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排序方式: 共有75条查询结果,搜索用时 15 毫秒
1.
M. Ya. Amusia N. A. Cherepkov L. V. Chernysheva 《Journal of Experimental and Theoretical Physics》2003,97(1):34-41
The results of calculations of the elastic scattering cross section of positrons on noble gas and alkali atoms are presented. The calculations are performed within the one-electron Hartree-Fock approximation with multielectron correlations in the so-called random phase approximation with exchange taken into account. Virtual positronium formation is taken into account and proved to be very important. Arguments are presented that the positron polarization potential is repulsive for alkali atoms. The results obtained are in a reasonable agreement with experiment and with some previously reported calculations. 相似文献
2.
M. Ya. Amusia R. Krivec E. Z. Liverts V. B. Mandelzweig 《Journal of Experimental and Theoretical Physics》2006,102(4):556-561
We discuss the results of the calculation of the photoionization with deexcitation of excited He and helium-like ions Li+ and B3+ at high but nonrelativistic photon energies θ. Several lower 1
S and 3
S states are considered. We present and analyze the ratios R
d
+
* of the cross sections of photoionization with deexcitation, σ
(d)
+
*(θ), and of the photoionization with excitation, σ+*(θ). The dependence of R
d
+
* on the excitation of the target object and the charge of its nucleus is presented. In addition to theoretical interest,
the results obtained can be verified using long-lived excited states such as 23
S of He.
The text was submitted by authors in English. 相似文献
3.
The appearance of the fermion condensation, which can be compared to the Bose-Einstein condensation, in different Fermi liquids is considered; its properties are discussed; and a large amount of experimental evidence in favor of the existence of the fermion condensate (FC) is presented. We show that the appearance of FC is a signature of the fermion condensation quantum phase transition (FCQPT), which separates the regions of normal and strongly correlated liquids. Beyond the FCQPT point, the quasiparticle system is divided into two subsystems, one containing normal quasiparticles and the other, FC, localized at the Fermi level. In the superconducting state, the quasiparticle dispersion in systems with FC can be represented by two straight lines, characterized by effective masses M FC * and M L * and intersecting near the binding energy E0, which is of the order of the superconducting gap. The same quasiparticle picture and the energy scale E0 persist in the normal state. We demonstrate that fermion systems with FC have features of a “quantum protectorate” and show that strongly correlated systems with FC, which exhibit large deviations from the Landau Fermi liquid behavior, can be driven into the Landau Fermi liquid by applying a small magnetic field B at low temperatures. Thus, the essence of strongly correlated electron liquids can be controlled by weak magnetic fields. A reentrance into the strongly correlated regime is observed if the magnetic field B decreases to zero, while the effective mass M* diverges as \(M^ * \propto {1 \mathord{\left/ {\vphantom {1 {\sqrt B }}} \right. \kern-\nulldelimiterspace} {\sqrt B }}\). The regime is restored at some temperature \(T^ * \propto \sqrt B \). The behavior of Fermi systems that approach FCQPT from the disordered phase is considered. This behavior can be viewed as a highly correlated one, because the effective mass is large and strongly depends on the density. We expect that FCQPT takes place in trapped Fermi gases and in low-density neutron matter, leading to stabilization of the matter by lowering its ground-state energy. When the system recedes from FCQPT, the effective mass becomes density independent and the system is suited perfectly to be conventional Landau Fermi liquid. 相似文献
4.
Amusia MY Chernysheva LV Manson ST Msezane AM Radojević V 《Physical review letters》2002,88(9):093002
A new and explicitly many-body aspect of the "leveraging" of the spin-orbit interaction is demonstrated, spin-orbit activated interchannel coupling, which can significantly alter the photoionization cross section of a spin-orbit doublet. As an example, it is demonstrated via a modified version of the spin-polarized random phase approximation with exchange, that a recently observed unexplained structure in the Xe 3d(5/2) photoionization cross section [A. Kivim?ki et al., Phys. Rev. A 63, 012716 (2000)] is entirely due to this effect. Similar features are predicted for Cs 3d(5/2) and Ba 3d(5/2). 相似文献
5.
The behavior of the specific heat cp, effective mass M*, and the thermal expansion coefficient of a Fermi system located near the fermion condensation quantum phase transition (FCQPT) is considered. We observe the first type behavior if the system is close to FCQPT: the specific heat
,
, while the thermal expansion coefficient
. Thus, the Grüneisen ratio Γ(T)=/cp does not diverges. At the transition region, where the system passes over from the non-Fermi liquid to the Landau Fermi liquid, the ratio diverges as
. When the system becomes the Landau Fermi liquid, Γ(T,r)∝1/r, with r being a distance from the quantum critical point. Provided the system has undergone FCQPT, the second type takes place: the specific heat behaves as
, M*∝1/T, and =a+bT with a,b being constants. Again, the Grüneisen ratio diverges as
. 相似文献
6.
The special features of magneto-dipole photoionization of atomic s states are analyzed and the possibilities of experimental observation of this effect are discussed. It has been shown that
despite the smallness of total cross sections for magnetic processes as compared with electric-dipole ones, the experimental
observation of magnetic effects is possible, in principle, if photoelectrons are detected in the directions perpendicular
to both the polarization vector of photon and its momentum; i.e. in the directions where the differential cross section for
electric-dipole ionization of atomic s states is close to zero. The capabilities of the derived general formulas for the magneto-dipole cross sections are illustrated
by numerical calculations for s subshells of He and Be atoms. 相似文献
7.
A strong influence of ns2np6 → ns2np5 εd transition on the outer ns subshell photoionization cross section of noble gas atomsis demonstrated. 相似文献
8.
Multiple energy scales are detected in measurements of the thermodynamic and transport properties in heavy fermion metals.
We demonstrate that the experimental data on the energy scales can be well described by the scaling behavior of the effective
mass at the fermion condensation quantum phase transition, and show that the dependence of the effective mass on temperature
and applied magnetic fields gives rise to the non-Fermi liquid behavior. Our analysis is placed in the context of recent salient
experimental results. Our calculations of the non-Fermi liquid behavior, of the scales and thermodynamic and transport properties
are in good agreement with the heat capacity, magnetization, longitudinal magnetoresistance and magnetic entropy obtained
in remarkable measurements on the heavy fermion metal YbRh2Si2. 相似文献
9.
The asymmetry parameter of the 3p photoelectrons in the region of the 3s-1 4p resonance in argon is calculated. It is demonstrated that going beyond the random phase approximation frame by inclusion of the “two-electron—two-hole” excitation gives results which are in good agreement with experiment. 相似文献
10.
The probability of single-photon decay of highly excited double hole state of atoms is considered. The concrete calculations are performed in the lowest order of perturbation theory in interelectron interaction for states (2s)-2 in Ne, (2s)-2 and (2p)-2 in double ionized Ar?Ar++ and (4d)-2 in Xe. 相似文献