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Title: Photodissociation experiments for p-process nuclei

Abstract

The near-threshold photodissociation of nuclides received an increased attention in recent years due to its relevance for heavy element production in astrophysical scenarios. Therefore, a research program has been started to study photodissociation reactions using energetic bremsstrahlung from the new ELBE electron linear accelerator. Special emphasis was devoted to the neutron deficient nuclei with A{approx_equal}100 which may have been produced in cosmic high-temperature regions by ({gamma},n) ({gamma},p), or ({gamma}, {alpha})-reactions. First data were obtained for the astrophysically important target nucleus 92Mo by observing the radioactive decay of the nuclides produced by bremsstrahlung irradiation at end-point energies between 11.8 and 14.0 MeV. The results are compared to recent statistical-model calculations.

Authors:
; ; ; ; ; ; ; ; ;  [1];  [1];  [2]
  1. Institut fuer Kern- und Hadronenphysik, Forschungszentrum Rossendorf, Postfach 51 01 19, 01314 Dresden (Germany)
  2. (Germany)
Publication Date:
OSTI Identifier:
20798525
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 831; Journal Issue: 1; Conference: International conference on frontiers in nuclear structure, astrophysics, and reactions - FINUSTAR, Isle of Kos (Greece), 12-17 Sep 2005; Other Information: DOI: 10.1063/1.2200892; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BREMSSTRAHLUNG; DISSOCIATION; IRRADIATION; LINEAR ACCELERATORS; MEV RANGE; MOLYBDENUM 92 TARGET; NEUTRON-DEFICIENT ISOTOPES; NUCLEAR DECAY; NUCLEOSYNTHESIS; PHOTON-NUCLEON INTERACTIONS; PHOTONUCLEAR REACTIONS; RESEARCH PROGRAMS; STATISTICAL MODELS

Citation Formats

Wagner, A., Erhard, M., Junghans, A. R., Klug, J., Kosev, K., Nair, C., Nankov, N., Rusev, G., Schilling, K. D., Schwengner, R., Grosse, E., and Institut fuer Kern- und Teilchenphysik, Technische Universitaet Dresden, 01062 Dresden. Photodissociation experiments for p-process nuclei. United States: N. p., 2006. Web. doi:10.1063/1.2200892.
Wagner, A., Erhard, M., Junghans, A. R., Klug, J., Kosev, K., Nair, C., Nankov, N., Rusev, G., Schilling, K. D., Schwengner, R., Grosse, E., & Institut fuer Kern- und Teilchenphysik, Technische Universitaet Dresden, 01062 Dresden. Photodissociation experiments for p-process nuclei. United States. doi:10.1063/1.2200892.
Wagner, A., Erhard, M., Junghans, A. R., Klug, J., Kosev, K., Nair, C., Nankov, N., Rusev, G., Schilling, K. D., Schwengner, R., Grosse, E., and Institut fuer Kern- und Teilchenphysik, Technische Universitaet Dresden, 01062 Dresden. Wed . "Photodissociation experiments for p-process nuclei". United States. doi:10.1063/1.2200892.
@article{osti_20798525,
title = {Photodissociation experiments for p-process nuclei},
author = {Wagner, A. and Erhard, M. and Junghans, A. R. and Klug, J. and Kosev, K. and Nair, C. and Nankov, N. and Rusev, G. and Schilling, K. D. and Schwengner, R. and Grosse, E. and Institut fuer Kern- und Teilchenphysik, Technische Universitaet Dresden, 01062 Dresden},
abstractNote = {The near-threshold photodissociation of nuclides received an increased attention in recent years due to its relevance for heavy element production in astrophysical scenarios. Therefore, a research program has been started to study photodissociation reactions using energetic bremsstrahlung from the new ELBE electron linear accelerator. Special emphasis was devoted to the neutron deficient nuclei with A{approx_equal}100 which may have been produced in cosmic high-temperature regions by ({gamma},n) ({gamma},p), or ({gamma}, {alpha})-reactions. First data were obtained for the astrophysically important target nucleus 92Mo by observing the radioactive decay of the nuclides produced by bremsstrahlung irradiation at end-point energies between 11.8 and 14.0 MeV. The results are compared to recent statistical-model calculations.},
doi = {10.1063/1.2200892},
journal = {AIP Conference Proceedings},
number = 1,
volume = 831,
place = {United States},
year = {Wed Apr 26 00:00:00 EDT 2006},
month = {Wed Apr 26 00:00:00 EDT 2006}
}
  • Expressions for the distributions of products originating from (p, p'n) and (p, p') reactions on halo nuclei involving one and two valence neutrons in the quasifree-collision mode are obtained by the method of spacetime correlation functions. A comparative analysis is given to the information content of experiments with these nuclei within both exclusive (p, p'n) and inclusive (p, p') approaches.
  • We find two empirical scaling laws in the solar system, which is evidence that the most probable origin of the p-nuclei is photodisintegration reactions in supernova explosions (p-process). We also find a novel concept of 'the universality of the p-process'. We discuss the mechanism of this universality in typical core-collapse supernova explosion models.
  • Results on inelastic scattering of polarized protons (p-italic-arrow-right, p') with energy E/sub p/ = 800 MeV with excitation of a number of 2/sup +/ levels of nuclei /sup 90,92/Zr have turned out to be rather indeterminate. We shall discuss the analysis of experiments of this type previously carried out for the nuclei /sup 90,92/Zr and /sup 92/Mo at E/sub p/ = 20 MeV. From comparison of the two nuclei it follows that only in the case of 2/sup +//sub 1/ is the value of A(theta) sigma (theta) for /sup 92/Mo larger than for /sup 90/Zr. This agrees with the datamore » on sigma(theta) for unpolarized protons at E/sub p/--60 MeV and is explained by the fact that /sup 92/Mo has more ''active'' valence protons than /sup 90/Zr. (AIP)« less
  • Strong orbital alignment is observed in the ground-state oxygen atom following photodissociation of NO{sub 2} at 212.8 nm using ion imaging. The imaging method allows for investigation of the angular distribution of this alignment, providing insight into the dynamics in the frame of the molecule. The results are analyzed using a rigorous quantum mechanical theory yielding alignment parameters having direct physical significance. This alignment is dominated by a strong incoherent parallel contribution. In addition, the results reveal direct evidence of coherence between parallel and perpendicular contributions to the excitation of a polyatomic molecule, showing that the electron cloud in themore » recoiling atom {open_quotes}remembers{close_quotes} the original molecular plane. {copyright} {ital 1999 American Institute of Physics.}« less
  • We present a generally applicable experimental method for the direct measurement of nascent spin-orbit state distributions of atomic photofragments based on the detection of vacuum ultraviolet (VUV)-excited autoionizing-Rydberg (VUV-EAR) states. The incorporation of this VUV-EAR method in the application of the newly established VUV-VUV laser velocity-map-imaging-photoion (VMI-PI) apparatus has made possible the branching ratio measurement for correlated spin-orbit state resolved product channels, CO(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}), formed by VUV photoexcitation of CO{sub 2} to the 4s(1{sub 0}{sup 1}) Rydberg state at 97,955.7 cm{sup −1}. The total kinetic energy releasemore » (TKER) spectra obtained from the O{sup +} VMI-PI images of O({sup 3}P{sub 0,1,2}) reveal the formation of correlated CO(ã{sup 3}Π; v = 0–2) with well-resolved v = 0–2 vibrational bands. This observation shows that the dissociation of CO{sub 2} to form the spin-allowed CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel has no potential energy barrier. The TKER spectra for the spin-forbidden CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel were found to exhibit broad profiles, indicative of the formation of a broad range of rovibrational states of CO(Χ{sup ~1}Σ{sup +})  with significant vibrational populations for v = 18–26. While the VMI-PI images for the CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel are anisotropic, indicating that the predissociation of CO{sub 2} 4s(1{sub 0}{sup 1}) occurs via a near linear configuration in a time scale shorter than the rotational period, the angular distributions for the CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel are close to isotropic, revealing a slower predissociation process, which possibly occurs on a triplet surface via an intersystem crossing mechanism.« less