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M. Freer,
N. L. Achouri,
C. Angulo,
N. I. Ashwood,
D. W. Bardayan,
S. Brown,
W. N. Catford,
K. A. Chipps, N. Curtis,
P. Demaret, [......],
T. Munoz-Britton,
N. A. Orr,
S. D. Pain,
D. Price,
R. Raabe,
N. Soić,
J. S. Thomas,
C. Wheldon,
G. Wilson,
V. A. Ziman
[show abstract]
[hide abstract]
ABSTRACT: Measurements of the 4He(7Be,α)7Be and 4He(7Be,p)10B reactions were performed using 7Be beam energies of 7.1 and 23 MeV and a helium-4 target, employing the thick target technique. Resonances were observed between Ex(11C)=8.6 to 13.8 MeV. An R-matrix analysis was performed to characterize the spins and partial widths. This analysis showed that the observed sequence of states was consistent with that found for 7Li + α resonant scattering populating resonances in 11B. A comparison of the proposed partial widths for decay with the Wigner limit indicates that several of the states are associated with cluster-like structures.
Phys. Rev. C. 01/2012; 85(1).
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M Freer,
N L Achouri,
C Angulo,
N I Ashwood,
D W Bardayan,
S Brown,
W N Catford,
K A Chipps, N Curtis,
P Demaret, [......],
T Munoz-Britton,
N A Orr,
S D Pain,
D Price,
R Raabe,
N Soiifmmode acutecelse 'cfi,
J S Thomas,
C Wheldon,
G Wilson,
V A Ziman
Phys. Rev. C. 01/2012; 85(1):014304.
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M Freer,
N L Achouri,
C Angulo,
N I Ashwood,
D W Bardayan,
S Brown,
W N Catford,
K A Chipps, N Curtis,
P Demaret, [......],
T Munoz-Britton,
N A Orr,
S D Pain,
D Price,
R Raabe,
N Soiifmmode acutecelse 'cfi,
J S Thomas,
C Wheldon,
G Wilson,
V A Ziman
Physical Review C. 01/2012; 85(1):014304.
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C Wheldon,
N I Ashwood,
M Barr, N Curtis,
M Freer,
Tz. Kokalova,
J D Malcolm,
V A Ziman,
Th. Faestermann,
H -F Wirth,
R Hertenberger,
R Lutter
Phys.Rev. C. 01/2012; 86:044328.
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M Freer,
N I Ashwood,
M Barr, N Curtis,
J Gibelin,
F Haas,
J D Malcolm,
T Munoz-Britton,
G Randisi,
N Soić,
V A Ziman
[show abstract]
[hide abstract]
ABSTRACT: A study of the 12C(13C,20Ne+α)n reaction has been performed at 13C beam energies of 12.0, 13.5 and 20.0 MeV. The measurements were to explore the extent to which 24Mg excited states could be populated in a quasi-free 12C+12C→ 20Ne+α reaction in which the last neutron in the 13C beam acts as a spectator. Excited states in 24Mg are found at 13.25 (0.20) and 14.25 (0.20) MeV. These states are found to be produced from the neutron evaporation from the 25Mg compound nucleus. The kinematic region associated with the quasi-free condition is dominated by contaminants from the reactions associated with neutron decay of excited states in 21Ne populated in the 12C(13C,21Ne)α reaction.
Journal of Physics G Nuclear and Particle Physics 10/2011; 38(11):115106. · 4.18 Impact Factor
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M. Freer,
S. Almaraz-Calderon,
A. Aprahamian,
N.I. Ashwood,
M. Barr,
B. Bucher,
P. Copp,
M. Couder, N. Curtis,
X. Fang,
F. Jung,
S. Lesher,
W. Lu,
J.D. Malcom,
A. Roberts,
W.P. Tang,
C. Wheldon,
V.A. Ziman
Physical Review C 01/2011; 83:034314. · 3.31 Impact Factor
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B. Fernandez-Dominguez,
J. S. Thomas,
W. N. Catford,
F. Delaunay,
S. M. Brown,
N. A. Orr,
M. Rejmund,
M. Labiche,
M. Chartier,
N. L. Achouri, [......],
N. Patterson,
B. Pietras,
E. C. Pollacco,
A. Leprince,
A. Ramus,
J. A. Scarpaci,
N. de Sereville,
I. Stephan,
O. Sorlin,
G. L. Wilson
Physical Review C 01/2011; · 3.31 Impact Factor
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B. Fernandez-Dominguez,
J S Thomas,
W. N. Catford,
F. Delaunay,
S. M. Brown,
N. A. Orr,
M. Rejmund,
N. L. Achouri,
H. Al Falou,
N. A. Ashwood, [......],
N. Patterson,
B. Pietras,
E.C. Pollacco,
A. Leprince,
A. Ramus,
J.A. Scarpaci,
N. De Séréville,
I. Stefan,
O. Sorlin,
G Wilson
[show abstract]
[hide abstract]
ABSTRACT: The spectroscopy of 21O has been investigated using a radioactive 20O beam
and the (d,p) reaction in inverse kinematics. The ground and first excited
states have been determined to be Jpi=5/2+ and Jpi=1/2+ respectively. Two
neutron unbound states were observed at excitation energies of 4.76 +- 0.10 and
6.16 +- 0.11. The spectroscopic factor deduced for the lower of these
interpreted as a 3/2+ level, reveals a rather pure 0d3/2 single-particle
configuration. The large energy difference between the 3/2+ and 1/2+ states is
indicative of the emergence of the N=16 magic number. For the higher lying
resonance, which has a character consistent with a spin-parity assignment of
3/2+ or 7/2-, a 71% branching ratio to the first 2+ state in 20O has been
observed. The results are compared with new shell model calculations.
12/2010;
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M Freer,
N I Ashwood,
M Barr, N Curtis,
J Gibelin,
F Haas,
J D Malcolm,
T Munoz-Britton,
G Randisi,
N Soić,
V A Ziman
[show abstract]
[hide abstract]
ABSTRACT: The 12C(13C,α)21Ne reaction has been measured with a 13C beam energy of 20 MeV. States in 21Ne have been populated between 0 and 12 MeV with a resolution of ~350 keV (FWHM). A coincidence experiment has been performed in which either the bound 21Ne nucleus or the 20Ne nucleus produced via neutron decay is detected. This permitted the 21Ne states undergoing gamma decay and neutron decay to the ground and first excited states in 20Ne to be determined. The current measurements suggest several errors in the current compilation for 21Ne.
Journal of Physics G Nuclear and Particle Physics 11/2010; 37(12):125102. · 4.18 Impact Factor
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N. Curtis
Phys. Rev. C. 08/2010; 82(2).
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T Muñoz-Britton,
M Freer,
N I Ashwood,
T A D Brown,
W N Catford, N Curtis,
S P Fox,
B R Fulton,
C W Harlin,
A M Laird,
P Mumby-Croft,
A St J Murphy,
P Papka,
D L Price,
K Vaughan,
D L Watson,
D C Weisser
[show abstract]
[hide abstract]
ABSTRACT: A search for the 2+ excitation of the Hoyle state in 12C has been performed using the 12C(12C,3α)12C reaction at a beam energy of 101.5 MeV. An angular correlation analysis was used to suppress known contributions to the excitation energy spectrum, enhancing the experimental sensitivity. No strong evidence was found for new states in 12C between 9 and 11 MeV; rather upper limits for their excitation in the 12C+12C inelastic scattering reaction are determined.
Journal of Physics G Nuclear and Particle Physics 07/2010; 37(10):105104. · 4.18 Impact Factor
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W N Catford,
C N Timis,
R C Lemmon,
M Labiche,
N A Orr,
B Fernández-Domínguez,
R Chapman,
M Freer,
M Chartier,
H Savajols, [......],
G de France,
W Gelletly,
X Liang,
S D Pain,
V P E Pucknell,
B Rubio,
O Sorlin,
K Spohr,
Ch Theisen,
D D Warner
[show abstract]
[hide abstract]
ABSTRACT: The transfer of neutrons onto 24Ne has been measured using a reaccelerated radioactive beam of 24Ne to study the (d,p) reaction in inverse kinematics. The unusual raising of the first 3/2+ level in 25Ne and its significance in terms of the migration of the neutron magic number from N=20 to N=16 is put on a firm footing by confirmation of this state's identity. The raised 3/2+ level is observed simultaneously with the intruder negative parity 7/2- and 3/2- levels, providing evidence for the reduction in the N=20 gap. The coincident gamma-ray decays allowed the assignment of spins as well as the transferred orbital angular momentum. The excitation energy of the 3/2+ state shows that the established USD shell model breaks down well within the sd model space and requires a revised treatment of the proton-neutron monopole interaction.
Physical Review Letters 05/2010; 104(19):192501. · 7.37 Impact Factor
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W. N. Catford,
C. N. Timis,
R. C. Lemmon,
M. Labiche,
N. A. Orr,
B. Fernandez-Dominguez,
R Chapman,
M. Freer,
M. Chartier,
H. Savajols, [......],
G. De France,
W Gelletly,
X Liang,
S. D. Pain,
V. P. E. Pucknell,
B Rubio,
O. Sorlin,
K Spohr,
Ch. Theisen,
D D Warner
[show abstract]
[hide abstract]
ABSTRACT: The transfer of neutrons onto 24Ne has been measured using a reaccelerated radioactive beam of 24Ne to study the (d,p) reaction in inverse kinematics. The unusual raising of the first 3/2+ level in 25Ne and its significance in terms of the migration of the neutron magic number from N=20 to N=16 is put on a firm footing by confirmation of this state's identity. The raised 3/2+ level is observed simultaneously with the intruder negative parity 7/2- and 3/2- levels, providing evidence for the reduction in the N=20 gap. The coincident gamma-ray decays allowed the assignment of spins as well as the transferred orbital angular momentum. The excitation energy of the 3/2+ state shows that the established USD shell model breaks down well within the sd model space and requires a revised treatment of the proton-neutron monopole interaction. Comment: Phys. Rev. Lett. in press (4 pages, 3 figures)
04/2010;
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N I Ashwood,
M Freer,
N L Achouri,
T R Bloxham,
W N Catford, N Curtis,
P J Haigh,
C W Harlin,
N P Patterson,
D L Price,
N Soić,
J S Thomas
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the α(12C, α) 12C reaction has been performed using resonant scattering with a gas target. Beam energies of 46, 52, 56 and 63 MeV were used to populate resonances in the excitation energy range of 11.6–22.9 MeV in 16O. The angular distributions of the elastic scattering were measured at zero degrees, using an array of segmented silicon strip detectors with a minimum range of 0°–30° in the centre-of-mass. The spins of 8 resonances between 14.1 and 18.5 MeV were obtained, confirming spin assignments made using elastic scattering in normal kinematics. An R-matrix analysis of the data was performed which indicates that the present understanding of 16O in this region is good, but not complete.
Journal of Physics G Nuclear and Particle Physics 04/2009; 36(5):055105. · 4.18 Impact Factor
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N Curtis,
N I Ashwood,
M Freer,
T Munoz-Britton,
C Wheldon,
V A Ziman,
S Brown,
W N Catford,
N P Patterson,
J S Thomas,
D C Weisser
[show abstract]
[hide abstract]
ABSTRACT: A search for the α + 6He decay of 10Be has been performed using the Li2O(18O,α6He) reaction at 80 and 100 MeV. An array of two Si–Si–CsI telescopes was used for the coincident detection of the breakup fragments. No evidence for the 16O(18O,α6He)24 Mg reaction was obtained, the cross-section being determined as σ< 1.9 µb and <3.9 µb at 80 and 100 MeV, respectively. The α + 15N decay of 19F was observed via the 7Li(18O,α15N)6He reaction. For the 19F excitation energy and centre-of-mass scattering angle ranges covered, the cross-sections are σ = (31.7 ± 6.6) µb at 80 MeV and (31.8 ± 6.6) µb at 100 MeV.
Journal of Physics G Nuclear and Particle Physics 10/2008; 36(1):015108. · 4.18 Impact Factor
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M Freer,
N I Ashwood, N Curtis,
T Munoz-Britton,
C Wheldon,
V A Ziman,
S Brown,
W N Catford,
N P Patterson,
J S Thomas,
D C Weisser
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the p(7Li, 4He)4He resonant reaction on a thick mylar target was used to probe resonances in 8Be in the excitation energy range 20–25 MeV. The 7Li beams, of energies 25.8 and 58 MeV, were stopped in the target and the resulting α-particles were detected at zero degrees. Evidence was found for resonances at ~20 and ~25 MeV with Jπ = 0+ and 2+ character, respectively. A simultaneous measurement of the p(7Li, 4He* → p + t)4He reaction was performed, in which one of the two final-state α-particles was produced in the 20.2 MeV excited state. These events were observed to arise from an excitation energy region 23–25 MeV and have been associated with the decay of the 25.2 MeV 2+ 8Be resonance. The 25.2 MeV resonance is found to have a dominant 4He + 4He* reduced width.
Journal of Physics G Nuclear and Particle Physics 10/2008; 35(12):125108. · 4.18 Impact Factor
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P. J. Haigh,
N. I. Ashwood,
T. Bloxham, N. Curtis,
M. Freer,
P. McEwan,
D. Price,
V. Ziman,
H. G. Bohlen,
Tz. Kokalova,
Ch. Schulz,
R. Torabi,
W. von Oertzen,
C. Wheldon,
W. Catford,
C. Harlin,
R. Kalpakchieva,
T. N. Massey
[show abstract]
[hide abstract]
ABSTRACT: The 12C(16O,14O)14C reaction was studied at a beam energy of 234 MeV. The 14O ejectile was detected by a Q3D spectrometer at forward angles. The energies and angles of the excited 14C recoil break-up fragments were measured in coincidence with the 14O ejectile using a double sided silicon strip detector array at backward angles. A complete kinematic reconstruction of the reaction was performed to reconstruct the 14C*→10Be+α and 14C*→13C+n decay channels and the branching ratios and widths of these decays were calculated. Theoretical decay branches were calculated using barrier penetrability factors and were compared to the measured ratios to provide information on the spins, parities, and configurations of the states. Neutron emission was found to be favored for the 11.73, 12.96, 14.87, 16.72, and 18.6 MeV states. The 14.87, 18.6, and 21.4 MeV states were found to have a considerable width for α-decay and are candidates for the three bodied molecular cluster structure of 14C.
Phys. Rev. C. 07/2008; 78(1).
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N Curtis,
N Achouri,
N Ashwood,
H Bohlen,
W Catford,
N Clarke,
M Freer,
P Haigh,
B Laurent,
N Orr,
N Patterson,
N Soić,
J Thomas,
V Ziman
[show abstract]
[hide abstract]
ABSTRACT: The 2α + 2p breakup and structure of the only known Brunnian nucleus, 10C, has been studied at 33.3 MeV/nucleon. Detection of the 2α + 2p breakup fragments using a highly segmented Si-Si-Si-CsI detector array has allowed the 10C → 9B + p, 9B → 8Be + p, 8Be → α + α and 10C → 6Be + α, 6Be → 5Li + p, 5Li → α + p decay channels to be reconstructed. Proton emission was seen to be favoured. Resonant breakup was observed from excited states at Ex = 4.20, 5.31 and 6.74 MeV. The previously unobserved state at 4.20 MeV may correspond to a 0+ α + 2p + α cluster structure.
Journal of Physics Conference Series 05/2008; 111(1):012022.
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P J Haigh,
N I Ashwood,
T Bloxham, N Curtis,
M Freer,
P McEwan,
D Price,
V Ziman,
H G Bohlen,
Tz Kokalova,
Ch Schulz,
R Torabi,
W Oertzen,
C Wheldon,
W Catford,
C Harlin,
R Kalpakchieva,
T N Massey
Physical Review C. 01/2008; 78(1).
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N. C. Summers,
S. D. Pain,
N. A. Orr,
W. N. Catford,
J.C. Angelique,
N. I. Ashwood,
V. Bouchat,
N. M. Clarke, N. Curtis,
M. Freer, [......],
D. Mahboub,
A. Ninane,
G. Normand,
F. M. Nunes,
N. Soic,
L. Stuttge,
C. N. Timis,
I. J. Thompson,
J.S. Winfield,
V. Ziman
[show abstract]
[hide abstract]
ABSTRACT: The $B$(E1;$1/2^+\to1/2^-$) strength for $^{11}$Be has been extracted from intermediate energy Coulomb excitation measurements, over a range of beam energies using a new reaction model, the extended continuum discretized coupled channels (XCDCC) method. In addition, a measurement of the excitation cross section for $^{11}$Be+$^{208}$Pb at 38.6 MeV/nucleon is reported. The $B$(E1) strength of 0.105(12) e$^2$fm$^2$ derived from this measurement is consistent with those made previously at 60 and 64 MeV/nucleon, i n contrast to an anomalously low result obtained at 43 MeV/nucleon. By coupling a multi-configuration description of the projectile structure with realistic reaction theory, the XCDCC model provides for the first time a fully quantum mechanical description of Coulomb excitation. The XCDCC calculations reveal that the excitation process involves significant contributions from nuclear, continuum, and higher-order effects. An analysis of the present and two earlier intermediate energy measurements yields a combined B(E1) strength of 0.105(7) e$^2$fm$^2$. This value is in good agreement with the value deduced independently from the lifetime of the $1/2^-$ state in $^{11}$Be, and has a comparable p recision.
04/2007;
