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Title: Stellar (n,{gamma}) cross sections of {sup 174}Hf and radioactive {sup 182}Hf

Abstract

The stellar neutron capture cross sections of {sup 174}Hf and the radioactive isotope {sup 182}Hf (t{sub 1/2}=8.9x10{sup 6} yr) have been measured for the first time at kT=25 keV by means of the activation technique. These isotopes originate from different stellar scenarios, {sup 174}Hf from the p-process by a series of photodisintegration reactions of heavier seed nuclei, and {sup 182}Hf from the s-process in asymptotic giant branch stars as well as from the r-process in supernovae or neutron star mergers. Both activation measurements were carried out at the Karlsruhe Van de Graaff accelerator using the {sup 7}Li(p,n){sup 7}Be reaction for simulating a Maxwellian neutron spectrum corresponding to a thermal energy of kT=25 keV. The Maxwellian averaged cross sections (MACS) extrapolated to the common s-process temperatures at kT=30 keV yield <{sigma}>{sub 30}=983{+-}46 and 141{+-}8 mb for {sup 174}Hf and {sup 182}Hf, respectively.

Authors:
; ; ; ; ; ; ; ; ; ;  [1];  [2];  [3];  [4];  [5];  [6]
  1. TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3 (Canada)
  2. (Germany)
  3. (VERA), Institut fuer Isotopenforschung und Kernphysik, Universitaet Wien, Waehringer Strasse 17, A-1090 Wien (Austria)
  4. (Austria)
  5. (Jordan)
  6. (Italy)
Publication Date:
OSTI Identifier:
20990981
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevC.75.015804; (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; BERYLLIUM 7; CROSS SECTIONS; HAFNIUM 174; HAFNIUM 182; KEV RANGE 10-100; LITHIUM 7; NEUTRON REACTIONS; NEUTRON SPECTRA; NEUTRON STARS; PHOTONUCLEAR REACTIONS; R PROCESS; S PROCESS; VAN DE GRAAFF ACCELERATORS

Citation Formats

Vockenhuber, C., Dillmann, I., Heil, M., Kaeppeler, F., Winckler, N., Kutschera, W., Wallner, A., Bichler, M., Dababneh, S., Bisterzo, S., Gallino, R., Institut fuer Kernphysik, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Vienna Environmental Research Accelerator, Atominstitut der Oesterreichischen Universitaeten, Stadionallee 2, A-1020 Wien, Faculty of Science and Information Technology, Al-Balqa Applied University, P.O. Box 7051, Salt 19117, and Dipartimento di Fisica Generale, Universita di Torino and Sezione INFN di Torino, I-10125 Torino. Stellar (n,{gamma}) cross sections of {sup 174}Hf and radioactive {sup 182}Hf. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.015804.
Vockenhuber, C., Dillmann, I., Heil, M., Kaeppeler, F., Winckler, N., Kutschera, W., Wallner, A., Bichler, M., Dababneh, S., Bisterzo, S., Gallino, R., Institut fuer Kernphysik, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Vienna Environmental Research Accelerator, Atominstitut der Oesterreichischen Universitaeten, Stadionallee 2, A-1020 Wien, Faculty of Science and Information Technology, Al-Balqa Applied University, P.O. Box 7051, Salt 19117, & Dipartimento di Fisica Generale, Universita di Torino and Sezione INFN di Torino, I-10125 Torino. Stellar (n,{gamma}) cross sections of {sup 174}Hf and radioactive {sup 182}Hf. United States. doi:10.1103/PHYSREVC.75.015804.
Vockenhuber, C., Dillmann, I., Heil, M., Kaeppeler, F., Winckler, N., Kutschera, W., Wallner, A., Bichler, M., Dababneh, S., Bisterzo, S., Gallino, R., Institut fuer Kernphysik, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Vienna Environmental Research Accelerator, Atominstitut der Oesterreichischen Universitaeten, Stadionallee 2, A-1020 Wien, Faculty of Science and Information Technology, Al-Balqa Applied University, P.O. Box 7051, Salt 19117, and Dipartimento di Fisica Generale, Universita di Torino and Sezione INFN di Torino, I-10125 Torino. Mon . "Stellar (n,{gamma}) cross sections of {sup 174}Hf and radioactive {sup 182}Hf". United States. doi:10.1103/PHYSREVC.75.015804.
@article{osti_20990981,
title = {Stellar (n,{gamma}) cross sections of {sup 174}Hf and radioactive {sup 182}Hf},
author = {Vockenhuber, C. and Dillmann, I. and Heil, M. and Kaeppeler, F. and Winckler, N. and Kutschera, W. and Wallner, A. and Bichler, M. and Dababneh, S. and Bisterzo, S. and Gallino, R. and Institut fuer Kernphysik, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe and Vienna Environmental Research Accelerator and Atominstitut der Oesterreichischen Universitaeten, Stadionallee 2, A-1020 Wien and Faculty of Science and Information Technology, Al-Balqa Applied University, P.O. Box 7051, Salt 19117 and Dipartimento di Fisica Generale, Universita di Torino and Sezione INFN di Torino, I-10125 Torino},
abstractNote = {The stellar neutron capture cross sections of {sup 174}Hf and the radioactive isotope {sup 182}Hf (t{sub 1/2}=8.9x10{sup 6} yr) have been measured for the first time at kT=25 keV by means of the activation technique. These isotopes originate from different stellar scenarios, {sup 174}Hf from the p-process by a series of photodisintegration reactions of heavier seed nuclei, and {sup 182}Hf from the s-process in asymptotic giant branch stars as well as from the r-process in supernovae or neutron star mergers. Both activation measurements were carried out at the Karlsruhe Van de Graaff accelerator using the {sup 7}Li(p,n){sup 7}Be reaction for simulating a Maxwellian neutron spectrum corresponding to a thermal energy of kT=25 keV. The Maxwellian averaged cross sections (MACS) extrapolated to the common s-process temperatures at kT=30 keV yield <{sigma}>{sub 30}=983{+-}46 and 141{+-}8 mb for {sup 174}Hf and {sup 182}Hf, respectively.},
doi = {10.1103/PHYSREVC.75.015804},
journal = {Physical Review. C, Nuclear Physics},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • The neutron capture cross sections of /sup 178,179,180/Hf were measured in the energy range 2.6 keV to 2 MeV. The average capture cross sections were calculated and fitted in terms of strength functions. Resonance parameters for the observed resonances below 10 keV were determined by a shape analysis. Maxwellian averaged capture cross sections were computed for thermal energies kT between 5 and 100 keV. The cross sections for kT = 30 keV were used to determine the population probability of the 8/sup -/ isomeric level in /sup 180/Hf by neutron capture as (1.24 +- 0.06) % and the r-process abundancemore » of /sup 180/Hf as 0.0290 (Si equivalent10/sup 6/). These quantities served to analyze s- and r-process nucleosynthesis of /sup 180/Ta.« less
  • A statistically reliable correlation is found between the intensities of two-quantum cascades in the reaction /sup 174/Yb (n, 2..gamma..)/sup 175/Yb and the spectroscopic factors in the reaction /sup 176/Yb(d, t)/sup 175/Yb. The results obtained are an experimental evidence of the fact that the hole-quasiparticle components of the wave function of the excited states of /sup 175/Yb play a significant role in the ..gamma..-decay mechanism for this compound nucleus.
  • The neutron-capture cross sections of {sup 168}Yb, {sup 180}W, {sup 184}Os, {sup 190}Pt, and {sup 196}Hg have been measured by means of the activation technique. The samples were irradiated in a quasistellar neutron spectrum of kT=25 keV, which was produced at the Karlsruhe 3.7-MV Van de Graaff accelerator via the {sup 7}Li(p,n){sup 7}Be reaction. Systematic uncertainties were investigated in repeated activations with different samples and by variation of the experimental parameters, that is, irradiation times, neutron fluxes, and {gamma}-ray counting conditions. The measured data were converted into Maxwellian-averaged cross sections at kT=30 keV, yielding 1214{+-}61, 624{+-}54, 590{+-}43, 511{+-}46, and 201{+-}11more » mb for {sup 168}Yb, {sup 180}W, {sup 184}Os, {sup 190}Pt, and {sup 196}Hg, respectively. The present results either represent first experimental data ({sup 168}Yb, {sup 184}Os, and {sup 196}Hg) or could be determined with significantly reduced uncertainties ({sup 180}W and {sup 190}Pt). These measurements are part of a systematic study of stellar (n,{gamma}) cross sections of the stable p isotopes.« less
  • We have investigated the (n,gamma) cross sections of p-process isotopes with the activation technique. The measurements were carried out at the Karlsruhe Van de Graaff accelerator using the {sup 7}Li(p,n){sup 7}Be source for simulating a Maxwellian neutron distribution of kT=25 keV. Stellar cross section measurements are reported for the light p-process isotopes {sup 102}Pd, {sup 120}Te, {sup 130,132}Ba, and {sup 156}Dy. In a following paper the cross sections of {sup 168}Yb, {sup 180}W, {sup 184}Os, {sup 190}Pt, and {sup 196}Hg will be discussed. The data are extrapolated to p-process energies by including information from evaluated nuclear data libraries. The resultsmore » are compared to standard Hauser-Feshbach models frequently used in astrophysics.« less