共查询到20条相似文献,搜索用时 15 毫秒
1.
O. V. Bespalova I. N. Boboshin V. V. Varlamov T. A. Ermakova B. S. Ishkhanov E. A. Romanovskii T. I. Spasskaya T. P. Timokhina 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(3):428-433
The change in the neutron single-particle structure of (1f?2p)-shell magic nuclei near the Fermi energy with an increase in the number of protons in the 1f 7/2 subshell from 0 for 48Ca to 8 for 56Ni has been investigated. Good agreement of the experimental and estimated values of the single-particle energies E nlj of the bound states of neutrons in these nuclei with the results of calculations within the dispersive optical model is obtained. 相似文献
2.
V. M. Maslov 《Physics of Atomic Nuclei》2008,71(1):9-26
The spectra of prompt fission neutrons from the reaction 238U(n, F) for neutrons of energy in the range E n ≤ 20 MeV are interpreted within the statistical model. It is shown that exclusive spectra of prefission neutrons emitted in (n, xnf) reactions play a decisive role in describing the observed promptfission-neutron spectra and determine the average energies of prompt-fission neutrons. The dependence of the effect of prefission neutrons on the fissility of a target nucleus is demonstrated for the reactions 232Th(n, F), 235U(n, F), and 239Pu(n, F). 相似文献
3.
G. N. Lovchikova A. M. Trufanov M. I. Svirin V. A. Vinogradov A. V. Polyakov 《Physics of Atomic Nuclei》2004,67(7):1246-1263
The time-of-flight technique is used to measure the ratios R(E, E n )=N(E, E n )/NCf(E) of the normalized (to unity) spectra N(E, E n ) of neutrons accompanying the neutron-induced fission of 238U at primary-neutron energies of E n =6.0 and 7.0 MeV to the spectrum NCf(E) neutrons from the spontaneous fission of 252Cf. These experimental data and the results of their analysis are discussed together with data that were previously obtained for the neutron-induced fission of 238U at the primary energies of E n =2.9, 5.0, 13.2, 14.7, 16.0, and 17.7 MeV. 相似文献
4.
A. V. Tsvyashchenko L. N. Fomicheva A. V. Salamatin A. I. Velichkov O. I. Kochetov G. K. Ryasny A. A. Sorokin M. Budzynski 《JETP Letters》2009,89(6):280-284
The parameters of nuclear quadrupole hyperfine interaction in intermetallic UGe2 and UAl2 compounds have been measured in a temperature range of 100–300 K using the perturbed angular γγ correlation method on 111Cd probe nuclei. The results obtained for UGe2 indicate a pronounced anisotropic character in the distribution of f electrons in agreement with the calculation of the electronic structure of this compound. The hybridization degree between f electrons of U and p electrons of Al in UAl2 is lower than the hybridization degree between f electrons of U and p electrons of Ge in UGe2. 相似文献
5.
In an experiment with an optical pumping of 133Cs atoms in the 62 S 1/2 ground state, the line shape of the D 2f magnetic resonance signal for the transverse alignment component oscillating at a double frequency f of a radio-frequency (RF) magnetic field is found to strongly depend on the polarization of pumping radiation. On passage from a linearly polarized pumping light to a circularly polarized (CP) light with a sufficiently strong RF field the ordinary three-peak line with the highest central peak transforms into a two-peak line with a minimum at the center, so that the D 2f signal line resembles the M f signal line of a transverse orientation oscillating at the RF field frequency f. This suggests that the orientation (the first-rank polarization moment (PM)) arising upon CP pumping affects the alignment (the second-rank PM); i.e., the PMs of Cs atoms with different parities of their ranks become coupled. No influence of the polarization of a pumping radiation on the line shape of the D 2f signal is observed in a similar experiment with the 4He atoms in the 23 S 1 metastable state. 相似文献
6.
S. Chakraborty H. P. Sharma S. S. Tiwary C. Majumder P. K. Prajapati S. Rai P. Popli M. Singh S. S. Bhattacharjee R. P. Singh S. Muralithar P. Banerjee S. Ganguly S. Kumar A. Kumar R. Palit 《Brazilian Journal of Physics》2017,47(4):406-410
High spin states in 127Xe have been investigated via 9Be induced fusion-evaporation reaction at 48 MeV. Spin and parity of excited states up to \( \sim \frac {47}{2} \hbar \) have been confirmed from angular correlation and linear polarization results. Rotational alignment of the second pair of h 11/2 neutrons has been observed at \(\hbar \omega \sim \) 0.44 MeV; beyond that, the band is associated with ν[h 11/2]3 configuration. The alignment phenomena has been discussed in comparison with the neighboring 125,129Xe. 相似文献
7.
V. N. Makhov T. V. Uvarova M. Kirm S. Vielhauer 《Bulletin of the Lebedev Physics Institute》2016,43(12):348-351
Thermal quenching of interconfigurational 5d-4f luminescence of Er3+ and Tm3+ ions in BaY2F8 crystals is studied in the temperature range of 330–790 K. The quenching temperatures are ~575 and ~550 K for Er3+ and Tm3+, respectively. It is shown that quenching of 5d-4f luminescence of Tm3+ ions is caused by thermally stimulated ionization of 5d electrons to the conduction band. 相似文献
8.
S. S. Belyshev A. N. Ermakov B. S. Ishkhanov I. M. Kapitonov I. V. Makarenko V. A. Chetvertkova V. I. Shvedunov 《Moscow University Physics Bulletin》2008,63(3):208-210
The relative yields of multiparticle photoneutron reactions on the 209Be isotope with emission of two to seven neutrons from the nucleus are measured. The experiment was carried out with the bremsstrahlung beam from the RTM-70 pulsed race-track microtron (INP, MSU) with a maximum photon energy E γ m = 67.7 MeV. 相似文献
9.
V. V. Anisovich 《JETP Letters》2004,80(12):715-720
It is shown that new data on the (JPC=2++) resonances in the mass range M~1700–2400 MeV support the linearity of the (n, M2) trajectories, where n is the radial quantum number of the quark-antiquark state. In this way, all the vacancies for the isoscalar tensor qq mesons in the range up to 2450 MeV are filled in. This allows one to fix the broad f2 state with M=2000±30 MeV and Г=530±40 MeV as the lowest-tensor glueball. 相似文献
10.
The absorption spectra of the Er3+ ions embedded in the AlN matrix have been investigated. The admixture of erbium was introduced in bulk AlN crystals by diffusion. The absorption lines, which are associated with the intraconfigurational electronic f–f-transitions from the ground 4 I 15/2-state to the levels of ion Er3+ excited states have been observed in the spectral range of 370–700 nm. The transitions to the state levels 4 F 9/2, 2 H 11/2, 4 F 7/2, 4 F 5/2, 2 H 9/2, and 4 G 11/2 have been investigated in detail at the temperature T = 2 K. The number of the observed lines for these transitions coincides with the theoretically possible one for the electronic f–f-transitions in the ions Er3+, which are in the crystal field with the symmetry below cubic. The narrowness of the observed lines and their number convincingly testify the replacement of preferably one regular crystalline position by erbium ions. The implementation of Er3+ in the Al3+ position with the local symmetry C 3v appears the most probable. The energy positions of the levels of excited states for the investigated transitions have been determined. The diagram of the Er3+ ion energy levels in the AlN crystals has been built. 相似文献
11.
Yu. P. Gangrsky S. G. Zemlyanoi D. V. Karaivanov K. P. Marinova B. N. Markov 《Physics of Particles and Nuclei Letters》2008,5(1):29-32
High-resolution laser spectroscopy measurements of optical hyperfine splitting on the 151, 152, 153Eu isotopes were performed on the atomic transition 4f 76s 2 8 S 7/2 → 4f 76s6p 6 P 5/2 at λ ≈ 564.58 nm. Values of the nuclear magnetic dipole and electric quadrupole moments are obtained from the measured hyperfine splitting and the magnetic hyperfine anomalies in the isotope pairs 151, 152Eu and 152, 153Eu are deduced. The absolute values of the hyperfine anomaly in both cases are unusually large: 5 (1)%. The possible sources causing these anomalies are discussed. 相似文献
12.
The absorption, luminescence, and excitation spectra of CaF2, SrF2, and BaF2 crystals with EuF3 or YbF3 impurity have been investigated in the range 1–12 eV. In all cases, strong wide absorption bands (denoted as CT1) were observed at energies below the 4f n -4f n ? 15d absorption threshold of impurity ions. Weaker absorption bands (denoted as CT2) with energies 1.5–2 eV lower than those of the CT1 bands have been found in the spectra of CaF2 and SrF2 crystals with EuF3 or YbF3 impurities. The fine structure of the luminescence spectra of CaF2 crystals with EuF3 impurities has been investigated under excitation in the CT bands. Under excitation in the CT1 band, several Eu centers were observed in the following luminescence spectra: C 4v , O h , and R aggregates. Excitation in the CT2 bands revealed luminescence of only C 4v defects. 相似文献
13.
A. I. Svirikhin A. V. Andreev A. V. Yeremin I. N. Izosimov A. V. Isaev A. N. Kuznetsov A. A. Kuznetsova O. N. Malyshev A. G. Popeko Y. A. Popov E. A. Sokol M. L. Chelnokov V. I. Chepigin T. M. Schneidman B. Gall O. Dorvaux P. Brione K. Hauschild A. Lopez-Martenz K. Rezynkina S. Mullins P. Jones P. Mosat 《Physics of Particles and Nuclei Letters》2017,14(4):571-575
This study describes an experiment on investigating the properties of spontaneous fission of shortlived neutron-deficient nuclei synthesized in the reaction of complete fusion 48Ca + 204Pb = 252No*. The experiment is performed using the SHELS separator and the beam of multicharged ions at U-400 accelerator (LNR, JINR). Two activities undergoing spontaneous fission, which can be related to the ground and isomeric states of 250No nucleus, are registered. The half-lives, total kinetic energies of fission fragments, and neutron multiplicities are measured for the short-lived nuclei. The average number of neutrons per fission for the activity with t 1/2 = 5.1 ± 0.3 μs is = 4.38 ± 0.13 μs, and for nuclei with the half-life t 1/2 = 36 ± 3 μs it is xxxxx. 相似文献
14.
On the basis of the shell model with an extended basis, the structure of 9Li-9Be to 11Li-11Be nuclei is examined with allowance for the competition of jj coupling and Majorana exchange forces via considering the sequential addition of neutrons, and the respective wave functions are determined. A formalism for calculating the spectroscopic factor for a dineutron and for individual neutrons in nuclei whose wave functions incorporate the mixing of shell configurations is developed. The reactions 9Li(t, p)11Li and 9Be(t, p)11Be treated with allowance for the mechanisms of dineutron stripping and a sequential transfer of two neutrons are considered as an indicator of the proposed structure of lithium and berylliumisotopes. The parameters of the optical potentials, the wave functions for the bound states of transferred particles, and the interaction potentials corresponding to them are determined from a comparison of the theoretical angular distribution of protons from the reaction 9Be(t, p)11Be with its experimental counterpart. It is shown that a dineutron periphery of size about 6.4 fm is present in the 11Li nucleus and that a single-neutron periphery of size about 8 fm is present in the 11Be nucleus. 相似文献
15.
K. V. Ivanovskikh V. A. Pustovarov B. V. Shul’gin M. Kirm 《Physics of the Solid State》2005,47(8):1446-1449
Time-resolved excitation and emission spectra of SrF2: Er3+ upon selective excitation with synchrotron radiation in the VUV and ultrasoft x-ray ranges at T = 8 K were studied. The VUV luminescence of SrF2: Er3+ derives from high-energy interconfiguration 4f105d-4f11 transitions in the Er3+ ion. The VUV emission spectrum revealed, in addition to the 164.5-nm band (millisecond-range kinetics), a band at 146.4 nm (with a decay time of less than 600 ps). The formation of excitation spectra for the f-f and f-d transitions in the Er3+ ion is discussed. 相似文献
16.
A. A. Kulko N. A. Demekhina R. Kalpakchieva Yu. A. Muzychka Yu. E. Penionzhkevich D. N. Rassadov N. K. Skobelev D. A. Testov 《Physics of Atomic Nuclei》2007,70(4):613-618
Excitation functions are measured for the fusion reactions 197Au(4He, xn)201?xn Tl that are induced by alpha-particle interaction with gold nuclei in the energy range 14–36 MeV and in which x neutrons (0 ≤ x ≤ 3) are evaporated. The stack-activation technique was used to record and separate reaction products. Experimental data on the fusion reactions followed by evaporation of one to three neutrons agree with results of previous studies. For the radiative-capture reaction 197Au(4He,γ)201Tl, the upper limit on the cross section proved to be much lower. The excitation functions for the reactions subjected to measurements are compared with the results of calculations based on the statistical model and with the results of an experiment performed previously in a 6He beam. 相似文献
17.
V. V. Varlamov V. N. Orlin N. N. Peskov 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(6):670-678
Using objective physical criteria for data reliability, cross sections of partial photoneutron reactions (γ, 1n), (γ, 2n) and (γ, 3n) that are free of the shortcomings of neutron multiplicity sorting methods used on beams of quasimonoenergetic annihilation photons are obtained for 141Pr and 186W nuclei. Evaluation is performed using the experimental–theoretical method (ETM), based on the experimental cross section of neutron yield reaction σexp(γ, xn) = σexp(γ, 1n) + 2 σexp(γ, 2n) + 3 σexp(γ, 3n) + … and ratios F i theor= σtheor(γ, in)/σtheor(γ, xn) calculated within the combined model (CM) of photonuclear reactions, which stipulates that σeval(γ, in) = F i theor σexp(γ, xn). It is found that for 141Pr and 186W, ratios F exp i do not contradict the data reliability criteria only at energies up to ~21 and ~22 MeV, respectively. At the same time, there are notable discrepancies between F i theor and F exp i, and thus between the evaluated and experimental cross sections of reactions. It is shown that the discrepancies between the evaluated and experimental cross sections are due to the assumed unreliable experimental distribution of neutrons in the channels with multiplicities 1, 2, and 3. 相似文献
18.
A. D. Molchanova 《Physics of the Solid State》2018,60(10):1957-1965
The results of studies of the absorption spectra of nickel orthoborate Ni3(BO3)2 in the range of electronic d–d-transitions are reported. The obtained data are analyzed in the framework of the crystal field theory. The Ni2+ ions are located in two crystallographically nonequivalent positions 2a and 4f with point symmetry groups C2h and C2, respectively, surrounded by six oxygen ions forming deformed octahedra. The absorption spectra exhibit three intense bands corresponding to spin-resolved transitions from the ground state of nickel ion 3A2g (3F) to the sublevels of the 3T2g (3F), 3T1g (3F) and 3T1g (3P) triplets split by the spinorbit interaction and the rhombic component of the crystal field. At temperatures below 100 K, the spectra exhibit a thin structure, in which phonon-free lines can be distinguished. Comparison of the calculated frequencies of the zero-phonon transitions with the experimental data allows estimating parameters of the crystal field acting on the nickel ions in the 2a- and 4f-positions, as well as the parameters of electrostatic interaction between the 3d electrons and spin-orbit interaction constants. 相似文献
19.
V. V. Ogloblichev A. M. Potapov S. V. Verkhovskii A. V. Mirmelstein 《JETP Letters》2018,108(9):616-622
The spin susceptibility of a polycrystalline sample of uranium mononitride UN is studied by measuring the 14N NMR line shift, spin–lattice relaxation rates of the nuclear spin, and static magnetic susceptibility in the temperature region of 1.5TN < T < 7TN A joint analysis of the results obtained has revealed the temperature dependence of the characteristic energy of spin fluctuations of the uranium 5f electrons: Γnmr(T) ∝ T0.54(4) close to the dependence Γ(T) ∝ T0.5 characteristic of concentrated Kondo systems above the coherent state formation temperature. 相似文献
20.
A scheme is proposed for computing the probability of the dipole-forbidden f–f transition at the interaction of the RE3+ impurity ion with the field of an inhomogeneous exciting radiation. It is shown that in the case under consideration, the prohibition on electric dipole transitions can be repealed without involving the Judd–Ofelt theory of induced electric dipole transitions. The quantitative estimation of the absorption cross-section of YAG:Er3+ crystal at the wavelength of 1530 nm (4I15/2 → 4I13/2) was carried out for the simplest model of the inhomogeneous exciting radiation. 相似文献