SwePub - sökning: WFRF:(Afanasjev A. V.)

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1.	Evans, A. O., et al. (författare) Magnetic properties of deformed dipole bands in Te-110,Te-112 2006 Ingår i: Physica Scripta. - 0031-8949. ; T125, s. 192-193 Tidskriftsartikel (refereegranskat)abstract A lifetime analysis using the Doppler-shift attenuation method has been performed on the Tellurium isotopes Te-110,Te-112. The experiment was performed using the Gammasphere array in conjunction with the MICROBALL charged-particle detector. Three strongly coupled bands were previously established in Te-110,Te-112 which were observed up to unusually high spins. In the current experiment, it has been possible to extract lifetime measurements using a Doppler broadened lineshape analysis on one of the Delta I = 1 band structures in Te-110. In contrast to similar Delta I = 1 structures in other nuclei in this mass region, the extracted B(M1) values did not rapidly decrease with increasing angular momentum. Instead, the strongly coupled band in Te-110 represents a deformed 1p-1h structure, rather than a weakly deformed structure showing the shears mechanism.
2.	Paul, E. S., et al. (författare) Smooth terminating bands in Te-112: Particle-hole induced collectivity 2007 Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 75:1 Tidskriftsartikel (refereegranskat)abstract The Gammasphere spectrometer, in conjunction with the Microball charged-particle array, was used to investigate high-spin states in Te-112 via Ni-58(Ni-58, 4p gamma) reactions at 240 and 250 MeV. Several smooth terminating bands were established, and lifetime measurements were performed for the strongest one using the Doppler-shift attenuation method. Results obtained in the spin range 18-32h yield a transition quadrupole moment of 4.0 +/- 0.5eb, which corresponds to a quadrupole deformation epsilon(2)=0.26 +/- 0.03; this value is significantly larger than the ground-state deformation of tellurium isotopes. It was also possible to extract a transition quadrupole moment for the yrast band in Xe-114, produced via the 58Ni (58Ni, 2p gamma) reaction. A value of 3.0 +/- 0.5eb was found in the spin range 16-24h, which corresponds to a quadrupole deformation epsilon(2)=0.19 +/- 0.03. Cranked Nilsson-Strutinsky calculations are used to interpret the results.
3.	Plettner, C., et al. (författare) Very high rotational frequencies and band termination in 73Br 2000 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 62:1, s. 143131-143136 Tidskriftsartikel (refereegranskat)abstract Rotational bands in 73Br have been investigated up to spins of I = 65/2 using the EUROBALL III spectrometer. One of the negative-parity bands displays the highest rotational frequency ℏω= 1.85 MeV reported to date in nuclei with A ≥ 25. At high frequencies, the experimental J(2) dynamic moment of inertia for all bands decreases to very low values, J(2) ≤ 10ℏ2 MeV-1. The bands are described in the configuration-dependent cranked Nilsson-Strutinsky model. The calculations indicate that one of the negative-parity bands is observed up to its terminating single-particle state at spin 63/2. This result establishes the first band termination in the A ≈ 70 mass region.
4.	Simpson, J., et al. (författare) Discrete line γ-ray spectroscopy in the (50-60)ℏ spin domain of 161,162Er 2000 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 62:2, s. 243211-243218 Tidskriftsartikel (refereegranskat)abstract Very high spin states (I=50-60ℏ) have been observed in the transitional nuclei 161Er and 162Er using the Euroball γ-ray spectrometer. In 161Er, three bands are observed well above spin 50ℏ. In the positive parity, positive signature (+, + 1/2) band a discontinuity in the regular rotational behavior occurs at 109/2+ and a splitting into two branches occurs at 97/2- in the negative parity, positive signature (-, + 1/2) band. The ( -, - 1/2) band continues in a regular fashion to 115/2-, tentatively (119/2-). In 162Er the positive parity, even spin (+, 0) yrast band is observed to continue smoothly up to 58+ (60+) and the negative parity, even spin (-,0) and odd spin (-,1) bands are extended from 30- to 34- and from 31- to 47- (49-), respectively. The high spin experimental spectra are compared with both a simple model involving the occupation of specific single neutron states in the absence of neutron pair correlations and with more detailed cranked Nilsson-Strutinsky calculations in which both proton and neutron pairing correlations are neglected. The very high spin domain is found to comprise a series of unpaired rotational bands. Unpaired band crossings between bands with different neutron and proton configurations are identified in 161Er. There is no evidence for aligned oblate or terminating states being close to the yrast line in 161,162Er up to spin ≈60ℏ in contrast to the lighter Er isotopes.
5.	Svensson, C. E., et al. (författare) Decay Out of the Doubly Magic Superdeformed Band in the N=Z Nucleus 60Zn 1999 Ingår i: Physical Review Letters. - 1079-7114. ; 82:17, s. 3400-3403 Tidskriftsartikel (refereegranskat)abstract The doubly magic superdeformed band in the N = Z nucleus Zn-60 has been identified. Linking transitions connecting this band to the yrast line provide the first spin, parity, and excitation energy measurements for superdeformed states in the A similar to 60 region. The stretched-E2 character and relatively large B(E2) values of these transitions suggest a nonstatistical decay-out process.
6.	Kelsall, N. S., et al. (författare) Testing mean-field models near the N=Z line : gamma-ray spectroscopy of the T-z=1/2 nucleus Kr-73 2002 Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 65:4 Tidskriftsartikel (refereegranskat)abstract Excited states in the N=Z+1 nucleus Kr-73 have been investigated using the Ca-40(Ar-36,2pn) and Ca-40(Ca-40,alpha2pn) reactions at 145 and 160 MeV, respectively. gamma rays were detected using the Gammasphere array and events were recorded in coincidence with charged-particle and neutron detectors. The three previously observed bands were extended to high spin, and a new unfavored positive-parity band has been observed. The alignment characteristics and decay properties of the bands are all consistent with large-deformation prolate rotation, with no clear evidence for oblate bands or shape coexistence. This is quite different from neighboring Kr-72,Kr-74, indicating a strong shape-stabilizing role for the valence neutron. The experimental results are compared to extended total Routhian surface, cranked Nilsson Strutinsky, and cranked relativistic mean-field calculations. The results suggest that the paired calculations lack some important physics. Neutron-proton correlations may be the missing ingredient. There is also evidence for an unusual band crossing in the negative-parity bands, which may indicate the presence of T=0 pairing correlations. At high spin all the models can reproduce the experimental data.
7.	Svensson, C. E., et al. (författare) Smooth Termination of Rotational Bands in 62Zn: Evidence for a Loss of Collectivity 1998 Ingår i: Physical Review Letters. - 1079-7114. ; 80:12, s. 2558-2561 Tidskriftsartikel (refereegranskat)abstract Two sets of strongly coupled rotational bands have been identified in Zn-62. These bands have been observed up to the terminating states of their respective configurations. Lifetime measurements indicate that the transition quadrupole moments in these bands decrease as termination is approached. These results establish the first terminating states of rotational bands in the A similar to 60 mass region and confirm the predicted loss of collectivity associated with smooth band termination.
8.	Döring, J., et al. (författare) Band terminations in the valence space of 86Zr 2000 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 61:3, s. 343101-343106 Tidskriftsartikel (refereegranskat)abstract High-spin states in 86Zr up to 30+ and 27- were observed via the 58Ni(32S,4p) reaction at 135 MeV beam energy using the combined GAMMASPHERE and MICROBALL systems. Calculations performed with the configuration-dependent shell-correction approach show that these states are built from six g9/2 neutrons and at most four protons excited from the p1/2,p3/2,f5/2 subshells to the g9/2 subshell at small deformation. The highest observed states at 27- and 30+ are interpreted as band-terminating states with the latter having the highest spin available in the valence space for 86Zr.
9.	Gizon, J., et al. (författare) Terminating bands in the doubly odd nucleus [Formula Presented] 1999 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 59:2, s. 570-574 Tidskriftsartikel (refereegranskat)abstract High spin states have been populated in [Formula Presented] using the reaction [Formula Presented] at 130 MeV. The γ rays have been detected with the EUROGAM2 array. The level structure of [Formula Presented] has been investigated. Several bands have been identified and established over a wide range of spin. They are interpreted using the Nilsson-Strutinsky cranking formalism and explained in terms of band terminations. Their configurations are built from the valence particles and valence holes relative to a [Formula Presented] core: [Formula Presented] protons (and [Formula Presented] proton holes) and [Formula Presented] and [Formula Presented] neutrons. After [Formula Presented] is the second heavy nucleus and the first odd-odd nucleus in which configurations in the valence space are followed from low spin up to their termination.
10.	Ideguchi, E., et al. (författare) Superdeformation in the Doubly Magic Nucleus 40Ca 2001 Ingår i: Physical Review Letters. - 1079-7114. ; 87:22 Tidskriftsartikel (refereegranskat)abstract A rotational band with seven gamma -ray transitions between states with spin 2 (h) over bar and 16 (h) over bar has been observed in the doubly magic, self-conjugate nucleus Ca-40(20)20. The measured transition quadrupole moment of 1.80(-0.29)(+0.39)eb indicates a superdeformed shape with a deformation beta (2) = 0.59(-0.07)(+0.11). The features of this band are explained by cranked relativistic mean field calculations to arise from an 8-particle 8-hole excitation.
11.	LaFosse, D. R., et al. (författare) Collective structures and band termination in 107Sb 2000 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 62:1 Tidskriftsartikel (refereegranskat)abstract High-spin states in the near proton-dripline nucleus 107Sb have been identified, and collectivity in this nucleus has been observed for the first time in the form of two rotational bands. One of the observed rotational structures is a ΔI = 1 band, and is interpreted as based on a π(g9/2)-1 ⊗ π(g7/2d5/2)2 proton configuration. A second structure has ΔI = 2 character, and is explained as being based on a πh11/2⊗[π(g9/2)-2 ⊗ π(g7/2d5/2)2] proton configuration through comparison with cranked Nilsson-Strutinsky model calculations. The calculations predict that this band terminates at a spin of 79/2 (Latin small letter h with stroke).
12.	O'Leary, C. D., et al. (författare) Evidence for isovector neutron-proton pairing from high-spin states in N = Z 74Rb 2003 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 67:2, s. 213011-213015 Tidskriftsartikel (refereegranskat)abstract High-spin states in the odd-odd N = Z nucleus 3774Rb37 were studied using the 40Ca(40Ca,αnp) reaction. A previously observed odd-spin T = 0 band has been extended to Iπ = (31+) and an even-spin T = 0 band has been observed for the first time to Iπ = (22+); both have a π(g9/2)⊗ν(g9/2) structure. A strongly coupled low-spin T = 0, K = 3 band has been interpreted as being based upon a π[312]3/2 ⊗ ν[312]3/2 configuration. Cranked relativistic Hartree-Bogoliubov calculations, which are corrected for the t = 1 np-pair field by restoring isospin symmetry, reproduce the observed spectrum. These new results provide evidence for the existence of an isovector pair field that contains a neutron-proton component with the proper strength for ensuring isospin conservation.
13.	Mullins, S. M., et al. (författare) Strong population of a superdeformed band in Eu142 1995 Ingår i: Physical Review C. - 0556-2813. ; 52:1, s. 99-103 Tidskriftsartikel (refereegranskat)abstract A superdeformed band has been found in Eu142. It is populated with 1.2(2)% of the total -ray intensity that decayed into Eu142 via the reaction Sn120(27Al,5n)142Eu at 152 MeV. The strength of the band is similar to that previously reported in Eu143, where the superdeformed band is populated with an intensity of 1.1(1)%. This is unexpected, since both total Routhian surface (TRS) and cranked modified oscillator (MO) calculations predict that the superdeformed band in Eu143 becomes yrast at lower spin than that in Eu142. This difference is 4Latin small letter h with stroke in the MO calculations and 8Latin small letter h with stroke in the TRS. Extrapolation of the normal-deformed yrast states in Eu143 shows, however, that a difference of 8Latin small letter h with stroke in spin corresponds to a change in the relative energy of the superdeformed and normal-deformed yrast lines of only 1 MeV.
14.	Petrache, C. M., et al. (författare) Stable triaxiality at the highest spins in 138Nd and 139Nd 2000 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 61:1, s. 113051-113055 Tidskriftsartikel (refereegranskat)abstract The nuclei 138Nd and 139Nd have been studied at very high spins via the 48Ca+94Zr reaction. Several new rotational bands were observed, four in 138Nd and two in 139Nd. The J(2) moments of inertia calculated from the observed γ-ray energies are very small and almost constant, indicating that these bands are triaxial. Cranked Nilsson-Strutinsky calculations reproduce the general behavior of the bands, supporting this interpretation and suggesting an approximately constant γ value of ∼ + 35° over a large spin range up to the highest observed spins. These bands and a few similar bands in other nuclei of the N≈80 region are a unique example of almost undisturbed triaxial bands.
15.	Rudolph, Dirk, et al. (författare) Shell-model Influence in the Rotational Nucleus 86Mo 1996 Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 54:1, s. 117-124 Tidskriftsartikel (refereegranskat)abstract High-spin states in Mo-86 were studied by means of the fusion evaporation reaction Ni-58(S-32,2p2n) Mo-86 at 135 MeV beam energy. Charged-particle-gamma gamma and -gamma gamma gamma coincidences recorded with the early implementation of the GAMMASPHERE array and the MICROBALL charged-particle detection system were used to largely extend the level scheme of the T-tau=1 nucleus Mo-86 to a possible spin of I=24h at 13 MeV excitation energy. The excitation scheme is compared to neighboring nuclei. There is evidence for enhanced shell-model influence in the 4 quasiparticle region (I=12-16h). The observed (pi=+,alpha=0) sequence at spin I greater than or equal to 16 h appears to be associated with a triaxial collective rotational band. This interpretation is supported by calculations within the configuration-dependent shell-correction approach with the cranked Nilsson potential.
16.	Sarantites, D. G., et al. (författare) Triaxial superdeformed bands in [Formula Presented] 1998 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 57:1, s. 1-5 Tidskriftsartikel (refereegranskat)abstract Four new superdeformed bands have been found in the nucleus [Formula Presented]. The good agreement between experiment and configuration-dependent shell correction calculations suggests that three of the bands have triaxial superdeformed shapes. Such unique features in mass [Formula Presented] superdeformed bands have been predicted, but not observed experimentally until now. A fourth band in [Formula Presented] is interesting due to a fairly constant and unusually high dynamic moment of inertia. Possible interpretations of this structure are discussed.
17.	Smith, J. F., et al. (författare) Identification of excited states in 119Ba 2000 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 61:4 Tidskriftsartikel (refereegranskat)abstract Excited states have been identified in the very neutron-deficient 119Ba nucleus. Two bands have been observed, which are likely to be based on h11/2 and (g7/2d5/2) neutron orbitals. Despite this being the first observation of excited states in 119Ba, the bands extend to (75/2)ℏ and (79/2)ℏ, respectively. The bands have been assigned to 119Ba using gamma-recoil and gamma-x-ray coincidences. Several quasiparticle alignments have been identified, involving neutron (h11/2)2 and proton (h11/2)2 aligned configurations. Furthermore, the bands show features which are reasonably consistent with smooth band termination at high spin. Theoretical results for 119Ba are discussed within the framework of cranked Woods-Saxon and Nilsson-Strutinsky calculations.
18.	Svensson, C. E., et al. (författare) Observation and Quadrupole Moment Measurement of the First Superdeformed Band in the A~60 Mass Region 1997 Ingår i: Physical Review Letters. - 1079-7114. ; 79:7, s. 1233-1236 Tidskriftsartikel (refereegranskat)abstract A high-spin rotational cascade of six gamma rays has been observed in Zn-62. The quadrupole moment of 2.7(-0.5)(+0.7) e b measured for this band corresponds to a deformation beta(2) = 0.45(-0.07)(+0.10). The properties of this band are in excellent agreement with calculations that predict high-spin superdeformed bands in Zn-62 with deformations beta(2) = 0.41-0.49. These results establish a new region of superdeformation for nuclei with neutron and proton numbers N, Z approximate to 30-32.
19.	Devlin, M., et al. (författare) Superdeformation in 68Zn: Evidence for a New, Neutron-rich Island of Superdeformation in A~70 Nuclei 1999 Ingår i: Physical Review Letters. - 1079-7114. ; 82, s. 5217-5220 Tidskriftsartikel (refereegranskat)abstract A superdeformed rotational structure is reported in the stable nucleus Zn-68. It has a transition quadrupole moment (Q(t)) of 2.5(-0.4)(+0.7) e b (beta(2) approximate to 0.4), as measured by the residual Doppler shift method. Theoretical calculations suggest that two different configurations are possible candidates for this band. One is built without h(11/2) neutrons, as seen in superdeformed bands in the A similar to 60 region, while the other involves one h(11/2) neutron in analogy with superdeformed bands in the A similar to 80 region. The second of these candidate configurations is preferred, thus establishing a new, neutron-rich (relative to the line of beta stability) region of superdeformation with Z similar to 30 and N similar to 38.
20.	Ideguchi, E., et al. (författare) High-spin intruder band in In-107 2010 Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 81:3, s. 034303- Tidskriftsartikel (refereegranskat)abstract High-spin states in the neutron-deficient nucleus In-107 were studied via the Ni-58(Cr-52,3p) reaction. In-beam gamma rays were measured using the JUROGAM detector array. A rotational cascade consisting of ten gamma-ray transitions, which decays to the 19/2(+) level at 2.002 MeV, was observed. The band exhibits the features typical for smooth terminating bands that also appear in rotational bands of heavier nuclei in the A similar to 100 region. The results are compared with total Routhian surface and cranked Nilsson-Strutinsky calculations.
21.	Lane, G. J., et al. (författare) Identification of excited states in doubly odd [Formula Presented]Sb : Smooth band termination 1997 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 55:5, s. 2127-2131 Tidskriftsartikel (refereegranskat)abstract Excited states in [Formula Presented]Sb have been identified for the first time in a series of [Formula Presented]-spectroscopy experiments using both thin and backed targets, including neutron-fold and recoil-mass measurements to provide unambiguous channel identification. The three decoupled intruder bands observed in [Formula Presented]Sb are based upon configurations involving 2p-2h excitations across the [Formula Presented] shell gap and show the features of smooth band termination. The yrast intruder band, which has been connected to the low-spin levels, is tentatively identified up to its predicted termination at [Formula Presented]. Excellent agreement with configuration-dependent cranked Nilsson-Strutinsky calculations is obtained for the high-spin states near termination.
22.	Paul, E.S., et al. (författare) Gamma-ray spectroscopy of neutron-deficient Te-110. II. High-spin smooth-terminating structures 2007 Ingår i: Physical Review C: covering nuclear physics. ; 76, s. 1-034323 Tidskriftsartikel (refereegranskat)abstract High-spin states have been populated in Te-110(52) via Ni-58(Ni-58,alpha 2p gamma) reactions at 240 and 250 MeV. The Gammasphere gamma-ray spectrometer was used in conjunction with the Microball charged-particle detector. The high-spin (I>30) collective level scheme of Te-110, up to similar to 45h, is discussed in this paper. Four new decoupled (Delta I=2) high-spin structures have been observed for the first time, together with two strongly coupled (Delta I=1) bands. These bands all show the characteristics of smooth band termination, and are discussed within the framework of the cranked Nilsson-Strutinsky approach.
23.	Pfohl, J., et al. (författare) Highly deformed rotational structures in 136Pm 2000 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 62:3, s. 313041-313045 Tidskriftsartikel (refereegranskat)abstract Four highly deformed structures in the odd-odd nucleus 13661Pm75 were observed via the 105Pd(35Cl,2p2n) reaction at 180 and 173 MeV using the GAMMASPHERE γ-ray spectrometer and the Microball charged-particle detector array. Quadrupole moment measurements were performed on all of the bands. In contrast to lighter odd-Ζ Pm and Pr nuclei, bands based on the g9/2[404]9/2 proton orbital were not observed. Instead, the four observed sequences are assigned as a coupling of an i13/2 neutron with the low-Ω h11/2 and mixed d5/2g7/2 orbitals. Comparisons with neighboring highly deformed structures are discussed and cranked Nilsson-Strutinsky calculations for 136Pm are presented.
24.	Afanasjev, A. V., et al. (författare) Comparative study of superdeformed and highly deformed bands in the [Formula Presented] mass region 1999 Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 59:6, s. 3166-3171 Tidskriftsartikel (refereegranskat)abstract Superdeformed and highly deformed rotational bands in the [Formula Presented] mass region are studied within cranked relativistic mean field theory and the configuration-dependent cranked Nilsson-Strutinsky approach. Both approaches describe the experimental data well. Low values of the dynamic moments of inertia [Formula Presented] compared with the kinematic moments of inertia [Formula Presented] seen both in experiment and in calculations at high rotational frequencies indicate the high energy cost to build the states at high spin and reflect the limited angular momentum content in these configurations.
25.	Afanasjev, A. V., et al. (författare) The coexistence of the intruder vi13/2, superdeformed and terminating bands in the A ∼ 135 mass region 1996 Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 608:2, s. 176-201 Tidskriftsartikel (refereegranskat)abstract The configuration-dependent shell-correction approach with the cranked Nilsson potential is employed for a systematic investigation of the high-spin spectra of the nuclei in the A ∼ 135 (Z = 57-61, N = 72-78) mass region, where superdeformed bands have been observed. Main attention is paid to the coexistence of intruder νi13/2, superdeformed and terminating bands in the yrast region. Recent developments of the formalism allow the identification of the high-j orbitals in each N-shell, for example, the g9/2 orbitals in the N = 4 shell, after the diagonalization of the cranked Nilsson potential. This turns out to be quite important for the understanding of the high collectivity of the observed bands. It is shown that the equilibrium deformation of the superdeformed bands is strongly dependent on the number of the proton holes in the g9/2 orbitals. With increasing neutron number above N = 75, the intruder νi13/2 bands are calculated triaxial. Especially for Z = 57, but also for higher proton numbers, we calculate some coexistent oblate non-collective states which are yrast for specific spin values at I ≥ 40h.

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