Ground state photoneutron angular distributions in the giant resonance of 16O

1970 ◽  
Vol 48 (14) ◽  
pp. 1635-1648 ◽  
Author(s):  
J. W. Jury ◽  
J. S. Hewitt ◽  
K. G. McNeill
Keyword(s):  
Cross Section ◽  
Ground State ◽  
Giant Resonance ◽  
Flight Path ◽  
Angular Distributions ◽  
Interference Effects ◽  
Experimental Runs ◽  
High Neutron ◽  
High Neutron Energy ◽  
Short Flight

Photoneutron spectra for transitions to the ground state in the giant resonance of 16O were measured with high neutron energy resolution (ΔE ~ 60 keV) at angles of 50, 66, 82, 98, 114, 130, and 146 degrees relative to the direction of the incident bremsstrahlung beam. The spectra at the various angles were measured during successive experimental runs using a single 50 m time-of-flight spectrometer. The different angles were obtained by bending the electron beam relative to the direction of the flight path. Angular normalization was achieved by using a fast neutron monitor located at the end of a short flight path which was always normal to the reaction plane. Legendre coefficients for the angular distributions were extracted as functions of the excitation energy. From the energy dependence of the coefficients, interference effects are evident in the ground state (γ,n) cross section in the region from 17 to 30 MeV.

Cross section for the reaction 16O(γ,n0)15O at giant resonance energies

1969 ◽  
Vol 47 (9) ◽  
pp. 1037-1046 ◽  
Author(s):  
T. A. Khan ◽  
J. S. Hewitt ◽  
K. G. McNeill
Keyword(s):  
Differential Cross Section ◽  
Cross Section ◽  
Ground State ◽  
Giant Resonance ◽  
Theoretical Work ◽  
Laboratory System ◽  
Photoneutron Reaction ◽  
Neutron Spectra ◽  
Recent Theoretical Work ◽  
Resonance Energies

The cross section for that photoneutron reaction in 16O which leaves 15O in its ground state has been measured for photon energies ranging from 17 to 30 MeV, i.e. at energies corresponding to giant resonance excitations in 16O. Time-of-flight methods, yielding resolutions equal to 100 keV at a neutron energy of 6 MeV, were used to measure neutron spectra emitted at an angle of 98° when targets of ordinary and heavy water were irradiated with pulsed bremsstrahlung. The differential cross section at 22.3 MeV excitation was found to be 1.00 ±.05 mb/sr, assuming a photodisintegration cross section at 98° equal to 55.3 μb/sr (laboratory system) for deuterium, this latter value having been derived from calculations which have been substantiated experimentally to within ± 10%. The results are discussed with reference to other photodisintegration experiments and to recent theoretical work.

Possible structure dependence in the Al reaction

1979 ◽  
Vol 57 (11) ◽  
pp. 1949-1951 ◽  
Author(s):  
M. A. M. Shahabuddin ◽  
J. C. Waddington
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ground State ◽  
Angular Distributions ◽  
Structure Dependence ◽  
Analyzing Powers ◽  
The Cross ◽  
Back Angle ◽  
Analyzing Power

In the [Formula: see text] Al reaction at Ep = 17.0 MeV, the cross section and analyzing power angular distributions for several Jπ = 5/2+ states are found to be quite different. Except for the ground state, neither the back angle cross sections nor the analyzing powers for these states can be reproduced by cluster DWBA or CCBA calculations. It is thus inferred that this might be due to the dependence of the reaction on the structure of these states.

scholarly journals Engineering Reflective Metasurfaces with Ising Hamiltonian and Quantum Annealing

2021 ◽  
Author(s):  
Zhen Peng ◽  
Charles Ross ◽  
Qi Jian Lim ◽  
Gabriele Gradoni
Keyword(s):  
Cross Section ◽  
Mobile Networks ◽  
Ground State ◽  
Energy Minimization ◽  
Phase Modulation ◽  
Optimization Problem ◽  
Ground State Solution ◽  
Quantum Annealing ◽  
Adiabatic Evolution ◽  
Annealing Algorithms

<div><div><div><p>We present a novel and flexible method to optimize the phase response of reflective metasurfaces towards a desired scattering profile. The scattering power is expressed as a spin-chain Hamiltonian using the radar cross section formalism. For metasurfaces reflecting an oblique plane wave, an Ising Hamiltonian is obtained. Thereby, the problem of achieving the scattering profile is recast into finding the ground-state solution of the associated Ising Hamiltonian. To rapidly explore the configuration states, we encode the Ising coefficients with quantum annealing algorithms, taking advantage of the fact that the adiabatic evolution efficiently performs energy minimization in the Ising model. Finally, the optimization problem is solved on the D-Wave 2048-qubit quantum adiabatic optimizer machine for binary phase as well as quadriphase reflective metasurfaces. Even though the work is focused on the phase modulation of metasurfaces, we believe this approach paves the way to fast optimization of reconfigurable intelligent surfaces that are mod- ulated in both amplitude and phase for multi-beam generation in and beyond 5G/6G mobile networks.</p></div></div></div>

scholarly journals Photoionisation Cross Sections of Chlorine Atoms and Molecules at 584 Å

1986 ◽  
Vol 39 (5) ◽  
pp. 779 ◽  
Author(s):  
WJ van der Meer ◽  
RJ Butselaar ◽  
CA de Lange
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ground State ◽  
Modulation Method ◽  
Absolute Cross Section ◽  
Molecular Chlorine ◽  
Chlorine Atoms ◽  
Atoms And Molecules ◽  
Ionic States ◽  
State Ionic

A recently developed modulation method is used to obtain cross sections for the photoionisation of ground state neutral to ground state ionic, atomic and molecular chlorine relative to that of the HCl + (X2n 1IZ,3IZ) +-- HCl(XI ~ +) transition at the He Ia wavelength. With the known absolute cross section of the latter process, determined by (e,2e) coincidence spectroscopy, the present ell,periments provide absolute photoionisation cross sections of the CI + epz,l,o) +-- Clep) and Cli (XZ n g, 1IZ,3 IZ) +-- Clz (X I ~ t) transitions. Relative cross sections, previously determined for the transitions to the additional Cl and Clz ionic states accessible with He Ia radiation, are used to obtain absolute cross sections for the Cl+(IDz, ISO) +-- Clep) and Cli(AZnu,1IZ,3IZ, BZ~t) +-- Clz(XI~t) ionisation processes.

scholarly journals Spatial Non-uniformity in Discharges in Low Pressure Helium and Neon

1987 ◽  
Vol 40 (3) ◽  
pp. 383 ◽  
Author(s):  
J Fletcher ◽  
PH Purdie
Keyword(s):  
Monte Carlo Simulation ◽  
Cross Section ◽  
Cross Sections ◽  
Ground State ◽  
Low Pressure ◽  
Photon Flux ◽  
Cross Section Data ◽  
Section Data ◽  
Neon Gas ◽  
Wavelength Distribution

Low current, low pressure, steady state Townsend discharges in helium and neon gas have been investigated using the photon flux technique. Such discharges have been found to exhibit spatial non-uniformity resulting in luminous layers throughout the discharge. The separation and structure of these layers has been investigated experimentally in both gases along with the wavelength distribution of the photon flux. A Monte Carlo simulation of the discharge in neon has been used to gain information on the cross sections necessary to describe these discharges. It is found that direct excitaton of ground state atoms to the resonance level of each gas is less than indicated by some published cross section data.

scholarly journals Preliminary results for the 19F(ρ,α)16O reaction cross section measured at INFN-LNS

2020 ◽  
Vol 227 ◽  
pp. 02009
Author(s):  
T Petruse ◽  
G. L. Guardo ◽  
M. La Cognata ◽  
D. Lattuada ◽  
C. Spitalieri ◽  
...  
Keyword(s):  
Nuclear Reaction ◽  
Cross Section ◽  
Theoretical Models ◽  
Calibration Procedure ◽  
Reaction Rates ◽  
Reaction Cross ◽  
Asymptotic Giant Branch ◽  
Angular Distributions ◽  
Agb Stars ◽  
Indirect Measurements

The 19F(ρ,α)16O reaction is an important fluorine destruction chan- nel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogen-deficient post-AGB star nucleosynthesis. At present, theoretical models overproduce F abundances in AGB stars with re-spect to the observed values, thus calling for further investigation of the nuclear reaction rates involved in the production and destruction of fluorine. In the last years, new direct and indirect measurements improved significantly the knowl- edge of 19F(ρ,α)16O cross section at deeply sub-Coulomb energies (below 0.8 MeV). However, those data are larger by a factor of 1.4 with respect the previ- ous data reported in the NACRE compilation in the energy region 0.6-0.8 MeV. Using the Large High resolution Array of Silicons for Astrophysics (LHASA), we performed a new direct measurement of the 19F(ρ,α)16O. The goal of this experiment is to reduce the uncertainties in the nuclear reaction rate of the 19F(ρ,α)16O reaction. Here, experimental details, the calibration procedure and angular distributions are presented.

Screened Collision-Induced Quantum Interference in Collisional Plasmas

2009 ◽  
Vol 64 (3-4) ◽  
pp. 233-236 ◽  
Author(s):  
Sang-Chul Na ◽  
Young-Dae Jung
Keyword(s):  
Cross Section ◽  
Quantum Interference ◽  
Potential Model ◽  
Collision Cross Section ◽  
Electron Collision ◽  
Particle Collision ◽  
Interference Effects ◽  
Particle Collisions ◽  
Collision System ◽  
Electron Collisions

Abstract The effects of neutral particle collisions on the quantum interference in electron-electron collisions are investigated in collisional plasmas. The effective potential model taking into account the electronneutral particle collision effects is employed in order to obtain the electron-electron collision cross section including the total spin states of the collision system. It is found that the collision effects significantly enhance the cross section. In addition, the collision-induced quantum interference effects are found to be significant in the singlet spin state. It is shown that the quantum interference effects decrease with increasing the thermal energy of the plasma. It is also shown that the quantum interference effects increase with an increase of the collision energy

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