共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
3.
《Physics letters. [Part B]》1988,211(3):259-264
We show that a wide range of deformed actinides can be described in terms of an interacting boson model hamiltonian with three parameters, two of them [including the coefficient of the only SU(3) symmetry breaking term] remaining almost constant over the whole region. In addition to ground γ1 and β1 spectra, B(E2:0g+ → 2g+) values are well reproduced with no extra adjustable parameters for nuclei with 136⩽N⩽146, while for nuclei beyond N = 146 an effective boson number has to be considered in order to fit the observed in the B(E2:0+g → 2+g) values, which is due to the presensce of a subshell closure at N = 152. The sensitive dependence of the B(E2:0g+→2g+) values on the effective boson numbers is emphasized. β1 → ground and β1 → ground transitions are fitted by breaking the SU(3) symmetry of the E2 transition operator. 相似文献
4.
O. Scholten K. Heyde P. van Isacker J. Jolie J. Moreau M. Waroquier J. Sau 《Nuclear Physics A》1985,438(1):41-77
States of mixed proton-neutron symmetry are investigated in different dynamical symmetries of the interacting boson model. We discuss in each of the limits the energy spectrum, the wave functions and the B(M1; 01+ → 1 1+) values. We also study three classes of transitional nuclei namely the Pd nuclei [U(5) → O(6)], the Sm nuclei [U(5) → SU(3)] and the Pt nuclei [O(6) → SU(3)] with respect to the energy of the lowest non-symmetric Jπ = 1+, 3+ levels as well as the M1 and M3 strengths for exciting these levels from the ground state. For 98Pd we compare this calculation with a shell-model calculation. Finally, we adress the problem of the mixing of the non-symmetric Jπ = 1+ state with nearby hexadecapole (g-boson) configurations. 相似文献
5.
L. Ricken D. Bohle G. Domogala K. Glasner E. Kuhlmann 《Zeitschrift für Physik A Hadrons and Nuclei》1982,306(1):67-71
Electric quadrupole transition strengths for the 2 1 + ,T=1→0 1 + ,T=1γ-decay branches are summarized for 10≦A≦42 nuclei. In10B the corresponding branch has been remeasured by use of the9Be(p, γ)10B resonance reaction atE p =320 keV; an upper limit of 0.6% is found. The variation of theE2 strengths within each individualT=1 isobaric multiplet reveals the particleor hole-character of the levels involved. The isoscalar 2 1 + →0 1 + transition strengths in 10≦A≦48 nuclei vary between 2 and 20 Weißkopf units showing drastic shell effects. Results for the ratio of neutron and proton matrix elements deduced from analogγ-decay studies and from inelastic pion scattering are compared. 相似文献
6.
The energies and spectroscopic factors ofJ π=5/2+ states of nucleus91Nb excited via a reaction transferring a proton to the 2d 5/2 orbit of90Zr target state have been calculated. Effective two-body interaction used has been extracted from the experimentally observed two-body energies of (1g 9 2/?1 (n) 2d 5/2(n)), (1g 9 2/?1 (n) 1g 9/2(p)) and (1g 9/2(p)-2d 9/2(n)) multiplets in90Zr,90Nb and92Nb nuclei respectively. Most of the calculated energies and the strengths ofJ π=5/2+ levels have reasonably good counterparts in the experimental spectrum, however the calculation shows about 17% strength lying at 6.8 MeV, without having a confirmed counterpart in the observed level scheme. The reduced transition strengthsB(M1) forM l transitions from 5/2? T>(11/2) state to the various components of 5/2+ T<(=9/2) state have also been reported; but the corresponding experimental values are not available. The main feature of the reduced transition strengths is that theM1 transition to the state at 3.69 MeV is inhibited whereas that to the state at 6.79 MeV is enhanced, the relevant core-configuration, interfering destructively in the former case and constructively in the latter. 相似文献
7.
N.-G. Jonsson A. Bäcklin J. Kantele R. Julin M. Luontama A. Passoja 《Nuclear Physics A》1981,371(2):333-348
0+, 2+, 44 and 3? states in 112–124Sn have been studied with the (p, p′γ) reaction and in Coulomb excitation. Absolute E2 transition rates between these levels have been extracted with the aid of the Winther-de Boer code. For 116,118Sn, B(E2; 41+ → 21+) ≈ 20 W.u., suggesting a two-phonon character of the 41+ states. For the lighter and heavier isotopes, this value is significantly smaller. All observed values of B(E2; 22+ → 21+) and B(E2; 23+→ 21+) are about 5 W.u. Also. values of B(E3; 01+ → 3?1) have been measured for all stable even Sn nuclei. In 116Sn the branching ratio (31? → 01+)/(31? → 21+) has been measured. From this we obtain a half-life of 0.34±0.07 ps for the first 3? level in 116Sn and B(E1; 31? → 21+) = (1.4±0.3) × 10?5'e2 · b, corresponding to a hindrance factor of 103. 相似文献
8.
9.
Takaharu Otsuka 《Hyperfine Interactions》1992,75(1-4):23-42
The M1 transitions between low-lying collective states are discussed from the viewpoint of the Proton-Neutron Interacting
Boson Model, with particular emphasis on the mixed-symmetry states. Mixed-symmetry 2+ states are studied for56Fe and54Cr in terms of realistic and large-scale shell-model calculations, including M1 properties. The Doorway-state character of
the mixed-symmetry 2+ state is proposed with examples in these nuclei. The possible candidate of the mixed-symmetry 2+ state in134Ba is analyzed based on recent experiment by Molnaret al. on M1 transitions. The M1 transitions from the quasi-γ to quasi-g bands in γ-unstable or O(6) nuclei are discussed next,
by taking Ba isotopes as an example. It is suggested that such M1 transitions are enhanced compared to axially symmetric nuclei
as an indication of softness towards proton-neutron incoherent motion in γ-unstable nuclei,i.e., mixture of mixed-symmetry states. A new mirror-type symmetry is introduced for γ-unstable nuclei, and the M1 selection rule
due to this symmetry is presented, making 4
2
+
→4
1
+
transition allowed but 3
1
+
→2
1
+
forbidden, for instance. 相似文献
10.
R. Majumdar 《Zeitschrift für Physik A Hadrons and Nuclei》1985,320(2):307-309
The three proton-hole states ?2d5/2, 1g7/2 and 1g9/2 are found to be fragmented as a result of coupling of these states with the 3?, 5?, 2+, 4+ and 6+ collective states of208Pb. The excited states in208Pb (t,α) reaction can be quantitatively explained in terms of altered 2d5/2, 1g7/2 and 1g9/2 states with the hole-core coupling model. 相似文献
11.
R. Diller K. P. Lieb L. Lühmann T. Osipowicz P. Sona B. Wörmann L. Cleemann J. Eberth 《Zeitschrift für Physik A Hadrons and Nuclei》1985,321(4):659-669
High spin states in85Y have been excited in the reaction72Ge(16O,p2n) at 48–60 MeV beam energy. From measurements ofnγ andγγ coincidences, excitation functions and angular distributions, the high spin spectrum of85Y has been established up to 5.4 MeV excitation energy and spinI≦29/2. Lifetimes or limits of lifetimes have been determined for 14 levels via the recoil distance and Doppler shift attenuation method. Theg 9/2 decoupled proton band is found to backbend atI π=17/2+ as also seen in the reduction of the 17/2+→13/2+ and 21/2+→17/2+ E2 transition strengths. The lowest (3qp) positive parity band has predominantly aν 2 g 9/2×πg 9/2 structure. The observed negative parity yrast states in the spin range 15/2?≦I≦29/2? are most probably of (g 9/2)2 ×(f 5/2,p 1/2) (3qp) nature as suggested by a comparison of the84Sr and85Y level structures and electromagnetic transition strengths. 相似文献
12.
《Nuclear Physics A》1986,451(3):481-497
Results of shell-model calculations of Gamow-Teller strength distributions are presented for 50Ti → 50Sc, 52Cr → 52V and 54Fe → 54Mn. The results support the previous shell-model estimates that a large fraction of Gamow-Teller strength is concentrated at low excitation energy in the daughter nuclei. The strength distributions are in fairly good agreement with those of forward-angle cross sections of T0 + 1 isospin states of the intermediate-energy (p, p') reaction on N = 28 isotones. An estimate of quenching in the T0 → T0 + 1 τσ mode transition is attempted. Calculations are performed also for the first 2+ and 4+ parent states in the context of electron capture at the late stages of stellar evolution. 相似文献
13.
CW Optical-Optical Double Resonance studies of the 23Πg, 33Πg, 43Πg+, and 13Δg Rydberg states of Na2
《Journal of Molecular Spectroscopy》1986,117(2):245-282
The 23Πg, 33Πg, 43Σg+, and 13Δg states of the Na2 molecule are observed by sub-Doppler Perturbation Facilitated Optical-Optical Double Resonance (PFOODR) spectroscopy. Absolute vibrational assignments and molecular constants are obtained for two of these states (33Πg, v = 0–25 observed, and 43Σg+, v = 3–5, 13, 14 observed). Tentative vibrational assignments and provisional molecular constants are obtained for the 23Πg (v = 43–89 observed) and 13Δg (v = 31–35, 40, 46–51 observed) states. Spin-orbit, spin-spin, and hyperfine splittings are observed. The direct 3Λg+ → a3Σu, 23Πg ∼ 33Πg perturbation-induced, and collision-induced contributions of these four 3Λg states to the ubiquitous Na-vapor violet and ultraviolet emission bands are discussed. 相似文献
14.
Theβ ?, (n→p) and (p→n), transition strengths and excitation energies for first forbidden resonances with λπ=0? and 2? in spherical nuclei are calculated in the framework of the linear response theory. The results show that the intensities associated with these modes are strongly fragmented, particularly, for the λπ=2? states. 相似文献
15.
The twelve transition moments which connect each of the three 1Σg+ states EF, GK, and with the three 1Σu+ states B,B′, and with the state C1Πu were computed in the range of internuclear distances 1.25 ≤ R ≤ 15 a.u. using accurate electronic wavefunctions. The relative phases of the wavefunctions, which determine the signs of the transition moments, were consistently defined at all R values. The strong R dependences of the transition moments reflect the R-dependent changes in electronic character of the states involved in these transitions. At large R values the 1Σg+-1Σu+ transition moments are dominated by the two-electron charge resonance in the ionic configuration H+ + H? whose transition moment is . 相似文献
16.
We investigated the properties of low-lying states in 94Mo within the framework of the proton-neutron interacting boson model (IBM-2), with special focus on the characteristics of mixed-symmetry states. We calculated level energies and M1 and E2 transition strengths. The IBM-2 results agree with the available quantitative and qualitative experimental data on 94Mo. The properties of mixed-symmetry states can be well described by IBM-2 given that the energy of the d proton boson is different from that of the neutron boson, especially for the transition of B(M1; 4 2 + → 4 1 + ). 相似文献
17.
Bożena Nerlo-Pomorska Jerzy Ludziejewski 《Zeitschrift für Physik A Hadrons and Nuclei》1978,287(3-4):337-342
The microscopic calculation of the potential energies in the ground and excited states of Ag and Sn nuclei has been performed. The single particle Nilsson potential and the shell correction Strutinski method have been used. The weak sensitivness to nonaxial deformation has been found for even neighbours of these nuclei. The small tendency towards prolate deformation of the ground and excited one-quasiparticle states originating from theg 9/2 proton subshell in101–105Ag odd isotopes has been noticed. The behaviour with quadrupole e and hexadecapole ε4 deformation of the ground and two-quasiparticle excited 0+ states originating from thed 5/2,g 9/2 andg 7/2 proton subshells andh 11/2 neutron subshell in112–118Sn has been investigated. The small quadrupole deformation of the excited 0+ states has been found what is in agreement with the experimental data concerning the rotational bands build on the first excited 0+ states in Sn isotopes. 相似文献
18.
19.
The properties of the low-lying states,especially the relevant shape coexistence in~(80)Ge,close to one of most neutron-rich doubly magic nuclei at N=50 and Z=28,have been investigated within the framework of the proton-neutron interacting model(IBM-2).Based on the fact that the relative energy of the d neutron boson is different from that of the proton boson,the calculated energy levels of low-lying states and E2 transition strengths can reproduce the experimental data very well.Particularly,the first excited state 0_2~+,which is intimately related to the shape coexistence phenomenon,is reproduced quite nicely.Theρ~2(E0,0_2~+→0_1~+)transition strength is also predicted.The experimental data and theoretical results indicate that both collective spherical andγ-soft vibration structures coexist in~(80)Ge. 相似文献
20.
We have investigated the properties of low-lying states in 96Ru within the framework of the neutron-proton interacting boson model (IBM-2), with special attention paid to the characteristics of the mixed symmetry states. By considering the relative energy of d proton boson to be different from that of neutron boson, the level energies and M1, E2 transition strengths have been calculated. The IBM-2 calculation is consistent with the experimental data of 96Ru both quantitatively and qualitatively. Particularly, the strong M1 transition between the 42 + and 41 + states has been reproduced nicely. The calculated results show that the M1 transition strength of B(M1; 42 + → 41 +) in 96Ru can be described successfully by the IBM-2. 相似文献