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1.
A. V. Mel’nichuk 《Journal of Experimental and Theoretical Physics》1999,89(2):344-348
The coefficient R(ν) of reflection from the surface of 6H-SiC single crystals is studied in the case in which the long-wavelength optical vibrations
of the lattice are coupled with the electron plasma. It is shown for the first time that the anisotropy of the properties
of electrons and phonons in 6H-SiC gives rise to special features in the spectrum of the coupled vibrations and the transparency
regions. It is found, in particular, that if the axis of the crystal lies in the polarization plane of the incident radiation
(0<θ<90°), for 30 cm−1⩽ν
p⊥<320 cm−1 the spectrum of R(ν) acquires three regions of transparency and opacity, and for ν
p⊥⩾320 cm−1 four such regions, which are absent in an isotropic medium. The width of these regions is found to depend on the electron
concentration in the conduction band and on the angle θ.
Zh. éksp. Teor. Fiz. 116, 646–654 (August 1999) 相似文献
2.
Surface plasmon-phonon polaritons (SPPP’s) of types 3 and 4 are investigated in doped anisotropic single crystals of hexagonal
silicon carbide (6H-SiC) in the orientation corresponding to K⊥C and xy⊥C. It is shown that a dispersion dependence of the type-3 SPPP’s bounded by K appears in 6H-SiC when the plasmon frequency increases to ν
p⊥⩾350 cm−1. At ν
p⊥⩾400 cm−1, ν
s(K) exists for type-4 SPPP’s in the frequency range Ω
∥
+
<ν<
⊥
+
. When the concentration of free charge carriers is increased, the dispersion curves are displaced toward higher frequencies.
The conditions for the existence of type-3 and type-4 SPPP’s in 6H-SiC are determined.
Fiz. Tverd. Tela (St. Petersburg) 40, 636–639 (April 1998) 相似文献
3.
We investigate the potential of eγ collisions to probe anomalous Wtb couplings via the polarized single top quark production
process e+γ→tb̄νē. We find 95% confidence level limits on the anomalous coupling parameters F2L and F2R with an integrated luminosity of 500 fb-1 and , 1 and 1.5 TeV energies. The effects of top quark spin polarization on the anomalous Wtb couplings are discussed. It is shown
that polarization leads to a considerable improvement in the sensitivity limits.
PACS 14.65.Ha; 13.88.+e 相似文献
4.
S. P. Dmitriev N. A. Dovator R. A. Zhitnikov V. A. Kartoshkin V. D. Mel’nikov 《JETP Letters》1997,65(5):399-401
An experiment on the observation of spin polarization of metastable helium atoms interacting with optically oriented sodium
atoms under continuous rf discharge conditions is described. Laser radiation with alternating-sign circular polarization,
tuned to the resonance excitation of the 32
S
1/2–32
P
1/2 transition in Na atoms, is used as the source for optical pumping of ground-state sodium atoms.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 385–387 (10 March 1997) 相似文献
5.
J. Dietel 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(2):195-205
We reconsider energy calculations of the spin polarized ν = 1/2 Chern-Simons theory. We show that one has to be careful in
the definition of the Chern-Simons path integral in order to avoid an IR divergent magnetic ground state energy in RPA as
in [J. Dietel et al, Eur. Phys. J. B 5, 439 (1998)]. We correct the path integral and get a well behaved magnetic energy by considering the energy of the maximal
divergent graphs as well as the Hartree-Fock graphs. Furthermore, we consider the ν = 1/2 and the ν = 5/2 system with spin
degrees of freedom. In doing this we formulate a Chern-Simons theory of the ν = 5/2 system by transforming the interaction
operator to the next lower Landau level. We calculate the Coulomb energy of the spin polarized as well as the spin unpolarized
ν = 1/2 and the ν = 5/2 system as a function of the interaction strength in RPA. These energies are in good agreement with
numerical simulations of interacting electrons in the first as well as in the second Landau level. Furthermore, we calculate
the compressibility, the effective mass and the excitations of the spin polarized ν = 2 + 1/ systems where is an even number.
Received 13 June 2000 相似文献
6.
Magnetoplastic effect in irradiated NaCl and LiF crystals 总被引:2,自引:0,他引:2
V. I. Al’shitz E. V. Darinskaya O. L. Kazakova 《Journal of Experimental and Theoretical Physics》1997,84(2):338-344
The effect of low x-ray irradiation doses (≈102 rad) on the magnetoplastic effect — the detachment of dislocations from paramagnetic centers under the action of an external
magnetic field B — in alkali-halide crystals has been investigated. The measurements were performed on LiF crystals and three types of NaCl
crystals, differing in impurity content. The dependence of the mean free path l of the dislocations on the rotational frequency ν of a sample in a magnetic field was especially sensitive to low irradiation doses. In unirradiated crystals this dependence
is a single-step dependence and is characterized by a critical frequency ν
c ∝B
2 above which the magnetoplastic effect is not observed. The frequency ν
c depends only on the type of paramagnetic centers, and not on their density. Even the lowest irradiation dose employed (<100
rad) leads to a sharp restructuring of the dependence l(ν), converting it into a two-step dependence (for edge dislocations) with an additional critical frequency ν
c2, that is insensitive to the irradiation dose, and that corresponds to the appearance of magnetically sensitive stoppers
of a new type under irradiation. The initial critical frequency ν
c1, as a rule, also varies with the dose, reflecting the change in state of the impurity complexes (Ca in NaCl and Mg in LiF).
Specifically, it is shown for NaCl(Ca) crystals that as the irradiation dose increases, the frequency ν
c1 increases, gradually approaching the value ν
c2, so that by the time the dose is ≈300 rad, the dependence l(ν) once again becomes a single-step dependence, dropping sharply only for ν⩾ν
c2. It is shown that the addition of a small number of Ni atoms to a NaCl crystal makes the Ca complexes radiation resistant,
and the critical frequency ν
c1 corresponding to them initially equals ν
c2 for crystals with no Ni. The recombination kinetics of radiation defects in the case in which the samples are irradiated
under a tungsten lamp was investigated. A possible physical model of the observed dependences is discussed.
Zh. éksp. Teor. Fiz. 111, 615–626 (February 1997) 相似文献
7.
A. Surzhykov T. Radtke P. Indelicato S. Fritzsche 《The European physical journal. Special topics》2009,169(1):29-34
We have applied the density matrix and second-order perturbation theory in order to re-analyze the two-photon decay of hydrogen-like
ions for the polarization of emitted light. Special attention is paid to the linear polarization of one of the photons, while
the spin state of the second photon is supposed to be unobserved. For such an “angle-polarization” correlation of the two
photons we investigate the contributions that arise from non electric-dipole terms in the expansion of the electron-photon interaction. Detailed calculations are performed for the 2s1/2 →1s1/2 and 3d5/2 →1s1/2 transitions in neutral hydrogen as well as in hydrogen-like uranium. 相似文献
8.
I. O. Troyanchuk L. S. Lobanovskii D. D. Khalyavin V. P. Yarunichev N. V. Pushkarev H. Szymczak 《Journal of Experimental and Theoretical Physics》1999,89(2):321-324
A study is performed of the crystalline structure, magnetization, and magnetotransport properties of the system La2/3Ba1/3(Mn1−x
Cox)O3 with perovskite structure. It is shown that cubic solid solutions exist over the entire range of cobalt concentrations 0⩽x⩽1. Compositions with x⩽0.2 are ferromagnets with maximum resistance near T
C
. Compositions with 0.2<x<0.4 manifest properties of inhomogeneous ferromagnets. Measurements of magnetic properties indicate the absence of long-range
magnetic order in compositions with 0.5⩽x⩽0.9, which are probably spin glasses. The spontaneous magnetization of cobaltate (2μ
B
per formula unit) corresponds to ferromagnetic ordering of the moments of the Co3+ and Co4+ ions found in the intermediate spin state. It is conjectured that the magnetoresistance consists of an extrinsic and an intrinsic
contribution. The first arises as a result of intergrain transport of spin-polarized charge carriers, and the second, as a
result of magnetic ordering near T
C
. The magnetoresistance is essentially independent of the spontaneous magnetization and decreases abruptly as the cobalt concentration
is increased with a corresponding transition from long-range to short-range magnetic order.
Zh. éksp. Teor. Fiz. 116, 604–610 (August 1999) 相似文献
9.
We use the spin non-degenerate single impurity Anderson model to investigate the influence of the local spin polarization
to the Kondo effect. By using the Schrieffer-Wolff transformation, we obtain a generalized s-d exchange Hamiltonian, which
describes the interaction between a polarized local spin and conduction electrons. In this case, the singlet is no longer
an eigenstate as shown by variational calculations where the splitting of the local energy Δ = ɛ
d↑ − ɛ
d↓ can be arbitrarily small. The local spin polarization generates the instability of the singlet ground state of the S = 1/2 s-d exchange model.
相似文献
10.
L. I. Buravov 《Russian Physics Journal》2009,52(1):25-32
Masses of a number of elementary particles are calculated on the basis of the model suggested in [1] with the use of one parameter. In this model, an electron is considered as an electric cloud enclosed inside an elastic
lepton shell, electron neutrino ν
е
is considered as an elastic lepton shell contracted to a minimal size, and muon, pion and kaon are considered as resonators
for quanta of virtual neutrinos excited inside the elastic lepton shell. The number and type of these quanta are determined
from the decay scheme for μ, π, and K: 2 for the muon (ν
е
and ), 3 for the pion (ν
е
,
ν
μ, and ), and at least 21 for the kaon. The model allows mass ratios approximating the experimental data for these particles to be
obtained for the first time, with the ratio of μ and е masses equal to (6πℏс/е
2)2/3 ≅ 188, the ratio of π
0 and μ masses equal to (3/2)2/3, and the ratio of K
0 and π
0
equal masses to 72/3. The calculated e, μ
,
π
0, and K
0 masses are in the 0.547:105.707:134.963:493.87 (MeV) ratios (normalized by the neutral pion mass). This is in good agreement
with the available experimental data. The mass ν
е
(≅ 0.02 eV) is also estimated in this model, and the variety of K-meson decay schemes is naturally explained as a result of the variety of excited intrinsic neutrino field structures with
the same energy.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 23–29, January, 2009. 相似文献
11.
S. V. Demishev A. V. Semeno H. Ohta S. Okubo I. E. Tarasenko T. V. Ishchenko N. E. Sluchanko 《JETP Letters》2006,84(5):249-253
Anomalous polarization characteristics of magnetic resonance in CuGeO3 doped with 2% Co impurity are reported. For the Faraday geometry, this mode is damped for the microwave field B
ω aligned along a certain crystallographic direction, showing that the character of magnetic oscillation differs from the standard
spin precession. The observed resonance coexists with the ESR on Cu2+ chains; it is argued not to be caused by “impurity” EPR, as previously claimed, but to correspond to a previously unknown
collective mode of magnetic oscillations in an S = 1/2 AF quantum spin chain.
The text was submitted by the authors in English. 相似文献
12.
A. I. Parkhomenko 《Journal of Experimental and Theoretical Physics》1999,88(5):913-920
The sudden approximation in energy is used to derive analytic formulas that describe the anomalous light-induced drift (LID)
of linear molecules absorbing radiation in the rovibrational transition nJ
i
−mJ
f
(n and m are the ground and excited vibrational states, and J
α
is the rotational quantum number in the vibrational state α=m, n). It is shown that for all linear molecules with moderate values B≲1 cm−1 of the rotational constant, anomalous LID can always by observed under the proper experimental conditions; temperature T, rotational quantum number J
i
, and type of transition (P or R). The parameter γ=B[J
i
(J
i
+1)−J
f
(J
f
+1)] ν
n
/2k
BT
(ν
m
−ν
n
) is used to derive a condition for observing anomalous LID: γ∼1 (k
B
is the Boltzmann constant and ν
α
is the transport rate of collisions of molecules in the vibrational state α and buffer particles at moderate molecular velocities
, where
is the most probable velocity of the buffer particles). For ν
m
>ν
n
anomalous LID can be observed only in P-transitions, while for ν
m
<ν
n
it can be observed only in R-transitions. It is shown that anomalous LID is possible for all ratios β=M
b
/M of the masses of the buffer particles (M
b
) and of the resonant particles (M) and any absorption-line broadening (Doppler or homogeneous). The optimum conditions for observing anomalous LID are realized
when the absorption line is Doppler-broadened in an atmosphere of medium-weight (β∼1) and heavy (β≫1) buffer particles. In this case, anomalous LID can be observed in the same transition within a broad temperature interval
ΔT∼T. If the buffer particles are light (β≪1) or if the broadening of the absorption line is homogeneous, anomalous LID in the same transition can be observed only
within a narrow temperature range ΔT≪T.
Zh. éksp. Teor. Fiz. 115, 1664–1679 (May 1999) 相似文献
13.
R. Kumar D. Mehta N. Singh H. Kaur A. Görgen S. Chmel R.P. Singh S. Murlithar 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):5-8
The band structures built on the 5- isomeric state ( T
1/2 = 3.46 m) in the doubly odd 130Cs nucleus have been established up to I = 24? via the 124Sn(11B, 5n)130Cs reaction. The previously observed bands based on the πh
11/2⊗νh
11/2, πg
7/2⊗νh
11/2 and πd
5/2⊗νh
11/2 configurations and a positive-parity side band with multiple connections to the α = 0 signature partner of the yrast πh
11/2⊗νh
11/2 band have been extended to higher spins. A new band based on the πh
11/2⊗νg
7/2 configuration is observed. The yrast πh
11/2⊗νh
11/2 band exhibits anomalous signature splitting whose magnitude decreases up to spin 15 and then increases without restoring
the normal signature splitting.
Received: 20 February 2001 / Accepted: 9 May 2001 相似文献
14.
Yu. A. Shitov 《Physics of Atomic Nuclei》2006,69(12):2090-2095
The NEMO-3 detector has been taking data in the Fréjus underground laboratory (LSM, France) since February 2003 and is devoted
to the search for neutrinoless double-beta decay (0νββ). After 389 effective days of data collection from February 2003 until September 2004 (Phase I), no evidence for neutrinoless
double-beta decay was found from ∼7 kg of 100Mo and ∼1 kg of 82Se. The corresponding limits for the half-lives are T
1/2(0νββ) > 4.6 × 1023 yr for 100Mo and T
1/2(0νββ) > 1.0 × 1023 yr for 82Se (90% C.L.). They lead to the following limits for the effective Majorana neutrino mass: 〈m
ν〉 < 0.7–2.8 eV for 100Mo and 〈m
ν〉 < 1.8–4.9 eV for 82Se. The half-lives of the two-neutrino double-beta decay (2νββ) have been measured for 100Mo, 82Se, 116Cd, 150Nd, and 96Zr and reported here as well.
on behalf of NEMO Collaboration
The text was submitted by the author in English. 相似文献
15.
The energy level structure of F
3
+
laser color centers in crystals of LiF is discussed. A high-power laser (λ
ex=920 nm) is used to excite luminescence from LiF crystals with F
3
+
centers via two-photon absorption, and the dependence of the polarization and intensity of this luminescence on the polarization
of the laser light is measured and calculated. It is shown that the two-photon transition involves the excitation of a previously
unknown state of the F
3
+
center—a spin singlet whose wave function has 1
A
1 symmetry.
Fiz. Tverd. Tela (St. Petersburg) 39, 1373–1379 (August 1996) 相似文献
16.
The colossal negative magnetoresistance Δρ observed in La0.6Y0.1Ca0.3MnO3 at B=1 T shows an unusual, nearly perfect symmetry (around the peak temperature T
0=160 K), suggestive of a Curie-Weiss-dominated transport mechanism in this material both above and below the field-dependent
Curie temperature T
C ≡ T
0. Attributing this symmetry to strong magnetic fluctuations below T
C (which are triggered by the Y substitution and cause a “bootstrap” destruction of the ferromagnetic phase), the data are
interpreted in terms of the nonthermal spin hopping and magnetization-dependent charge carrier localization scenario leading
to
, with the magnetization M(T,B)=CB/|T−T
C(B)|ν. The separate fits through all the data points above and below T
C yield C
+≃2C
− and ν+≃ν−≃1, in agreement with the predictions of the Landau mean-field theory.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 2, 136–140 (25 July 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
17.
We investigate the effects of Ru-doping in polycrystalline TbMn1−x
Ru
x
O3 (x≤0.10) on the multiferroicity. It is observed that the Ru substitution gradually melts away the dielectric anomaly at the
ferroelectric transition point and the ferroelectricity by suppressing the polarization, accompanied with a surprising low-temperature
dielectric plateau. While it is reasonable to observe the significant suppression of ferroelectricity, owing to the fact that
the Ru-doping disrupts the Mn spiral spin ordering and reduces the Mn–Mn spin angle, quantum fluctuations associated with
the Ru substitution, responsible for the low-temperature dielectric plateau, seems to be significant. 相似文献
18.
The role of mesomethyl substitution and of steric interaction of peripheral substituents in the formation of nonplanar distortions
of the porphyrin macrocycle is studied for a series of Ni(II)-porphyrins. Resonance Raman spectra are recorded for Ni(II)-5-methyl-2,3,7,8,12,13,17,18-octaethylporphyrin
(1); Ni(II)-2,5,8,12,18-pentamethyl-3,7,13,17-tetraethylporphyrin (2); and Ni(II)-3,5,7,12,17-pentamethyl-2,8,12,17-tetraethylporphyrin
(3). The obtained spectra are compared with spectra of Ni-octaethylporphyrin (Ni-OEP) and Ni-etioporphyrin II. It is found
that introducing one methyl group into a mesoposition leads to significant low-frequency distortions of the structure-sensitive
lines of resonance Raman scattering. Specifically, frequenciesν
3
,ν
11
,ν
19
,ν
2
, andν
10
decrease by 10–44 cm−1 while frequencyν
4
remains practically unchanged. It is shown that the observed spectral variations are caused by nonplanar distortions of the
structure of Ni-porphyrins. The same tendency of the line displacement for tetragonal Ni-OEP and for compounds 1, 2, and 3
indicates that CH3-mesosubstituted Ni-porphyrins have a “corrugated” structure. The degree of nonplanarity is modulated by alkyl groups on pyrrole
rings and increases in the porphyrin series 3→2→1. All mesomethyl-substituted Ni-porphyrins have spectral indications that
the considered compounds are structurally heterogeneous in solution due to the presence of conformers with different degrees
of planarity.
Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 170–176, March–April, 1999. 相似文献
19.
J. R. Suárez F. Estrada O. Navarro M. Avignon 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(1):53-58
We have studied the effect of cationic disorder on the spin polarization of the double
perovskite system
Sr2Fe1+x
Mo1−x
O6
with −1 ≤ x ≤ 1/3. The composition x = 0 corresponds
to the well-known double-perovskite Sr2FeMoO6, which is expected to
have complete spin polarization, however all samples present some degree of Fe/Mo disorder
which reduces the tunneling magnetoresistance in granular samples. We consider an
electronic model within the renormalized perturbation expansion Green’s functions,
consisting in a correlated electron picture with localized Fe-ions and itinerant electrons
interacting with the local spins via a double-exchange type mechanism. Our results show
the influence of disorder on the density of states and the ground-state properties,
particularly on the spin polarization over the whole range of x. 相似文献
20.
YeBing Xing XiaoHong Zhou YuHu Zhang YingXiang Guo Long Ma XiangGuo Lei WenTao Guo M. Oshima Y. Toh M. Koizumi A. Osa Y. Hatsukawa FuRong Xu M. Sugawara 《中国科学G辑(英文版)》2008,51(8):1053-1071
High-spin states in 187Pt were studied via the 173Yb(18O, 4n) reaction. Rotational bands based on the νi13/2, ν7/2−[503], νi2
13/2νj, ν3/2−[512] and ν1/2−[521] configurations were observed, and interpreted within the framework of the cranked shell model. The TRS calculations
show that the νi13/2 band has an appreciable negative γ deformation, and the negative-parity bands tend to have a near prolate shape with small positive γ values. Experimental values of B(M1)/B(E2) ratios have been extracted and compared with theoretical values from the semi-classical D?nau and Frauendof approach,
strongly suggesting a low frequency πh9/2 alignment in the ν7/2−[503] band.
Supported by the National Natural Science Foundation of China (Grant Nos. 10475097 and 10505025) and the Chinese Academy of
Sciences 相似文献