scholarly journals Charge Transfer, Complexes Formation and Furan Fragmentation Induced by Collisions with Low-Energy Helium Cations

2019 ◽  
Vol 20 (23) ◽  
pp. 6022 ◽  
Author(s):  
Tomasz J. Wasowicz ◽  
Marta Łabuda ◽  
Boguslaw Pranszke
Keyword(s):  
Gas Phase ◽  
Cross Section ◽  
Cross Sections ◽  
Emission Lines ◽  
Charge Transfer Complexes ◽  
Electronic Charge ◽  
Helium Atoms ◽  
Relative Cross Section ◽  
High Level ◽  
Projectile Charge

The present work focuses on unraveling the collisional processes leading to the fragmentation of the gas-phase furan molecules under the He+ and He2+ cations impact in the energy range 5–2000 eV. The presence of different mechanisms was identified by the analysis of the optical fragmentation spectra measured using the collision-induced emission spectroscopy (CIES) in conjunction with the ab initio calculations. The measurements of the fragmentation spectra of furan were performed at the different kinetic energies of both cations. In consequence, several excited products were identified by their luminescence. Among them, the emission of helium atoms excited to the 1s4d 1D2, 3D1,2,3 states was recorded. The structure of the furan molecule lacks an He atom. Therefore, observation of its emission lines is spectroscopic evidence of an impact reaction occurring via relocation of the electronic charge between interacting entities. Moreover, the recorded spectra revealed significant variations of relative band intensities of the products along with the change of the projectile charge and its velocity. In particular, at lower velocities of He+, the relative cross-sections of dissociation products have prominent resonance-like maxima. In order to elucidate the experimental results, the calculations have been performed by using a high level of quantum chemistry methods. The calculations showed that in both impact systems two collisional processes preceded fragmentation. The first one is an electron transfer from furan molecules to cations that leads to the neutralization and further excitation of the cations. The second mechanism starts from the formation of the He−C4H4O+/2+ temporary clusters before decomposition, and it is responsible for the appearance of the narrow resonances in the relative cross-section curves.

scholarly journals VUV and Soft X-ray Spectroscopy of Actinides

2003 ◽  
Vol 802 ◽  
Author(s):  
Clifford G. Olson ◽  
John J. Joyce ◽  
Tomasz Durakiewicz ◽  
Elzbieta Guziewicz ◽  
Martin Butterfield
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Spectral Characteristics ◽  
Electronic States ◽  
Momentum Dependence ◽  
Auger Electrons ◽  
X Ray ◽  
Relative Cross Section ◽  
Initial States ◽  
Valence Bands

ABSTRACTOptical and photoelectron spectroscopies using VUV and Soft X-ray photons are powerful tools for studies of elemental and compound actinides. Large changes in the relative atomic cross sections of the 5f, 6d and sp electrons allow decomposition of the character of the valence bands using photoemission. Resonant enhancement of photoelectrons and Auger electrons at the 5d core threshold further aids the decomposition and gives a measure of elemental specificity. Angle-resolved photoemission can be used to map the momentum dependence of the electronic states. The large changes in relative cross section with photon energy yields further details when the mapping is done at equivalent points in multiple zones. Spectra for well understood rare earth materials will be presented to establish spectral characteristics for known atomic character initial states. These signatures will be applied to the case of USb to investigate f-d hybridization near the Fermi level.

scholarly journals Calculation of harmonic losses and ampacity in low-voltage power cables when used for feeding large LED lighting loads

2014 ◽  
Vol 3 (1) ◽  
pp. 50 ◽  
Author(s):  
N. J. Milardovich ◽  
L. Prevosto ◽  
M. A. Lara
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Low Voltage ◽  
High Harmonic ◽  
Frequency Domain Analysis ◽  
Element Analysis ◽  
Lighting Loads ◽  
Emission Limits ◽  
Phase Conductors ◽  
High Level

A numerical investigation on the harmonic disturbances in low-voltage cables feeding large LED loads is reported. A frequency domain analysis on several commercially-available LEDs was performed to investigate the signature of the harmonic current injected into the power system. Four-core cables and four single-core cable arrangements (three phases and neutral) of small, medium, and large conductor cross sections, with the neutral conductor cross section approximately equal to the half of the phase conductors, were examined. The cables were modelled by using electromagnetic finite-element analysis software. High harmonic power losses (up to 2.5 times the value corresponding to an undistorted current of the same rms value of the first harmonic of the LED current) were found. A generalized ampacity model was employed for re-rating the cables. It was found that the cross section of the neutral conductor plays an important role in the derating of the cable ampacity due to the presence of a high-level of triplen harmonics in the distorted current. The ampacity of the cables should be derated by about 40 %, almost independent of the conductor cross sections. The calculation have shown that an incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severely harmonic emission limits should be defined for LED lamps.

Absorption cross-sections of atmospheric gases for use in aeronomy

1969 ◽  
Vol 47 (10) ◽  
pp. 1823-1834 ◽  
Author(s):  
Robert E. Huffman
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Emission Lines ◽  
Current Status ◽  
Absorption Cross ◽  
Atmospheric Gases ◽  
Ionization Cross ◽  
Atmospheric Absorption ◽  
Ionization Cross Sections

The current status of absorption cross-section measurements for aeronomic use is reviewed. Recommended values for the gases O2, N2, O, and O3 are given at wavelengths where there is strong atmospheric absorption in the 3500–10 Å region. A table of absorption and ionization cross-sections at important solar emission lines is given. The problem of insufficient resolution at some wavelengths is discussed, and information on photolysis products is given where available.

scholarly journals Accurate laser measurements of ozone absorption cross-sections in the Hartley band

2014 ◽  
Vol 7 (8) ◽  
pp. 8067-8100 ◽  
Author(s):  
J. Viallon ◽  
S. Lee ◽  
P. Moussay ◽  
K. Tworek ◽  
M. Petersen ◽  
...  
Keyword(s):  
Gas Phase ◽  
Cross Section ◽  
Cross Sections ◽  
Radiative Forcing ◽  
Nitrogen Monoxide ◽  
Air Pollutant ◽  
Tropospheric Chemistry ◽  
Absorption Cross ◽  
Ozone Absorption ◽  
Hartley Band

Abstract. Ozone plays a crucial role in tropospheric chemistry, is the third largest contributor to greenhouse radiative forcing after carbon dioxide and methane and also a toxic air pollutant affecting human health and agriculture. Long-term measurements of tropospheric ozone have been performed globally for more than 30 years with UV photometers, all relying on the absorption of ozone at the 253.65 nm line of mercury. We have re-determined this cross-section and report a value of 11.27 × 10−18 cm2 molecule−1 with an expanded relative uncertainty of 0.84 %. This is lower than the conventional value currently in use and measured by Hearn in 1961 with a relative difference of 1.8%, with the consequence that historically reported ozone concentrations should be increased by 1.8%. In order to perform the new measurements of cross sections with reduced uncertainties, a system to generate pure ozone in the gas phase together with an optical system based on a UV laser with lines in the Hartley band, including accurate path length measurement of the absorption cell and a careful evaluation of possible impurities in the ozone sample by mass spectrometry and Fourier Transform Infrared spectroscopy was setup. This resulted in new measurements of absolute values of ozone absorption cross sections of 9.48 × 10−18, 10.44 × 10−18, and 11.07 × 10−18 cm2 molecule−1, with relative expanded uncertainties better than 0.6%, for the wavelengths (in vacuum) of 244.062, 248.32, and 257.34 nm respectively. The cross-section at the 253.65 nm line of mercury was determined by comparisons using a Standard Reference Photometer equipped with a mercury lamp as the light source. The newly reported value should be used in the future to obtain the most accurate measurements of ozone concentration, which are in closer agreement with non UV photometry based methods such as the gas phase titration of ozone with nitrogen monoxide.

Diffusion and excitation transfer of metastable helium in normal gaseous helium

1952 ◽  
Vol 213 (1115) ◽  
pp. 506-519 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Elastic Scattering ◽  
Potential Barrier ◽  
Cross Section ◽  
Cross Sections ◽  
Excitation Transfer ◽  
Experimental Results ◽  
Metastable Helium ◽  
Helium Atoms ◽  
Gaseous Helium

The resonance collision of normal and metastable helium atoms has been investigated, and cross-sections calculated for total elastic scattering, diffusion and transfer of excitation. The theoretical diffusion coefficient of metastable atoms in normal helium agrees reasonably well with experimental results of Ebbinghaus and Biondi. As a consequence of a potential barrier in the interaction of the atoms at large separations, the transfer cross-section shows an unusual variation, being small for low collision energies and reaching a maximum of the order of 10 πa 2/0 for collisions about 0.25 eV energy. Comparison is made with experiments by Reynolds.

Numerical Simulation of Push-Bending Process of Aluminum Section Profile

2010 ◽  
Vol 97-101 ◽  
pp. 90-95
Author(s):  
Zhen Zhong Sun ◽  
Sheng Gui Chen ◽  
Ye Jing
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Section Thickness ◽  
Spring Back ◽  
Deformation Degree ◽  
Relative Cross Section ◽  
Bending Process ◽  
Section Profile ◽  
Complicated Part ◽  
Deformation Procedure

The aluminum profile can be formed into a complicated part such as 360º abnormity section circle parts that is difficult to be manufactured by other techniques. A new bending method was proposed for bending process. The push-bending principle, deformation procedure, curvature spring-back, section distortion and wrinkling are studied numerically. All cross-sections for the profile are provided a rather homogenous deformation degree. The curvature value of component and the distortion of section keep high consistence in push-bending process. The wrinkling tendency is reduced with increasing relative cross section thickness t/H and die radius R. The numerical model represents the observed response in the laboratory tests fairly well.

scholarly journals What can we learn from (n,xnγ) cross sections about reaction mechanism and nuclear structure?

2020 ◽  
Vol 239 ◽  
pp. 01023
Author(s):  
Maëlle Kerveno ◽  
Marc Dupuis ◽  
Catalin Borcea ◽  
Marian Boromiza ◽  
Roberto Capote ◽  
...  
Keyword(s):  
Nuclear Structure ◽  
Cross Section ◽  
Cross Sections ◽  
Level Density ◽  
Total N ◽  
Fission Process ◽  
Stringent Test ◽  
High Level ◽  
Scattering Cross Sections

Inelastic (n,n') cross section is a key quantity to accurately simulate reactor cores, and its precision was shown to need significant improvements. To bypass the experimental difficulties to detect neutrons from (n,xn) reaction and to discriminate inelastically scattered neutrons from those following the fission process in case of fissile targets, an indirect but yet powerful method is used: the prompt γ-ray spectroscopy. Along this line, our collaboration has developed the GRAPhEME setup, optimized for actinides, at the GELINA facility to measure partial (n,xn γ) cross sections, from which the total (n,xn) cross section can be inferred. (n,xn γ) experiments with actinides are still particularly challenging, as their structure presents a high level density at low energy, and the competing neutron-induced fission reaction contaminates the γ-energy distribution. New precise measurements of the partial (n,xn γ) cross sections provide a stringent test to theoretical model and offer a way to improve them. This is a path to a better determination of the total inelastic scattering cross sections. In this contribution we discuss modeling aspects of the 238U and 182W (n,n' γ) reactions, also measured with GRAPhEME, using the three codes TALYS, EMPIRE and CoH. We will highlight the needed/expected improvements on reaction modeling and nuclear structure input.

scholarly journals Matching in $$ pp\to t\overline{t}W/Z/h+ $$ jet SMEFT studies

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Reza Goldouzian ◽  
Jeong Han Kim ◽  
Kevin Lannon ◽  
Adam Martin ◽  
Kelci Mohrman ◽  
...  
Keyword(s):  
Standard Model ◽  
Cross Section ◽  
Cross Sections ◽  
Parton Shower ◽  
Inclusive Cross Section ◽  
Relative Impact ◽  
Matrix Elements ◽  
Leading Order ◽  
Relative Cross Section ◽  
The Impact

Abstract In this paper, we explore the impact of extra radiation on predictions of $$ pp\to \mathrm{t}\overline{\mathrm{t}}\mathrm{X},\mathrm{X}=\mathrm{h}/{\mathrm{W}}^{\pm }/\mathrm{Z} $$ pp → t t ¯ X , X = h / W ± / Z processes within the dimension-6 SMEFT framework. While full next-to-leading order calculations are of course preferred, they are not always practical, and so it is useful to be able to capture the impacts of extra radiation using leading-order matrix elements matched to the parton shower and merged. While a matched/merged leading-order calculation for $$ \mathrm{t}\overline{\mathrm{t}}\mathrm{X} $$ t t ¯ X is not expected to reproduce the next-to-leading order inclusive cross section precisely, we show that it does capture the relative impact of the EFT effects by considering the ratio of matched SMEFT inclusive cross sections to Standard Model values, $$ {\sigma}_{\mathrm{SM}\mathrm{EFT}}\left(\mathrm{t}\overline{\mathrm{t}}\mathrm{X}+\mathrm{j}\right)/{\sigma}_{\mathrm{SM}}\left(\mathrm{t}\overline{\mathrm{t}}\mathrm{X}+\mathrm{j}\right)\equiv \mu $$ σ SMEFT t t ¯ X + j / σ SM t t ¯ X + j ≡ μ . Furthermore, we compare leading order calculations with and without extra radiation and find several cases, such as the effect of the operator $$ \left({\varphi}^{\dagger }i{\overleftrightarrow{D}}_{\mu}\varphi \right)\left(\overline{t}{\gamma}^{\mu }t\right) $$ φ † i D ↔ μ φ t ¯ γ μ t on $$ \mathrm{t}\overline{\mathrm{t}}\mathrm{h} $$ t t ¯ h and $$ \mathrm{t}\overline{\mathrm{t}}\mathrm{W} $$ t t ¯ W , for which the relative cross section prediction increases by more than 10% — significantly larger than the uncertainty derived by varying the input scales in the calculation, including the additional scales required for matching and merging. Being leading order at heart, matching and merging can be applied to all operators and processes relevant to $$ pp\to \mathrm{t}\overline{\mathrm{t}}\mathrm{X},\mathrm{X}=\mathrm{h}/{\mathrm{W}}^{\pm }/\mathrm{Z}+\mathrm{jet} $$ pp → t t ¯ X , X = h / W ± / Z + jet , is computationally fast and not susceptible to negative weights. Therefore, it is a useful approach in $$ \mathrm{t}\overline{\mathrm{t}}\mathrm{X} $$ t t ¯ X + jet studies where complete next-to-leading order results are currently unavailable or unwieldy.

scholarly journals Energy Dependence of Total Cross Section for Scattering of Helium Atoms from Isolated Atomic Steps

1970 ◽  
Vol 34 (1) ◽  
pp. 23-31
Author(s):  
Kazi Shamim Sultana ◽  
MZ Hafiz
Keyword(s):  
Total Cross Section ◽  
Energy Dependence ◽  
Cross Section ◽  
Cross Sections ◽  
Helium Atoms ◽  
Surface Steps ◽  
Realistic Interaction ◽  
Academy Of Sciences ◽  
Scattering Cross Sections ◽  
Realistic Potentials

The scattering of helium atoms from growing metal. surfaces is dominated by the interactionbetween incident atoms and isolated surface steps. Understanding the process has been constrainedby the lack of both a realistic interaction potential and a satisfactory method for treating thescattering from a defect, which, because of the height difference of the adjoining terraces, extendsto infinity. We have calculated step scattering cross sections for Cu(001) surface. The calculationsmake use of realistic potentials that reproduce the scattering from low index planes and are createdfrom non-spherical, pairwise repulsive and attractive terms. The step scattering is isolated from thatof adjoining terraces using the linearity of summation of scattering amplitudes in the singlescattering regime. The results for equivalent step and terrace-site potentials give a total crosssection significantly less than the experimental value. The total cross section increases with heliumbeam energy, contrary to the expectations that it is dominated by scattering from the attractive partof the potential. The present work confirms the prediction of our previous study that not the Vander Waals interaction but the hard wall of the scattering potential dominates the step scattering.Key words: Energy dependence; Scattering; Helium atoms; Atomic stepsDOI: 10.3329/jbas.v34i1.5489Journal of Bangladesh Academy of Sciences, Vol.34, No.1, 23-31, 2010

scholarly journals Accurate measurements of ozone absorption cross-sections in the Hartley band

2015 ◽  
Vol 8 (3) ◽  
pp. 1245-1257 ◽  
Author(s):  
J. Viallon ◽  
S. Lee ◽  
P. Moussay ◽  
K. Tworek ◽  
M. Petersen ◽  
...  
Keyword(s):  
Gas Phase ◽  
Cross Section ◽  
Cross Sections ◽  
Radiative Forcing ◽  
Nitrogen Monoxide ◽  
Air Pollutant ◽  
Tropospheric Chemistry ◽  
Absorption Cross ◽  
Ozone Absorption ◽  
Hartley Band

Abstract. Ozone plays a crucial role in tropospheric chemistry, is the third largest contributor to greenhouse radiative forcing after carbon dioxide and methane and also a toxic air pollutant affecting human health and agriculture. Long-term measurements of tropospheric ozone have been performed globally for more than 30 years with UV photometers, all relying on the absorption of ozone at the 253.65 nm line of mercury. We have re-determined this cross-section and report a value of 11.27 x 10−18 cm2 molecule−1 with an expanded relative uncertainty of 0.86% (coverage factor k= 2). This is lower than the conventional value currently in use and measured by Hearn (1961) with a relative difference of 1.8%, with the consequence that historically reported ozone concentrations should be increased by 1.8%. In order to perform the new measurements of cross-sections with reduced uncertainties, a system was set up to generate pure ozone in the gas phase together with an optical system based on a UV laser with lines in the Hartley band, including accurate path length measurement of the absorption cell and a careful evaluation of possible impurities in the ozone sample by mass spectrometry and Fourier transform infrared spectroscopy. This resulted in new measurements of absolute values of ozone absorption cross-sections of 9.48 x 10−18, 10.44 x 10−18 and 11.07 x 10−18 cm2 molecule−1, with relative expanded uncertainties better than 0.7%, for the wavelengths (in vacuum) of 244.06, 248.32, and 257.34 nm respectively. The cross-section at the 253.65 nm line of mercury was determined by comparisons using a Standard Reference Photometer equipped with a mercury lamp as the light source. The newly reported value should be used in the future to obtain the most accurate measurements of ozone concentration, which are in closer agreement with non-UV-photometry based methods such as the gas phase titration of ozone with nitrogen monoxide.

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