Nuclear shapes studied with low-energy Coulomb excitation

Coulomb excitation is one of the rare methods available to obtain information on static electromagnetic moments of short-lived excited nuclear states, including collective non-yrast levels. It is thus an ideal tool to study shape coexistence and shape evolution throughout the nuclear chart. Historically, these experiments were limited to stable isotopes, however the advent of new facilities, providing intense beams of short-lived radioactive species, has opened the possibility to apply this powerful technique to a much wider range of nuclei. Here, we present some recent complex Coulomb-excitation studies and use the example of superdeformed states in 42Ca to demonstrate the sensitivity of the method to second-order effects such as relative signs of electromagnetic matrix elements and quadrupole moments.

Download Full-text

Low-Energy Coulomb Excitation for the Shell Model

10.20944/preprints202108.0224.v1 ◽

2021 ◽

Author(s):

Marco Rocchini ◽

Magda Zielińska

Keyword(s):

Stable Isotopes ◽

Shell Model ◽

Nuclear Structure ◽

Coulomb Excitation ◽

Low Energy ◽

Structure Parameters ◽

Shape Coexistence ◽

Powerful Technique ◽

Radioactive Species ◽

New Facilities

Low-energy Coulomb excitation is capable of providing unique information on static electromagnetic moments of short-lived excited nuclear states, including non-yrast states. The process selectively populates low-lying collective states and is therefore ideally suited to study phenomena such as shape coexistence and development of exotic deformation (triaxial or octupole shapes). Historically, these experiments were restricted to stable isotopes. However, the advent of new facilities providing intense beams of short-lived radioactive species has opened the possibility to apply this powerful technique to a much wider range of nuclei. We discuss the observables that can be measured in a Coulomb-excitation experiment, their relation to nuclear structure parameters with an emphasis on the nuclear shape, and present some recent examples of Coulomb-excitation studies that provided outcomes relevant for the Shell Model.

Download Full-text

Low-Energy Coulomb Excitation for the Shell Model

Physics ◽

10.3390/physics3040078 ◽

2021 ◽

Vol 3 (4) ◽

pp. 1237-1253

Author(s):

Marco Rocchini ◽

Magda Zielińska

Keyword(s):

Stable Isotopes ◽

Shell Model ◽

Nuclear Structure ◽

Coulomb Excitation ◽

Low Energy ◽

Structure Parameters ◽

Shape Coexistence ◽

Powerful Technique ◽

Radioactive Species ◽

New Facilities

Low-energy Coulomb excitation is capable of providing unique information on static electromagnetic moments of short-lived excited nuclear states, including non-yrast states. The process selectively populates low-lying collective states and is, therefore, ideally suited to study phenomena such as shape coexistence and the development of exotic deformation (triaxial or octupole shapes). Historically, these experiments were restricted to stable isotopes. However, the advent of new facilities providing intense beams of short-lived radioactive species has opened the possibility to apply this powerful technique to a much wider range of nuclei. The paper discusses the observables that can be measured in a Coulomb-excitation experiment and their relation to the nuclear structure parameters with an emphasis on the nuclear shape. Recent examples of Coulomb-excitation studies that provided outcomes relevant for the Shell Model are also presented.

Download Full-text

SHAPE EVOLUTION IN HEAVIEST STABLE EVEN-EVEN MOLYBDENUM ISOTOPES STUDIED VIA COULOMB EXCITATION

International Journal of Modern Physics E ◽

10.1142/s0218301311017831 ◽

2011 ◽

Vol 20 (02) ◽

pp. 443-450 ◽

Cited By ~ 3

Author(s):

K. WRZOSEK-LIPSKA ◽

M. ZIELIŃSKA ◽

K. HADYŃSKA-KLȨK ◽

Y. HATSUKAWA ◽

J. IWANICKI ◽

...

Keyword(s):

Sum Rules ◽

Coulomb Excitation ◽

Quadrupole Deformation ◽

Shape Evolution ◽

Shape Coexistence ◽

Matrix Elements ◽

Deformation Parameters ◽

Molybdenum Isotopes ◽

Hamiltonian Model ◽

Mo Isotopes

The quadrupole shape evolution in heaviest stable Mo isotopes is studied in terms of the shape coexistence phenomenon occurrence in this region of nuclear chart. Quadrupole deformation parameters of the 96,98,100 Mo isotopes in the low-lying (ground and excited) 0+ states were deduced using Coulomb excitation method. In all cases rich sets of electromagnetic reduced matrix elements were determined using the GOSIA code and then analysed using the Quadrupole Sum Rules formalism. Discussion of the experimental results in comparison with the predictions of microscopic calculations within the general quadrupole collective Bohr Hamiltonian model is presented for 100 Mo .

Download Full-text

EXPERIMENTAL MEASUREMENT OF THE DEFORMATION THROUGH THE ELECTROMAGNETIC PROBE: SHAPE COEXISTENCE IN EXOTIC KR AND SR ISOTOPES

International Journal of Modern Physics E ◽

10.1142/s0218301311017806 ◽

2011 ◽

Vol 20 (02) ◽

pp. 415-421 ◽

Cited By ~ 2

Author(s):

E. CLÉMENT ◽

G. DE FRANCE ◽

J.M. CASANDJIAN ◽

A. GÖRGEN ◽

W. KORTEN ◽

...

Keyword(s):

Coulomb Excitation ◽

Theoretical Calculations ◽

Effective Interaction ◽

Shape Coexistence ◽

Quadrupole Moments ◽

Radioactive Beams ◽

Hartree Fock ◽

Electromagnetic Probe ◽

Model Configuration ◽

Band Mixing

The light krypton isotopes were studied in a series of Coulomb excitation experiments using radioactive beams at GANIL. The static quadrupole moments found in these experiments give firm experimental evidence for the shape coexistence scenario that is based on theoretical calculations and on the systematics of low-lying excited 0+ states. The experimental results are interpreted within a phenomenological two-band mixing model. Configuration mixing calculations based on triaxial Hartree-Fock-Bogolyubov calculations with the Gogny D1S effective interaction have been performed and compared to experimental data.

Download Full-text

COULOMB EXCITATION OF 150Nd

International Journal of Modern Physics E ◽

10.1142/s0218301304001746 ◽

2004 ◽

Vol 13 (01) ◽

pp. 71-74 ◽

Cited By ~ 12

Author(s):

MAGDALENA ZIELIŃSKA

Keyword(s):

Spectroscopic Data ◽

Coulomb Excitation ◽

Low Energy ◽

Matrix Elements ◽

Electromagnetic Structure ◽

Data Points ◽

Model Independent

The nucleus 150 Nd was Coulomb excited using 14 N , 58 Ni and 92 Mo beams. The overall result of the experiments performed consists of 780 measured gamma yields, which combined with available spectroscopic data gave about 800 data points to overdetermine the set of matrix elements needed to describe the observed processes. A number of E1, E2 and E3 matrix elements coupling the low-lying states has been determined in a model-independent way. In addition, an influence of E4 moments, competing with double E2 excitations, was tested with the low energy 14 N beam. Possible interpretations of the unusual electromagnetic structure found experimentally may pose the challenge to the theorists.

Download Full-text

The determination of the static quadrupole moments of the first 2+ states in 114Cd and 116Cd by higher order effects in Coulomb excitation

Nuclear Physics A ◽

10.1016/0375-9474(67)90221-7 ◽

1967 ◽

Vol 92 (2) ◽

pp. 319-344 ◽

Cited By ~ 59

Author(s):

R.G. Stokstad ◽

I. Hall ◽

G.D. Symons ◽

J. de Boer

Keyword(s):

Coulomb Excitation ◽

Higher Order ◽

Order Effects ◽

Quadrupole Moments ◽

Higher Order Effects ◽

Static Quadrupole

Download Full-text

Shape coexistence in 94Zr studied via Coulomb excitation

EPJ Web of Conferences ◽

10.1051/epjconf/201922301038 ◽

2019 ◽

Vol 223 ◽

pp. 01038

Author(s):

Naomi Marchini ◽

Marco Rocchini ◽

Adriana Nannini ◽

Daniel T. Doherty ◽

Magdalena Zielińska ◽

...

Keyword(s):

Coulomb Excitation ◽

National Laboratory ◽

Experimental Investigations ◽

Shape Coexistence ◽

Quadrupole Moments ◽

Model Calculations ◽

Lanthanum Bromide ◽

Monte Carlo Shell Model ◽

First Time

In recent years, a number of both theoretical and experimental investigations have been performed focusing on the zirconium isotopic chain. In particular, state-of-the-art Monte Carlo shell-model calculations predict shape coexistence in these isotopes. In this context, the 94Zr nucleus, which is believed to possess a nearly spherical ground state, is particularly interesting since the purported deformed structure is basedon the low-lying 02+ state, making it amenable for detailed study. In order to provide definitive conclusionson the shapes of the low-lying states, two complementary experiments to study 94Zr by means of low-energy Coulomb excitation were performed. This data will allow the quadrupole moments of the 21,2+ levels to be extracted as well as for the deformation parameters of the 01,2+ states to be determined and, thus, definitive conclusions to be drawn on the role of shape coexistence in this nucleus for the first time. The first experiment was performed at the INFN Legnaro National Laboratory with the GALILEO-SPIDER setup, which, for the first time, was coupled with 6 lanthanum bromide scintillators (LaBr3:Ce) in order to maximize the γ-ray detection effciency. The second experiment was performed at the Maier-Leibnitz Laboratory (MLL) in Munich and used a Q3D magnetic spectrograph to detect the scattered 12C ions following Coulomb excitation of 94Zr targets.

Download Full-text

SHAPE EVOLUTION OF HIGHLY DEFORMED 75Kr AND PROJECTED SHELL MODEL DESCRIPTION

International Journal of Modern Physics E ◽

10.1142/s0218301310016181 ◽

2010 ◽

Vol 19 (08n09) ◽

pp. 1754-1762 ◽

Cited By ~ 2

Author(s):

YING-CHUN YANG ◽

YANG SUN ◽

T. TRIVEDI ◽

R. PALIT ◽

J. A. SHEIKH

Keyword(s):

Shell Model ◽

Negative Parity ◽

Model Description ◽

Shape Evolution ◽

Quadrupole Moments ◽

Projected Shell Model ◽

Model Calculations ◽

High Spin States ◽

Parity Band ◽

Insight Into

A study of recently-measured high spin states of 75 Kr is carried out by using the Projected Shell Model. Calculations are performed up to spin I = 33/2 for the positive parity band and I = 27/2 for the negative parity band. Irregularities found in moment of inertia and in the deduced transition quadrupole moments Q t of the two bands are discussed in terms of the alignment of g 9/2 protons. Our study provides an insight into the shape evolution of the well-deformed nucleus 75 kr .

Download Full-text