scholarly journals Tuning the Re/Os Clock: Stellar-Neutron Cross Sections

2009 ◽  
Vol 26 (3) ◽  
pp. 250-254 ◽  
Author(s):  
A. Mengoni ◽  
M. Mosconi ◽  
K. Fujii ◽  
F. Käppeler ◽  
Keyword(s):  
Cross Sections ◽  
Reaction Rates ◽  
Experimental Information ◽  
Nuclear Model ◽  
Time Duration ◽  
Model Calculations ◽  
Neutron Time ◽  
Neutron Cross Sections ◽  
Capture Cross Sections

AbstractThe neutron-capture cross sections of 186,187Os have been recently measured at the CERN neutron time-of-flight facility n_TOF for an improved evaluation of the Re/Os cosmo-chronometer. This experimental information was complemented by nuclear model calculations for obtaining the proper astrophysical reaction rates at s-process temperatures. The calculated results and their implications for the determination of the time-duration of nucleosynthesis during galactic chemical evolution is discussed.

scholarly journals A systematic study of proton capture reactions in the Se-Sn region relevant to p-process nucleosynthesis

2019 ◽  
Vol 11 ◽  
Author(s):  
S. Harissopulos ◽  
P. Demetriou ◽  
S. Galanopoulos ◽  
G. Kriembardis ◽  
M. Kokkoris ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Nuclear Physics ◽  
Nuclear Reactions ◽  
Reaction Network ◽  
Reaction Rates ◽  
Compton Suppression ◽  
Experimental Information ◽  
Systematic Investigation ◽  
Model Calculations

The synthesis of the so-called ρ nuclei, i.e. a certain class of proton rich nuclei that are heavier than iron, requires a special mechanism known as ρ process. This process consists of various nucleosynthetic scenaria. In some of them proton and alpha-capture reactions are strongly involved, p-process nucleosynthesis is assumed to occur in the Oxygen/Neon rich layers of type II supernovae during their explosion, ρ nuclei are typically 10-100 times less abundant than the corresponding more neutron-rich isotopes. The prediction of their abundances is one of the major puzzles of all models of p-process nucleosynthesis. Until now all these models are capable of reproducing these abundances within a factor of 3. However, they all fail in the case of the light ρ nuclei with A<100. The observed discrepancies could be attributed to uncertainties in the pure "astrophysical" part of the p-process modelling. However, they could also be the result of uncertainties in the nuclear physics data entering the corresponding abundance calculations. In order to perform these calculations the cross sections of typically 10000 nuclear reactions of an extended reaction network involving almost 1000 nuclei from A=12 to 210 are used as input data. Such a huge amount of experimental cross section data are not available. Hence, all extended network calculations rely almost completely on cross sections predicted by the Hauser-Feshbach (HF) theory. It is therefore of paramount importance, on top of any astrophysical model improvements, to test also the reliability of the HF calculations, i.e. to investigate the uncertainties associated with the evaluation of the nuclear properties, like nuclear level densities and nucleon-nucleus potentials, entering the calculations. Until now, this check has been hindered significantly by the fact that in the Se-Sn region there has been scarce experimental information on cross sections at astrophysically relevant energies. In the present work, a systematic investigation of (p,7) cross sections of nuclei from Se to Sb is presented for the first time. The in-beam cross section measurements reported were carried out at energies relevant to p-process nucleosynthesis, i.e. from 1.4 to 5 MeV. The experiments were performed by using either an array of 4 HPGe detectors of 100% relative efficiency shielded with BGO crustals for Compton suppression, or a 4π Nal summing detector. The resulting cross sections, astrophysical S-factors and reaction rates of more than 10 nuclear reactions are compared with the predictions of various statistical model calculations.

Determination of capture cross sections for as-grown electron traps in HfO2∕HfSiO stacks

2006 ◽  
Vol 100 (9) ◽  
pp. 093716 ◽  
Author(s):  
C. Z. Zhao ◽  
J. F. Zhang ◽  
M. B. Zahid ◽  
B. Govoreanu ◽  
G. Groeseneken ◽  
...  
Keyword(s):  
Cross Sections ◽  
Capture Cross ◽  
Electron Traps ◽  
Capture Cross Sections

Analytical Determination of Generation-Recombination Rate In Amorphous Silicon

1986 ◽  
Vol 70 ◽  
Author(s):  
Jože Furlan ◽  
Slavko Amon
Keyword(s):  
Analytical Solution ◽  
Amorphous Silicon ◽  
Cross Sections ◽  
Recombination Rate ◽  
Exponential Model ◽  
Localized States ◽  
Analytical Determination ◽  
Capture Cross ◽  
Capture Cross Sections

ABSTRACTA general expression for generation-recombination rate in a-Si based on classical SRH theory including different electron and hole capture cross-sections for donor-like and acceptor-like centers inside the mobility gap is derived. Applying appropriate approximations and two-exponential model for localized states distribution two methods of analytical solution are presented and discussed.

The Taco Experiment for the Determination of Integral Neutron Cross-Sections in a Fast Reactor

1983 ◽  
pp. 175-177 ◽  
Author(s):  
A. Cricchio ◽  
R. Ernstberger ◽  
L. Koch ◽  
R. Wellum
Keyword(s):  
Cross Sections ◽  
Fast Reactor ◽  
Integral Neutron ◽  
Neutron Cross Sections

The (??SF) Method - Determination of Radiative Neutron Capture Cross Sections for Unstable Nuclei

2011 ◽  
Vol 59 (2(3)) ◽  
pp. 1713-1716 ◽  
Author(s):  
H. Utsunomiya ◽  
S. Goriely ◽  
H. Akimune ◽  
H. Harada ◽  
F. Kitatani ◽  
...  
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Capture Cross ◽  
Unstable Nuclei ◽  
Radiative Neutron ◽  
Radiative Neutron Capture ◽  
Capture Cross Sections

Determination of Intermediate Energy Neutron Cross Sections Using the Ramsauer Model

2006 ◽  
Vol 152 (3) ◽  
pp. 320-324
Author(s):  
M. Azam ◽  
R. S. Gowda ◽  
S. Ganesan
Keyword(s):  
Cross Sections ◽  
Intermediate Energy ◽  
Energy Neutron ◽  
Neutron Cross Sections

(n, p) Reaction Cross Sections Calculations of Some Stellar Iron Group Fusion Materials

2017 ◽  
Vol 6 (1) ◽  
pp. 18-25 ◽  
Author(s):  
Tarik Siddik
Keyword(s):  
Cross Sections ◽  
Reaction Cross ◽  
Nuclear Model ◽  
Incident Neutron ◽  
Excitation Functions ◽  
Model Calculations ◽  
Model Code ◽  
Group Target ◽  
Reaction Cross Sections ◽  
Group Fusion

The excitation functions for (n, p) reactions from reaction threshold to 24 MeV on some important iron (Fe) group target elements (20 ≤ Z ≤ 28) for astrophysical (n, p) reactions such as Si, Ca, Sc, Ti, Cr, Fe, Co and Ni were calculated using TALYS-1.0 nuclear model code. The new calculations on the excitation functions of 28Si(n, p)28Al, 29Si(n, p)29Al, 42Ca(n, p)42K, 45Sc(n, p)45Ca, 46Ti(n, p)46Sc, 53Cr(n, p)53V, 54Fe(n, p)54Mn, 57Fe(n, p)57Mn, 59Co(n, p)59Fe, 58Ni(n, p)58Co and 60Ni(n, p)60Co reactions have been carried out up to 24 MeV incident neutron energy. In these calculations, the compound nucleus and pre-equilibrium reaction mechanism studied extensively. According to these calculations, we assume that these model calculations can be applied to some heavy elements, ejected into interstellar medium by dramatic supernova events.

scholarly journals Determination of interface trap capture cross sections using three-level charge pumping

1990 ◽  
Vol 11 (8) ◽  
pp. 339-341 ◽  
Author(s):  
N.S. Saks ◽  
M.G. Ancona
Keyword(s):  
Cross Sections ◽  
Interface Trap ◽  
Capture Cross ◽  
Charge Pumping ◽  
Capture Cross Sections
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