Universität zu Köln

Heim, F., Mayer, J., Mueller, M., Scholz, P. and Zilges, A. (2021). Deducing primary gamma-ray intensities and the dipole strength function in Mo-94 via radiative proton capture. Phys. Rev. C, 103 (2). COLLEGE PK: AMER PHYSICAL SOC. ISSN 2469-9993

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Abstract

Background: The nucleosynthesis of heavy nuclei is affected by the reaction rates of radiative capture reactions. Many of the astrophysical relevant rates cannot be obtained from experiments but are obtained from theoretical models. The gamma-decay widths that are derived from radiative strength functions are one of the key nuclear physics input parameters in those calculations. The explicit study of gamma-ray strength functions has been thoroughly addressed in the last decade and various methods have been established to extract the dipole strength in atomic nuclei. Purpose: The investigation of primary gamma-ray transitions from the Nb-93(p, gamma) Mo-94 reaction allows deducing the gamma-ray strength function in Mo-94. The results are compared to results obtained using other techniques and the impact of level densities, excitation mechanism, and excitation energy will be thoroughly investigated. Method: The proton beam was delivered by the 10 MV FN-Tandem accelerator located at the Institute for Nuclear Physics at the University of Cologne, Germany. By means of in-beam gamma-ray spectroscopy the intensity of primary gamma rays is determined. Additionally, the first generation gamma-ray intensity is deduced from the secondary gamma rays using their branching and the coincidence detection efficiency. Absolute gamma-ray strength function values as well as relative values using the ratio method will be extracted. Results: Numerous states in Mo-94 at excitation energies above 3 MeV have been identified for the first time and their decay behavior has been studied. We disentangled the effects of M1 and E1 radiation for the gamma-ray emission channel in Mo-94 and extracted strength function curves for both radiation types. Our results are in good agreement with experimental results using the Oslo method and photoinduced experiments as well as with recent theoretical quasiparticle random-phase approximation (QRPA) calculations. An enhancement of the gamma-ray strength below the neutron separation energy was found that is most likely of E1 character. In addition, a significant increase of the dipole strength at low gamma-ray energies was found which is most likely due to M1 strength. Conclusion: Radiative proton capture reactions are a well-suited tool to study the gamma-ray strength function in atomic nuclei. From the intensity of primary gamma-ray transitions as well as from secondary gamma-rays, information about the radiative dipole strength can be extracted. The gamma-ray emission seems to be independent of the excitation energy in the studied mass and energy range. Detailed knowledge about the intrinsic properties of the nuclear states is very important and their uncertainties affect the uncertainty of the extracted gamma-ray strength functions heavily.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Heim, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Mayer, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Mueller, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Scholz, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Zilges, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-572266
DOI:	10.1103/PhysRevC.103.025805
Journal or Publication Title:	Phys. Rev. C
Volume:	103
Number:	2
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 NUCLEAR-DATA SHEETS; P-PROCESS; S-PROCESS; R-PROCESS; NUCLEOSYNTHESIS; SPECTROSCOPY; RESONANCE; PHYSICS; ALPHA Multiple languages Physics, Nuclear Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/57226