Torgeir Engeland

• Osnes, Eivind; Engeland, Torgeir & Hjorth-Jensen, Morten (2015). Large-scale shell-model study of the Sn isotopes. The European Physical Journal Conferences.  ISSN 2101-6275.  95:01010, s 1- 4 . doi: 10.1051/epjconf/20159501010
• Engeland, Torgeir; Hjorth-Jensen, Morten; Kartamyshev, Maxim & Osnes, Eivind (2014). The Kuo–Brown effective interaction: From 18O to the Sn isotopes. Nuclear Physics A.  ISSN 0375-9474.  928, s 51- 63 . doi: 10.1016/j.nuclphysa.2014.03.012
• Ekstrom, A; Cederkall, Joakim; Fahlander, Claes; Hjorth-Jensen, Morten; Engeland, Torgeir; Butler, PA; Davinson, T; Eberth, J; Finke, F; Görgen, Andreas; Gorska, M; Hurst, AM; Ivanov, O; Iwanicki, J; Koster, U; Marsh, BA; Mierzejewski, J; Reiter, P; Siem, Sunniva; Sletten, G; Stefanescu, I; Tveten, Gry Merete; Van de Walle, J; Voulot, D; Warr, N; Weisshaar, D; Wenander, F; Zielinska, M & Blazhev, A. (2010). Coulomb excitation of the odd-odd isotopes 106, 108In. European Physical Journal A.  ISSN 1434-6001.  44, s 355- 361 . doi: 10.1140/epja/i2010-10945-7 Vis sammendrag

  The low-lying states in the odd-odd and unstable isotopes 106, 108In have been Coulomb excited from the ground state and the first excited isomeric state at the REX-ISOLDE facility at CERN. With the additional data provided here the $ \pi$ g 9/2 -1 ⊗ $ \nu$ d 5/2 and $ \pi$ g 9/2 -1 ⊗ $ \nu$ g 7/2 multiplets have been re-analyzed and are modified compared to previous results. The observed $ \gamma$ -ray de-excitation patterns were interpreted within a shell model calculation based on a realistic effective interaction. The agreement between theory and experiment is satisfactory and the calculations reproduce the observed differences in the excitation pattern of the two isotopes. The calculations exclude a 6+ ground state in 106In . This is in agreement with the conclusions drawn using other techniques. Furthermore, based on the experimental results, it is also concluded that the ordering of the isomeric and ground state in 108In is inverted compared to the shell model prediction. Limits on B(E2) values have been extracted where possible. A previously unknown low-lying state at 367keV in 106In is also reported.

• Kartamychev, Maxim; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (2007). Effective interactions and shell model studies of heavy tin isotopes. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  76 . doi: 10.1103/PhysRevC.76.024313 Vis sammendrag

  We present results from large-scale shell model calculations of even and odd tin isotopes from 134Sn to 142Sn with a shell model space defined by the 1f7/2, 2p3/2, 0h9/2, 2p1/2, 1f5/2, and 0i13/2 single-particle orbits. An effective two-body interaction based on modern nucleon-nucleon interactions is employed. The shell model results are in turn analyzed for their pairing content using a generalized seniority approach. Our results indicate that a pairing model picture captures a great deal of the structure and the correlations of the lowest lying states for even and odd isotopes.

• Leske, J; Speidel, KH; Schielke, S; Gerber, J; Maier-Komor, P; Engeland, Torgeir & Hjorth-Jensen, Morten (2006). Experimental g factor and B(E2) value of the 4(1)(+) state in Coulomb-excited Zn-66 compared to shell-model predictions. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  73
• Leske, j.k.; Speidel, Karl-heinz; Schielke, S; Gerber, J; Maier-komor, P; Hjorth-Jensen, Morten & Engeland, Torgeir (2005). Dominant (g(9/2) 2-neutron configuration in the 4+ state of 68Zn based on new g-factor measurements. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  72 . doi: 10.1103/PhysRevC.72.044301 Vis sammendrag

  The g factor of the 4₁⁺ state in 68Zn was remeasured with improved energy resolution of the detectors used. The value obtained is consistent with the previous result of a negative g factor, thus confirming the dominant 0g9/2 neutron nature of the 4₁⁺ state. In addition, the accuracy of the g factors of the 2₁⁺,2₂⁺, and 3₁^- states has been improved and their lifetimes were well reproduced. New large-scale shell-model calculations based on a 56Ni core and a 0f5/21p0g9/2 model space yield a theoretical value, g(4₁⁺)=+0.008. Although the calculated value is small, it cannot fully explain the experimental value, g(4₁⁺)=-0.37(17). The magnitude of the deduced B(E2) of the 4₁⁺ and 2₁⁺ transitions is, however, rather well described. These results demonstrate again the importance of g factor measurements for nuclear structure determinations because of their specific sensitivity to detailed proton and neutron components in the nuclear wave functions.

• Banu, A; Gerl, J; Fahlander, C; Gorska, M; Grawe, H; Wollersheim, HJ; Caurier, E; Engeland, Torgeir; Gniady, A; Hjorth-Jensen, Morten; Nowacki, F; Beck, T; Becker, F; Bednarczyk, P; Bentley, MA; Burger, A; Cristancho, F; de Angelis, G; Dombradi, Z; Doornenbal, P; Geissel, H; Grebosz, J; Hammond, G; Hellstrom, M; Jolie, J; Kojouharov, I; Kurz, N; Lozeva, R; Mandal, S; Marginean, N; Muralithar, S; Nyberg, J; Pochodzalla, J; Prokopowicz, W; Reiter, P; Rudolph, D; Rusu, C; Saito, N; Schaffner, H; Sohler, D; Weick, H; Wheldon, C & Winkler, M (2005). Sn-108 studied with intermediate-energy Coulomb excitation. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  72(6) . doi: 10.1103/PhysRevC.72.061305 Vis sammendrag

  The unstable neutron-deficient 108Sn isotope has been studied in inverse kinematics by intermediate-energy Coulomb excitation using the RISING/FRS experimental setup at GSI. This is the highest Z nucleus studied so far with this method. Its reduced transition probability B (E2;0_g.s.⁺-->2₁⁺) has been measured for the first time. The extracted B(E2) value of 0.230(57)e2 b2 has been determined relative to the known value in the stable 112Sn isotope. The result is discussed in the framework of recent large-scale shell model calculations performed with realistic effective interactions. The roles of particle-hole excitations of the 100Sn core and of the Z=50 shell gap for the E2 polarization are investigated.

• Ellis, Paul; Engeland, Torgeir; Hjorth-Jensen, Morten; Kartamyshev, Maximx & Osnes, Eivind (2005). Model calculation of effective three-body forces. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  71, s 034301 Vis sammendrag

  We propose a scheme for extracting an effective three-body interaction originating from a two-nucleon interaction. This is based on the Q-box method of Kuo and collaborators, where folded diagrams are obtained by differentiating a sum of nonfolded diagrams with respect to the starting energy. To gain insight we have studied several examples using the Lipkin model where the perturbative approach can be compared with exact results. Numerically the three-body interactions can be significant and in a matrix example good accuracy was not obtained simultaneously for both eigenvalues with two-body interactions alone.

• Dean, David J.; Engeland, Torgeir; Hjorth-Jensen, Morten; Kartamychev, Maxim & Osnes, Eivind (2004). Effective interactions and the nuclear shell-model. Progress in Particle and Nuclear Physics.  ISSN 0146-6410.  53, s 419- 500 Vis sammendrag

  This review aims at a critical discussion of the interplay between effective interactions derived from various many-body approaches and spectroscopic data extracted from large scale shell-model studies. To achieve this, our many-body scheme starts with the free nucleon-nucleon (NN) interaction, typically modelled on various meson exchanges. The NN interaction is in turn renormalized in order to derive an effective medium dependent interaction. The latter is in turn used in shell-model calculations of selected nuclei. We also describe how to sum up the parquet class of diagrams and present initial uses of the effective interactions in coupled cluster many-body theory.

• Gausemel, Håvar; Fogelberg, Birger; Engeland, Torgeir; Hjorth-Jensen, Morten; Hoff, Per; Mach, Hendryk; Mezilev, K.A. & Omtvedt, Jon Petter (2004). Decay of In-127 and In-129. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  69, s art. no.- 054307
• Lipoglavsek, M.; Baktash, C.; Blomqvist, Jan; Dean, David J.; Engeland, Torgeir; Fahlander, C.; Hjorth-Jensen, Morten; Janssens, Robert V. F.; Likar, A.; Osnes, Eivind & Paul, S.D. (2002). Break-up of the Doubly-magic 100Sn core. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  66, s 011302
• Lipoglavsek, M.; Baktash, C.; Carpenter, M.P.; Dean, David J.; Engeland, Torgeir; Fahlander, C.; Hjorth-Jensen, Morten & Osnes, Eivind (2002). Excited states of the proton emitter 105Sb. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  65, s 051037
• Lipoglavsek, M.; Baktash, C.; Carpenter, M.P.; Dean, David J.; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (2002). Core excitations in 102In. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  65, s 021302(R
• Elgarøy, Øystein; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (2001). Pairing correlations in nuclear systems, from infinite nuclear matter to finite nuclei. International Journal of Modern Physics B.  ISSN 0217-9792.  15, s 1501- 1509
• Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (2000). Shell model studies of the proton drip line nucleus ¹⁰⁶Sb. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  61, s r00010- r00015
• Holt, Anne; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (2000). Applications of realistic effective interactions to the structure of Zr isotopes. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  61
• Holt, Anne; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (1998). Shell-model calculations of heavy Sn isotopes. Nuclear Physics A.  ISSN 0375-9474.  634, s 41- 56
• Suhonen, Jouni; Toivanen, Jussi; Engeland, Torgeir; Hjorth-Jensen, Morten; Holt, Anne & Osnes, Eivind (1998). Study of odd-mass N=82 isotones: comparison of the microscopic quasiparticle-phonon model and the nuclear shell model. Nuclear Physics A.  ISSN 0375-9474.  628, s 41- 61
• Holt, Anne; Engeland, Torgeir; Hjorth-Jensen, Morten; Osnes, Eivind & Suhonen, Jouni (1997). The structure of the N=82 isotones with realistic effective interactions. Nuclear Physics A.  ISSN 0375-9474.  618, s 107- 125
• Sandulescu, N.; Liotta, Roberto; Blomqvist, Jan; Engeland, Torgeir; Hjorth-Jensen, Morten; Holt, Anne & Osnes, Eivind (1997). Generalized seniority scheme in light tin isotopes. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  55, s 2708- 2710
• Engeland, Torgeir; Hjorth-Jensen, Morten; Holt, Anne & Osnes, Eivind (1995). Large shell model calculations with realistic effective interactions. Physica Scripta.  ISSN 0031-8949.  T56, s 58- 66
• Ellis, P.J.; Engeland, Torgeir; Hjorth-Jensen, Morten; Holt, Anne & Osnes, Eivind (1994). Convergence properties of the effective interaction. Nuclear Physics A.  ISSN 0375-9474.  573, s 216- 230
• Hjorth-Jensen, Morten; Engeland, Torgeir; Holt, Anne & Osnes, Eivind (1994). Perturbative many-body approaches to finite nuclei. Physics reports.  ISSN 0370-1573.  242, s 37- 69
• Holt, Anne; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (1994). The structure of the neutron deficient Sn isotopes. Nuclear Physics A.  ISSN 0375-9474.  570, s 137c- 144c
• Engeland, Torgeir; Hjorth-Jensen, Morten; Holt, Anne & Osnes, Eivind (1993). The structure of the neutron deficient Sn isotopes. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  48, s R535- R538
• Hjorth-Jensen, Morten; Engeland, Torgeir; Holt, Anne & Osnes, Eivind (1992). Effective interactions for valence-hole nuclei with modern meson-exchange potential models. Nuclear Physics A.  ISSN 0375-9474.  541, s 105- 130
• Ramsøy, Tore; Engeland, Torgeir; Guttormsen, Magne Sveen; Rekstad, John Bernhard; Løvhøiden, Gunnar; Vaagen, Jan S & et al.,, - (1987). Particle-vibration coupled states in 161Dy. Nuclear Physics A.  ISSN 0375-9474.  470, s 79
• Rekstad, John Bernhard; Guttormsen, Magne Sveen; Engeland, Torgeir; Løvhøiden, Gunnar & et al.,, - (1981). The level structure of the 153Gd nucleus studied in the 150Sm(α, n)153Gd reaction. Nuclear Physics A.  ISSN 0375-9474.  371, s 364
• Guttormsen, Magne Sveen; Pedersen, Torstein; Rekstad, John Bernhard; Engeland, Torgeir; Osnes, Eivind & Ingebretsen, Finn (1980). The particle-rotor model with pairing in the s-d shell: An analysis of the 23Na nucleus. Nuclear Physics A.  ISSN 0375-9474.  338, s 141
• Rekstad, John Bernhard; Guttormsen, Magne Sveen; Engeland, Torgeir; Løvhøiden, Gunnar & et al.,, - (1979). The 153Sm nucleus: An experimental and theoretical study. Nuclear Physics A.  ISSN 0375-9474.  320, s 239

Se alle arbeider i Cristin

• Engeland, Torgeir; Hjorth-Jensen, Morten & Jansen, Gustav (2008). CENS, a computational environment for nuclear structure. Vis sammendrag

  We present a recently developed software written in Python which merges several Fortran95 and C++ codes for doing `ab initio' nuclear structure calculations. Combined with a pedagogical graphical user interface, the software allows the user to perform nuclear structure calculations starting from the free nucleon-nucleon interaction, and via various renormalization techniques one obtains an effective interaction for shell-model calculations. The included shell-model code allow the user to compute spectra and transition probabilities for practically all mass areas. Several methods for renormalizing a nucleon-nucleon interaction and taylor it to specific model spaces are available, ranging from no-core shell-model interaction to interactions derived from many-body perturbation theory.

• Jansen, Gustav Ragnar; Hjorth-Jensen, Morten & Engeland, Torgeir (2008). CENS - Computational Environment for Nuclear Structure.
• Kartamychev, Maxim; Hjorth-Jensen, Morten; Engeland, Torgeir & Osnes, Eivind (2007). Three-body effective interactions in nuclear structure studies.
• Kartamychev, Maxim; Hjorth-Jensen, Morten; Engeland, Torgeir & Osnes, Eivind (2007). Three-body interactions in nuclear structure studies.
• Kartamyshev, Maxim; Hjorth-Jensen, Morten; Engeland, Torgeir & Osnes, Eivind (2007). Realistic three-nucleon effective interactions in nuclear structure studies.
• Kartamyshev, Maxim; Hjorth-Jensen, Morten; Engeland, Torgeir & Osnes, Eivind (2007). Three-body effective interactions in nuclear structure studies.
• Kartamychev, Maxim; Hjorth-Jensen, Morten; Engeland, Torgeir & Osnes, Eivind (2006). Realistic Three-Nucleon Effective Interaction from the Folded-Diagram Theory.
• Kartamychev, Maxim; Hjorth-Jensen, Morten; Engeland, Torgeir & Osnes, Eivind (2006). Realistic Three-Nucleon Effective Interaction from the Folded-Diagram Theory.
• Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (2000). Effective interactions for medium heavy nuclei.
• Elgarøy, Øystein; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (1999). Pairing correlations, from finite nuclei to infinite matter.
• Engeland, Torgeir (1999). Large Scale Shell Model Calculation. Vis sammendrag

  Abstract: We describe the properties of complex nuclear shell model systems in terms of the free nucleon-nucleon interaction as obtained from meson-exchange theory. This amounts to first calculating an effective interaction in which the free interaction is modified by the presence of the appropriate nuclear medium. The short-range correlations are included within the framework of Brueckner theory yielding the nuclear reaction matrix and the long--range correlations by using the reaction matrix in many--body perturbation theory to obtain an effective interaction. The resulting effective interaction is then employed in calculating properties in nuclear systems with large degrees of freedom using a m--scheme shell model code and with Lanczos iteration procedure. In this work we will report on its application to structure calculations of complex nuclei, in particular the Sn isotopes. Special emphasis is placed on the ability of our calculation to describe systematic trends of the properties of these nuclei. Both successful achievements and problematic features are pointed out. In particular, we analyze the role pairing and generalized seniority seem to play in these nuclei and examine whether this feature may be used in designing a simplified scheme for shell-model calculations.

• Engeland, Torgeir (1999). Large-Scale Shell model Calculations.
• Engeland, Torgeir; Hjorth-Jensen, Morten; Holt, Anne & Osnes, Eivind (1998). Realistic Effective Interactions and Large-Scale Nuclear Structure Calculation.
• Engeland, Torgeir; Hjorth-Jensen, Morten; Holt, Anne & Osnes, Eivind (1996). Extensive Shell-Model calculations in the tin isotopes.
• Engeland, Torgeir; Hjorth-Jensen, Morten; Holt, Anne & Osnes, Eivind (1996). Realistic Large basis shell-model calculation in the low-mass tin isotopes.
• Osnes, Eivind; Hjorth-Jensen, Morten; Engeland, Torgeir & Holt, Anne (1993). Shell model calculations with realistic effective interactions.

Se alle arbeider i Cristin