Compound-nuclear reaction cross sections via surrogate reactions
TL;DR: The surrogate reaction method as mentioned in this paper is an indirect technique for determining cross sections for nuclear reactions that proceed through a well-defined compound nucleus, where the same compound nucleus is produced by an alternate (surrogate) reaction and its decay products measured.
About: This article is published in Nuclear Physics.The article was published on 2007-05-01. It has received 5 citations till now. The article focuses on the topics: Nuclear reaction.
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TL;DR: In this article, the authors present a review of the state-of-the-art in the area of observations, nuclear and atomic physics, and stellar modeling, and the corresponding interplay is illustrated by the general abundance patterns of the elements beyond iron and by the effect of sensitive branching points along the $s$-process path.
Abstract: Nucleosynthesis in the $s$ process takes place in the He-burning layers of low-mass asymptotic giant branch (AGB) stars and during the He- and C-burning phases of massive stars. The $s$ process contributes about half of the element abundances between Cu and Bi in solar system material. Depending on stellar mass and metallicity the resulting $s$-abundance patterns exhibit characteristic features, which provide comprehensive information for our understanding of the stellar life cycle and for the chemical evolution of galaxies. The rapidly growing body of detailed abundance observations, in particular, for AGB and post-AGB stars, for objects in binary systems, and for the very faint metal-poor population represents exciting challenges and constraints for stellar model calculations. Based on updated and improved nuclear physics data for the $s$-process reaction network, current models are aiming at an ab initio solution for the stellar physics related to convection and mixing processes. Progress in the intimately related areas of observations, nuclear and atomic physics, and stellar modeling is reviewed and the corresponding interplay is illustrated by the general abundance patterns of the elements beyond iron and by the effect of sensitive branching points along the $s$-process path. The strong variations of the $s$-process efficiency with metallicity bear also interesting consequences for galactic chemical evolution.
667 citations
Cites methods from "Compound-nuclear reaction cross sec..."
...Another indirect approach for obtaining information on (n, γ) cross sections of unstable nuclei is the surrogate method (Dietrich and Escher, 2007; Escher et al., 2005), which uses the assumption that the reaction of interest proceeds via the formation of a compound nucleus and that formation and…...
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TL;DR: In this paper, the probability of neutron transfer between nuclei at close low-energy collisions has been investigated as a function of the energy of the neutron separation, the energy in a center-of-mass system E and the collision impact parameter.
Abstract: The probability of neutron transfer between nuclei at close low-energy collisions has been investigated as a function of the energy of the neutron separation, the energy in a center-of-mass system E and the collision impact parameter The energy dependence of the neutron transfer cross section in the 6He + 197Au reaction has been explained
14 citations
TL;DR: In this paper, the Schrodinger equation for transfer probability of neutrons at energies in the vicinity of the Coulomb barrier was solved by difference method for external neutrons of a spherical 48Ca nucleus and a deformed 238U nucleus experiencing grazing collisions.
Abstract: Time-dependent Schrodinger equations are solved by difference method for external neutrons of a spherical 48Ca nucleus and a deformed 238U nucleus experiencing grazing collisions. At energies in the vicinity of the Coulomb barrier, the probabilities for the transfer of neutrons are determined as a function of the minimum internuclear distance, deformed nucleus orientation, and quantum numbers of the initial neutron states.
3 citations
Journal Article•
TL;DR: In this paper, the evolution of N/Z in both rapidity regimes with increasing centrality is examined, and the reconstructed ratio for the quasiprojectile is below that of the overall system.
Abstract: Simultaneous measurement of both neutrons and charged particles emitted in the reaction {sup 64}Zn + {sup 64}Zn at 45 MeV/nucleon allows comparison of the neutron to proton ratio at midrapidity with that at projectile rapidity. The evolution of N/Z in both rapidity regimes with increasing centrality is examined. For the completely reconstructed midrapidity material one finds that the neutron to proton ratio is above that of the overall {sup 64}Zn + {sup 64}Zn system. In contrast, the reconstructed ratio for the quasiprojectile is below that of the overall system. This difference provides the most complete evidence to date of neutron enrichment of midrapidity nuclear matter at the expense of the quasiprojectile.
1 citations
TL;DR: In this paper, the Schrodinger equation is solved numerically using the difference approach for outer nucleons of the spherical nuclei 40Ca, 90Zr, and 208Pb upon their grazing collisions.
Abstract: The time-dependent Schrodinger equation is solved numerically using the difference approach for outer nucleons of the spherical nuclei 40Ca, 90Zr, and 208Pb upon their grazing collisions. The neutron and proton transfer probabilities are determined for energies near the Coulomb barrier as functions of the minimum internuclear distance and quantum numbers of initial nucleon states.
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108 citations
TL;DR: Experiments were performed using the (t, p) stripping reaction followed by fission to provide experimental measurements of fission probabilities The neutron-induced fission cross section of the co.
Abstract: Experiments were performed using the (t, p) stripping reaction followed by fission to provide experimental measurements of fission probabilities The neutron-induced fission cross section of the co
89 citations
TL;DR: In this article, the angular momentum and parity distributions for the $(t,p)$ channel were improved by incorporating realistic angular momentum distribution and updating transmission-coefficient values used in the neutron capture and emission contributions that compete with the fission process.
Abstract: Neutron-induced fission cross sections on ${}^{235}\mathrm{U}$ and ${}^{235}{\mathrm{U}}^{m}$ targets in the incident neutron energy range ${E}_{n}=0.1--2.5\mathrm{MeV}$ have been deduced from surrogate ${}^{234}\mathrm{U}(t,pf)$ measurements. The surrogate $(t,pf)$ reaction is used to populate the same compound system as the $(n,f)$ reaction before fission, and modeling is used to compensate for the difference in population mechanisms. The calculations presented in this paper improve on previous results by incorporating realistic angular momentum and parity distributions for the $(t,p)$ channel, and by updating transmission-coefficient values used in the neutron-capture and emission contributions that compete with the fission process. The results are generally reliable within the 10% systematic uncertainties of the $(t,pf)$ data.
76 citations
TL;DR: In this article, the double peaked fission barrier was measured using a statistical model to obtain estimates of the heights and curvatures of one or both peaks of the double-humped barrier.
Abstract: Fission probability distributions have been measured using ($d,pf$), ($t,pf$), ($^{3}\mathrm{He},df$), ($^{3}\mathrm{He},\ensuremath{\alpha}f$), and ($t,\ensuremath{\alpha}f$) reactions to excite a variety of odd-$A$ and odd-odd actinide nuclei. Fission of the residual nuclei $^{229,231}\mathrm{Th}$, $^{231,232,233}\mathrm{Pa}$, $^{234,235,236,237,238,239}\mathrm{Np}$, $^{241}\mathrm{Pu}$, $^{240,241,243,245,247}\mathrm{Am}$, $^{249}\mathrm{Cm}$, and $^{249}\mathrm{Bk}$ was studied. These results and other data available from previous ($d,pf$), ($t,pf$), and ($n,f$) studies are analyzed with a statistical model to obtain estimates of the heights and curvatures of one or both peaks of the double humped fission barrier. Estimates of barrier parameters are obtained for the above nuclei and for $^{233}\mathrm{Th}$, $^{235,237,239}\mathrm{U}$, $^{239,243,245}\mathrm{Pu}$, $^{242,244}\mathrm{Am}$, $^{245,247}\mathrm{Cm}$, and $^{253}\mathrm{Cf}$. Systematic variations of the barrier parameters are discussed.NUCLEAR REACTIONS, FISSION Measured fission probabilities, ${E}^{*}\ensuremath{\le}7.5$ MeV for $^{229,231}\mathrm{Th}$, $^{231,232,233}\mathrm{Pa}$, $^{234,235,236,237,238,239}\mathrm{Np}$, $^{241}\mathrm{Pu}$, $^{240,241,243,245,247}\mathrm{Am}$, $^{249}\mathrm{Cm}$, and $^{249}\mathrm{Bk}$ using ($d,pf$), ($t,pf$), ($^{3}\mathrm{He},df$), ($^{3}\mathrm{He},\ensuremath{\alpha}f$), and ($t,\ensuremath{\alpha}f$) reactions. Deduced properties of the double peaked fission barrier for these nuclei and for $^{233}\mathrm{Th}$, $^{235,237,239}\mathrm{U}$, $^{239,243,245}\mathrm{Pu}$, $^{242,244}\mathrm{Am}$, $^{245,247}\mathrm{Cm}$, and $^{253}\mathrm{Cf}$.
67 citations
TL;DR: In this article, the fission probability distributions of 232, 233, 234 Pa and 231 Th have been measured up to an excitation energy of 15 MeV, using the transfer reactions 232 Th( 3 He, t) 232 Pa, 232 Th ( 3 He,d) 233 Pa, and 232 Th 3 He 4 He) 231 Th.
67 citations