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Title: The {sup 139}La(n,{gamma}) cross section: Key for the onset of the s-process

Abstract

The nuclear resonance parameters and the capture cross section of the neutron magic isotope {sup 139}La have been measured relative to {sup 197}Au in the energy range of 0.6 eV to 9 keV at the neutron time-of-flight (n{sub T}OF) facility at CERN. We describe the experimental apparatus and the data analysis procedures, which concerned mainly the efficiency correction by means of the pulse height weighting function technique and the determination of different background components. We extracted the resonance parameters and the main nuclear quantities such as the resonance integral RI=10.8{+-}1.0b, the average {gamma} widths for s and p waves <{gamma}{sub {gamma}}>{sub l=0}=50.7{+-}5.4 meV and <{gamma}{sub {gamma}}>{sub l=1}=33.6{+-}6.9 meV, the nuclear level densities <D>{sub l=0}=252{+-}22 eV and <D>{sub l=1}<250 eV, and the neutron strength functions S{sub 0}=(0.82{+-}0.05)x10{sup -4} and S{sub 1}=(0.55{+-}0.04)x10{sup -4}. These results represent a significant improvement over previous data. The deduced Maxwellian-averaged capture cross sections are important for the interpretation of the most recent spectroscopic observations in low-metallicity stars.

Authors:
; ; ;  [1]; ; ; ;  [2]; ; ; ; ; ; ; ;  [3]; ; ;  [4];  [5]
  1. Dipartimento di Fisica and Istituto Nazionale di Fisica Nucleare, Bari (Italy)
  2. Istituto Nazionale di Fisica Nucleare, Trieste (Italy)
  3. CEA/Saclay-DSM, Gif-sur-Yvette (France)
  4. Universidade de Santiago de Compostela (Spain)
  5. Centro de Investigaciones Energeticas Medioambientales y Technologicas, Madrid (Spain) (and others)
Publication Date:
OSTI Identifier:
20995174
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevC.75.035807; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CAPTURE; CERN; CROSS SECTIONS; EV RANGE 01-10; GOLD 197; KEV RANGE 01-10; LANTHANUM 139; MEV RANGE; NEUTRONS; P WAVES; RESONANCE INTEGRALS; S PROCESS; STRENGTH FUNCTIONS; WEIGHTING FUNCTIONS

Citation Formats

Terlizzi, R., Colonna, N., Marrone, S., Tagliente, G., Abbondanno, U., Fujii, K., Milazzo, P. M., Moreau, C., Aerts, G., Andriamonje, S., Berthoumieux, E., Dridi, W., Gunsing, F., Pancin, J., Perrot, L., Plukis, A., Alvarez, H., Duran, I., Paradela, C., and Alvarez-Velarde, F. The {sup 139}La(n,{gamma}) cross section: Key for the onset of the s-process. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.035807.
Terlizzi, R., Colonna, N., Marrone, S., Tagliente, G., Abbondanno, U., Fujii, K., Milazzo, P. M., Moreau, C., Aerts, G., Andriamonje, S., Berthoumieux, E., Dridi, W., Gunsing, F., Pancin, J., Perrot, L., Plukis, A., Alvarez, H., Duran, I., Paradela, C., & Alvarez-Velarde, F. The {sup 139}La(n,{gamma}) cross section: Key for the onset of the s-process. United States. doi:10.1103/PHYSREVC.75.035807.
Terlizzi, R., Colonna, N., Marrone, S., Tagliente, G., Abbondanno, U., Fujii, K., Milazzo, P. M., Moreau, C., Aerts, G., Andriamonje, S., Berthoumieux, E., Dridi, W., Gunsing, F., Pancin, J., Perrot, L., Plukis, A., Alvarez, H., Duran, I., Paradela, C., and Alvarez-Velarde, F. Thu . "The {sup 139}La(n,{gamma}) cross section: Key for the onset of the s-process". United States. doi:10.1103/PHYSREVC.75.035807.
@article{osti_20995174,
title = {The {sup 139}La(n,{gamma}) cross section: Key for the onset of the s-process},
author = {Terlizzi, R. and Colonna, N. and Marrone, S. and Tagliente, G. and Abbondanno, U. and Fujii, K. and Milazzo, P. M. and Moreau, C. and Aerts, G. and Andriamonje, S. and Berthoumieux, E. and Dridi, W. and Gunsing, F. and Pancin, J. and Perrot, L. and Plukis, A. and Alvarez, H. and Duran, I. and Paradela, C. and Alvarez-Velarde, F.},
abstractNote = {The nuclear resonance parameters and the capture cross section of the neutron magic isotope {sup 139}La have been measured relative to {sup 197}Au in the energy range of 0.6 eV to 9 keV at the neutron time-of-flight (n{sub T}OF) facility at CERN. We describe the experimental apparatus and the data analysis procedures, which concerned mainly the efficiency correction by means of the pulse height weighting function technique and the determination of different background components. We extracted the resonance parameters and the main nuclear quantities such as the resonance integral RI=10.8{+-}1.0b, the average {gamma} widths for s and p waves <{gamma}{sub {gamma}}>{sub l=0}=50.7{+-}5.4 meV and <{gamma}{sub {gamma}}>{sub l=1}=33.6{+-}6.9 meV, the nuclear level densities <D>{sub l=0}=252{+-}22 eV and <D>{sub l=1}<250 eV, and the neutron strength functions S{sub 0}=(0.82{+-}0.05)x10{sup -4} and S{sub 1}=(0.55{+-}0.04)x10{sup -4}. These results represent a significant improvement over previous data. The deduced Maxwellian-averaged capture cross sections are important for the interpretation of the most recent spectroscopic observations in low-metallicity stars.},
doi = {10.1103/PHYSREVC.75.035807},
journal = {Physical Review. C, Nuclear Physics},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • The nuclear resonance parameters and the capture cross section of the neutron magic isotope {sup 139}La have been measured relative to {sup 197}Au in the energy range of 0.6 eV to 9 keV at the neutron time-of-flight (n{_}TOF) facility at CERN. We describe the experimental apparatus and the data analysis procedures, which concerned mainly the efficiency correction by means of the pulse height weighting function technique and the determination of different background components. We extracted the resonance parameters and the main nuclear quantities such as the resonance integral RI=10.8{+-}1.0b, the average {gamma} widths for s and p waves <{Gamma}{sub gamma}>{submore » l=0}=50.7{+-}5.4 meV and <{Gamma}{sub gamma}>{sub l=0}=33.6{+-}6.9 meV, the nuclear level densities <D>{sub l=0}=252{+-}22 eV and <D>{sub l=1}<250 eV, and the neutron strength functions S{sub 0}=(0.82{+-}0.05)x10{sup -4} and S{sub 1}=(0.55{+-}0.04)x10{sup -4}. These results represent a significant improvement over previous data. The deduced Maxwellian-averaged capture cross sections are important for the interpretation of the most recent spectroscopic observations in low-metallicity stars.« less
  • Cross sections of the {sup 139}La({gamma},n) and {sup 141}Pr({gamma},n) reactions were measured using quasi-monochromatic {gamma}-ray beams from laser Compton scattering. The results are compared to the predictions of Hauser-Feshbach statistical calculations using different models for the {gamma}-ray strength function. The model parameters are constrained by the present experimental data and used to estimate the stellar photoneutron rates and their associated uncertainties and to study the implication for the production of the rare odd-odd nuclide {sup 138}La by the p process. No evidence for a large thermonuclear p-process contribution to the solar {sup 138}La is found. The need to further exploremore » the photodestruction rate of {sup 138}La is emphasized.« less
  • Photoneutron cross sections were measured for {sup 80}Se near the neutron separation energy with laser Compton-backscattered {gamma}-ray beams at AIST. Neutron capture rates are evaluated for {sup 79}Se with the photoreaction data as experimental constraints on the El {gamma}-strength function, a key parameter in the Hauser-Feshbach statistical model calculation. Solving the set of differential equations under a single neutron exposure, we analyzed the solar abundance ratio of the weak components of {sup 80}Kr and {sup 82}Kr in terms of the s-process branching at {sup 79}Se. We discuss the region of temperature and neutron density allowed for the weak s-process nucleosynthesis.
  • The gamma-ray strength function is an important input quantity for the determination of the photoreaction rate and the neutron capture rate for astrophysics as well as for nuclear technologies. Recent studies show that extra gamma-ray strength near the neutron separation energy S{sub n}(pygmy resonance) affects the stellar reaction rate strongly. In this work, the photoabsorption cross section for {sup 139}La below S{sub n} was measured using bremsstrahlung produced at the electron accelerator ELBE of Eorschungszentrum Dresden-Rossendorf with an electron beam of 11.5 MeV kinetic energy. Experimental result of {sup 139}La is presented.