共查询到20条相似文献,搜索用时 46 毫秒
1.
S. B. Dubovichenko 《Russian Physics Journal》2011,54(2):157-164
The experimental data on the astrophysical S-factor of the p
2H radiative capture are well described for energies from 1 keV to 10 MeV using the potential cluster model and the Young schemes
of orbital cluster state classification with allowance for the E1 and M1 transitions. 相似文献
2.
The experimental data for (n, 2n) reaction cross-sections around 14 MeV neutron energy have been collected from the literature and analysed for the isotopes
having 1 ≤ Z ≤ 82. The empirical relations for the reaction cross-sections have been obtained, which show fairly good fits with the experimental
values. The shell effects have been established at magic nucleon numbers for (n, 2n) reaction cross-sections around 14 MeV neutron energy. The odd-even effects have also been observed as the cross-sections
for odd-mass nuclei are higher than their neighbouring even-even nuclei.
相似文献
3.
S. P. Kamerdzhiev D. A. Voitenkov E. E. Saperstein S. V. Tolokonnikov M. I. Shitov 《JETP Letters》2017,106(3):139-144
Transition probabilities between low-lying one-phonon states of magic nuclei are for the first time computed self-consistently within an approach to anharmonic effects based on the quantum theory of many-body systems. In the adopted approach, three-quasiparticle correlations in the ground state are taken into account, and the nuclear mean field is interrelated with the effective nucleon–nucleon interaction. These quantities are derived using the energy density functional method with known parameters of the Fayans functional. The E1 and E2 transitions in the 132Sn and 208Pb nuclei are considered as an example, and a reasonably good agreement with the data on these nuclei is reached. Three-quasiparticle correlations in the ground state are shown to make a significant contribution to the probabilities of the discussed transitions. 相似文献
4.
The probabilities for E2 transitions between low-lying excited 3? and 5? single-phonon states in the 208Pb and 132Sn magic nuclei are estimated on the basis of the theory of finite Fermi systems. The approach used involves a new type of ground-state correlations, that which originates from integration of three (rather than two, as in the random-phase approximation) single-particle Green’s functions. These correlations are shown to make a significant contribution to the probabilities for the aforementioned transitions. 相似文献
5.
The experimental study of the proton-rich nuclei close to the N = Z line is a constant challenge for nuclear spectroscopy, mainly due to the difficulty to produce them with the currently available beam/target combinations. Significant advances on this direction were obtained from experiments performed with the GASP array during the last two years: the yrast line of 84Mo was extended up to 10 + , 88Ru observed for the first time, and the N = Z + 1 line was mapped from 81Zr to 95Ag. These new results allow us to have a more complete image of the transition from the well-deformed shell closure at N,Z = 40 to the spherical-shell closure at N,Z = 50, and highlights some particular effects that can be observed only in the vicinity of the N = Z line.Received: 10 January 2003, Published online: 23 March 2004PACS:
21.10.-k Properties of nuclei; nuclear energy levels - 21.10.Pc Single-particle levels and strength functions - 21.10.Re Collective levels - 23.20.-g Electromagnetic transitions 相似文献
6.
During the last decade, as the experimental and computing means and techniques have rapidly evolved, the experimental investigation of the f7/2-shell nuclei has gained renewed interest. TheN = Z nuclei studied with the GASP array range from 44Ti to 52Fe. The results extended the knowledge of their structure up to high spins and excitation energies, above band terminations, where the competition with the charged-particles emission was initially thought to obscure the possibility of gamma-ray spectroscopy investigation. The paper highlights some of the most outstanding properties of these nuclei such as the nuclear rotation and backbending effects, band termination states, yrast traps, non-natural parity bands, competition between T = 0 and T = 1 pn pairing modes.Received: 30 October 2002, Published online: 16 March 2004PACS:
21.10.-k Properties of nuclei; nuclear energy levels - 21.60.Cs Shell model - 23.20.Lv
transitions and level energies - 27.40. + z
C.A. Ur: On leave from NIPNE Bucharest, Romania 相似文献
7.
Corrections of order α
5 and α
6 to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear
structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, −1334.73
meV (1S), −166.64 meV (2S), −58 712.90 μeV (2P
1/2), and −24 290.69 μeV (2P
3/2), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of Δ12 = 8ΔE
hfs(2S) − ΔE
hfs(1S) = 1.59 meV can be used to test QED predictions. 相似文献
8.
Yu. P. Gangrsky V. I. Zhemenik N. N. Kolesnikov V. G. Lukashik B. N. Markov G. V. Myshinskiy O. D. Maslov G. A. Bozhikov 《Physics of Atomic Nuclei》2010,73(9):1477-1481
The yields of 135Cs nuclei in a high-spin (19/2) isomeric state and of nuclei neighboring it were measured for photonuclear reactions of the
(γ, f) and (γ, α) types. The experiments in question were performed by using bremsstrahlung from a microtron at the maximum electron energy
of 25 MeV. The product nuclei were identified by their half-lives and by the lines of gamma radiation emitted in their decay,
and the reaction yields R were determined by the ratios of the intensities of these lines to the bremsstrahlung flux. The cross sections for isomer
production were calculated, and the angular momenta of product nuclei immediately before the cascade of gamma transitions
populating the ground or an isomeric nuclear state were evaluated on the basis of these results. An enhanced yield of the
high-spin isomer of 135Cs in the fission reaction in relation to the respective (γ, α) reaction and in relation to the results of the calculations is found. 相似文献
9.
Feng Hu Jiamin Yang Chuanke Wang Gang Jiang Xuefeng Zhao Huaping Zang 《Central European Journal of Physics》2011,9(5):1228-1236
Relativistic configuration interaction calculations with the inclusion of the Breit interaction, quantum electrodynamics and
finite nuclear mass corrections have been carried out in the extended optimal level scheme using multiconfiguration Dirac-Fock
wavefunctions on the forbidden transition probabilities for the 2p
4 ground state configuration of the oxygen isoelectronic sequence for 8 ⩽ Z ⩽ 42. Electric quadrupole and magnetic dipole transition probabilities are reported for transitions between several of these
levels. Our results are compared with those from other theories and experiments. Our energy levels are in better agreement
with experiment than other theories. 相似文献
10.
The dielectron widths of Y(nS)(n = 1, …, 7) and vector decay constants are calculated using the relativistic string Hamiltonian with a universal interaction.
For Y(nS) (n = 1, 2, 3) the dielectron widths and their ratios are obtained in full agreement with the latest CLEO data. For Y(10580)
and Y(11020) a good agreement with experiment is reached only if the 4S-3D mixing (with a mixing angle θ = 27°± 4°) and 6S-5D mixing (with θ = 40°±5°) are taken into account. The possibility to observe higher “mixed D-wave” resonances, $
\tilde \Upsilon
$
\tilde \Upsilon
(n
3
D
1) with n = 3, 4, 5 is discussed. In particular, $
\tilde \Upsilon
$
\tilde \Upsilon
(≈11120), originating from the pure 53
D
1 state, can acquire a rather large dielectron width, ∼130 eV, so that this resonance may become manifest in the e
+
e
− experiments. On the contrary, the widths of pure D-wave states are very small, Γ
ee
(n
3
D
1)≤ 2 eV. 相似文献
11.
In this study quasiparticle random-phase approximation with the translational invariant Hamiltonian using deformed mean field
potential has been conducted to describe electric dipole excitations in 136Xe, 138Ba, 140Ce, 142Nd, 144Sm and 146Gd isotones. The distribution of the calculated E1 strength shows a resonance like structure at energies between 6–8 MeV exhausting up to 1% of the isovector electric dipole
Energy Weighted Sum Rule and in some aspects nicely confirms the experimental data. It has been shown that the main part of
E1 strength, observed below the threshold in these nuclei may be interpreted as main fragments of the Pygmy Dipole resonance.
The agreement between calculated mean excitation energies as well as summed B(E1) value of the 1− excitations and the available experimental data is quite good. The calculations indicate the presence of a few prominent
positive parity 1+ States in heavy N = 82 isotones in the energy interval 6–8 MeV which shows not all dipole excitations were of electric character in this energy
range. 相似文献
12.
Cosmological models with variable G in C-field cosmology for barotropic fluid distribution in FRW space-time are investigated. To get the deterministic model of the
universe, we have assumed that G=R
n
where R is the scale factor and n the constant. To obtain the results in terms of cosmic time t, we have assumed n=−1. We find that for n=−1, Creation field (C) and spatial volume increase with time, G and ρ (matter density) decreases with time, the model represent accelerating universe. Thus inflationary scenario exists in the
model. The model is also free from horizon. The results so obtained match with the astronomical observations. 相似文献
13.
An ensemble of figures required for the analysis of the atomic-vacancy ordering in nonstoichiometric compounds M
2
X
y
(M
2
X
y
▭1 − y
) with an L′3 hexagonal structure has been determined by the order-parameter functional method. It has been demonstrated reasoning from
the crystal lattice geometry that, in order to describe M
2
X
y
compounds with an L′3 structure, it is necessary to use the basis cluster in the form of a trigonal prism consisting of six sites of the nonmetal
lattice with a metal atom at the center. The overlapping figures that, together with the basis cluster, form a sequence of
special figures uniquely describing the L′3 structure have been found. The equilibrium conditions for disorder-order transformations in nonstoichiometric compounds
M
2
X
y
have been determined in the general form. 相似文献
14.
D. Sarkisyan T. Becker A. Papoyan P. Thoumany H. Walther 《Applied physics. B, Lasers and optics》2003,76(6):625-631
An extremely thin cell (ETC) with the thickness of a Rb atomic vapor layer in the range of 100–300 nm was fabricated. It is
demonstrated that a simple laser-diode technique with a single resonant light beam is sufficient to observe separately all
of the atomic hyperfine transitions of the D
2 line of Rb (780 nm) and also allows us to measure the relative transition probabilities of the hyperfine transitions. The
onset of collisional self-broadening of the hyperfine transitions as the number density of atoms increases was studied. The
detrimental role of the atoms with slow longitudinal velocity in the sub-Doppler response of the Rb ETC is demonstrated by
studies in which the cell is tilted from normal incidence of the laser beam. It is also shown that using an ETC allows us
to resolve in a moderate external magnetic field the Zeeman splitting of the hyperfine transitions of the 87Rb D
1 transition F
g=1F
e=1,2.
Received: 19 February 2003 / Revised version: 4 April 2003 / Published online: 2 June 2003
RID="*"
ID="*"Corresponding author. Fax: +374/32-31172, E-mail: david@ipr.sci.am 相似文献
15.
V. E. Tarasov V. V. Khabarov A. E. Kudryavtsev V. M. Weinberg 《Physics of Atomic Nuclei》2008,71(8):1410-1423
The Kd reactions are considered in the impulse approximationwithNN final-state interactions (FSI) taken into account. Realistic parameters for the KN phase shifts are used. The “quasi-elastic” energy region, in which the elementary KN interaction is predominantly elastic, is considered. The theoretical predictions are compared with the data on the K
+
d → K
+
pn, K
+
d → K0
pp, K
+
d → K
+
d, and K
+
d total cross sections. The NN FSI effect in the reaction K
+
d → K
+
pn has been found to be large. The predictions for the Kd cross sections are also given for slow kaons, produced from ϕ(1020) decays, as the functions of the isoscalar KN scattering length a
0. These predictions can be used to extract the value of a
0 from the data.
The text was submitted by the authors in English. 相似文献
16.
S. S. Drapey V. A. Zheltonozhsky L. V. Sadovnikov N. V. Strilchuk O. G. Shkulkova 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(6):887-889
Conversion coefficients for the E1 and M1 transitions in the 44Ti decay have been measured with high accuracy using the sum peak and multidimensional coincidence methods. The following values have been obtained: αK(E1) = 0.077 ± 0.003 and αK(M1) = 0.014 ± 0.001. A significant contribution of the penetration effects for the M1 transition has been shown. The penetration parameter λ is determined to be ?260 ± 30 has been determined. 相似文献
17.
We obtain exact results in α′ for open and closed A-model topological string amplitudes on a large class of toric Calabi-Yau threefolds by using their correspondence with five
dimensional gauge theories. The toric Calabi-Yaus that we analyze are obtained as minimal resolution of cones over Y
p,q
manifolds and give rise via M-theory compactification to SU(p) gauge theories on . As an application we present a detailed study of the local case and compute open and closed genus zero Gromov-Witten invariants of the orbifold. We also display the modular structure of the topological wave function and give predictions for higher genus amplitudes.
The mirror curve in this case is the spectral curve of the relativistic A
1 Toda chain. Our results also indicate the existence of a wider class of relativistic integrable systems associated to generic
Y
p,q
geometries. 相似文献
18.
Beatriz Pérez-Artacho Visitación Gallardo M. Adolfina Ruiz José L. Arias 《Journal of nanoparticle research》2012,14(4):768
A reproducible methodology is described for the synthesis, by following the double emulsion/solvent evaporation technique,
of magnetic nanocomposites (average diameter ≈ 135 nm) consisting of maghemite nuclei and a biodegradable poly(d,l-lactide-co-glycolide) matrix. The heterogeneous structure of the nanoparticles can confer them the responsiveness to magnetic gradients,
giving both the possibility of their use as a drug delivery system and adequate heating characteristics for a hyperthermia
effect. The physical chemistry of the nanocomposites was extensively characterized, this establishing that their surface properties
were similar to that of pure poly(d,l-lactide-co-glycolide). From an electrokinetic point of view, zeta potential determinations (as a function of the ionic strength, and
pH) pointed out that the nanocomposites were almost indistinguishable from the copolymer. The surface thermodynamic analysis
agreed with the electrophoretic one in suggesting that the coverage of the magnetic nuclei was complete, since the hydrophilic
nature of maghemite was modified and the nanoparticles turned into hydrophobic, just like the copolymer, when they were embedded
into poly(d,l-lactide-co-glycolide). The magnetic behaviours of the composite nanoparticles were also checked. Their heating properties were studied
in vitro in a high-frequency alternating gradient of magnetic field: a stable maximum temperature of 47 °C was satisfactorily
achieved within 45 min. Blood compatibility of the nanocomposites was also defined in vitro. To our knowledge, this is the
first time that such kind of magnetic-sensitive nanoformulation with very promising characteristics (e.g. blood compatibility,
magnetic drug targeting capabilities, and hyperthermia) has been developed for therapeutic purposes. 相似文献
19.
A comparative investigation of the magnetic properties of amorphous nanogranular composites (Co41Fe39B20)
x
(SiO
n
)100 − x
and (Co86Nb12Ta2)
x
(SiO
n
)100 − x
has been performed in the subpercolation region at temperatures in the range 4.2–300 K. The thermomagnetic dependences in
the range 4.2–300 K and the processes of magnetization reversal and remanent magnetization relaxation at liquid-helium temperatures
have been studied. It has been established that the average anisotropy constants of amorphous nanograins are equal to 3.6–7.0
kJ/m3 for the (Co41Fe39B20)
x
(SiO
n
)100 − x
composites and 5–8 kJ/m3 for the (Co86Nb12Ta2)
x
(SiO
n
)100 − x
composites. The fundamental differences in the concentration dependences of the anisotropy constant K
eff and the coercive force H
C
have been revealed for the two systems under investigation. It has been demonstrated that, as the concentration of the metal
phase increases, the quantities K
eff and H
C
increase for the (Co86Nb12Ta2)
x
(SiO
n
)100 − x
composites and decrease for the (Co41Fe39B20)
x
(SiO
n
)100 − x
composites. 相似文献
20.
S. R. Gevorkyan A. N. Sissakian A. V. Tarasov H. T. Torosyan O. O. Voskresenskaya 《Physics of Atomic Nuclei》2010,73(6):961-964
The final-state interaction of pions in K
e4 decay allows to obtain the value of the isospin and angular-momentum-zero ππ scattering length a
00.We take into account the electromagnetic interaction of pions and isospin-symmetry-breaking effects caused by different masses
of neutral and charged pions and estimate the impact of these effects on the procedure of scattering-length extraction from
K
e4 decays. 相似文献