Electric and magnetic dipole strength in 58Ni from forward-angle proton scattering

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F24%3A10493797" target="_blank" >RIV/00216208:11320/24:10493797 - isvavai.cz</a>

Výsledek na webu

<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=a4ro1BkGJs" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=a4ro1BkGJs</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1103/PhysRevC.110.034319" target="_blank" >10.1103/PhysRevC.110.034319</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Electric and magnetic dipole strength in 58Ni from forward-angle proton scattering

Popis výsledku v původním jazyce

Background: Electric and magnetic dipole strengths in nuclei at excitation energies well below the giant resonance region are of interest for a variety of nuclear structure problems including a possible electric dipole toroidal mode or the quenching of spin-isospin flip modes. Purpose: The aim of the present work is a state-by-state analysis of possible E 1 and M 1 transitions in 58 Ni with a high-resolution (p, p , p &apos; ) experiment at 295 MeV and very forward angles including 0 degrees degrees and a comparison to results from studies of the dipole strength with the ( gamma , gamma &apos; ) and (e, e , e &apos; ) reactions. Methods: The E 1 and M 1 cross sections of individual peaks in the spectra are deduced with a multipole decomposition analysis (MDA). They are converted to reduced E 1 and spin M 1 transition strengths using the virtual photon method of relativistic Coulomb excitation and the unit cross-section method, respectively. The experimental M 1 strength distribution is compared to large-scale shell-model calculations with the effective GXPF1A and KB3G interactions. Results: In total, 11 E 1 and 26 M 1 transitions could be uniquely identified in the excitation energy region 6-13 MeV. In addition, 22 dipole transitions with preference for either E 1 or M 1 multipolarity and 57 transitions with uncertain multipolarity were found. Despite the high level density good agreement is obtained for the deduced excitation energies of J = 1 states in the three types of experiments indicating that the same states are excited. The B ( E 1) and B ( M 1) strengths deduced in the ( gamma , gamma &apos; ) experiments are systematically smaller than in the present work because of the lack of information on branching ratios to lower-lying excited states and the competition of particle emission. Fair agreement with the B ( M 1) strengths extracted from the (e, e , e &apos; ) data is obtained after removal of E 1 transitions uniquely assigned in the present work belonging to a low-energy toroidal mode with unusual properties mimicking M 1 excitations in electron scattering. The shell-model calculations provide a good description of the isospin splitting and the running sum of the M 1 strength. A quenching factor 0.74 for the spin-isospin part of the M 1 operator is needed to attain quantitative agreement with the data. Conclusions: High-resolution forward-angle inelastic proton scattering experiments at beam energies of about 300 MeV are a highly selective tool for an extraction of resolved E 1 and M 1 strength distributions in medium- mass nuclei. Fair agreement with results from electron scattering experiments is obtained indicating a dominance of spin contributions to the M 1 strength. Shell-model calculations are in good agreement with gross properties of the M 1 strength distribution when a quenching factor for the spin-isospin part comparable to the one needed for a description of Gamow-Teller (GT) strength is included.

Název v anglickém jazyce

Electric and magnetic dipole strength in 58Ni from forward-angle proton scattering

Popis výsledku anglicky

Background: Electric and magnetic dipole strengths in nuclei at excitation energies well below the giant resonance region are of interest for a variety of nuclear structure problems including a possible electric dipole toroidal mode or the quenching of spin-isospin flip modes. Purpose: The aim of the present work is a state-by-state analysis of possible E 1 and M 1 transitions in 58 Ni with a high-resolution (p, p , p &apos; ) experiment at 295 MeV and very forward angles including 0 degrees degrees and a comparison to results from studies of the dipole strength with the ( gamma , gamma &apos; ) and (e, e , e &apos; ) reactions. Methods: The E 1 and M 1 cross sections of individual peaks in the spectra are deduced with a multipole decomposition analysis (MDA). They are converted to reduced E 1 and spin M 1 transition strengths using the virtual photon method of relativistic Coulomb excitation and the unit cross-section method, respectively. The experimental M 1 strength distribution is compared to large-scale shell-model calculations with the effective GXPF1A and KB3G interactions. Results: In total, 11 E 1 and 26 M 1 transitions could be uniquely identified in the excitation energy region 6-13 MeV. In addition, 22 dipole transitions with preference for either E 1 or M 1 multipolarity and 57 transitions with uncertain multipolarity were found. Despite the high level density good agreement is obtained for the deduced excitation energies of J = 1 states in the three types of experiments indicating that the same states are excited. The B ( E 1) and B ( M 1) strengths deduced in the ( gamma , gamma &apos; ) experiments are systematically smaller than in the present work because of the lack of information on branching ratios to lower-lying excited states and the competition of particle emission. Fair agreement with the B ( M 1) strengths extracted from the (e, e , e &apos; ) data is obtained after removal of E 1 transitions uniquely assigned in the present work belonging to a low-energy toroidal mode with unusual properties mimicking M 1 excitations in electron scattering. The shell-model calculations provide a good description of the isospin splitting and the running sum of the M 1 strength. A quenching factor 0.74 for the spin-isospin part of the M 1 operator is needed to attain quantitative agreement with the data. Conclusions: High-resolution forward-angle inelastic proton scattering experiments at beam energies of about 300 MeV are a highly selective tool for an extraction of resolved E 1 and M 1 strength distributions in medium- mass nuclei. Fair agreement with results from electron scattering experiments is obtained indicating a dominance of spin contributions to the M 1 strength. Shell-model calculations are in good agreement with gross properties of the M 1 strength distribution when a quenching factor for the spin-isospin part comparable to the one needed for a description of Gamow-Teller (GT) strength is included.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10300 - Physical sciences

Projekt

<a href="/cs/project/GA23-06439S" target="_blank" >GA23-06439S: Kolektivní dynamika jaderných elektromagnetických excitací</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2024

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Physical Review C

ISSN

2469-9985

e-ISSN

2469-9993

Svazek periodika

110

Číslo periodika v rámci svazku

3

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

15

Strana od-do

034319

Kód UT WoS článku

001317702100002

EID výsledku v databázi Scopus

2-s2.0-85204433285