A SCHEMATIC MODEL FOR (p, xn) CROSS SECTIONS IN HEAVY ELEMENTS

1956 ◽  
Vol 34 (8) ◽  
pp. 767-779 ◽  
Author(s):  
J. D. Jackson
Keyword(s):  
Cross Sections ◽  
Reaction Cross ◽  
Heavy Elements ◽  
Total Reaction Cross Section ◽  
Schematic Model ◽  
Nuclear Temperature ◽  
A Minor ◽  
Neutron Evaporation ◽  
Average Neutron ◽  
Evaporation Stage

A schematic model for the description of (p, xn) reactions in heavy elements is presented. Reactions are divided into two steps, a prompt multiple collision process, followed by an evaporation stage. The various prompt processes are given by the results of Monte Carlo calculations, while the evaporation processes are described by a simplified model assuming constant nuclear temperatures and only neutron evaporation. The resulting (p, xn), and to a minor degree (p, pxn), cross sections are compared with the experimental data of Bell and Skarsgard (1956) in the energy range up to 100 Mev. With an average neutron binding energy of around 7.3 Mev., a nuclear temperature of about 1.8 Mev., and a nuclear radius of 8.0 × 10−13 cm., a reasonable over-all fit can be made to the data for Pb206, Pb207, Pb208, and Bi209. Characteristic fluctuations in the experimental results for the (p, 2n), (p, 3n), and (p, 4n) reactions for all targets seem to be attributable to variations in the total reaction cross section, and are not reproduced by the present model.

SPALLATION YIELDS FROM HIGH ENERGY PROTON BOMBARDMENT OF HEAVY ELEMENTS

1957 ◽  
Vol 35 (1) ◽  
pp. 21-37 ◽  
Author(s):  
J. D. Jackson
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Heavy Elements ◽  
Collective Effects ◽  
Comparison With Experiment ◽  
Energy Proton ◽  
Stringent Test ◽  
Neutron Evaporation ◽  
Nuclear Processes ◽  
Mev Protons

The Monte Carlo calculations of McManus and Sharp (unpublished) for the prompt nuclear processes occurring upon bombardment of heavy elements by 400 Mev. protons are combined with a description of the subsequent neutron evaporation to determine spallation cross sections for comparison with experiment. The model employed is a schematic one which suppresses the detailed characteristics of individual nuclei, but gives the over-all behavior to be expected. Many-particle and collective effects such as alpha particle emission and fission are ignored. The computed cross sections are presented in a variety of different graphical forms which illustrate quantitatively the qualitative picture of high energy reactions first given by Serber (1947). The calculations are in general agreement with existing data when fission is not an important effect, but the agreement does not imply a very stringent test of the various features of the model.

scholarly journals 7Be and 8B reaction dynamics at Coulomb barrier energies

2018 ◽  
Vol 184 ◽  
pp. 02015
Author(s):  
E. Strano ◽  
M. Mazzocco ◽  
A. Boiano ◽  
C. Boiano ◽  
M. La Commara ◽  
...  
Keyword(s):  
Cross Sections ◽  
Coulomb Barrier ◽  
Reaction Cross Section ◽  
Optical Model ◽  
Reaction Dynamics ◽  
Reaction Cross ◽  
Total Reaction Cross Section ◽  
Weakly Bound ◽  
Total Reaction ◽  
Reaction Cross Sections

We investigated the reaction dynamics induced by the 7Be,8B+208Pb collisions at energies around the Coulomb barrier. Charged particles originated by both the col- lisions were detected by means of 6 ΔE-Eres telescopes of a newly developed detector array. Experimental data were analysed within the framework of the Optical Model and the total reaction cross-sections were compared together and with the 6,7Li+208Pb colli-sion data. According to the preliminary results, 7Be nucleus reactivity is rather similar to the 7Li one whereas the 8B+208Pb total reaction cross section appears to be much larger than those measured for reactions induced by the other weakly-bound projectiles on the same target.

ALPHA-NUCLEUS TOTAL REACTION CROSS SECTION IN THE RIGID PROJECTILE MODEL USING MICROSCOPIC N-α AMPLITUDE

2001 ◽  
Vol 10 (01) ◽  
pp. 43-53 ◽  
Author(s):  
I. AHMAD ◽  
M. A. ABDULMOMEN ◽  
L. A. AL-KHATTABI
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Reaction Cross Section ◽  
Scattering Amplitude ◽  
Reaction Cross ◽  
Glauber Model ◽  
Total Reaction Cross Section ◽  
Total Reaction ◽  
Rigid Projectile ◽  
Optical Limit Approximation

Coulomb modified Glauber model has been applied to calculate α total reaction cross-section for 12 C , 16 O and 40 Ca nuclei in the rigid projectile model using microscopic N-α amplitude which is evaluated in terms of NN scattering amplitude parameters. Using realistic densities for target nuclei and the same input information, we find that the predictions of the rigid projectile approximation for α reaction cross sections are, in general, in better agreement with the experimental data than those of the optical limit approximation.

scholarly journals Large Basis Calculation of Positron?Hydrogen Scattering at Low Energies

1995 ◽  
Vol 48 (4) ◽  
pp. 645 ◽  
Author(s):  
Jim Mitroy
Keyword(s):  
Cross Sections ◽  
Reaction Cross ◽  
Positronium Formation ◽  
Total Reaction Cross Section ◽  
Close Coupling ◽  
Variational Calculations ◽  
Low Energies ◽  
Coupling Approach ◽  
Channel Space ◽  
Basis Calculation

Calculations of low energy positron-hydrogen scattering using the close coupling approach are reported at low energies. The channel space includes nine physical hydrogen and positronium states and in addition twelve hydrogen and positronium pseudo-states. For energies below the positronium formation threshold, phase shifts are reported for J = 0 to 6 and are believed to have an absolute accuracy of 0�0015 radian or better. Elastic scattering and positronium formation cross sections in the Ore gap for the J = 0 and J = 1 partial waves are essentially identical with previous variational calculations. Total elastic and positronium formation cross sections are reported at incident energies below the ionisation threshold. Cross sections for the excitation of the H(n=2), H(n=3) and Ps( n=2) levels are also reported over a restricted energy range, and the total reaction cross section has been computed and compared with experiment.

PRODUCTION OF HEAVY ELEMENTS BY TRANSFER OF MASSIVE CLUSTERS

1992 ◽  
Vol 01 (02) ◽  
pp. 221-247 ◽  
Author(s):  
M. T. MAGDA ◽  
J. D. LEYBA
Keyword(s):  
Experimental Data ◽  
Cross Sections ◽  
Target Nucleus ◽  
Heavy Elements ◽  
Transfer Reactions ◽  
Isotopic Distribution ◽  
Neutron Evaporation ◽  
Massive Clusters ◽  
Multinucleon Transfer Reactions ◽  
Good Agreement

A review of various models of multinucleon transfer reactions leading to heavy elements is given. A mechanism is proposed to describe these reactions based on the assumption that massive clusters are separated from the projectile and captured as a whole by the target nucleus. The modification of the primary isotopic distribution by fission and neutron evaporation is considered. Calculated isotopic distributions and cross sections are in good agreement with experimental data for the production of Z = 96–103 elements. Predictions of the model are used to explore the possibilities of producing transfermium elements by transfer reactions.

scholarly journals Positron - Hydrogen Scattering at Intermediate Energies

1996 ◽  
Vol 49 (5) ◽  
pp. 919 ◽  
Author(s):  
Jim Mitroy
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Maximum Energy ◽  
Reaction Cross ◽  
Impact Excitation ◽  
Total Reaction Cross Section ◽  
Positron Impact ◽  
Close Coupling ◽  
Formation Cross Section ◽  
Intermediate Energies

Calculations of positron–hydrogen scattering at intermediate energies up to a maximum energy of 10 Ryd are performed using the close coupling (CC) approach. A large L2 basis of positron–hydrogen channels (28 states) is supplemented by the Ps(1s), Ps(2s) and Ps(2p) channels. The inclusion of the positronium states in the CC expansion leads to a model which can describe most of the physics of the positron–hydrogen system with a reasonable degree of accuracy. In particular, the positronium formation cross section, the total reaction cross section and the ionisation cross section are all in agreement with experiment. The elastic scattering cross section and the cross sections for positron impact excitation of the H(2s) and H(2p) levels are also reported.

scholarly journals 12C + 16O Elastic Scattering and Total Reaction Cross Sections Near the Coulomb Barrier

1977 ◽  
Vol 30 (2) ◽  
pp. 149 ◽  
Author(s):  
BN Nagorcka ◽  
GD Symons ◽  
PB Treacy ◽  
IC Maclean
Keyword(s):  
Elastic Scattering ◽  
Cross Sections ◽  
Reaction Cross Section ◽  
Optical Potential ◽  
Reaction Cross ◽  
Scattering Data ◽  
Total Reaction Cross Section ◽  
Total Reaction ◽  
Peak Widths ◽  
Reaction Cross Sections

Elastic scattering and total reaction cross sections (via y ray yields) have been measured for 160+ 12C in the c.m. energy range 5� 5-10,0 MeV. Some well-defined structure is observed, with peak widths of order 250 keV. An optical potential which fits peaks in the total reaction cross section is shown to be inadequate to explain the elastic scattering data. Possible reasons for this inconsistency, which imply the need for a more general optical potential, are discussed.

Fermi motion and medium effects on reaction cross sections of 13,14,15B + C, Al at intermediate and high energies

2020 ◽  
Vol 35 (36) ◽  
pp. 2050297
Author(s):  
M. Rashdan ◽  
T. A. Abdel-Karim
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Reaction Cross Section ◽  
Reaction Cross ◽  
Glauber Model ◽  
Total Reaction Cross Section ◽  
Boron Isotopes ◽  
Medium Effects ◽  
Fermi Motion ◽  
Reaction Cross Sections

Analysis of reaction cross sections of [Formula: see text] are performed with Glauber model (GM) including medium modifications arising from Fermi motion and in-medium nucleon–nucleon (NN) total reaction cross section. The density distributions of Boron isotopes are described by a deformed-average Fermi shape, whose proton and neutron radii and deformation parameters are derived from relativistic mean field (RMF), harmonic oscillator (HO) and two-parameter Fermi (2pF). These densities can describe the reaction cross section of Boron isotopes except for [Formula: see text] which is better described by an HO core plus extended Gaussian (HOG) or HO plus a modified Yukawa (HOMY) tail, which depends on the 1n separation energy. It is found that Fermi motion effects dominated at intermediate energy, and they are important to describe the data in addition to in-medium effects. In-medium effects, which are incorporated locally, reduced the reaction cross section by about 3–5% at all energies. [Formula: see text] is confirmed as a one-neutron halo nucleus, where a large extended tail is observed in the extracted HOMY and HOG model densities as well as in the extracted radii, where the matter radius of [Formula: see text] is found to be about 2.92 fm, which is larger than that of [Formula: see text] (2.5 fm) and [Formula: see text] (2.82 fm) predicted using the GM model including Fermi motion and in-medium effects.

scholarly journals ESTIMATION OF THE BREAKUP CROSS-SECTIONS IN 6He + 12C REACTION WITHIN HIGH-ENERGY APPROXIMATION AND MICROSCOPIC OPTICAL POTENTIAL

2011 ◽  
Vol 20 (09) ◽  
pp. 2039-2047 ◽  
Author(s):  
V. K. LUKYANOV ◽  
E. V. ZEMLYANAYA ◽  
K. V. LUKYANOV
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Reaction Cross Section ◽  
High Energy ◽  
Reaction Cross ◽  
Total Reaction Cross Section ◽  
Total Reaction ◽  
Energy Approximation ◽  
Double Folding ◽  
Microscopic Optical Potential

The breakup cross-sections in the reaction 6 He + 12 C are calculated at about 40 MeV/nucleon using the high-energy approximation (HEA) and with the help of microscopic optical potentials (OP) of interaction with the target nucleus 12 C of the projectile nucleus fragments 4 He and 2n. Considering the di-neutron h = 2n as a single particle the relative motion hα wave function is estimated so that to explain both the separation energy of h in 6 He and the rms radius of the latter. The stripping and absorbtion total cross-sections are calculated and their sum is compared with the total reaction cross-section obtained within a double-folding microscopic OP for the 6 He + 12 C scattering. It is concluded that the breakup cross-sections contribute to about 50% of the total reaction cross-section.

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