Cross Sections For Elastic Electron Research Articles

Investigating theoretical and experimental cross sections for elastic electron scattering from isoflurane.

We present a comprehensive analysis of elastic electron scattering from isoflurane in the intermediate energy range of 50-300 eV. This research is motivated by the significant impact of this molecule on global warming effects. We conducted this investigation through experimental measurements using a crossed-beam apparatus and covering a wide angular range from 25 to 125 degrees. Relative differential cross sections (DCSs) were obtained and subsequently normalized on an absolute scale by using the relative flow technique, with argon as the reference gas. These DCS values were then extrapolated and integrated to determine the experimental integral cross sections (ICSs). Additionally, we employed the independent atom model and the screening corrected additivity rule with incorporated Interference effects (IAM-SCAR+I) to calculate the theoretical differential and integral cross-sections. Remarkably, the calculated cross sections align closely with the experimental measurements across the entire energy and angular range. Furthermore, this study involved a comparison of the DCSs for isoflurane with previously published DCS values for two other volatile anesthetics, sevoflurane and halothane.

Cross sections for elastic electron scattering by benzene at low and intermediate energies

We present experimental and theoretical differential cross sections for elastic electron scattering from benzene. The present experimental results are obtained at incident electron energies ranging from 1 to 50 eV and for scattering angles from ${10}^{\ensuremath{\circ}}$ to ${130}^{\ensuremath{\circ}}$. The experimental measurements are compared to available results from 1 to 10 eV and to theoretical results from 10 to 50 eV, both based on the Schwinger multichannel (SMC) method. Different electron scattering calculations are carried out by employing varied basis sets and multichannel coupling schemes. This allows us to (i) obtain relatively converged cross sections with respect to the inclusion of Rydberg excited states, (ii) observe significant variations in the forward scattering as a function of the multichannel coupling scheme, and (iii) explore possible effects stemming from states lying above the ionization threshold. Overall, the agreement between experiments and models is found to be very good to excellent. The remaining discrepancies point out areas in which the SMC method should be improved.

Low-energy elastic electron scattering cross sections of acrylic acid and its methylated derivatives

In the present work we report elastic cross sections for electron scattering from acrylic acid (CH2 = CH-COOH) and its methylated derivatives, crotonic acid (CH3-CH = CH-COOH), methacrylic acid (H2C = C(CH3)COOH) and methyl acrylate (CH2 = CHCOOCH3). The calculations were performed with the Schwinger multichannel method for impact energies up to 15 eV. Two π* shape resonances were found in the component of the integral cross sections (ICSs) for the A″ symmetry of all molecules. The resonance positions obtained for the acrylic acid are compared with existing experimental results for dissociative electron attachment. We investigated the influence of methylation through the comparison of the positions and widths of the shape resonances in the component of the ICS of the A″, and the oscillation patterns in the differential cross sections of all molecules. We also present the momentum transfer cross section for electron scattering from all molecules studied.

Ramsauer\u2013Townsend minimum in electron scattering from CF_4: modified effective range analysis

Elastic cross sections for electron scattering on tetrafluoromethane (CF_4) from 0 up to 5 eV energy are analyzed using semi-analytical approach to the modified effective range theory (MERT). It is shown that energy and angular variations of differential, integral and momentum transfer cross sections can be parameterized accurately by six MERT coefficients up to the energy region of the resonant scattering. In particular, the model is used to determine the depth and the position of the Ramsauer–Townsend minimum as well as the s-wave scattering length. Moreover, we investigate the influence of the dipole polarizability value on the predictions of present model. To further validate our approach, the elastic data are combined with the Born-dipole cross sections for vibrational excitations as the input data for Monte Carlo simulation of electron swarm coefficients.Graphic

Cancellation of Leading Contributions to Radiative Corrections to the Cross Section for Elastic Electron–Proton Scattering in Experiments Devoted to Measuring the Proton Charge Radius

A cancellation of leading contributions to radiative corrections to the cross section for elastic electron–proton scattering for experiments devoted to measuring the proton charge radius is studied. The cancellations occur in the contribution of electron interaction with the electromagnetic field. It is shown that, under experimental conditions where the recoil proton is detected, there occurs cancellation in the one-loop approximation not only for the terms containing large logarithms but also for the constants at these logarithms and that a nonzero electron contribution to radiative corrections appears starting from terms that are proportional to $$Q/E$$ , where $$Q$$ is the momentum transfer and $$E$$ is the electron energy in the rest frame of the primary proton.

Integral cross sections for elastic electron scattering by methane molecule

SynopsisWe have performed a combined experimental and theoretical study of electron elastic differential and integral cross sections from methane molecule (CH4) in the intermediate energy range. Data have been compared with available data sets in the literature as well as with recommended data set [Song et al J. Phys. Chem. Ref.Data 44 023101 (2015)].

Experimental and theoretical cross sections for elastic electron scattering from zinc

We report on experimental elastic differential and integral cross sections for electron scattering from zinc. The energy range of these measurements is 10--100 eV, while the scattered electron angular range in the differential cross-section data is ${10}^{\ensuremath{\circ}}\text{--}{150}^{\ensuremath{\circ}}$. We also supplement our measured data with applications of our optical potential and relativistic optical potential approaches to this problem. Where possible, the present results are compared against those from earlier B-spline R-matrix [O. Zatsarinny and K. Bartschat, Phys. Rev. A 71, 022716 (2005)] and convergent close coupling [D. V. Fursa, I. Bray, R. Panajotovi\ifmmode \acute{c}\else \'{c}\fi{}, D. \ifmmode \check{S}\else \v{S}\fi{}evi\ifmmode \acute{c}\else \'{c}\fi{}, V. Pej\ifmmode \check{c}\else \v{c}\fi{}ev, D. M. Filipovi\ifmmode \acute{c}\else \'{c}\fi{}, and B. P. Marinkovi\ifmmode \acute{c}\else \'{c}\fi{}, Phys. Rev. A 72, 012706 (2005)] computations. Good overall qualitative accord is typically observed.

Interference in electron–molecule elastic scattering

General formulas describing the multiple scattering of electron by polyatomic molecules have been derived within the framework of the model of non-overlapping atomic potentials. These formulas are applied to different carbon molecules, both for fixed-in-space and randomly oriented molecules. The molecular continuum wave function is represented as a plane wave plus a linear combination of the Green’s functions for free motion and the derivatives of these functions. Far from the target the electron spherical waves interfere as in the case of the Young’s double slits experiment. This interference manifests itself as diffraction oscillations in the differential and total cross sections for elastic electron scattering. The amplitude of electron scattering by a molecule is defined by the phase shifts for each of the atoms forming the target and its geometry. The numerical calculation of the scattering amplitude in closed form (rather than in the form of S-matrix expansion) is reduced to solving a system of algebraic equations. The number of atoms in a molecule and the atomic phase shifts for the orbital angular momenta included in the calculation define the number of equations.

Electrons and positrons elastic collisions with pyrimidine and tetrahydrofuran

The present study shows results of theoretical calculations for positrons and electrons elastic scattering from pyrimidine and tetrahydrofuran over a broad energy range. The work has been motivated by the fact that very few experimental data exist for most of the nucleobases in particular for positrons. Concerning the theoretical tool, we have made improvements on the method using the independent atom-screened additivity rule by calculating differential elastic cross sections and its integrals in a straightforward manner. Moreover, elastic scattering of electrons and positrons by atoms of the biomolecule was evaluated by means of relativistic (Dirac) partial wave analysis. Results concerning the total elastic cross sections (ECS) for electrons and positrons are shown and discussed in comparison to existing experimental and theoretical data. As central result, our electron ECS from pyrimidine and tetrahydrofuran are in good agreement with existing experimental data in the range 10 eV to 1 keV. Another important improvement concerns our data for positron; as it will be shown in the present study, our positron ECS can be considered as a correction of existing data in the literature using the independent atom screened additivity rule. Parameterization of our electron and positron total ECS, elastic mean free paths, first elastic transport cross sections and first elastic transport mean free paths are provided for pyrimidine and tetrahydrofuran in the energy range 10 eV to 100 keV.

Elastic electron scattering from formamide

Differential cross sections for elastic electron scattering by formamide (NH2CHO) were measured in the 30–800 eV and 10°–120° ranges. The angular distribution of scattered electrons was obtained using a crossed electron beam-molecular beam geometry. The relative flow technique was applied to normalize our data. Integral and momentum-transfer cross sections were derived from the measured differential cross sections. Theoretical results in the framework of the independent-atom model at the static-exchange-polarization plus absorption level of approximation are also given. The present measured and calculated results are compared with those available in the literature showing a generally good agreement.

Absolute differential cross sections for elastic electron scattering from trifluoromethane and 1,1 difluoroethylene

Differential cross sections for elastic scattering of electrons from Trifluoromethane and 1,1 Difluoroethylene have been measured in the energy range 30–500eV using a crossed-beam, high resolution electron spectrometer. The measured cross sections have been put on an absolute scale using the relative flow technique. The differential cross sections were extrapolated to zero and 180° in the forward and backward angles respectively using tenth order Legendre polynomials. The total and momentum transfer cross sections have been determined by integrating the differential cross sections over all angles. A theoretical calculation using independent atom model with static, exchange and polarization potentials is presented. The measured cross sections are compared with theoretical and other experimental data wherever available. It is seen that the theoretical calculation based on the independent atom model agrees well with our experimental data at high energies while at low and intermediate energies the model proves inadequate.

Resonance effects in elastic cross sections for electron scattering on pyrimidine: Experiment and theory.

We measured differential cross sections for elastic (rotationally integrated) electron scattering on pyrimidine, both as a function of angle up to 180(∘) at electron energies of 1, 5, 10, and 20 eV and as a function of electron energy in the range 0.1-14 eV. The experimental results are compared to the results of the fixed-nuclei Schwinger variational and R-matrix theoretical methods, which reproduce satisfactorily the magnitudes and shapes of the experimental cross sections. The emphasis of the present work is on recording detailed excitation functions revealing resonances in the excitation process. Resonant structures are observed at 0.2, 0.7, and 4.35 eV and calculations for different symmetries confirm their assignment as the X̃(2)A2, Ã(2)B1, and B̃(2)B1 shape resonances. As a consequence of superposition of coherent resonant amplitudes with background scattering the B̃(2)B1 shape resonance appears as a peak, a dip, or a step function in the cross sections recorded as a function of energy at different scattering angles and this effect is satisfactorily reproduced by theory. The dip and peak contributions at different scattering angles partially compensate, making the resonance nearly invisible in the integral cross section. Vibrationally integrated cross sections were also measured at 1, 5, 10 and 20 eV and the question of whether the fixed-nuclei cross sections should be compared to vibrationally elastic or vibrationally integrated cross section is discussed.

Hyperfine-changing transitions in 3He II and other one-electron ions by electron scattering

SynopsisWe present short-range phase shifts and spin-exchange cross sections for elastic electron scattering from selected one-electron ions from He+ to Fe25+. The results are explained in a simple physical picture based on quantum defect theory.

Absolute differential cross sections for elastic electron scattering from small biomolecules

The results of an experimental investigation of electrons colliding with a set of biomolecules that are assumed to be analogues of the building blocks of DNA (furan, 3- hydroxytetrahydrofuran and pyrimidine) and proteins (formamide, N-methylformamide) are presented. Absolute differential cross sections at medium incident electron energies 40 eV- 300 eV are presented and compared for these different targets. The experimental results are also compared with available calculations, based on the corrected form of independent atom model and show good agreement over the energy range studied.

Modified effective range analysis of electron scattering from krypton

The elastic cross sections for electron scattering on krypton from zero energy up to 10 eV have been analyzed by the modified effective range method. A simple model based on the analytical solution of the Schrödinger equation with the polarization potential using explicitly determined scattering phase shifts for the three lowest partial waves describes the elastic differential, integral and momentum transfer cross sections up to the energy threshold of the first inelastic process well. In detail, the contribution of the long-range polarization potential to the scattering phase shift is exactly expressed, while the contribution of the short-range effects is modelled by simple quadratic expressions (the effective range expansions). The effective range parameters are determined empirically by comparison with the latest experimental differential cross sections. Presently, the calculated integral and momentum transfer cross sections are validated against numerous electron scattering experiments and the most recent quantum-mechanical theories. To complete the picture, the two-term Boltzmann analysis is employed to determine the electron transport coefficients; the agreement with the electron swarm experimental data is found to be very good.

Calculation of Average Collision Cross Sections of Low Energy for Elastic e-Ar Scattering Using MERT4

Cross sections in the very low energy range are also represented by the modified effective-range theory (MERT) for low-energy electron scattering from the rare gas (argon). Simulations using published (theoretical) phase shifts indicate that extended versions of the standard effective-range theory with four adjustable parameters are required to give an adequate description of the phase shifts for argon. A four-parameter MERT fit gives a good representation of a recent electron–argon (e-Ar) total cross section experiment at energies less than 10.0 eV. Cross section Q(l) (E) for collision in dilute gases is given for any order l. Here Q(l) (E) are presented for l = 1. . .6. We present calculations for the elastic cross sections for electron scattering from argon. The improvement in the agreement between our theoretical calculations and the experimental measurements in the case of argon in scattering calculations are showed. Differential scattering experiments have been performed for the systems e-Ar in the energy range E = 0–10 eV and the angular range θ = 0–20° using a crossed-beam arrangement. Differential and integrated cross sections for the elastic scattering of low- and intermediate-energy (0–50 eV) electrons by argon atoms are calculated. For each impact energy, the phase shifts of the lower partial waves are obtained exactly by numerical integration of the radial equation. Transport coefficients of argon plasma are requested exactly, which is why we calculated the average collision cross sections for s = 1. . .11, l = 1. . .6.

Momentum transfer cross sections for the heavy noble gases

We present momentum transfer cross sections for elastic electron scattering from argon, krypton and xenon atoms over the energy range from zero to 1 keV. These have been calculated using the Dirac equations with a relativistic complex optical potential which includes polarization of the target atom by the incident electron and allows for the absorption of some of the incident electron flux into channels representing excitation and ionization of the atom. In order to aid in plasma modelling calculations, we provide simple analytic fits to these cross sections as well as to the elastic scattering cross sections. Comparisons are made with previous experimental and theoretical results.

Peculiarities of elastic scattering of intermediate-energy electrons related to their capture at quasi-stationary levels of an atom in a continuous spectrum

A theoretical model of electron scattering on an atom is constructed to study elastic atomic scattering of intermediate-energy electrons. The proposed model is based upon the combined Mensing potential with two spheres of atomic electrons, which admits analytical solutions of the radial Schrobinger equation. A procedure for matching the parameters of this scatterer to an approximate electrostatic potential of an atom in the form of a screened Coulomb potential has been determined. The screening radius of the latter potential has been calculated proceeding from the properties corresponding to the Thomas-Fermi method. A model of a scatterer determined according to the aforementioned procedure can be used to calculate the energy dependence of the cross section of elastic electron scattering on some atoms with s, p, and d shells representing elements neighboring zirconium. The main result is the establishment of factors responsible for the appearance of maxima on the energy dependences of the cross section of elastic electron scattering. These maxima are related to the resonant trapping of impinging electrons by quasi-stationary levels in a continuous spectrum.

Low-energy elastic electron scattering by acetaldehyde

We report results from a combined experimental and computational study of low-energy electron interactions with acetaldehyde in the gas phase. Differential cross sections for elastic electron scattering were measured at selected incident energies from 1 to 50 eV, while corresponding first-principles calculations were carried out up to 30 eV. Integral and momentum-transfer cross sections were derived from the angle-differential data. The role of resonances in the scattering is examined and comparison is made to previous results for acetaldehyde and for its analogs, formamide and formic acid.

Rescattering photoelectron spectroscopy of small molecules

We have measured angle-resolved rescattering photoelectron spectra of three small molecules (O2, CO2, and C2H4) using intense near-infrared laser pulses at several laser intensities. Based on the factorization formula for rescattering processes, we have extracted, from the electron spectra, the field-free differential cross sections of elastic electron scattering by the molecular ions. The detail of the extraction procedure is described. The experimentally extracted differential cross sections are compared with theoretical calculations of the field-free differential cross sections. Fairly good agreement between the experimentally extracted and theoretically calculated DCSs for wide range of the collision momentum indicates the validity of the present extraction procedure for the molecules.