scholarly journals Statistical Hauser-Feshbach theory with width-fluctuation correction including direct reaction channels for neutron-induced reactions at low energies

2016 ◽  
Vol 94 (1) ◽  
Author(s):  
T. Kawano ◽  
R. Capote ◽  
S. Hilaire ◽  
P. Chau Huu-Tai
Keyword(s):  
Direct Reaction ◽  
Low Energies ◽  
Reaction Channels

ISOSPIN SYMMETRY BREAKING AND BRANCHING RATIO IN THE DEUTERON REACTIONS AT VERY LOW ENERGIES

2011 ◽  
Vol 20 (02) ◽  
pp. 576-581 ◽  
Author(s):  
A.I. KILIÇ ◽  
K. CZERSKI ◽  
P. HEIDE ◽  
A. HUKE ◽  
G. RUPRECHT ◽  
...  
Keyword(s):  
Cross Sections ◽  
Nuclear Reactions ◽  
Branching Ratio ◽  
Target Material ◽  
Direct Reaction ◽  
Isospin Symmetry ◽  
Total Cross Sections ◽  
Theoretical Approaches ◽  
Low Energies ◽  
Isospin Symmetry Breaking

The target-material dependence of the neutron-proton branching ratio and breaking of the isospin symmetry in the the 2H(d, n)3He and 2H(d, p)3H reactions at very low deuteron energies have been investigated. Angular distributions and total cross sections of the proton and neutron mirror channels have been measured for nuclear reactions taking place in different metallic environments. For Sr , Li , Na targets, we have found a first evidence for an alteration of the neutron-proton branching ratio and angular anisotropy of the neutron channel. We discuss various theoretical approaches explaining isospin mixing effects both in gas and metallic target experiments including a deuteron polarization in the crystal lattice. Direct reaction contribution has been calculated within the zero range distorted wave Born approximation (DWBA).

scholarly journals Elastic and Inelastic Alpha Transfer in the \(^{16}\)O+\(^{12}\)C Scattering

2021 ◽  
Vol 31 (4) ◽  
Author(s):  
Nguyen Tri Toan Phuc ◽  
Nguyen Hoang Phuc ◽  
Dao Tien Khoa
Keyword(s):  
Cross Section ◽  
Heavy Ion ◽  
Scattering Cross Section ◽  
Transition Strength ◽  
Valence Nucleon ◽  
The Core ◽  
Scattering Cross ◽  
Oscillatory Pattern ◽  
Low Energies ◽  
Reaction Channels

The elastic scattering cross section measured at energies \(E\lesssim 10\) MeV/nucleon for some light heavy-ion systems having two identical cores like \(^{16}\)O+\(^{12}\)C exhibits an enhanced oscillatory pattern at the backward angles. Such a pattern is known to be due to the transfer of the valence nucleon or cluster between the two identical cores. In particular, the elastic \(\alpha\) transfer has been shown to originate directly from the core-exchange symmetry in the elastic \(^{16}\)O+\(^{12}\)C scattering. Given the strong transition strength of the $2^+_1$ state of $^{12}$C and its large overlap with the $^{16}$O ground state, it is natural to expect a similar \(\alpha\) transfer process (or inelastic \(\alpha\) transfer) to take place in the inelastic \(^{16}\)O+\(^{12}\)C scattering. The present work provides a realistic coupled channel description of the \(\alpha\) transfer in the inelastic \(^{16}\)O+\(^{12}\)C scattering at low energies. Based on the results of the 4 coupled reaction-channels calculation, we show a significant contribution of the \(\alpha\) transfer to the inelastic \(^{16}\)O+\(^{12}\)C scattering cross section at the backward angles. These results suggest that the explicit coupling to the \(\alpha\) transfer channels is crucial in the studies of the elastic and inelastic scattering of a nucleus-nucleus system with the core-exchange symmetry.

Dominance of direct reaction channels at deep sub-barrier energies for weakly bound nuclei on heavy targets: The case B8+Pb208

2020 ◽  
Vol 102 (3) ◽  
Author(s):  
A. Pakou ◽  
L. Acosta ◽  
P. D. O'Malley ◽  
S. Aguilar ◽  
E. F. Aguilera ◽  
...  
Keyword(s):  
Direct Reaction ◽  
Weakly Bound ◽  
Reaction Channels

Fresnel interference in point-projection imaging of purple membrane

1995 ◽  
Vol 53 ◽  
pp. 846-847
Author(s):  
X. Zhang ◽  
J. Spence ◽  
W. Qian ◽  
D. Taylor ◽  
K. Taylor
Keyword(s):  
Detection Efficiency ◽  
Mean Free Path ◽  
Purple Membrane ◽  
Unit Cell Dimension ◽  
Experimental Point ◽  
Membrane Thickness ◽  
Low Energies ◽  
Channel Plate ◽  
Point Projection ◽  
Inelastic Mean Free Path

Experimental point-projection shadow microscope (PPM) images of uncoated, unstained purple membrane (PM, bacteriorhodopsin, a membrane protein from Halobacterium holobium) were obtained recently using 100 volt electrons. The membrane thickness is about 5 nm and the hexagonal unit cell dimension 6 nm. The images show contrast around the edges of small holes, as shown in figure 1. The interior of the film is opaque. Since the inelastic mean free path for 100V electrons in carbon (about 6 Å) is much less than the sample thickness, the question arises that how much, if any, transmission of elastically scattered electrons occurs. A large inelastic contribution is also expected, attenuated by the reduced detection efficiency of the channel plate at low energies. Quantitative experiments using an energy-loss spectrometer are planned. Recently Shedd has shown that at about 100V contrast in PPM images of thin gold films can be explained as Fresnel interference effects between different pinholes in the film, separated by less than the coherence width.

Electrical Damage Due to Low Energy Plasma Processing of GaAs Structures

1991 ◽  
Vol 223 ◽  
Author(s):  
Hans P. Zappe ◽  
Gudrun Kaufel
Keyword(s):  
Chemical Processes ◽  
Low Energy ◽  
Electrical Behavior ◽  
Rapid Thermal Anneal ◽  
High Temperature Anneal ◽  
Significant Damage ◽  
Low Energies ◽  
Long Time ◽  
Physical Plasma

ABSTRACTThe effect of numerous plasma reative ion etch and physical milling processes on the electrical behavior of GaAs bulk substrates has been investigated by means of electric microwave absorption. It was seen that plasma treatments at quite low energies may significantly affect the electrical quality of the etched semiconductor. Predominantly physical plasma etchants (Ar) were seen to create significant damage at very low energies. Chemical processes (involving Cl or F), while somewhat less pernicious, also gave rise to electrical substrate damage, the effect greater for hydrogenic ambients. Whereas rapid thermal anneal treatments tend to worsen the electrical integrity, some substrates respond positively to long-time high temperature anneal steps.

Continuous Ozonation of Polycyclic Aromatic Hydrocarbons in Oil/Water-Emulsions and Biodegradation of Oxidation Products

1999 ◽  
Vol 40 (4-5) ◽  
pp. 107-114 ◽  
Author(s):  
A. Kornmüller ◽  
U. Wiesmann
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Biological Treatment ◽  
Reaction Rate ◽  
Oxidation Products ◽  
Direct Reaction ◽  
Biological Degradation ◽  
Polycyclic Aromatic ◽  
Oil Water ◽  
Treatment Step

The continuous ozonation of polycyclic aromatic hydrocarbons (PAH) was studied in a two stage ozonation system followed by serobic biological degradation. The highly condensed PAH benzo(e)pyrene and benzo(k)fluoranthene were oxidized selectiely in synthetic oil/water-emulsions. The influence of the ozone mass transfer gas-liquid on the reaction rate of benzo(k)fluoranthene was studied for process optimization. The dissolved ozone concentration is influenced by temperature to a higher degree than the reaction rate of PAH. In dependence on pH, PAH oxidation occurs by a direct reaction with ozone inside the oil droplets. Two main ozonation products of benzo(e)pyrene were quantified at different retention times during ozonation and their transformation could be shown in the biological treatment step.

scholarly journals Effects of the solar wind termination shock and heliosheath on theheliospheric modulation of galactic and anomalous Helium

2004 ◽  
Vol 22 (8) ◽  
pp. 3063-3072 ◽  
Author(s):  
U. W. Langner ◽  
M. S. Potgieter
Keyword(s):  
Solar Wind ◽  
Cosmic Ray ◽  
Magnetic Polarity ◽  
Termination Shock ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
Cosmic Ray Modulation ◽  
Low Energies ◽  
Solar Wind Termination Shock ◽  
Charge Sign

Abstract. The interest in the role of the solar wind termination shock and heliosheath in cosmic ray modulation studies has increased significantly as the Voyager 1 and 2 spacecraft approach the estimated position of the solar wind termination shock. The effect of the solar wind termination shock on charge-sign dependent modulation, as is experienced by galactic cosmic ray Helium (He++) and anomalous Helium (He+), is the main topic of this work, and is complementary to the previous work on protons, anti-protons, electrons, and positrons. The modulation of galactic and anomalous Helium is studied with a numerical model including a more fundamental and comprehensive set of diffusion coefficients, a solar wind termination shock with diffusive shock acceleration, a heliosheath and particle drifts. The model allows a comparison of modulation with and without a solar wind termination shock and is applicable to a number of cosmic ray species during both magnetic polarity cycles of the Sun. The modulation of Helium, including an anomalous component, is also done to establish charge-sign dependence at low energies. We found that the heliosheath is important for cosmic ray modulation and that its effect on modulation is very similar for protons and Helium. The local Helium interstellar spectrum may not be known at energies

Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und n-Pentylbenzol in der Gasphase / Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes

1979 ◽  
Vol 34 (3) ◽  
pp. 495-501 ◽  
Author(s):  
C. Wesdemiotis ◽  
H. Schwarz ◽  
C. C. Van de Sande ◽  
F. Van Gaever
Keyword(s):  
Hydrogen Exchange ◽  
Closed Shell ◽  
Open Shell ◽  
Molecular Ions ◽  
Exchange Reactions ◽  
Intramolecular Exchange ◽  
Carbon Carbon Bond ◽  
Exchange Processes ◽  
Reaction Channels ◽  
Alkyl Benzenes

Abstract The investigation of several 13carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations.

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