Observation of the proton emitter $${}_{\,57}^{116}$$La59



Zhang, Wei, Cederwall, Bo, Aktas, Özge, Liu, Xiaoyu, Ertoprak, Aysegül, Nyberg, Ayse, Auranen, Kalle, Alayed, Betool, Badran, Hussam, Boston, Helen ORCID: 0000-0003-0721-3458
et al (show 26 more authors) (2022) Observation of the proton emitter $${}_{\,57}^{116}$$La59. Communications Physics, 5 (1). 285-.

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Abstract

<jats:title>Abstract</jats:title><jats:p>The quantum tunneling and emission of a single constituent nucleon provide a beautifully simple and unique window into the complex properties of atomic nuclei at the extreme edge of nuclear existence. In particular, for odd-odd proton emitting nuclides, the associated decay energy and partial half-life can be used to probe the correlations between the valence neutrons and protons which have been theoretically predicted to favour a new type of nuclear superfluidity, isoscalar neutron-proton pairing, for which the experimental “smoking gun" remains elusive. In the present work, proton emission from the lanthanum isotope <jats:inline-formula><jats:alternatives><jats:tex-math>$${}_{\,57}^{116}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mspace /> <mml:mn>57</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>116</mml:mn> </mml:mrow> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula>La<jats:sub>59</jats:sub>, 23 neutrons away from the only stable isotope <jats:inline-formula><jats:alternatives><jats:tex-math>$${}_{\,57}^{139}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mspace /> <mml:mn>57</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>139</mml:mn> </mml:mrow> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula>La<jats:sub>82</jats:sub>, is reported. <jats:sup>116</jats:sup>La nuclei were synthesised in the fusion-evaporation reaction <jats:sup>58</jats:sup>Ni(<jats:sup>64</jats:sup>Zn, <jats:italic>p</jats:italic>5<jats:italic>n</jats:italic>)<jats:sup>116</jats:sup>La and identified via their proton radioactivity using the mass spectrometer MARA (Mass Analysing Recoil Apparatus) and the silicon detectors placed at its focal plane. Comparisons of the measured proton energy (<jats:italic>E</jats:italic><jats:sub><jats:italic>p</jats:italic></jats:sub> = 718 ± 9 keV) and half-life (<jats:italic>T</jats:italic><jats:sub>1/2</jats:sub> = 50 ± 22 ms) with values calculated using the Universal Decay Law approach indicate that the proton is emitted with an orbital angular momentum <jats:italic>l</jats:italic> = 2 and that its emission probability is enhanced relative to its closest, less exotic, odd-even lanthanum isotope (<jats:inline-formula><jats:alternatives><jats:tex-math>$${}_{\,57}^{117}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mspace /> <mml:mn>57</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>117</mml:mn> </mml:mrow> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula>La<jats:sub>60</jats:sub>) while the proton-emission <jats:italic>Q</jats:italic>-value is lower. We propose this to be a possible signature for the presence of strong neutron-proton pair correlations in this exotic, neutron deficient system. The observations of <jats:italic>γ</jats:italic> decays from isomeric states in <jats:sup>116</jats:sup>La and <jats:sup>117</jats:sup>La are also reported.</jats:p>

Item Type: Article
Depositing User: Symplectic Admin
Date Deposited: 28 Nov 2022 09:43
Last Modified: 15 Mar 2024 01:15
DOI: 10.1038/s42005-022-01069-w
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3166407