nucl-ex digest · Nov 21, 2019

01*

Measurement and microscopic description of odd-even staggering of charge radii of exotic copper isotopes

R. P. de Groote🇫🇮 · J. Billowes🇬🇧 · C. L. Binnersley🇬🇧 · M. L. Bissell🇬🇧 · T. E. Cocolios🇧🇪 · T. Day Goodacre🇨🇭 · G. J. Farooq-Smith🇧🇪 · D. V. Fedorov🇷🇺 · K. T. Flanagan🇬🇧 · S. Franchoo🇫🇷 · R. F. Garcia Ruiz🇨🇭 · W. Gins🇧🇪 and 14 other authors

The mesoscopic nature of the atomic nucleus gives rise to a wide array of macroscopic and microscopic phenomena. The size of the nucleus is a window into this duality: while the charge radii globally scale as $A^{1/3}$ , their evolution across isotopic chains reveals unanticipated structural phenomena [1-3]. The most ubiquitous of these is perhaps the Odd-Even Staggering (OES) [4]: isotopes with an odd number of neutrons are usually smaller in size than the trend of their even-neutron neighbours suggests. This OES effect varies with the number of protons and neutrons and poses a significant challenge for nuclear theory [5-7]. Here, we examine this problem with new measurements of the charge radii of short-lived copper isotopes up to the very exotic $^{78}$ Cu $(Z = 29, N = 49)$ , produced at only 20 ions/s, using the highly-sensitive Collinear Resonance Ionisation Spectroscopy (CRIS) method at ISOLDE-CERN. Due to the presence of a single proton outside of the closed Z=28 shell, these measurements provide crucial insights into the single-particle proton structure and how this affects the charge radii. We observe an unexpected reduction in the OES for isotopes approaching the $N = 50$ shell gap. To describe the data, we applied models based on nuclear Density Functional Theory [2,8] (DFT) and ab-initio Valence-Space In-Medium Similarity Renormalization Group (VS-IMSRG) theory [9,10]. Through these comparisons, we demonstrate a relation between the global behavior of charge radii and the saturation density of nuclear matter, and show that the local charge radii variations, which reflect the many-body polarization effects due to the odd neutron, naturally emerge from the VS-IMSRG calculations.

nucl-exnucl-thNat.Phys.(2020)·132 citations

Low-energy

^{23}

β

-delayed proton decay and

^{22}

Na destruction in novae

The radionuclide

^{22}

Na is a target of

γ

-ray astronomy searches, predicted to be produced during thermonuclear runaways driving classical novae. The

^{22}

Na(p,

γ

)

^{23}

Mg reaction is the main destruction channel of

^{22}

Na during a nova, hence, its rate is needed to accurately predict the

^{22}

Na yield. However, experimental determinations of the resonance strengths have led to inconsistent results. In this work, we report a measurement of the branching ratios of the

^{23}

β

-delayed protons, as a probe of the key 204--keV (center-of-mass)

^{22}

Na(p,

γ

)

^{23}

Mg resonance strength. We report a factor of 5 lower branching ratio compared to the most recent literature value. The variation in

^{22}

Na yield due to nuclear data inconsistencies was assessed using a series of hydrodynamic nova outburst simulations and has increased to a factor of 3.8, corresponding to a factor of

\sim

2 uncertainty in the maximum detectability distance. This is the first reported scientific measurement using the Gaseous Detector with Germanium Tagging (GADGET) system.

nucl-exPRC(2020)·15 citations

Thu·Nov 21, 2019Thursday·November 21, 2019

Measurement and microscopic description of odd-even staggering of charge radii of exotic copper isotopes

Low-energy $^{23}$ Al $β$ -delayed proton decay and $^{22}$ Na destruction in novae

Measurement and microscopic description of odd-even staggering of charge radii of exotic copper isotopes

Low-energy 23Al β-delayed proton decay and 22Na destruction in novae

Low-energy $^{23}$ Al $β$ -delayed proton decay and $^{22}$ Na destruction in novae