A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

scholarly journals Resonance phenomena in the interaction of fast neutrons with beryllium and aluminium

1947 ◽  
Vol 192 (1028) ◽  
pp. 114-127 ◽  
Keyword(s):  
Energy Level ◽  
Cross Section ◽  
Neutron Energy ◽  
Cross Sections ◽  
Accurate Determination ◽  
Fast Neutrons ◽  
Transmission Method ◽  
The Cross ◽  
Scattering Cross Sections

The total scattering cross-sections of beryllium and aluminium have been measured by a transmission method for neutrons of energies between 0∙35 and 0∙55 MeV and 1∙8 and 4∙0 MeV. Resonances have been found in the scattering by beryllium at a neutron energy of 2∙6 MeV and in the scattering by aluminium at neutron energies of 2∙4 and 2∙9 MeV. It has been shown that the cross-section for the reaction 9 Be ( n , α ) 6 He also has a resonance at 2∙6 MeV, and an accurate determination of the cross-section for this reaction has been made. A discussion is given of the properties of the energy level in 10 Be responsible for the resonances in the case of beryllium.

scholarly journals Elastic Electron Scattering from Methane Molecule in the Energy Range from 50–300 eV

2021 ◽  
Vol 22 (2) ◽  
pp. 647
Author(s):  
Jelena Vukalović ◽  
Jelena B. Maljković ◽  
Karoly Tökési ◽  
Branko Predojević ◽  
Bratislav P. Marinković
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Electron Gun ◽  
Methane Molecule ◽  
Edge Plasma ◽  
Electron Interaction ◽  
Outer Planet ◽  
Elastic Electron

Electron interaction with methane molecule and accurate determination of its elastic cross-section is a demanding task for both experimental and theoretical standpoints and relevant for our better understanding of the processes in Earth’s and Solar outer planet atmospheres, the greenhouse effect or in plasma physics applications like vapor deposition, complex plasma-wall interactions and edge plasma regions of Tokamak. Methane can serve as a test molecule for advancing novel electron-molecule collision theories. We present a combined experimental and theoretical study of the elastic electron differential cross-section from methane molecule, as well as integral and momentum transfer cross-sections in the intermediate energy range (50–300 eV). The experimental setup, based on a crossed beam technique, comprising of an electron gun, a single capillary gas needle and detection system with a channeltron is used in the measurements. The absolute values for cross-sections are obtained by relative-flow method, using argon as a reference. Theoretical results are acquired using two approximations: simple sum of individual atomic cross-sections and the other with molecular effect taken into the account.

scholarly journals Study of the 232Th(n,f) Cross section at NCSR ‘Demokritos’ using Micromegas Detectors

2020 ◽  
Vol 27 ◽  
pp. 106
Author(s):  
Sotirios Chasapoglou ◽  
A. Tsantiri ◽  
A. Kalamara ◽  
M. Kokkoris ◽  
V. Michalopoulou ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Nuclear Reactions ◽  
Detection Efficiency ◽  
High Energy ◽  
Tandem Accelerator ◽  
Line Detector ◽  
Accelerator Driven Systems ◽  
The Masses

The accurate knowledge of neutron-induced fission cross sections in actinides, is of great importance when it comes to the design of fast nuclear reactors, as well as accelerator driven systems. Specifically for the 232Th(n,f) case, the existing experimental datasets are quite discrepant in both the low and high energy MeV regions, thus leading to poor evaluations, a fact that in turn implies the need for more accurate measurements.In the present work, the total cross section of the 232Th(n,f) reaction has been measured relative to the 235U(n,f) and 238U(n,f) ones, at incident energies of 7.2, 8.4, 9.9 MeV and 14.8, 16.5, 17.8 MeV utilizing the 2H(d,n) and 3H(d,n) reactions respectively, which generally yield quasi-monoenergetic neutron beams. The experiments were performed at the 5.5 MV Tandem accelerator laboratory of N.C.S.R. “Demokritos”, using a Micromegas detector assembly and an ultra thin ThO2 target, especially prepared for fission measurements at n_ToF, CERN during its first phase of operations, using the painting technique. The masses of all actinide samples were determined via α-spectroscopy. The produced fission yields along with the results obtained from activation foils were studied in parallel, using both the NeusDesc [1] and MCNP5 [2] codes, taking into consideration competing nuclear reactions (e.g. deuteron break up), along with neutron elastic and inelastic scattering with the beam line, detector housing and experimental hall materials. Since the 232Th(n,f) reaction has a relatively low energy threshold and can thus be affected by parasitic neutrons originating from a variety of sources, the thorough characterization of the neutron flux impinging on the targets is a prerequisite for accurate cross-section measurements, especially in the absence of time-of-flight capabilities. Additional Monte-Carlo simulations were also performed coupling both GEF [3] and FLUKA [4] codes for the determination of the detection efficiency.

scholarly journals Activation cross section of the (n,2n) reaction on Hf isotopes

2019 ◽  
Vol 23 ◽  
pp. 47
Author(s):  
A. Kalamara ◽  
M. Serris ◽  
A. Spiliotis ◽  
D. Sigalos ◽  
N. Patronis ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Reaction Cross Section ◽  
Beam Energy ◽  
Reaction Cross ◽  
Activation Technique ◽  
Incident Neutron ◽  
Activation Cross Section ◽  
Reference Reaction

Cross sections of the 174Hf(n,2n)173Hf and 176Hf(n,2n)175Hf reactions have been experimentally determined relative to the 27Al(n,α)24Na reference reaction at incident neutron energies of 15.3 and 17.1 MeV by means of the activation technique. The irradiations were carried out at the 5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" with monoenergetic neutron beams provided via the 3H(d,n)4He reaction, using a new Ti-tritiated target of 373 GBq activity. In the determination of the 176Hf(n,2n)175Hf reaction cross section the contamination of the 174Hf(n,γ)175Hf and 177Hf(n,3n)175Hf reactions has been taken into account. Moreover, the neutron beam energy has been studied by means of Monte Carlo simulation codes and the neutron flux has been determined via the 27Al(n,α)24Na reference reaction.

scholarly journals Determination of the absorption cross-sections of higher order iodine oxides at 355 nm and 532 nm

2020 ◽  
Author(s):  
Thomas R. Lewis ◽  
Juan Carlos Gómez Martin ◽  
Mark A. Blitz ◽  
Carlos A. Cuevas ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
Time Resolved ◽  
Flight Mass Spectrometry ◽  
Iodine Oxides ◽  
Photo Ionization

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layer and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x = 2, 3, 5, y = 1–12 at λ = 355 nm by combining pulsed laser photolysis of I2/O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross section determinations are those presenting the strongest signals in the mass spectra, where signals containing 4 iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355 nm, IO = (1.2 ± 0.1) ×  10–18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are: σ355 nm, I2O3 

scholarly journals Quantitative Ausmessung des Brom-Affinitätskontinuums und Bestimmung der Detachment-und Attachment-Querschnitte

1970 ◽  
Vol 25 (11) ◽  
pp. 1617-1626 ◽  
Author(s):  
H. Frank ◽  
M. Neiger ◽  
H.-P. Popp
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Electron Affinity ◽  
Elastic Cross Section ◽  
Electron Atom ◽  
Intensity Measurements ◽  
Long Wave ◽  
The Mean ◽  
Intense Electron

Abstract A wall stabilized low-current cylindric arc was used to produce the radiation of the negative Bromine-ions. The radiation consists of an affinity-continuum with a long-wave threshold of 3682 Å, yielding an electron affinity for Bromine of 3.366 eV, and of an intense electron-atom Bremsstrahlung in the visible. Intensity measurements of the continua allow the determination of the photo-detachment-and attachment-cross-sections of Bromine and also the determination of the mean elastic cross-section of electrons against Bromine atoms.

The determination of the cross sections for the reactions 27 Al( n , α ) and 56 Fe( n , p ) for 14 MeV neutrons by an absolute method

1966 ◽  
Vol 292 (1429) ◽  
pp. 180-192 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Standard Error ◽  
Particle Method ◽  
Systematic Errors ◽  
Aluminium Foil ◽  
The Mean ◽  
The Cross ◽  
Experimental Values

Measurements of the cross sections for the reactions 27 Al( n , α ) 24 Na and 56 Fe( n, p ) 56 Mn for neutrons of energy 13.5 ± 0.1 MeV have been made by a radioactivation method. The neutron flux was determined by a variant of the 'associated particle’ method, in which the α -particles produced concurrently with the neutrons from the D + T reaction were estimated in terms of the volume of helium which accumulated when they were brought to rest in an aluminium foil. Cross section values obtained at 13.5 MeV were: for 27 Al( n , α ): 118.1 ± 6.0 mb : for 56 Fe( n, p ): 106.7 ± 4.7 mb. The errors quoted include both the standard error on the mean of the experimental values and an estimate of possible residual systematic errors. The excitation functions for both reactions in the energy region 13.5 to 14.8 MeV have also been investigated, in order to provide secondary cross section values over this range of energies. At 14.8 MeV the values found were: 27 Al( n , α )103.6 ± 5.5 mb; 56 Fe( n, p )96.7 ± 4.5 mb.

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