0000000001238199
AUTHOR
Torbjörn Bäck
showing 32 related works from this author
Evidence for a spin-aligned neutron-proton paired phase from the level structure of (92)Pd
2011
4 páginas, 4 figuras.-- El Pdf es la versión pre-print.-- et al.
γ-ray linear polarization measurements and(g9/2)−3neutron alignment in91Ru
2013
The authors would like to thank the operators of the GANIL cyclotrons for providing the 36Ar beam. We would also like to thank the EXOGAM Collaboration for use of the clover Ge detector array, the DIAMANT Collaboration for use of the charged particle detector system, and the European gamma-ray Spectroscopy Pool for use of the neutron detector system. We acknowledge funding support from the French-Polish LEA COPIGAL and the IN2P3-Polish laboratories COPIN Agreement No. 06-122, from the UK STFC, from the Swedish Research Council (Contracts No. 2007-4067 and No. 2008-5793), from the Goran Gustafsson Foundation, from the OTKA under Contract No. K100835, and from the Bolyai Janos Foundation. AG …
Electromagnetic transition strengths in 109Te
2012
Lifetime measurements have been made in the neutron-deficient nucleus 109Te using the coincident recoil distance Doppler-shift method. The experimental B(E2) values have been compared with state-of-the-art shellmodel calculations using the monopole-corrected realistic charge-dependent Bonn nucleon-nucleon potential. Lifetimes in the νh11/2 band are consistent with an interpretation based on the deformation driving properties of a single valence neutron outside of the even-even tellurium core and highlight the unexpected presence of collective behavior as the N = 50 shell closure is approached. Lifetime measurements for the low-lying positive-parity states also appear to correlate well with …
Collective rotational – vibrational transition in the very neutron-deficient nuclei Pt
1998
Excited states have been identified for the first time in very neutron deficient Pt-171.172 nuclei using the recoil-or-decay tagging technique. The ground-state band in Pt-172 has been established up to I-pi = 8+. A similar level sequence, presumably built on the I-pi = 13/2(+) state, is observed for Pt-171. The data are compared with theoretical calculations based on the mean field approach and the random phase approximation and are put into the context of the systematics of platinum isotopes. (C) 1998 Elsevier Science B.V. All rights reserved.
Recoil-decay tagging spectroscopy of74162W88
2015
Excited states in the highly neutron-deficient nucleus W-162 have been investigated via the Mo-92(Kr-78, 2 alpha) W-162 reaction. Prompt gamma rays were detected by the JUROGAM II high-purity germa ...
Reduced transition probabilities along the yrast line in W-166
2017
WOS: 000406755100001
Anomalous transition strength in the proton-unbound nucleus I5653109
2011
A lifetime measurement has been made for the first excited 11/2(+) state in the proton-unbound nucleus (109)(53)I56 using the recoil-distance Doppler-shift method in conjunction with recoil-proton ...
Maximally aligned states in the proton drip line nucleus 106Sb
2005
High-spin states in Sb-106 have been investigated in the Fe-54(Ni-58, 1α 1p1n) reaction by in-beam γ-spectroscopic methods using the EUROBALL detector array equipped with charged particle and neutr ...
Coexistence of triaxial and prolate shapes in 171Ir
1999
Abstract Excited states in 171Ir have been observed for the first time. Gamma-rays were assigned to the nucleus by the recoil-decay tagging method. The ground-state band has a structure consistent with an h 11 2 proton coupled to a core of large triaxial deformation. At high spins, a bandcrossing occurs which is interpreted as a change in shape to a prolate deformation. Band-mixing calculations are performed for 171–175Ir. These show that shape-coexistence between triaxial and prolate states in these nuclei follows the same systematics found in their Pt and Os neighbours. The systematics are also compared with deformations calculated for 171–179Ir using the code “Ultimate Cranker”. Dipole b…
First observation of excited states inHg17595
2009
Excited states of the neutron-deficient nucleus Hg-175, populated using fusion-evaporation reactions, are reported for the first time. The spin and parity of the ground state has been determined to ...
Feasibility study for the measurement of πN transition distribution amplitudes at P¯ANDA in p¯p→J/ψπ0
2017
The exclusive charmonium production process in (P) over barp annihilation with an associated pi 0 meson (p) over barp -> J/psi pi(0) is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the J/psi -> e(+) e(-) decay channel with the AntiProton ANnihilation at DArmstadt ((P) over bar ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the (P) over barp -> pi(+)pi(-)pi(0) and (p) over barp -> J/psi pi(0)pi(0) reactions are performed with PANDAROOT, the simulation and analysis software framework of the (P) over bar ANDA experiment. It is show…
Neutron Excitations Across the N=50 Shell Gap in 102In
2002
The structure of In-102 has been investigated by in-beam gamma-spectroscopic methods. Knowledge on the excited states of this nucleus has significantly been extended. Three cascades of transitions were observed to exceed the spin-energy domain spanned by the pig(9/2)(-1)v(d(5/2),g(7/2))(3) configurations. The new high spin states at similar to 4 MeV excitation energy could be assigned to the pig(9/2)(-1)v(d(5/2), g(7/2))(2)h (11/2) configuration, while at least those at 4.733, 5.192 and 5.853 MeV most likely arise from the vg(9/2) --> vd(5/2), g(7/2) one-particle-one-hole excitation across the N = 50 shell closure.
Lifetime measurements in 166Re : Collective versus magnetic rotation
2016
WOS: 000371740600004
Lifetime measurement of neutron-rich even-even molybdenum isotopes
2017
D. Ralet et al. -- 11 pags., 10 figs., 3 tabs.
Quasiparticle alignments andα-decay fine structure of175Pt
2014
Excited states and decay properties of ${}^{175}$Pt have been investigated using the ${}^{92}$Mo${(}^{86}\mathrm{Sr},2pn)$ fusion-evaporation reaction. The JUROGAM I $\ensuremath{\gamma}$-ray spectrometer and the GREAT spectrometer were used in conjunction with the gas-filled recoil separator RITU for the measurement of the radiation at the target and focal plane positions, respectively. Two new band structures, assigned to be based on the ${I}^{\ensuremath{\pi}}=({{}^{7}{/}_{2}}^{\ensuremath{-}})$ ground state in ${}^{175}$Pt, have been established and the known yrast band has been extended up to ${I}^{\ensuremath{\pi}}=({{}^{49}{/}_{2}}^{+})$. Rotational properties of the excited states i…
Strongly coupled bands in the neutron-deficient nucleus167Re
2003
Excited states in the neutron-deficient nucleus Re-167 have been observed in a recoil-tagging experiment performed with the Jurosphere gamma-ray spectrometer in conjunction with the RITU gas-filled ...
Lifetime measurement of the first excited2+state inTe112
2015
The lifetime of the 2(+) --> 0(g.s.)(+) transition in the neutron-deficicient nucleus Te-112 has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift te ...
Spectroscopy of the neutron-deficientN=50nucleusRh95
2014
The neutron-deficient semimagic (neutron number N = 50) Rh-95 nucleus has been produced at high spins using the projectile-target system Ca-40 + Ni-58 at 125 MeV beam energy. The gamma-decays of le ...
Spectroscopy of the neutron-deficient nuclide 171Pt
2003
A number of previously unobserved gamma-rays emitted from the neutron-deficient nuclide Pt-171 have been identified using the recoil decay tagging technique. The level scheme has been updated using ...
Gamma-ray linear polarization measurement and $(g9/2)-3$ neutron alignment in 91Ru
2013
Linear polarization measurements have been performed for γ rays in 91Ru produced with the 58Ni(36Ar, 2p1nγ ) 91Ru reaction at a beam energy of 111 MeV. The EXOGAM Ge clover array has been used to measure the γ -γ coincidences, γ -ray linear polarization, and γ -ray angular distributions. The polarization sensitivity of the EXOGAM clover detectors acting as Compton polarimeters has been determined in the energy range 0.3–1.3 MeV. Several transitions have been observed for the first time. Measurements of linear polarization and angular distribution have led to the firm assignments of spin differences and parity of high-spin states in 91Ru. More specifically, calculations using a semiempirical…
Probing structural changes in the very neutron-deficient Os isotopes with recoil-decay tagging
2005
In recent years, the exploitation of the iecoil-decay tagging (RDT) technique with,large arrays of germanium detectors has revealed much information about the structure of heavy nuclei approaching the proton drip line. The yrast bands of the N <= 93 osmium isotopes have been identified in a campaign of tagging experiments using various spectrometer arrays coupled to the RITU gas-filled separator based at the University of Jyvaskyla. Trends in the yrast state excitation energies have indicated a transition from gamma-soft triaxial to near-spherical shapes with decreasing neutron number. Recent experimental results for Os-162 obtained with the JUROGAM and GREAT spectrometers also indicate the…
Bandcrossings in 171Os
1999
The nucleus Os-171 has been populated using the reaction Sn-116(Ni-58,2pn). Four new bands are identified, and the previously known bands are extended in spin, to a maximum of 53/2 (h) over bar. On ...
Character of particle-hole excitations in94Ru deduced fromγ-ray angular correlation and linear polarization measurements
2014
Linear polarization and angular correlations of gamma-rays depopulating excited states in the neutron-deficient nucleus Ru-94(44)50 have been measured, enabling firm spin-parity assignments for several excited states in this nucleus. The deduced multipolarities of strong transitions in the yrast structure were found to be mostly of stretched M1, E1, and E2 types and, in most cases, in agreement with previous tentative assignments. The deduced multipolarity of the 1869 keV and the connecting 257 and 1641 keV transitions indicates that the state at 6358 keV excitation energy has spin parity 12(1)(-) rather than 12(3)(+) as proposed in previous works. The presence of a 12(1)(-) state is interp…
First observation of gamma-rays from the proton emitter 171Au
2003
Gamma-rays from the alpha- and proton-unstable nuclide 171Au have been observed for the first time. The gamma-rays were correlated with both a proton- and an alpha-particle decay branch, confirming that the nucleus decays by alpha and proton emission from a single (11/2-) state. The measurement confirms the previously determined half-lives for these particle decays but the present values are of higher precision. In addition, a longer half-life than determined in previous work was measured for the proton-unstable tentative ground state. The results are discussed in relation to structures in neighbouring nuclei and compared with a Strutinsky-type TRS calculation.
First identification of rotational band structures inRe9175166
2015
Despite that it is more than 100 years since the atomic nucleus was first dis- covered by Ernest Rutherford and coworkers, many of its features still elude our understanding. The fact that the fundamental interactions between the nuclear constituents; nucleons, and ultimately quarks, are not yet known in detail, and the complexity of the nuclear many-body system compound the great challenges facing theoretical interpretations of experimental data. It is therefore important to focus on distinct phenomena where experimental mea- surements can be compared with theoretical predictions, providing stringent tests of theory. One such area is the nuclear phenomenology of collective excitations rela…
First observation of excited states in the neutron deficient nuclei Pt and Pt
1998
Abstract Excited states have been observed for the first time in 168 Pt and 170 Pt using the α -decay recoil-tagging technique. The trend of decreasing deformation moving away from the N =104 mid-shell continues for 170 Pt but the structure of 168 Pt is significantly different. The low spin level energy systematics in 168 – 184 Pt are presented and discussed within the framework of the interacting boson model.
Isomer-tagged differential-plunger measurements in 113Xe
2013
The 278-keV M2 γ decay from the νh11/2 isomeric state in 113Xe has been observed for the first time using the recoil-isomer tagging technique. The half-life of the isomer has been measured to be 6.9(3) μs. The derived B(M2) value is in agreement with the trend of systematic measurements of M2 transition strengths in neutron-deficient tellurium and tin isotopes. The lifetime of the first excited state in the νh11/2 band has been measured using the recoil distance Doppler-shift method. The extracted B(E2) value has been compared to theoretical CD-Bonn calculations and recent lifetime measurements in 109Te. This comparison of B(E2) values has been used to shed light on the possible influence o…
Identification of excited states in 167Os and 168Os: shape coexistence at extreme neutron deficiency
2001
Excited states in the very neutron-deficient isotopes Os-167 and Os-168 have been observed using the reaction Sn-112(Ni-58, 2pxn). The JUROSPHERE gamma -ray spectrometer array was used in conjuncti ...
Competing single-particle and collective states in the low-energy structure of 113I
2013
To understand the low-energy structure of the neutron deficient iodine isotopes, lifetimes for the low-lying 9/2+ and 11/2+ positive-parity states in 113I have been measured as τ = 28(4) ps and τ = 3.7(7) ps, respectively. The lifetime for the 11/2− state, which feeds the 9/2+ and 11/2+ states, was remeasured with improved accuracy as τ = 216(7) ps. The reduced transition probability, B(E2) = 32(5) W.u., for the 9/2+ → 5/2+ transition agrees with that calculated within the shell model using a Hamiltonian based on the charge-dependent Bonn nucleon-nucleon interaction. In contrast, the much larger transition probability, B(E2) = 209(39) W.u., measured for the 11/2+ → 7/2+ transition has been …
Application of ultra-fast timing techniques to the study of exotic and weakly produced nuclei
2005
Ultra-fast time-delayed techniques have been recently applied in a number of studies where exotic nuclei were identified using advanced selection techniques. These include large Compton-suppressed Ge arrays, in-flight separators or recoil separators. Some of the new results are discussed in this presentation. Besides the results for $^{32}$Mg and $^{96}$Pd, they include the first determination of the half-life of the $8^+$ state in $^{80}$Ge, $T_1/2$ = 2.95(6) ns, and significantly more precise results for $^{51}$Mn (3680 keV level) and $^{48}$V (421 keV level), $T_1/2$ = 1760(40) ps and $T_1/2$ $\leq$ 135 ps, respectively. Development of new scintillators will steadily improve precision an…
Lifetime measurement of the first excited2+state in108Te
2011
The lifetime of the first excited 2(+) state in the neutron deficient nuclide (108)Te has been measured for the first time, using a combined recoil decay tagging and recoil distance Doppler shift t ...
Isospin Properties of Nuclear Pair Correlations from the Level Structure of the Self-Conjugate Nucleus Ru88
2020
The low-lying energy spectrum of the extremely neutron-deficient self-conjugate (N = Z) nuclide 88 44Ru44 has been measured using the combination of the Advanced Gamma Tracking Array (AGATA) spectrometer, the NEDA and Neutron Wall neutron detector arrays, and the DIAMANT charged particle detector array. Excited states in 88Ru were populated via the 54Fe(36Ar; 2n )88Ru fusion-evaporation reaction at the Grand Acc�el�erateur National d'Ions Lourds (GANIL) accelerator complex. The observed -ray cascade is assigned to 88Ru using clean prompt - -2-neutron coincidences in anti-coincidence with the detection of charged particles, con�rming and extending the previously assigned sequence of low-lyin…