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Brunet, M.*; Podolyk, Zs.*; Berry, T. A.*; Brown, B. A.*; Carroll, R. J.*; Lica, R.*; Sotty, Ch.*; Andreyev, A. N.; Borge, M. J. G.*; Cubiss, J. G.*; et al.
Physical Review C, 103(5), p.054327_1 - 054327_13, 2021/05
被引用回数:2 パーセンタイル:39.09(Physics, Nuclear)The structure of Po populated through the EC/
decay of
At is investigated using
-ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed
rays which have been (re)assigned a position. Through the analysis using the shell model calculations approximately half of the
-decay strength of
At is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations.
Cubiss, J. G.*; Harding, R. D.*; Andreyev, A. N.; Althubiti, N.*; Andel, B.*; Antalic, S.*; Barzakh, A. E.*; Cocolios, T. E.*; Day Goodacre, T.*; Farooq-Smith, G. J.*; et al.
Physical Review C, 101(1), p.014314_1 - 014314_4, 2020/01
被引用回数:5 パーセンタイル:56.26(Physics, Nuclear)Ptの基底状態から娘核
Osの基底状態への
崩壊分岐比を0.52(5)%と、過去の値と比較してより高精度で再決定した。
PtはCERN-ISOLDE実験施設において
Hgを単離し、その
崩壊孫核種として生成した。今回の結果を用いて導出した
崩壊の換算崩壊幅は、中性子欠損Pt同位体の
崩壊幅の系統性について新しい描像を与えることとなった。
Ghys, L.*; Andreyev, A. N.; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; Cocolios, T. E.*; Cubiss, J.*; Derkx, X.*; et al.
Physical Review C, 100(5), p.054310_1 - 054310_13, 2019/11
被引用回数:11 パーセンタイル:76.94(Physics, Nuclear)The aim of this work was to investigate the -decay properties of
Fr and daughter products. Neutron-deficient francium nuclei are produced at ISOLDE-CERN bombarding a UCx target with 1.4 GeV protons. Due to the very high statistics and the high beam purity, improved decay data for
Fr and its daughters were obtained. The observation of crossover transitions positioned the isomeric high-spin level of
At at an excitation energy of 265(3) keV. Half-life values of 4.47(5) s and 1.28(10) s were extracted for the ground state and isomeric state of
At and 52(3) ms for the ground-state decay of
Fr.
Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieliska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.
European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08
被引用回数:10 パーセンタイル:76.94(Physics, Nuclear)The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0
, 2
, and 4
states was observed in all nuclei under study. Reduced
matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.
Cubiss, J. G.*; Andreyev, A. N.; Barzakh, A. E.*; Andel, B.*; Antalic, S.*; Cocolios, T. E.*; Day Goodacre, T.*; Fedorov, D. V.*; Fedosseev, V. N.*; Ferrer, R.*; et al.
Physical Review C, 99(6), p.064317_1 - 064317_6, 2019/06
被引用回数:6 パーセンタイル:56.41(Physics, Nuclear)Atの
崩壊について、CERN-ISOLDE施設においてレーザーイオン化法を使うことで研究した。
-
同時計数データを初めて取得し、より精度の良い半減期の値として1.27(6)秒を得た。
崩壊の微細構造を基に新しい
崩壊図式を構築した。それらの結果から、
Atの基底状態のスピン・パリティは(3
)がより確からしいことが解ったが、(2)
の可能性も完全には否定しきれない。
Berry, T. A.*; Podolyk, Zs.*; Carroll, R. J.*; Lic
, R.*; Grawe, H.*; Timofeyuk, N. K.*; Alexander, T.*; Andreyev, A. N.; Ansari, S.*; Borge, M. J. G.*; et al.
Physics Letters B, 793, p.271 - 275, 2019/06
被引用回数:5 パーセンタイル:50.19(Astronomy & Astrophysics)Gamow-Teller decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This
= 0 requirement plays a major role in the
decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical
-process pathway below both
= 50 (for
82) and
= 82 (for
126). The level of forbiddenness of the
= 1
1
0
transition has been investigated from the
decay of the ground state of
Hg into the single-proton-hole nucleus
Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible
-ray transitions depopulating the
0
state in
Tl, an upper limit of 3.9
10
% was obtained for the probability of this decay, corresponding to log
8.8 within a 95% confidence limit. This is the most stringent test of the
= 0 selection rule to date.
Barzakh, A. E.*; Cubiss, J. G.*; Andreyev, A. N.; Seliverstov, M. D.*; Andel, B.*; Antalic, S.*; Ascher, P.*; Atanasov, D.*; Beck, D.*; Biero, J.*; et al.
Physical Review C, 99(5), p.054317_1 - 054317_9, 2019/05
被引用回数:12 パーセンタイル:79.18(Physics, Nuclear)Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in At have been measured at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy technique. Magnetic dipole and electric quadrupole moments, and changes in the nuclear mean-square charge radii, have been deduced. A large inverse odd-even staggering in radii, which may be associated with the presence of octupole collectivity, has been observed. Namely, the radius of the odd-odd isotope
At has been found to be larger than the average.
Andel, B.*; Andreyev, A. N.; Antalic, S.*; Barzakh, A.*; Bree, N.*; Cocolios, T. E.*; Comas, V. F.*; Diriken, J.*; Elseviers, J.*; Fedorov, D. V.*; et al.
Physical Review C, 96(5), p.054327_1 - 054327_11, 2017/12
被引用回数:3 パーセンタイル:28.57(Physics, Nuclear)A detailed -decay spectroscopy study of
Tl has been performed at ISOLDE (CERN). Z-selective ionization by the Resonance Ionization Laser Ion Source (RILIS) coupled to mass separation provided a high-purity beam of
Tl. Fine-structure
decays to excited levels in the daughter
Au were identified and an
-decay scheme of
Tl was constructed based on an analysis of
-
and
-
-
coincidences. Multipolarities of several
-ray transitions deexciting levels in
Au were determined. Based on the analysis of reduced
-decay widths, it was found that all
decays are hindered, which signifies a change of configuration between the parent and all daughter states.
Lic, R.*; Rotaru, F.*; Borge, M. J. G.*; Gr
vy, S.*; Negoita, F.*; Poves, A.*; Sorlin, O.*; Andreyev, A. N.; Borcea, R.*; Costache, C.*; et al.
Physical Review C, 95(2), p.021301_1 - 021301_6, 2017/02
被引用回数:15 パーセンタイル:78.93(Physics, Nuclear)The decay of
Mg was used to study the
Al nucleus through
spectroscopy at the Isotope Separator On-Line facility of CERN. Previous studies identified two
-decaying states in
Al having spin-parity assignments
=4
dominated by the normal configuration
(d5/2)
(f7/2) and
= 1
by the intruder configuration
(d5/2)
(d3/2)
(f7/2)
. Their unknown ordering and relative energy have been the subject of debate for the placement of
Al inside or outside the
= 20 "island of inversion". We report here that the 1
intruder lies only 46.6 keV above the 4
ground state. In addition, a new half-life of
=44.9(4)ms, that is twice as long as thepreviously measured 20(10) ms, has been determined for
Mg. Large-scale shell-model calculations with the recently developed SDPF-U-MIX interaction are compared with the new data and used to interpret the mechanisms at play at the very border of the
= 20 island of inversion.
Barzakh, A.*; Andreyev, A. N.; Cocolios, T. E.*; de Groote, R. P.*; Fedorov, D. V.*; Fedosseev, V. N.*; Ferrer, R.*; Fink, D. A.*; Ghys, L.*; Huyse, M.*; et al.
Physical Review C, 95(1), p.014324_1 - 014324_12, 2017/01
被引用回数:22 パーセンタイル:87.41(Physics, Nuclear)Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron deficient isotopes Tl using the 276.9 nm transition. The experiment has been performed at the CERN Isotope Separator On-Line facility using the in-source resonance-ionization laser spectroscopy technique. Spins for the ground states in
Tl have been determined as
= 1/2. Magnetic moments and changes in the nuclear mean-square charge radii have been deduced. By applying the additivity relation for magnetic moments of the odd-odd Tl nuclei the leading configuration assignments were confirmed. A deviation of magnetic moments for isomeric states in
Tl from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes
Tl follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of
Tl has been observed, suggesting a larger deformation for the intruder-based 9/2
and 10
states compared to the ground states. An unexpected growth of the isomer shift for
Tl has been found.
Lund, M. V.*; Andreyev, A. N.; Borge, M. J. G.*; Cederkll, J.*; De Witte, H.*; Fraile, L. M.*; Fynbo, H. O. U.*; Greenlees, P. T.*; Harkness-Brennan, L. J.*; Howard, A. M.*; et al.
European Physical Journal A, 52(10), p.304_1 - 304_14, 2016/10
被引用回数:16 パーセンタイル:76.79(Physics, Nuclear)Beta-delayed proton emission from Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station setup including both charged-particle and
-ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in
Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State in
Na is observed. This may allow studies of the 4032.9(2.4) keV resonance in
Ne through the beta decay of
Mg, which is important for the astrophysically relevant reaction
O(
,
)
Ne. Beta-delayed protons were used to obtain a more precise value for the half-life of
Mg, 91.4(1.0) ms.
Truesdale, V. L.*; Andreyev, A. N.; Ghys, L.*; Huyse, M.*; Van Duppen, P.*; Sels, S.*; Andel, B.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; et al.
Physical Review C, 94(3), p.034308_1 - 034308_11, 2016/09
被引用回数:9 パーセンタイル:58.53(Physics, Nuclear)A nuclear-decay spectroscopy study of the neutron-deficient isotope At is reported where an isotopically pure beam was produced using the selective Resonance Ionization Laser Ion Source and On-Line Isotope Mass Separator (CERN). The fine-structure
decay of
At allowed the low-energy excited states in the daughter nucleus
Bi to be investigated. A
-delayed fission study of
At was also performed. A mixture of symmetric and asymmetric fission-fragment mass distributions of the daughter isotope
Po (populated by
decay of
At) was deduced based on the measured fission-fragment energies. A
DF probability
(
At) = 9(1)
10
was determined.
Andel, B.*; Andreyev, A. N.; Antalic, S.*; Heberger, F. P.*; Ackermann, D.*; Hofmann, S.*; Huyse, M.*; Kalaninov
, Z.*; Kindler, B.*; Kojouharov, I.*; et al.
Physical Review C, 93(6), p.064316_1 - 064316_12, 2016/06
被引用回数:4 パーセンタイル:34.27(Physics, Nuclear)Isomeric states in Po and
Po were studied at the velocity filter SHIP. The isotopes were produced in the fusion-evaporation reactions
Pr(
Fe,
)
Po and
Sm(
V,
)
Po. Several new
-ray transitions were attributed to the isomers and
-
coincidences for both isomers were studied for the first time. The 459-keV transition earlier, tentatively proposed as de-exciting the isomeric level in
Po, was replaced by a new 248-keV transition, and the spin of this isomer was reassigned from (11
) to (10
). The de-excitation of the (11
) isomeric level in
Po by the 154-keV transition was confirmed and a parallel de-excitation by a 733-keV (E3) transition to (8
) level of the ground-state band was suggested. Moreover, side feeding to the (4
) level of the ground-state band was proposed. The paper also discusses strengths of transitions de-exciting 11
isomers in neighboring Po and Pb isotopes.
Nowak, K.*; Wimmer, K.*; Hellgartner, S.*; Mcher, D.*; Bildstein, V.*; Diriken, J.*; Elseviers, J.*; Gaffney, L. P.*; Gernh
user, R.*; Iwanicki, J.*; et al.
Physical Review C, 93(4), p.044335_1 - 044335_10, 2016/04
被引用回数:15 パーセンタイル:76.79(Physics, Nuclear)The Ar(
)
Ar two-neutron transfer reaction at 2.16 MeV/u was studied at CERN using a
Ar radioactive beam and a tritium loaded radioactive target. Angular distributions for three final states were measured and based on the shape of the differential cross section an excited state at 3695 keV was identified as the first excited 0
state. The differential cross-sections for the 0
-ground state, and first excited 2
and 0
states are compared to DWBA calculations including two-step reactions through the intermediate nucleus
Ar. By comparison large scale shell model calculations using state-of-the-art effective interactions, with and without the tensor components of the interactions, it was observed that the cross-shell proton-neutron tensor interaction has measurable effects on the observables at low excitation energy in
Ar.
Lic, R.*; Mach, H.*; Fraile, L. M.*; Gargano, A.*; Borge, M. J. G.*; M
rginean, N.*; Sotty, C. O.*; Vedia, V.*; Andreyev, A. N.; Benzoni, G.*; et al.
Physical Review C, 93(4), p.044303_1 - 044303_7, 2016/04
被引用回数:5 パーセンタイル:40.22(Physics, Nuclear)The levels in Sn populated from the
decay of
In isomers were investigated at the ISOLDE facility of CERN using the newly commissioned ISOLDE Decay Station. The lowest 1/2
state and the 3/2
ground state in
Sn are expected to have configurations dominated by the neutron
(
=0) and
(
=2) single-particle states, respectively. Consequently, these states should be connected by a somewhat slow
-forbidden
transition. Using fast-timing spectroscopy we have measured the half-life of the 1/2
315.3-keV state,
= 19(10) ps, which corresponds to a moderately fast
transition. Shell-model calculations using the CD-Bonn effective interaction, with standard effective charges and
factors, predict a 4-ns half-life for this level. We can reconcile the shell-model calculations to the measured
value by the renormalization of the
effective operator for neutron holes.
Van Beveren, C.*; Andreyev, A. N.; Barzakh, A. E.*; Cocolios, T. E.*; de Groote, R. P.*; Fedorov, D.*; Fedosseev, V. N.*; Ferrer, R.*; Ghys, L.*; Huyse, M.*; et al.
Journal of Physics G; Nuclear and Particle Physics, 43(2), p.025102_1 - 025102_22, 2016/02
被引用回数:11 パーセンタイル:64.09(Physics, Nuclear)-decay spectroscopy of
Tl has been performed at the CERN isotope separator on-line (ISOLDE) facility. New fine-structure
decays have been observed for both isotopes.
-decay branching ratios of 0.089(19)
, 0.047(6)
and 1.22(30)
have been deduced for the (10
), (7
) and (2
) states respectively in
Tl and a lower limit of 0.49
for the
-decay branching ratio of
Tl. A new half-life of 9.5(2) s for the (2
) state in
Tl and 1.9(1) s for the low-spin state in
Tl has been deduced. Using
-
coincidence analysis, multiple
rays were observed de-exciting levels in
Au fed by
Tl
decays. The
transitions connecting these low-lying states in
Au are essential to sort the data and possibly identify bands from inbeam studies in these isotopes. Owing to the complex fine-structure
decays and limited knowledge about the structure of the daughter nuclei, only partial level schemes could be constructed for both gold isotopes in the present work. Reduced
-decay widths have been calculated and are compared with values obtained in neighboring odd-A and even-A thallium isotopes. Except for the allowed
decay of the
Tl (10
) state, the other fine-structure
decays observed in this study are hindered. This points to strong structural changes between parent thallium and daughter gold isotopes.
Van Beveren, C.*; Andreyev, A. N.; Barzakh, A.*; Cocolios, T. E.*; Fedorov, D.*; Fedosseev, V. N.*; Ferrer, R.*; Huyse, M.*; Kster, U.*; Lane, J. F. W.*; et al.
Physical Review C, 92(1), p.014325_1 - 014325_8, 2015/07
被引用回数:9 パーセンタイル:55.91(Physics, Nuclear)Decay spectroscopy of Tl has been performed at the CERN Isotope Separator On-Line (ISOLDE) facility. An excitation energy of 506.1(1) keV and a half-life of 47.1(7) ms of the intruder based (10
) state have been extracted. The internal decay characteristics of this state are determined and discussed, extending the systematics of such states in the even-mass thallium nuclei below neutron midshell at N = 104. The retardation factors of the isomeric M2 and E3 transitions are deduced and compared with retardation factors in neighboring odd-mass and even-mass thallium isotopes. The new information is combined with a review of hindered and unhindered
-decay data of
Bi populating levels in daughter nuclei
Tl and supports the interpretation of the intruder character of the (10
) state in
Tl.
Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A. N.; Bender, M.*; Blazhev, A.*; Bree, N.*; Bruyneel, B.*; Butler, P.*; Cocolios, T. E.*; et al.
Physical Review C, 91(6), p.064313_1 - 064313_11, 2015/06
被引用回数:8 パーセンタイル:51.62(Physics, Nuclear)Radioactive ion beams of Rn were studied by means of low-energy Coulomb excitation at REX-ISOLDE, CERN. The electric-quadrupole (E2) matrix elements connecting the first excited 2
to the ground state of these nuclei was extracted, which permits to determine the collectivity of these isotopes, which in both cases is deduced to be weak, as expected from the low-lying level-energy scheme. Comparisons were also made with beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
Diriken, J.*; Patronis, N.*; Andreyev, A. N.; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.
Physical Review C, 91(5), p.054321_1 - 054321_15, 2015/05
被引用回数:9 パーセンタイル:55.91(Physics, Nuclear)Excited states up to an excitation energy of 5.8 MeV were populated in the neutron-rich isotope Ni via the
Ni(d,p) transfer reaction at REX-Isolde, CERN. In particular, single-neutron states above the N=40 sub-shell gap were populated, and the relative spectroscopic factors were extracted using distorted-wave Born approximation analysis. The positive parity g
, d
and s
neutron orbits above the shell closure are assumed to induce strong quadrupole collectivity in neutron-rich Fe and Cr isotopes. The extracted relative spectroscopic factors show that the strength of the d
orbit is mostly split over two states, hinting to substantial mixing of the neutron d
configuration with collective modes of the core. The size of the N=50 shell gap was also estimated, and found to be 2.6 MeV near
Ni, as also determined in lighter Ni isotopes.
Ghys, L.*; Andreyev, A. N.; Antalic, S.*; Huyse, M.*; Van Duppen, P.*
Physical Review C, 91(4), p.044314_1 - 044314_7, 2015/04
被引用回数:10 パーセンタイル:58.86(Physics, Nuclear)The process of -delayed fission (
DF) provides a versatile tool to study low-energy fission in nuclei far away from the
-stability line, especially for nuclei which do not fission spontaneously. The aim of this paper is to investigate systematic trends in
DF partial half-lives. A semi-phenomenological framework was developed to systematically account for the behavior of
DF partial half-lives. The
DF partial half-life appears to exponentially depend on the difference between the Q value for
decay of the parent nucleus and the fission-barrier energy of the daughter (after
decay) product. Such dependence was found to arise naturally from some simple theoretical considerations. This systematic trend was confirmed for experimental
DF partial half-lives spanning over seven orders of magnitude when using fission barriers calculated from either the Thomas-Fermi or the liquid-drop fission model. The same dependence was also observed, although less pronounced, when comparing to fission barriers from the finite-range liquid-drop model or the Thomas-Fermi plus Strutinsky integral method.