scholarly journals Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of N = 32

2021 ◽  
Author(s):  
Á. Koszorús ◽  
X. F. Yang ◽  
W. G. Jiang ◽  
S. J. Novario ◽  
S. W. Bai ◽  
...  
Keyword(s):  
Density Functional ◽  
Neutron Number ◽  
Nucleon Nucleon ◽  
Nuclear Size ◽  
Resonance Ionization ◽  
Resonance Ionization Spectroscopy ◽  
Β Decay ◽  
Nuclear Theory ◽  
Charge Radii ◽  
A Charge

AbstractNuclear charge radii are sensitive probes of different aspects of the nucleon–nucleon interaction and the bulk properties of nuclear matter, providing a stringent test and challenge for nuclear theory. Experimental evidence suggested a new magic neutron number at N = 32 (refs. 1–3) in the calcium region, whereas the unexpectedly large increases in the charge radii4,5 open new questions about the evolution of nuclear size in neutron-rich systems. By combining the collinear resonance ionization spectroscopy method with β-decay detection, we were able to extend charge radii measurements of potassium isotopes beyond N = 32. Here we provide a charge radius measurement of 52K. It does not show a signature of magic behaviour at N = 32 in potassium. The results are interpreted with two state-of-the-art nuclear theories. The coupled cluster theory reproduces the odd–even variations in charge radii but not the notable increase beyond N = 28. This rise is well captured by Fayans nuclear density functional theory, which, however, overestimates the odd–even staggering effect in charge radii. These findings highlight our limited understanding of the nuclear size of neutron-rich systems, and expose problems that are present in some of the best current models of nuclear theory.

scholarly journals Evidence of a sudden increase in the nuclear size of proton-rich silver-96

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
M. Reponen ◽  
R. P. de Groote ◽  
L. Al Ayoubi ◽  
O. Beliuskina ◽  
M. L. Bissell ◽  
...  
Keyword(s):  
Charge Radius ◽  
Density Functional ◽  
Theory Development ◽  
Density Functional Theory Calculations ◽  
Neutron Number ◽  
Nuclear Charge Radius ◽  
Sudden Increase ◽  
Nuclear Theory ◽  
Charge Radii ◽  
Proton Pairing

AbstractUnderstanding the evolution of the nuclear charge radius is one of the long-standing challenges for nuclear theory. Recently, density functional theory calculations utilizing Fayans functionals have successfully reproduced the charge radii of a variety of exotic isotopes. However, difficulties in the isotope production have hindered testing these models in the immediate region of the nuclear chart below the heaviest self-conjugate doubly-magic nucleus 100Sn, where the near-equal number of protons (Z) and neutrons (N) lead to enhanced neutron-proton pairing. Here, we present an optical excursion into this region by crossing the N = 50 magic neutron number in the silver isotopic chain with the measurement of the charge radius of 96Ag (N = 49). The results provide a challenge for nuclear theory: calculations are unable to reproduce the pronounced discontinuity in the charge radii as one moves below N = 50. The technical advancements in this work open the N = Z region below 100Sn for further optical studies, which will lead to more comprehensive input for nuclear theory development.

scholarly journals Publisher Correction: Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of N = 32

2021 ◽  
Author(s):  
Á. Koszorús ◽  
X. F. Yang ◽  
W. G. Jiang ◽  
S. J. Novario ◽  
S. W. Bai ◽  
...  
Keyword(s):  
Nuclear Theory ◽  
Charge Radii

scholarly journals Atom-at-a-time laser resonance ionization spectroscopy of nobelium

Nature ◽  
2016 ◽  
Vol 538 (7626) ◽  
pp. 495-498 ◽  
Author(s):  
Mustapha Laatiaoui ◽  
Werner Lauth ◽  
Hartmut Backe ◽  
Michael Block ◽  
Dieter Ackermann ◽  
...  
Keyword(s):  
Resonance Ionization ◽  
Resonance Ionization Spectroscopy ◽  
Laser Resonance

[sup 89,90]Sr-Determination in Various Environmental Samples by Collinear Resonance Ionization Spectroscopy

1997 ◽  
Author(s):  
K. Wendt ◽  
B. A. Bushaw ◽  
G. Bhowmick ◽  
V. A. Bystrow ◽  
N. Kotovski ◽  
...  
Keyword(s):  
Environmental Samples ◽  
Resonance Ionization ◽  
Resonance Ionization Spectroscopy

scholarly journals Electrochemical Lithium Storage Performance of Molten Salt Derived V2SnC MAX Phase

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Youbing Li ◽  
Guoliang Ma ◽  
Hui Shao ◽  
Peng Xiao ◽  
Jun Lu ◽  
...  
Keyword(s):  
Molten Salt ◽  
Redox Reaction ◽  
Density Functional ◽  
High Rate ◽  
Max Phase ◽  
Molten Salt Method ◽  
Lithium Storage ◽  
Max Phases ◽  
Storage Mechanism ◽  
A Charge

AbstractMAX phases are gaining attention as precursors of two-dimensional MXenes that are intensively pursued in applications for electrochemical energy storage. Here, we report the preparation of V2SnC MAX phase by the molten salt method. V2SnC is investigated as a lithium storage anode, showing a high gravimetric capacity of 490 mAh g−1 and volumetric capacity of 570 mAh cm−3 as well as superior rate performance of 95 mAh g−1 (110 mAh cm−3) at 50 C, surpassing the ever-reported performance of MAX phase anodes. Supported by operando X-ray diffraction and density functional theory, a charge storage mechanism with dual redox reaction is proposed with a Sn–Li (de)alloying reaction that occurs at the edge sites of V2SnC particles where Sn atoms are exposed to the electrolyte followed by a redox reaction that occurs at V2C layers with Li. This study offers promise of using MAX phases with M-site and A-site elements that are redox active as high-rate lithium storage materials.

scholarly journals Water-Mediated Electronic Structure of Oligopeptides Probed by Their UV Circular Dichroism, Absorption Spectra, and Time-Dependent DFT Calculations

2020 ◽  
Author(s):  
Anshuman Kumar ◽  
Siobhan E. Toal ◽  
David DiGuiseppi ◽  
Reinhard Schweitzer-Stenner ◽  
Bryan Wong
Keyword(s):  
Circular Dichroism ◽  
Absorption Spectra ◽  
Density Functional ◽  
Time Dependent ◽  
Water Model ◽  
Cd Spectra ◽  
Influence Of Water ◽  
Explicit Consideration ◽  
A Charge ◽  
Circular Dichroïsm

<p>We investigate the UV absorption spectra of a series of cationic GxG (where x denotes a guest residue) peptides in aqueous solution and find that the spectra of a subset of peptides with x = A, L, I, K, N, and R (and, to a lesser extent, peptides with x = D and V) vary as a function of temperature. To explore whether or not this observation reflects conformational dependencies, we carry out time-dependent density functional calculations for the polyproline II (pPII) and β-strand conformations of a limited set of tripeptides (x = A, V, I, L, and R) in implicit and explicit water. We find that the calculated CD spectra for pPII can qualitatively account for the experimental spectra irrespective of the water model. The reproduction of the <i>β</i>-strand UV-CD spectra, however, requires the explicit consideration of water. Based on the calculated absorption spectra, we explain the observed temperature dependence of the experimental spectra as being caused by a reduced dispersion (larger spectral density) of the overlapping NV<sub>2</sub> band and the influence of water on electronic transitions in the β-strand conformation. Contrary to conventional wisdom, we find that both the NV<sub>1</sub> and NV<sub>2</sub> band are the envelopes of contributions from multiple transitions that involve more than just the HOMOs and LUMOs of the peptide groups. A natural transition orbital analysis reveals that some of the transitions with significant oscillator strength have a charge-transfer character. The overall manifold of transitions, in conjunction with their strengths and characters, depends on the peptide’s backbone conformation, peptide hydration, and also on the side chain of the guest residue. It is particularly noteworthy that molecular orbitals of water contribute significantly to transitions in <i>β</i>-strand conformations. Our results reveal that peptide groups, side chains, and hydration shells must be considered as an entity for a physically valid characterization of UV absorbance and circular dichroism. </p>

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