J.M. Espino

Publications (5)0 Total impact

• Article: Interaction strength and shape difference for the h9/2 and h11/2 configurations in163Tm

  H. J. Jensen, G. B. Hagemann, P. O. Tjøm, S. Frauendorf, A. Atac, M. Bergström, A. Bracco, A. Brockstedt, H. Carlsson, P. Ekström, [......], R. M. Lieder, T. Lönnroth, A. Maj, B. Million, A. Nordlund, J. Nyberg, M. Piiparinen, H. Ryde, M. Sugawara, A. Virtanen
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  ABSTRACT: The strongly shape driving h9/2[541]l/2– configuration with =+1/2 exhibits some anomalous, and so far unexplained, features concerning the crossing frequency, c, the aligned angular momentum, ix, and interaction strength, at the alignment of the first pair of i13/2 quasineutrons in several odd-Z rare earth-nuclei. The h9/2[541]1/2– and h11/2[523]7/2– bands have been studied in the stably deformed rare-earth nucleus163Tm to investigate these features. A difference in band crossing frequency of 80 keV between the two bands is found. Rotational bands built on these two configurations have been found to cross in the spin range I=25/2–29/2 . The-decay pattern between the two bands is established in the crossing region and analysed in terms of a moderate shape difference between them. A theoretical estimate of the size of the interaction strength between the two bands is presented and compared to the experimental value. The observed band structure in163Tm is very similar to that of167Lu which has 2 protons and 2 neutrons in addition. This observation is discussed in relation to the similarity of the yrast bands of the two even-even core nuclei162Er and166Yb, for which the-transition energies are identical within 0.2 keV below the vi13/2 crossing.
  Zeitschrift für Physik A Hadrons and Nuclei 01/1991; 340(4):351-362.
• Chapter: Nuclear level repulsion, order vs. chaos and conserved quantum numbers

  J. D. Garrett, J. R. German, J. M. Espino
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  ABSTRACT: A statistical analysis of the distribution of level spacings for states with the same angular momentum and parity is described in which the average spacing is calculated for the total ensemble. Though the resulting distribution of level spacings for states of deformed nuclei with Z = 62–75 and A = 155–185 is the closest to that of a Poisson distribution yet obtained for nuclear levels, significant deviations are observed for small level spacings. Many, but not all, of the very closely-spaced levels have K-values differing by several units.
  01/1970: pages 263-271;
• Article: High-spin spectroscopic study of 167Lu

  C.-H. Yu, G.B. Hagemann, J.M. Espino, K. Furuno, J.D. Garrett, R. Chapman, D. Clarke, F. Khazaie, J.C. Lisle, J.N. Mo, M. Bergström, L. Carlén, P. Ekström, J. Lyttkens, H. Ryde
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  ABSTRACT: Three decay sequences associated with the Nilsson states of 167Lu have been established to high spin using the 123Sb(48Ca,4n)167Lu reaction. The quasineutron and quasiproton band crossings, the energy signature splittings, and the B(M1)/B(E2) values are discussed and compared with similar quantities for the lighter lutetium isotopes. Configuration-and isotopic-dependent deformations, reflected in such comparisons, indicate that 167Lu has a larger and more stable prolate deformation than the lighter isotopes and that the configuration has a larger quadrupole deformation than the configuration. The shift of the AB neutron band crossing occurring in the sequences to a larger rotational frequency cannot be understood in terms only of deformation differences. The configuration and neutron-number dependent shapes are also discussed in a “gauge”-space analysis.
  Nuclear Physics A.
• Source

  Available from: Ian G. Bearden

  Article: Structure of excited bands in 162Tm and residual interactions

  J.M. Espino, G.B. Hagemann, I.G. Bearden, R.A. Bark, M. Bergström, A. Bracco, B. Herskind, H.J. Jensen, S. Leoni, C. Martínez-Torre, B. Million, P.O. Tjøm
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  ABSTRACT: The nucleus 162Tm has been populated by the 130Te(37Cl,5n) reaction, and the γ-cascades detected with the NORDBALL array. Eight coupled rotational bands involving the proton orbitals, , , , and and neutron orbitals , and have been established in 162Tm, to spins varying from 18 to 47ℏ. Various phenomena which can be related to residual neutron-proton interactions are discussed. In particular, signature inversion in the bands based on the quasiproton and quasineutron, rewpectively, may be explained by a fairly large p-n interaction. In addition, interactions at the crossings of bands with constituent quasiparticles differing both in parity and signature have been extracted with strength of the order of a few (4–12) keV. Such interactions also require terms beyond the standard mean field description.
  Nuclear Physics A.
• Article: Signature inversion in semi-decoupled bands: residual interaction between h92 protons and i132 neutrons

  R.A. Bark, J.M. Espino, W. Reviol, P.B. Semmes, H. Carlsson, I.G. Bearden, G.B. Hagemann, H.J. Jensen, I. Ragnarsson, L.L. Riedinger, H. Ryde, P.O. Tjøm
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  ABSTRACT: Semi-decoupled bands based on the configuration are observed in 162Tm, 164Tm and 174Ta. Spins assigned to these bands imply an inversion of the expected signature splitting, which is interpreted as being the result of a residual proton-neutron interaction.
  Physics Letters B. 406(3):193-199.