We measured the angular distributions for theC(Be,He)O transfer reaction at 35 MeV leading to several excited states ofO. The angular distribution of the ground state ofO was measured for the first time in this reaction. The corresponding Asymptotic Normalization Coefficients (ANC) of all the observed states were determined. The ANC of ground state, 6.92 MeV (2 <math altimg='si11.svg'><msup><mrow /><mo>+</mo></msup></math>) and 7.12 MeV (1 <math altimg='si40.svg'><msup><mrow /><mo>&#8722;</mo></msup></math>) subthreshold states ofO obtained from this work are utilized to determine the astrophysical <math altimg='si85.svg'><mi>E</mi></math>1 and <math altimg='si85.svg'><mi>E</mi></math>2 <math altimg='si16.svg'><mi>S</mi></math>-factors of theC( <math altimg='si17.svg'><msup><mrow><mi>&#945;</mi><mo>,</mo><mi>&#947;</mi><mo>)</mo></mrow><mn>16</mn></msup></math>O reaction in an <math altimg='si13.svg'><mi>R</mi></math>-matrix analysis.

India

K. Kundalia

D. Gupta

Sk M. Ali

R. Mitra

Swapan K. Saha

Spain

O. Tengblad

A. Perea

I. Martel

Sweden

J. Cederkall

A.M. Moro

The ANC of <math altimg='si1.svg'><msup><mrow /><mn>16</mn></msup></math>O states from <math altimg='si2.svg'><msup><mrow /><mn>7</mn></msup></math>Be + <math altimg='si3.svg'><msup><mrow /><mn>12</mn></msup></math>C <math altimg='si4.svg'><mi>&#945;</mi></math>-transfer reaction to study <math altimg='si3.svg'><msup><mrow /><mn>12</mn></msup></math>C( <math altimg='si17.svg'><msup><mrow><mi>&#945;</mi><mo>,</mo><mi>&#947;</mi><mo>)</mo></mrow><mn>16</mn></msup></math>O

Significant continuum strength has been observed to be populated in 17C produced in the d( 16C,p) reaction at a beam energy of 17.2 MeV/nucleon. The strength appears at greater than &#8764;2 MeV above the single-neutron decay threshold and has been identified as arising from transfer into the neutron <math altimg='si1.svg'><mn>0</mn><msub><mrow><mi>d</mi></mrow><mrow><mn>3</mn><mo stretchy='false'>/</mo><mn>2</mn></mrow></msub></math> orbital. Guided by shell model predictions the greater majority of the strength is associated with a 3/2 + state at an excitation energy of 4.40 <math altimg='si2.svg'><msubsup><mrow /><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>0.14</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mn>0.33</mn></mrow></msubsup></math> MeV and a much weaker 3/2 + level at 5.60 <math altimg='si3.svg'><msubsup><mrow /><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>0.45</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mn>1.35</mn></mrow></msubsup></math> MeV. The corresponding total widths were determined to be 3.45 <math altimg='si4.svg'><msubsup><mrow /><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>0.78</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mn>1.82</mn></mrow></msubsup></math> and 1.6 <math altimg='si5.svg'><msubsup><mrow /><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>1.4</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mn>4.6</mn></mrow></msubsup></math> MeV, respectively. From the backward angle proton differential cross sections and the branching ratios for neutron decay to the 16C(2 <math altimg='si22.svg'><msubsup><mrow /><mrow><mn>1</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo></mrow></msubsup></math>) level, the corresponding spectroscopic factors to the ground state were deduced to be 0.47&#177;10 and &lt;0.09. Shell-model calculations employing the phenomenological SFO-tls interaction as well as Gamow Shell-Model calculations including continuum effects are in reasonable agreement with experiment, although the predicted strength lies at somewhat lower energy. The size of the N=16 shell gap ( <math altimg='si7.svg'><msub><mrow><mi>&#949;</mi></mrow><mrow><mi>&#957;</mi><mn>0</mn><msub><mrow><mi>d</mi></mrow><mrow><mn>3</mn><mo stretchy='false'>/</mo><mn>2</mn></mrow></msub></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>&#8722;</mo><msub><mrow><mi>&#949;</mi></mrow><mrow><mi>&#957;</mi><mn>1</mn><msub><mrow><mi>s</mi></mrow><mrow><mn>1</mn><mo stretchy='false'>/</mo><mn>2</mn></mrow></msub></mrow></msub></math>) was estimated to be 5.08 <math altimg='si8.svg'><msubsup><mrow /><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>0.33</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mn>0.43</mn></mrow></msubsup></math> MeV - some 1.3 MeV larger than found in the SFO-tls shell model calculation.

J. Lois-Fuentes

B. Fernández-Domínguez

France

F. Delaunay

South Korea

X. Pereira-López

N.A. Orr

M. Płoszajczak

N. Michel

Japan

T. Otsuka

T. Suzuki

United Kingdom

W.N. Catford

O. Sorlin

N.L. Achouri

M. Assié

S. Bailey

B. Bastin

Y. Blumenfeld

Romania

R. Borcea

M. Caamaño

L. Caceres

E. Clément

A. Corsi

N. Curtis

Q. Deshayes

F. Farget

Italy

M. Fisichella

G. de France

S. Franchoo

M. Freer

J. Gibelin

A. Gillibert

Canada

G.F. Grinyer

F. Hammache

O. Kamalou

A. Knapton

Tz. Kokalova

V. Lapoux

J.A. Lay

B. Le Crom

S. Leblond

F.M. Marqués

A. Matta

P. Morfouace

J. Pancin

L. Perrot

J. Piot

E. Pollacco

P. Punta

D. Ramos

C. Rodríguez-Tajes

T. Roger

F. Rotaru

M. Sénoville

N. de Séréville

R. Smith

M. Stanoiu

I. Stefan

C. Stodel

D. Suzuki

J.C. Thomas

N. Timofeyuk

M. Vandebrouck

J. Walshe

C. Wheldon

Unbound neutron <italic>&#957;</italic>0 <italic>d</italic> <inf>3/2</inf> strength in 17C and the N=16 shell gap

The intrinsic structure of the 9Be nucleus has been probed by virtue of its influence on reaction dynamics in the 9Be+ 110Pd collision. Extensive measurements of the complete fusion excitation function have been undertaken across the Coulomb barrier, in conjunction with the measurement of the elastic scattering angular distribution at a few overlapping incident energies. A unified treatment of both processes is carried out by employing 3-body and 4-body Continuum Discretized Coupled Channels calculations, which exclusively cater to the dynamical features of the collision contingent on the low threshold for dissociation of 9Be into either two or three clusters. A synergy between the complete fusion and elastic scattering measurements across different incident energies is attained when the pivotal description of 9Be as <italic>&#945;</italic>+ <italic>&#945;</italic>+ <italic>n</italic> configuration is invoked. While the elastic scattering angular distribution is observed to be sensitive to the continuum couplings, the fusion excitation function is primarily influenced by the structure of 9Be in its ground state. The <italic>&#945;</italic>+ <italic>&#945;</italic>+ <italic>n</italic> picture further reveals an absence of above-barrier fusion suppression when compared with the Universal Fusion Function, in contrast to the commonly reported signature for reactions induced by the 9Be projectile.

A. Kundu

R. Palit

M. Rodríguez-Gallardo

P. Dey

S. Santra

Md S.R. Laskar

Biswajit Das

Vishal Malik

A. Pal

A. Baishya

A. Sindhu

C. Majumder

Probing <italic>&#945;</italic>-clustering in 9Be via complete fusion and elastic scattering measurements

We address the problem of evaluating neutron-transfer induced breakup cross sections caused by the Borromean nucleus $^{9}$Be, using the reaction $^{197}$Au($^{9}$Be,$^{8}$Be)$^{198}$Au as a test case. This reaction was recently measured over a wide range of incident energies around the Coulomb barrier. To deal with the high density of $^{198}$Au states that can be potentially populated in this reaction, we employ the Ichimura, Austern, Vicent model, in which the spectrum of physical states for this system is replaced by the solutions of a complex n+$^{197}$Au potential, accounting effectively for the fragmentation of single-particle states into physical states. Furthermore, to account for the unbound nature of the emitted $^{8}$Be system, we employ a three-body model of $^{9}$Be. The calculated stripping cross sections are found to be in good agreement with existing data over a wide range of incident energies. The importance of taking into account the energy spread of the single-particle strength of the outgoing $^{8}$Be and the target-like residual nucleus is discussed.

G. Villanueva

J. Casal

China

Jin Lei

Neutron-transfer induced breakup of the Borromean nucleus Be

The measurement of the $^{7}$Be(d,$^{3}$He)$^{6}$Li* transfer cross section at 5 MeV/u is carried out. The population of the 2.186 MeV excited state of $^{6}$Li in this reaction channel is observed for the first time. The experimental angular distributions have been analyzed in the finite range DWBA and coupled-channel frameworks. The effect of the $^{7}$Be(d,$^{3}$He)$^{6}$Li reaction on both the $^{6}$Li and $^{7}$Li abundances are investigated at the relevant big-bang nucleosynthesis energies. The excitation function is calculated by TALYS and normalized to the experimental data. The S factor of the (d,$^{3}$He) channel from the present work is about 50% lower than existing data at nearby energies. At big-bang energies, the S factor is about three orders of magnitude smaller than that of the (<math><mi>d</mi><mo>,</mo><mi>p</mi></math>) channel. The (d,$^{3}$He) reaction rate is found to have a less than 0.1% effect on the $^{6,7}$Li abundances.

S. Maity

J.D. Ovejas

J. Park

Study of the Be( , He) Li* reaction at 5 MeV/u

The discrepancy between experimental data and theoretical calculations in one-nucleon removal reactions at intermediate energies (quantified by the so-called “quenching factors”) and its dependence on the isospin asymmetry of the nuclei has been an open problem in nuclear physics for the last fifteen years. In this work, we propose an explanation for this long-standing problem, which relies on the inclusion of the process of core destruction due to its interaction with the removed nucleon. To include this effect, we extend the commonly used eikonal formalism via an effective nucleon density, and apply it to a series of nucleon knockout reactions. The effect of core destruction is found to depend strongly on the binding energy of the removed nucleon, leading to a significant reduction of the cross section for deeply bound nucleons, which reduces the isospin dependence of the “quenching factors”, making them more consistent with the trends found in transfer and <math><mo>(</mo><mi>p</mi><mo>,</mo><mi>p</mi><mi>N</mi><mo>)</mo></math> reactions.

M. Gómez-Ramos

J. Gómez-Camacho

Isospin dependence in single-nucleon removal cross sections explained through valence-core destruction effects

The dineutron correlation is systematically studied in three different Borromean nuclei near the neutron dripline, $^{11}$Li, $^{14}$Be and $^{17}$B, via the <math><mo>(</mo><mi>p</mi><mo>,</mo><mi>p</mi><mi>n</mi><mo>)</mo></math> knockout reaction measured at the RIBF facility in RIKEN. For the three nuclei, the correlation angle between the valence neutrons is found to be largest in the same range of intrinsic momenta, which can be associated to the nuclear surface. This result reinforces the prediction that the formation of the dineutron is universal in environments with low neutron density, such as the surface of neutron-rich Borromean nuclei.

Germany

Y. Kubota

G. Authelet

H. Baba

C. Caesar

D. Calvet

A. Delbart

M. Dozono

J. Feng

F. Flavigny

J.M. Gheller

A. Giganon

K. Hasegawa

T. Isobe

Y. Kanaya

S. Kawakami

D. Kim

Y. Kiyokawa

M. Kobayashi

N. Kobayashi

T. Kobayashi

Y. Kondo

Hungary

Z. Korkulu

S. Koyama

Y. Maeda

T. Motobayashi

T. Miyazaki

T. Nakamura

N. Nakatsuka

Y. Nishio

A. Obertelli

A. Ohkura

S. Ota

H. Otsu

T. Ozaki

V. Panin

S. Paschalis

E.C. Pollacco

S. Reichert

J.Y. Rousse

A.T. Saito

S. Sakaguchi

M. Sako

C. Santamaria

M. Sasano

H. Sato

M. Shikata

Y. Shimizu

Y. Shindo

L. Stuhl

T. Sumikama

Y.L. Sun

M. Tabata

Y. Togano

J. Tsubota

T. Uesaka

Z.H. Yang

J. Yasuda

K. Yoneda

J. Zenihiro

Searching for universality of dineutron correlation at the surface of Borromean nuclei

The properties of nuclei with extreme neutron–to–proton ratios, far from those naturally occurring on Earth, are key to understand nuclear forces and how nucleons hold together to form nuclei. $^{7}$H, with six neutrons and a single proton, is the nuclear system with the most unbalanced neutron–to–proton ratio known so far. However, its sheer existence and properties are still a challenge for experimental efforts and theoretical models. Here we report experimental evidences on the formation of $^{7}$H as a resonance, detected with independent observables, and the first measurement of the structure of its ground state. The resonance is found at ∼0.7 MeV above the $^{3}$H+4n mass, with a narrow width of ∼0.2 MeV and a <math><mn>1</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msup></math> spin and parity. These data are consistent with a $^{7}$H as a $^{3}$H core surrounded by an extended four-neutron halo, with a unique four-neutron decay and a relatively long half-life thanks to neutron pairing; a prime example of new phenomena occurring in what would be the most pure-neutron nuclear matter we can access in the laboratory.

Netherlands

S. Bagchi

Belgium

S. Sambi

B. Fernández–Domínguez

N. Itagaki

J. Benlliure

D. Cortina–Gil

B. Jacquot

D. Pérez–Loureiro

B. Pietras

R. Raabe

C. Rodríguez Tajes

H. Savajols

Experimental investigation of ground-state properties of H with transfer reactions

The elastic and inelastic scattering of $^{7}$Be from $^{12}$C have been measured at an incident energy of 35 MeV. The inelastic scattering leading to the 4.439 MeV excited state of $^{12}$C has been measured for the first time. The experimental data cover an angular range of <math><msub><mrow><mi>θ</mi></mrow><mrow><mi>c</mi><mi>m</mi></mrow></msub></math> = 15$^{∘}$-120$^{∘}$. Optical model analyses were carried out with Woods-Saxon and double-folding potential using the density dependent M3Y (DDM3Y) effective interaction. The microscopic analysis of the elastic data indicates breakup channel coupling effect. A coupled-channel analysis of the inelastic scattering, based on collective form factors, shows that mutual excitation of both $^{7}$Be and $^{12}$C is significantly smaller than the single excitation of $^{12}$C. The larger deformation length obtained from the DWBA analysis could be explained by including the excitation of $^{7}$Be in a coupled-channel analysis. The breakup cross section of $^{7}$Be is estimated to be less than 10% of the reaction cross section. The intrinsic deformation length obtained for the $^{12}$C$^{⁎}$ (4.439 MeV) state is <math><msub><mrow><mi>δ</mi></mrow><mrow><mn>2</mn></mrow></msub></math> = 1.37 fm. The total reaction cross section deduced from the analysis agrees very well with Wong's calculations for similar weakly bound light nuclei on $^{12}$C target.

Finland

S. Szwec

Study of elastic and inelastic scattering of Be + C at 35 MeV

This paper reports on elastic scattering excitation functions for the reaction $^{9}$Li+$^{4}$He measured at backward angles in the centre of mass energy range 5 MeV ≤ E<math><mmultiscripts><mrow><mo>≤</mo></mrow><mprescripts></mprescripts><mrow><mtext>c.m.</mtext></mrow><none></none></mmultiscripts><mn>9.5</mn></math> MeV, with the aim of investigating the possible existence of molecular resonances which have been predicted to exist in the case of neutron-rich B-isotopes. Due to the short lifetime of $^{9}$Li, the experiment necessitated the use of inverse kinematics on a gaseous $^{4}$He target. The Thick Target Inverse Kinematics technique was used which allowed for the measurement of the full excitation function in a single $^{9}$Li run. Broad resonances were observed in the excitation region for $^{13}$B 15 MeV ≤ E<math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub><mspace width="0.25em"></mspace><mo>≤</mo></math>20 MeV. To understand the nature of such broad structures, various theoretical attempts are reported concerning possible reaction mechanisms for this neutron rich reaction. The most promising approach to interpret the data is within the orbiting reaction scenario.

A. Di Pietro

Hints of quasi-molecular states in B via the study of Li- He elastic scattering