
from vapour-cell MOT is ~2×107 atoms/s. About 5×106
caesium atoms are recaptured in the UHV MOT. 相似文献
5.
Effect of RF power on the properties of transparent conducting zirconium-doped zinc oxide films prepared by RF magnetron sputtering 总被引:2,自引:0,他引:2 下载免费PDF全文
Transparent and conducting zirconium-doped zinc oxide films with
high transparency and relatively low resistivity have been
successfully prepared by radio frequency (RF) magnetron sputtering
at room temperature. The RF power is varied from 75 to 150W. At
first the crystallinity and conductivity of the film are improved
and then both of them show deterioration with the increase of the RF
power. The lowest resistivity achieved is 2.07×10-3\Omegacm
at an RF power of 100W with a Hall mobility of
16cm2V-1s-1 and a carrier concentration of
1.95×1020cm-3. The films obtained are polycrystalline
with a hexagonal structure and a preferred orientation along the
c-axis. All the films have a high transmittance of approximately
92% in the visible range. The optical band gap is about 3.33eV
for the films deposited at different RF powers. 相似文献
6.
Unambiguously Resolving the Potential Neutrino Magnetic Moment Signal at Large Liquid Scintillator Detectors 下载免费PDF全文
《中国物理快报》2021,(11)
Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. The XENON1T experiment recently detected an excess of electron recoil events in the 1–7 keV energy range, which can be compatible with solar neutrino magnetic moment interaction at a most probable value of μ_v = 2.1 × 10-11μ_B.However, tritium backgrounds or solar axion interaction in this energy window are equally plausible causes.Upcoming multi-tonne noble liquid detectors will test these scenarios more in depth, but will continue to face similar ambiguity. We report a unique capability of future large liquid scintillator detectors to help resolve the potential neutrino magnetic moment scenario. With O(100) kton·year exposure of liquid scintillator to solar neutrinos, a sensitivity of μ_v 10-11μ_B can be reached at an energy threshold greater than 40 keV, where no tritium or solar axion events but only neutrino magnetic moment signal is still present. 相似文献
7.
Passive magnetic shielded spin polarized electron source with optical electron polarimeter 下载免费PDF全文
A new GaAs(100) spin polarized electron source with an optical
polarimeter, which is employed in the field of polarized electron
and gas atom collision, is presented in detail. The apparatus is
passive-magnetic-shielded by a box and a cylinder made of
nickel--iron--molybdenum soft magnetic alloy without Helmholtz coil
arrangement. And a uniformly distributed residual magnetic field of
less than 5×10-7,T is obtained near the collision area. The
spin polarized electron beam is transmitted and focused onto
collision point from photocathode by a set of electron optics with
more than 25% transmission 95cm distance through an 1mm
diameter aperture. Construction and operation of the apparatus, such
as vacuum and magnetic shielding system, photocathode, laser optics,
electron optics and polarimeter are discussed. The polarization of
the spin polarized electron beam is determined to be 30.8\pm3.5%
measured with a He optical polarimeter. 相似文献
8.
UlaşÖzdem 《中国物理C(英文版)》2021,(2):341-350
Using the light-cone QCD sum rules,we evaluate the magnetic moment of the P_c(4312) pentaquark state by considering both the \bar D\Sigma_c molecular and diquark-diquark-antiquark state,with quantum numbers J^P=2/1-1.In the calculations,we use the diquark-diquark-antiquark and molecular form of the interpolating currents for the Pc4312 pentaquark and the distribution amplitudes of the photon.The numerical results for the magnetic moment obtained using the two different pictures are quite different from each other,which can be used to pin down the underlying structure of Pc4312 .Any experimental measurement of the magnetic moment in the near future will provide an understanding of the internal structure of this pentaquark state. 相似文献
9.
We performed calculations of the electronic band structure and the Fermi surface,measured the longitudinal resistivity ρxx(T,H),Hall resistivity ρxy(T,H),and magnetic susceptibility as a function of temperature at various magnetic fields for VAs2 with a monoclinic crystal structure.The band structure calculations show that VAs2 is a nodal-line semimetal when spin-orbit coupling is ignored.The emergence of a minimum at around11 K in ρxx(T) measured at H=0 demonstrates that some additional magnetic impurities(V4+,S=1/2)exist in VAs2 single crystals,inducing Kondo scattering,evidenced by both the fitting of ρxx(T) data and the susceptibility measurements.It is found that a large positive magnetoresistance(MR) reaching 649% at 10 K and 9 T,its nearly quadratic field dependence,and a field-induced up-turn behavior of ρxx(T) also emerge in VAs2,although MR is not so large due to the existence of additional scattering compared with other topological nontrivial/trivial semimetals.The observed properties are attributed to a perfect charge-carrier compensation,which is evidenced by both the calculations relying on the Fermi surface and the Hall resistivity measurements.These results indicate that the compounds containing V(3d34s2) element can be as a platform for studying the influence of magnetic impurities to the topological properties. 相似文献
10.
CALCULATION OF THE FINE STRUCTURE OF OXYGEN-LIKE IONS USING THE POLARIZATION POTENTIAL FUNCTION 下载免费PDF全文
We have calculated the forbidden transition energies and magnetic dipole transition probabilities of 2s22p4(3P1-3P2) and 2s22p4 (3P0-3P1) of oxygen-like isoelectronic sequences (Z=10-32) by a method of polarization potential correction. The transition energies show good agreement with experiment and are much better than the calculations in the literature. These results also illustrate that it is feasible to use the dipole expansion of the polarization potential to deal with some dynamic and non-dynamic effects in the central field approach. The relation of polarizability and cut-off radius with atomic number is discussed. We also give the fitted formula between the polarizability α1 and atomic number Z as α1=0.73429-9.56644×10-4Z+7.43016×10-5Z2-2.53298×10-6Z3+2.08306×10-8Z4. 相似文献
11.
We have successfully grown an arsenopyrite marcasite type RhSb2 single crystal, and systematically investigated its crystal structure, electrical transport, magnetic susceptibility, heat capacity, and thermodynamic properties. We found that the temperature-dependent resistivity exhibits a bad metal behavior with a board peak around 200 K. The magnetic susceptibility of RhSb2 shows diamagnetism from 300 K to 2 K. The low-temperature specific heat shows a metallic behavior with a quite small electronic specific-heat coefficient. No phase transition is observed in both specific heat and magnetic susceptibility data. The Hall resistivity measurements show that the conduction carriers are dominated by electrons with ne = 8.62 × 1018 cm-3 at 2 K, and the electron carrier density increases rapidly above 200 K without change sign. Combining with ab-initio band structure calculations, we showed that the unusual peak around 200 K in resistivity is related to the distinct electronic structure of RhSb_2. In addition, a large thermopower S(T) about -140 μV/K is observed around 200 K, which might be useful for future thermoelectric applications. 相似文献
12.
Monte carlo simulation of magnetization and coercivity of free magnetic clusters 总被引:4,自引:0,他引:4 下载免费PDF全文
Based on Monte Carlo method, the oscillatory behaviour of the
average magnetic moment as a function of the cluster sizes and the
temperature dependences of magnetic moment with different sizes have
been studied. It is found that the oscillations superimposed on the
decreasing moment are associated with not only the geometrical
structure effects but also the thermal fluctuation. The hystereses
and thermal coercivities for free clusters with zero and finite
uniaxial anisotropies have been calculated. The simulated thermal
dependence of the coercivity is consistent with the experimental
result, but does not fit the Tα law in the whole temperature
range. It is evident that an easy magnetization direction and an
anisotropy resulting from the spin configurations exist in the free
clusters with the pure exchange interaction, which is also proved by
the natural angle and energy distribution of clusters. A systematic
theoretical analysis is also made to establish the relationship
between natural angle and coercivity. 相似文献
13.
Room-temperature ferromagnetism with high magnetic moment in Cu-doped AlN single crystal whiskers 下载免费PDF全文
Ferromagnetism is investigated in high-quality Cu-doped A1 N single crystal whiskers.The whiskers exhibit roomtemperature ferromagnetism with a magnetic moment close to the results from first-principles calculations.High crystallinity and low Cu concentrations are found to be indispensable for high magnetic moments.The difference between the experimental and theoretical moment values is explored in terms of the influence of nitrogen vacancies.The calculated results demonstrate that nitrogen vacancies can reduce the magnetic moments of Cu atom. 相似文献
14.
A novel dual-emitter vacuum Compton detector (D-VCD) with
higher gamma ray detecting efficiency is proposed. The emitters are
made of Ta--Al clad metal. The gamma ray sensitivity is studied by
Monte Carlo simulation using the MCNP code. A comparison
between calculations and results measured by using the 1.25~MeV
gamma ray of Co-60 is also performed. Experimental sensitivities for
two sample D-VCDs with the same materials and structures are
1.92×10^ - 20 and 2.02×10^ -
20~C.cm2/MeV separately, which are consistent with
the simulation result of 1.98×10^ -
20~C.cm2/MeV and are 4 times higher than that of
VCD with a single Fe emitter. According to the simulation results, in
a gamma energy range from 0.5 to 3~MeV, the maximum sensitivity
variance for the D-VCD is less than 15%, and less than 5% in a
range from 1 to 2~MeV in particular. The novel D-VCD is applicable to
the detection of intense pulse gamma rays. 相似文献
15.
Origin of the Downturn in Inverse Susceptibility Observed above the Curie Temperature in Perovskite Manganites 下载免费PDF全文
The measurement of low-field susceptibility X as a function of temperature T for La2/3Ca1/3MnO3 shows a significant downturn in 1/X(T) above the Curie temperature Tc, a behaviour generally observed in perovskite manganites. Such a downturn is argued to be due to the segregation of ferromagnetic clusters with larger spins in the paramagnetic matrix. Based on this consideration, a phenomenological expression for X(T) is proposed,in which the total susceptibility is assumed to be a sum of two susceptibilities arising from magnetic entities in the PM background and the FM clusters with T-dependent effective spins, respectively. The result is in good agreement with the experimental data obtained in La2/3Ca1/3MnO3. 相似文献
16.
An All-Polarization-Maintaining Multi-Branch Optical Frequency Comb for Highly Sensitive Cavity Ring-Down Spectroscopy 下载免费PDF全文
We demonstrate a multi-branch all polarization-maintaining Er:fiber frequency comb with five application ports for precise measurement of atomic/molecular transition frequencies in the near-infrared region. A fully stabilized Er:fiber frequency comb with a nonlinear amplifying loop mirror is achieved. The in-loop relative instability of stabilized carrier-envelope-offset frequency is 5.6 × 10-18 at 1 s integration time, while that of the repetition rate is well below 1.8 × 10-12<... 相似文献
17.
The magnetic properties and the magnetic entropy change AS have been investigated for Gd6Co1.67Si3 compounds with a second-order phase transition. The saturation moment at 5 K and the Curie temperature TC are 38.1μB and 298 K, respectively. The AS originates from a reversible second-order magnetic transition around TC and its value reaches 5.2 J/kg.K for a magnetic field change from 0 to 5T. The refrigerant capacity (RC) of Gd6Co1.67Si3 are calculated by using the methods given in Refs.[12] and [21], respectively, for a field change of 0 5T and its values are 310 and 440 J/kg, which is larger than those of some magnetocaloric materials with a first-order phase transition. 相似文献
18.
Mn-doped graphene is investigated using first-principles calculations based on the density functional theory(DFT).The magnetic moment is calculated for systems of various sizes,and the atomic populations and the density of states(DOS)are analyzed in detail.It is found that Mn doped graphene-based diluted magnetic semiconductors(DMS)have strong ferromagnetic properties,the impurity concentration influences the value of the magnetic moment,and the magnetic moment of the 8×8 supercell is greatest for a single impurity.The graphene containing two Mn atoms together is more stable in the 7×7 supercell.The analysis of the total DOS and partial density of states(PDOS)indicates that the magnetic properties of doped graphene originate from the p–d exchange,and the magnetism is given a simple quantum explanation using the Ruderman–Kittel–Kasuya–Yosida(RKKY)exchange theory. 相似文献
19.
郭子溢 Lars Bathe-Peters 陈少敏 Mourad Chouaki 窦威 郭磊 Ghulam Hussain 李进京 刘倩 罗光 骆文泰 祁鸣 邵文辉 唐健 万林焱 王喆 续本达 徐彤 徐蔚然 杨玉梓 Minfang Yeh 赵林 《中国物理C(英文版)》2021,(2):509-517
China Jinping Underground Laboratory(CJPL)is ideal for studying solar,geo-,and supernova neutrinos.A precise measurement of the cosmic-ray background is essential in proceeding with R&D research for these MeV-scale neutrino experiments.Using a 1-ton prototype detector for the Jinping Neutrino Experiment(JNE),we detected 264 high-energy muon events from a 645.2-day dataset from the first phase of CJPL(CJPL-I),reconstructed their directions,and measured the cosmic-ray muon flux to be (3.53±0.22_stat.±0.07_sys.)×-10-10cm-2.The observed angular distributions indicate the leakage of cosmic-ray muon background and agree with simulation data accounting for Jinping mountain's terrain.A survey of muon fluxes at different laboratory locations,considering both those situated under mountains and those down mine shafts,indicates that the flux at the former is generally a factor of (4±2) larger than at the latter,with the same vertical overburden.This study provides a convenient back-of-the-envelope estimation for the muon flux of an underground experiment. 相似文献
20.
Using a full configuration-interaction method with Hylleraas-Gaussian basis function, this paper investigates the 110+, 11(–1)+ and 11(–2)+ states of the hydrogen negative ion in strong magnetic fields. The total energies, electron detachment energies and derivatives of the total energy with respect to the magnetic field are presented as functions of magnetic field over a wide range of field strengths. Compared with the available theoretical data, the accuracy for the energies is enhanced significantly. The field regimes 3 < γ < 4 and 0.02 < γ < 0.05, in which the 11(–1)+ and 11(–2)+ states start to become bound, respectively, are also determined based on the calculated electron detachment energies. 相似文献