Neutron magicity in the proton drip-line nucleus <math><mmultiscripts><mi>Mg</mi><mprescripts/><none/><mn>20</mn></mmultiscripts></math>: First invariant-mass reconstruction of <math><mmultiscripts><mi>Mg</mi><mprescripts/><none/><mrow><mn>19</mn><mo>,</mo><mn>20</mn></mrow></mmultiscripts></math>

Ni, L.; Jin, Y.; Li, Z.H.; Brown, K.W.; Yuan, C.X.; Hua, H.; Niu, C.Y.; Anthony, A.K.; Barney, J.; Charity, R.J.

doi:10.1103/PhysRevC.110.L061301

Neutron magicity in the proton drip-line nucleus ${}^{20}{Mg}$ : First invariant-mass reconstruction of ${}^{19, 20}{Mg}$

Dec 5, 2024

8 pages

Published in:

Phys.Rev.C 110 (2024) 6, L061301

Published: Dec 5, 2024

DOI:

10.1103/PhysRevC.110.L061301 (publication)

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Abstract: (APS)

The resonant states in

{}^{20}{Mg}

and

{}^{19}{Mg}

have been studied by the invariant-mass reconstruction of

{}^{18}{Ne} + 2 p

and

{}^{17}{Ne} + 2 p

events, respectively. Two new resolved states (

4_{1}^{+}

and

2_{2}^{+}

) in

{}^{20}{Mg}

are found to decay through

{}^{19}{Na}

intermediate states to the ground state of

{}^{18}{Ne}

from the examination of the decay-energy spectra for

{}^{18}{Ne} + 1 p

subsystems. The deduced

R_{42} = E^{*} (4_{1}^{+}) / E^{*} (2_{1}^{+})

ratio of 2.10(1) is close to the expected harmonic-vibrator value and reveals a spherical or weakly deformed shape for

{}^{20}{Mg}

. Systematic comparison of

E^{*} (2_{1}^{+})

and

R_{42}

along isotopic and isotonic chains with shell model calculations, using the YSOX interaction, suggest the persistence of

N = 8

shell around the proton drip-line. The relatively higher

2_{1}^{+}

excitation energy in

{}^{18}{Mg}

relative to

{}^{20}{Mg}

can be ascribed to different excitation characters of the valence protons. The

1 / 2_{1}^{+}

state in

{}^{19}{Mg}

has been observed for the first time. The energy differences between the

1 / 2_{1}^{-}

and

1 / 2_{1}^{+}

states in

{}^{19}{Mg}

and its isotones manifest the magnitude of the

N = 8

shell gap on the proton-rich side.

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Neutron magicity in the proton drip-line nucleus Mg20: First invariant-mass reconstruction of Mg19,20

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Neutron magicity in the proton drip-line nucleus ${}^{20}{Mg}$ : First invariant-mass reconstruction of ${}^{19, 20}{Mg}$