Universität zu Köln

Isaak, J., Savran, D., Loeher, B., Beck, T., Friman-Gayer, U., Pietralla, N., Ponomarev, V. Yu, Scheck, M., Tornow, W., Werner, V, Zilges, A. and Zweidinger, M. (2021). Dipole response in Te-128,Te-130 below the neutron threshold. Phys. Rev. C, 103 (4). COLLEGE PK: AMER PHYSICAL SOC. ISSN 2469-9993

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Abstract

Background: Numerous studies of the ground-state decay of the pygmy dipole resonance (PDR) have been carried out in the past. However, data on the decay of the PDR to low-lying excited states is still very scarce due to limitations of the sensitivity to weak branching transitions of experimental setups. Purpose: We present a detailed examination of the low-energy dipole response of Te-128 and Te-130 below their neutron separation thresholds of 8.8 and 8.5 MeV, respectively. Methods: Photonuclear reactions with the subsequent gamma-ray spectroscopy of the decay channel with continuous-energy bremsstrahlung at varying endpoint energies and linearly polarized quasimonochromatic gamma-ray beams with energies ranging from 2.7 to 8.9 MeV in steps of roughly 250 keV were used for probing the decay behavior of the low-energy dipole response in Te-128 and Te-130. In addition, ((gamma) over right arrow, gamma ' gamma '') reactions were used to study the population of low-lying states of Te-128. Results: Spin-parity quantum numbers and reduced transition probabilities are determined for individual photo-excited states. The analysis of average decay properties for nuclear levels in narrow excitation-energy bins enable the extraction of photoabsorption cross sections, average branching ratios to the 2(1)(+) state, and the distinction between E1 and M1 transitions to the ground state and to the 2(1)(+) state accounting for resolved and unresolved transitions. Conclusions: Above 5 MeV, the experimental data are in reasonable agreement to calculations within the quasiparticle phonon model. The major fraction of the ground-state decay channel is due to E1 transitions, while less than 5-10% stem from M1 transitions. Furthermore, first direct experimental evidence is provided that the population of the 2(1)(+) state of Te-128 via primary gamma-ray transitions from excited states in the PDR region from 5 to 9 MeV is dominated by E1 transitions of 1(-) states.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Isaak, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Savran, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Loeher, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beck, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Friman-Gayer, U. UNSPECIFIED UNSPECIFIED UNSPECIFIED Pietralla, N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ponomarev, V. Yu UNSPECIFIED UNSPECIFIED UNSPECIFIED Scheck, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Tornow, W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Werner, V UNSPECIFIED UNSPECIFIED UNSPECIFIED Zilges, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Zweidinger, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-599021
DOI:	10.1103/PhysRevC.103.044317
Journal or Publication Title:	Phys. Rev. C
Volume:	103
Number:	4
Date:	2021
Publisher:	AMER PHYSICAL SOC
Place of Publication:	COLLEGE PK
ISSN:	2469-9993
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language PHOTON STRENGTH FUNCTIONS; NUCLEAR-DATA SHEETS; INELASTIC-SCATTERING; PYGMY; RESONANCE; STATES; MODES; EXCITATIONS; DECAY; ENERGY Multiple languages Physics, Nuclear Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/59902