Electron-impact excitation of the low-lying electronic states of HCN

NASA Technical Reports Server (NTRS)

Chutjian, A.; Tanaka, H.; Srivastava, S. K.; Wicke, B. G.

1977-01-01

The first study of the low-energy electron-impact excitation of low-lying electronic transitions in the HCN molecule is reported. Measurements were made at incident electron energies of 11.6 and 21.6 eV in the energy-loss range of 3-10 eV, and at scattering angles of 20-130 deg. Inelastic scattering spectra were placed on the absolute cross-section scale by determining first the ratio of inelastic-to-elastic scattering cross sections, and then separately measuring the absolute elastic scattering cross section. Several new electronic transitions are observed which are intrinsically overlapped in the molecule itself. Assignments of these electronic transitions are suggested. These assignments are based on present spectroscopic and cross-sections measurements, high-energy electron scattering spectra, optical absorption spectra, and ab initio molecular orbital calculations.

Electron scattering by highly polar molecules. III - CsCl

NASA Technical Reports Server (NTRS)

Vuskovic, L.; Srivastava, S. K.

1981-01-01

Utilizing a crossed electron-beam-molecular-beam scattering geometry, relative values of differential electron scattering cross sections for cesium chloride at 5 and 20 eV electron impact energies and at scattering angles between 10 and 120 deg have been measured. These relative cross sections have been normalized to the cross section at 15 deg scattering angle calculated by the hybrid S-matrix technique. In the angular range between 0 and 10 deg and between 120 and 180 deg extrapolations have been made to obtain integral and momentum transfer cross sections. An energy-loss spectrum is also presented which gives various spectral features lying between the 4 and 10 eV regions in CsCl.

Cross-sectional TEM specimen preparation for W/B{sub 4}C multilayer sample using FIB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mondal, Puspen, E-mail: puspen@rrcat.gov.in; Pradhan, P. C.; Tiwari, Pragya

2016-05-23

A recent emergence of a cross-beam scanning electron microscopy (SEM)/focused-ion-beam (FIB) system have given choice to fabricate cross-sectional transmission electron microscopy (TEM) specimen of thin film multilayer sample. A 300 layer pair thin film multilayer sample of W/B{sub 4}C was used to demonstrate the specimen lift-out technique in very short time as compared to conventional cross-sectional sample preparation technique. To get large area electron transparent sample, sample prepared by FIB is followed by Ar{sup +} ion polishing at 2 kV with grazing incident. The prepared cross-sectional sample was characterized by transmission electron microscope.

Electron collisions with ethylene

NASA Astrophysics Data System (ADS)

Panajotovic, R.; Kitajima, M.; Tanaka, H.; Jelisavcic, M.; Lower, J.; Campbell, L.; Brunger, M. J.; Buckman, S. J.

2003-04-01

We have measured absolute elastic scattering and vibrational excitation cross sections for electron impact on ethylene. The experimental data have been obtained on two different crossed-beam electron spectrometers and they cover the energy range from 1 to 100 eV and scattering angles between 10° and 130°. Both differential (in angle) and energy-dependent cross sections have been measured. The differential cross sections have also been analysed using a molecular phase shift analysis technique in order to derive the integral elastic and elastic momentum transfer cross sections. Comparison is made with earlier data, where available, and also with a number of recent theoretical calculations.

Electron impact cross sections for the 2,2P state excitation of lithium

NASA Technical Reports Server (NTRS)

Vuskovic, L.; Trajmar, S.; Register, D. F.

1982-01-01

Electron impact excitation of the 2p 2P state of Li was studied at 10, 20, 60, 100, 150 and 200 eV. Relative differential cross sections in the angular range 3-120 deg were measured and then normalized to the absolute scale by using the optical f value. Integral and momentum transfer cross sections were obtained by extrapolating the differential cross sections to 0 deg and to 180 deg. The question of normalizing electron-metal-atom collision cross sections in general was examined and the method of normalization to optical f values in particular was investigated in detail. It has been concluded that the extrapolation of the apparent generalized oscillator strength (obtained from the measured differential cross sections) to the zero momentum transfer limit with an expression using even powers of the momentum transfer and normalization of the limit to the optical f value yields reliable absolute cross sections.

Electron impact ionization in plasma technologies; studies on atomic boron and BN molecule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, Foram M., E-mail: foram29@gmail.com; Joshipura, K. N., E-mail: knjoshipura22@gmail.com; Chaudhari, Asha S., E-mail: ashaschaudhari@gmail.com

2016-05-06

Electron impact ionization plays important role in plasma technologies. Relevant cross sections on atomic boron are required to understand the erosion processes in fusion experiments. Boronization of plasma exposed surfaces of tokomaks has proved to be an effective way to produce very pure fusion plasmas. This paper reports comprehensive theoretical investigations on electron scattering with atomic Boron and Boron Nitride in solid phases. Presently we determine total ionization cross-section Q{sub ion} and the summed-electronic excitation cross section ΣQ{sub exc} in a standard quantum mechanical formalism called SCOP and CSP-ic methods. Our calculated cross sections are examined as functions of incidentmore » electron energy along with available comparisons.« less

Cross sections for the dissociative attachment of electrons to NO

NASA Technical Reports Server (NTRS)

Krishnakumar, E.; Srivastava, S. K.

1988-01-01

Cross sections for the production of O(-) by electron attachment to NO are reported. It is found that the maximum value of the cross section is about 52 percent higher than the measurement of Rapp and Briglia (1965). Cross sections for the process of polar dissociation, e + NO yields N(+) + O(_), have also been measured, and the threshold energy for this process has been obtained.

Eikonal approximation for proton-helium electron-capture processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, K.; Toshima, N.; Ishihara, T.

1985-09-01

We calculate the capture cross sections for H/sup +/+He..-->..H+He/sup +/, treating the passive electron explicitly in a distorted-wave formalism based on the eikonal approximation. It is found that the shape of the differential cross sections is influenced considerably by the interaction between the passive electron and the incident proton, while the integrated cross sections are much less sensitive to that. The differential cross section at 293 keV agrees well with the experimental data except at extremely small scattering angles. The forward peak is reproduced well at higher energies. The integrated cross sections are in excellent agreement with experiments for themore » incident energy above 250 keV.« less

Electron-exchange and quantum screening effects on the Thomson scattering process in quantum Fermi plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Gyeong Won; Jung, Young-Dae; Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180-3590

2013-06-15

The influence of the electron-exchange and quantum screening on the Thomson scattering process is investigated in degenerate quantum Fermi plasmas. The Thomson scattering cross section in quantum plasmas is obtained by the plasma dielectric function and fluctuation-dissipation theorem as a function of the electron-exchange parameter, Fermi energy, plasmon energy, and wave number. It is shown that the electron-exchange effect enhances the Thomson scattering cross section in quantum plasmas. It is also shown that the differential Thomson scattering cross section has a minimum at the scattering angle Θ=π/2. It is also found that the Thomson scattering cross section increases with anmore » increase of the Fermi energy. In addition, the Thomson scattering cross section is found to be decreased with increasing plasmon energy.« less

SU-E-I-43: Photoelectric Cross Section Revisited

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haga, A; Nakagawa, K; Kotoku, J

2015-06-15

Purpose: The importance of the precision in photoelectric cross-section value increases for recent developed technology such as dual energy computed tomography, in which some reconstruction algorithms require the energy dependence of the photo-absorption in each material composition of human being. In this study, we revisited the photoelectric cross-section calculation by self-consistent relativistic Hartree-Fock (HF) atomic model and compared with that widely distributed as “XCOM database” in National Institute of Standards and Technology, which was evaluated with localdensity approximation for electron-exchange (Fock)z potential. Methods: The photoelectric cross section can be calculated with the electron wave functions in initial atomic state (boundmore » electron) and final continuum state (photoelectron). These electron states were constructed based on the selfconsistent HF calculation, where the repulsive Coulomb potential from the electron charge distribution (Hartree term) and the electron exchange potential with full electromagnetic interaction (Fock term) were included for the electron-electron interaction. The photoelectric cross sections were evaluated for He (Z=2), Be (Z=4), C (Z=6), O (Z=8), and Ne (Z=10) in energy range of 10keV to 1MeV. The Result was compared with XCOM database. Results: The difference of the photoelectric cross section between the present calculation and XCOM database was 8% at a maximum (in 10keV for Be). The agreement tends to be better as the atomic number increases. The contribution from each atomic shell has a considerable discrepancy with XCOM database except for K-shell. However, because the photoelectric cross section arising from K-shell is dominant, the net photoelectric cross section was almost insensitive to the different handling in Fock potential. Conclusion: The photoelectric cross-section program has been developed based on the fully self-consistent relativistic HF atomic model. Due to small effect on the Fock potential for K-shell electrons, the difference from XCOM database was limited: 1% to 8% for low-Z elements in 10keV-1MeV energy ranges. This work was partly supported by the JSPS Core-to-Core Program (No. 23003)« less

Communication: Electron ionization of DNA bases.

PubMed

Rahman, M A; Krishnakumar, E

2016-04-28

No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve the existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.

Photon scattering cross sections of H2 and He measured with synchrotron radiation

NASA Technical Reports Server (NTRS)

Ice, G. E.

1977-01-01

Total (elastic + inelastic) differential photon scattering cross sections have been measured for H2 gas and He, using an X-ray beam. Absolute measured cross sections agree with theory within the probable errors. Relative cross sections (normalized to theory at large S) agree to better than one percent with theoretical values calculated from wave functions that include the effect of electron-electron Coulomb correlation, but the data deviate significantly from theoretical independent-particle (e.g., Hartree-Fock) results. The ratios of measured absolute He cross sections to those of H2, at any given S, also agree to better than one percent with theoretical He-to-H2 cross-section ratios computed from correlated wave functions. It appears that photon scattering constitutes a very promising tool for probing electron correlation in light atoms and molecules.

Electron impact ionisation cross section for organoplatinum compounds

NASA Astrophysics Data System (ADS)

Mahato, Dibyendu; Naghma, Rahla; Alam, Mohammad Jane; Ahmad, Shabbir; Antony, Bobby

2016-11-01

This article reports electron impact ionisation cross sections for platinum-based drugs viz., cisplatin (H6N2Cl2Pt), carboplatin (C6H12N2O4Pt), oxaliplatin (C8H14N2O4Pt), nedaplatin (C2H8N2O3Pt) and satraplatin (C10H22ClN2O4Pt) complexes used in the cancer chemotherapy. The multi-scattering centre spherical complex optical potential formalism is used to obtain the inelastic cross section for these large molecules upon electron impact. The ionisation cross section is derived from the inelastic cross section employing complex scattering potential-ionisation contribution method. Comparison is made with previous results, where ever available and overall a reasonable agreement is observed. This is the first attempt to report total ionisation cross sections for nedaplatin and satraplatin complexes.

Correlation between energy deposition and molecular damage from Auger electrons: A case study of ultra-low energy (5-18 eV) electron interactions with DNA.

PubMed

Rezaee, Mohammad; Hunting, Darel J; Sanche, Léon

2014-07-01

The present study introduces a new method to establish a direct correlation between biologically related physical parameters (i.e., stopping and damaging cross sections, respectively) for an Auger-electron emitting radionuclide decaying within a target molecule (e.g., DNA), so as to evaluate the efficacy of the radionuclide at the molecular level. These parameters can be applied to the dosimetry of Auger electrons and the quantification of their biological effects, which are the main criteria to assess the therapeutic efficacy of Auger-electron emitting radionuclides. Absorbed dose and stopping cross section for the Auger electrons of 5-18 eV emitted by(125)I within DNA were determined by developing a nanodosimetric model. The molecular damages induced by these Auger electrons were investigated by measuring damaging cross section, including that for the formation of DNA single- and double-strand breaks. Nanoscale films of pure plasmid DNA were prepared via the freeze-drying technique and subsequently irradiated with low-energy electrons at various fluences. The damaging cross sections were determined by employing a molecular survival model to the measured exposure-response curves for induction of DNA strand breaks. For a single decay of(125)I within DNA, the Auger electrons of 5-18 eV deposit the energies of 12.1 and 9.1 eV within a 4.2-nm(3) volume of a hydrated or dry DNA, which results in the absorbed doses of 270 and 210 kGy, respectively. DNA bases have a major contribution to the deposited energies. Ten-electronvolt and high linear energy transfer 100-eV electrons have a similar cross section for the formation of DNA double-strand break, while 100-eV electrons are twice as efficient as 10 eV in the induction of single-strand break. Ultra-low-energy electrons (<18 eV) substantially contribute to the absorbed dose and to the molecular damage from Auger-electron emitting radionuclides; hence, they should be considered in the dosimetry calculation of such radionuclides. Moreover, absorbed dose is not an appropriate physical parameter for nanodosimetry. Instead, stopping cross section, which describes the probability of energy deposition in a target molecule can be an appropriate nanodosimetric parameter. The stopping cross section is correlated with a damaging cross section (e.g., cross section for the double-strand break formation) to quantify the number of each specific lesion in a target molecule for each nuclear decay of a single Auger-electron emitting radionuclide.

Absolute cross-section measurements of inner-shell ionization

NASA Astrophysics Data System (ADS)

Schneider, Hans; Tobehn, Ingo; Ebel, Frank; Hippler, Rainer

1994-12-01

Cross section ratios for K- and L-shell ionization of thin silver and gold targets by positron and electron impact have been determined at projectile energies of 30 70 keV. The experimental results are confirmed by calculations in plane wave Born approximation (PWBA) which include an electron exchange term and account for the deceleration or acceleration of the incident projectile in the nuclear field of the target atom. We report first absolute cross sections for K- and L-shell ionization of silver and gold targets by lepton impact in the threshold region. We have measured the corresponding cross sections for electron (e-) impact with an electron gun and the same experimental set-up.

Gaseous insulators for high voltage electrical equipment

DOEpatents

Christophorou, Loucas G.; James, David R.; Pace, Marshall O.; Pai, Robert Y.

1979-01-01

Gaseous insulators comprise compounds having high attachment cross sections for electrons having energies in the 0-1.3 electron volt range. Multi-component gaseous insulators comprise compounds and mixtures having overall high electron attachment cross sections in the 0-1.3 electron volt range and moderating gases having high cross sections for inelastic interactions with electrons of energies 1-4 electron volts. Suitable electron attachment components include hexafluorobutyne, perfluorobutene-2, perfluorocyclobutane, perfluorodimethylcyclobutane, perfluorocyclohexene, perfluoromethylcyclohexane, hexafluorobutadiene, perfluoroheptene-1 and hexafluoroazomethane. Suitable moderating gases include N.sub.2, CO, CO.sub.2 and H.sub.2. The gaseous insulating mixture can also contain SF.sub.6, perfluoropropane and perfluorobenzene.

Gaseous insulators for high voltage electrical equipment

DOEpatents

Christophorou, Loucas G.; James, David R.; Pace, Marshall O.; Pai, Robert Y.

1981-01-01

Gaseous insulators comprise compounds having high attachment cross sections for electrons having energies in the 0-1.3 electron volt range. Multi-component gaseous insulators comprise compounds and mixtures having overall high electron attachment cross sections in the 0-1.3 electron volt range and moderating gases having high cross sections for inelastic interactions with electrons of energies 1-4 electron volts. Suitable electron attachment components include hexafluorobutyne, perfluorobutene-2, perfluorocyclobutane, perfluorodimethylcyclobutane, perfluorocyclohexene, perfluoromethylcyclohexane, hexafluorobutadiene, perfluoroheptene-1 and hexafluoroazomethane. Suitable moderating gases include N.sub.2, CO, CO.sub.2 and H.sub.2. The gaseous insulating mixture can also contain SF.sub.6, perfluoropropane and perfluorobenzene.

Electron-impact excitation of the BΣ1u+ and CΠ1u electronic states of H2

NASA Astrophysics Data System (ADS)

Kato, H.; Kawahara, H.; Hoshino, M.; Tanaka, H.; Campbell, L.; Brunger, M. J.

2008-06-01

Differential and integral cross sections for electron-impact excitation of the dipole-allowed BΣ1u+ and CΠ1u electronic states of molecular hydrogen have been measured. The differential cross sections were determined by analysis of normalized energy-loss spectra obtained using a crossed-beam apparatus at the electron-impact energies of 40, 100, and 200 eV. Integral cross sections were subsequently derived from these data. The present work was undertaken in order to investigate some ambiguities between earlier experimental data and recent BEf-scaled cross sections as defined and calculated by Kim [J. Chem. Phys. 126, 064305 (2007)] and also to extend the energy range of the available data. Optical oscillator strengths, also determined as a part of the present investigation, were found to be in fair accordance with previous measurements and some calculations.

Electron Impact Multiple Ionization Cross Sections for Solar Physics

NASA Astrophysics Data System (ADS)

Hahn, M.; Savin, D. W.; Mueller, A.

2017-12-01

We have compiled a set of electron-impact multiple ionization (EIMI) cross sections for astrophysically relevant ions. EIMI can have a significant effect on the ionization balance of non-equilibrium plasmas. For example, it can be important if there is a rapid change in the electron temperature, as in solar flares or in nanoflare coronal heating. EIMI is also likely to be significant when the electron energy distribution is non-thermal, such as if the electrons follow a kappa distribution. Cross sections for EIMI are needed in order to account for these processes in plasma modeling and for spectroscopic interpretation. Here, we describe our comparison of proposed semiempirical formulae to the available experimental EIMI cross section data. Based on this comparison, we have interpolated and extrapolated fitting parameters to systems that have not yet been measured. A tabulation of the fit parameters is provided for thousands of EIMI cross sections. We also highlight some outstanding issues that remain to be resolved.

Experimental and theoretical electron-scattering cross-section data for dichloromethane

NASA Astrophysics Data System (ADS)

Krupa, K.; Lange, E.; Blanco, F.; Barbosa, A. S.; Pastega, D. F.; Sanchez, S. d'A.; Bettega, M. H. F.; García, G.; Limão-Vieira, P.; Ferreira da Silva, F.

2018-04-01

We report on a combination of experimental and theoretical investigations into the elastic differential cross sections (DCSs) and integral cross sections for electron interactions with dichloromethane, C H2C l2 , in the incident electron energy over the 7.0-30 eV range. Elastic electron-scattering cross-section calculations have been performed within the framework of the Schwinger multichannel method implemented with pseudopotentials (SMCPP), and the independent-atom model with screening-corrected additivity rule including interference-effects correction (IAM-SCAR+I). The present elastic DCSs have been found to agree reasonably well with the results of IAM-SCAR+I calculations above 20 eV and also with the SMC calculations below 30 eV. Although some discrepancies were found for 7 eV, the agreement between the two theoretical methodologies is remarkable as the electron-impact energy increases. Calculated elastic DCSs are also reported up to 10000 eV for scattering angles from 0° to 180° together with total cross section within the IAM-SCAR+I framework.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Suvam; Naghma, Rahla; Kaur, Jaspreet

The total and ionization cross sections for electron scattering by benzene, halobenzenes, toluene, aniline, and phenol are reported over a wide energy domain. The multi-scattering centre spherical complex optical potential method has been employed to find the total elastic and inelastic cross sections. The total ionization cross section is estimated from total inelastic cross section using the complex scattering potential-ionization contribution method. In the present article, the first theoretical calculations for electron impact total and ionization cross section have been performed for most of the targets having numerous practical applications. A reasonable agreement is obtained compared to existing experimental observationsmore » for all the targets reported here, especially for the total cross section.« less

Cross sections for ionization of tetrahydrofuran by protons at energies between 300 and 3000 keV

NASA Astrophysics Data System (ADS)

Wang, Mingjie; Rudek, Benedikt; Bennett, Daniel; de Vera, Pablo; Bug, Marion; Buhr, Ticia; Baek, Woon Yong; Hilgers, Gerhard; Rabus, Hans

2016-05-01

Double-differential cross sections for ionization of tetrahydrofuran by protons with energies from 300 to 3000 keV were measured at the Physikalisch-Technische Bundesanstalt ion accelerator facility. The electrons emitted at angles between 15∘ and 150∘ relative to the ion-beam direction were detected with an electrostatic hemispherical electron spectrometer. Single-differential and total ionization cross sections have been derived by integration. The experimental results are compared to the semiempirical Hansen-Kocbach-Stolterfoht model as well as to the recently reported method based on the dielectric formalism. The comparison to the latter showed good agreement with experimental data in a broad range of emission angles and energies of secondary electrons. The scaling property of ionization cross sections for tetrahydrofuran was also investigated. Compared to molecules of different size, the ionization cross sections of tetrahydrofuran were found to scale with the number of valence electrons at large impact parameters.

Electron-impact Multiple-ionization Cross Sections for Atoms and Ions of Helium through Zinc

NASA Astrophysics Data System (ADS)

Hahn, M.; Müller, A.; Savin, D. W.

2017-12-01

We compiled a set of electron-impact multiple-ionization (EIMI) cross section for astrophysically relevant ions. EIMIs can have a significant effect on the ionization balance of non-equilibrium plasmas. For example, it can be important if there is a rapid change in the electron temperature or if there is a non-thermal electron energy distribution, such as a kappa distribution. Cross section for EIMI are needed in order to account for these processes in plasma modeling and for spectroscopic interpretation. Here, we describe our comparison of proposed semiempirical formulae to available experimental EIMI cross-section data. Based on this comparison, we interpolated and extrapolated fitting parameters to systems that have not yet been measured. A tabulation of the fit parameters is provided for 3466 EIMI cross sections and the associated Maxwellian plasma rate coefficients. We also highlight some outstanding issues that remain to be resolved.

Electron-impact excitation of Rydberg and valence electronic states of nitric oxide: II. Integral cross sections

NASA Astrophysics Data System (ADS)

Brunger, M. J.; Campbell, L.; Cartwright, D. C.; Middleton, A. G.; Mojarrabi, B.; Teubner, P. J. O.

2000-02-01

Integral cross sections (ICSs) for the excitation of 18 excited electronic states, and four composite excited electronic states, in nitric oxide (NO) have been determined for incident electron energies of 15, 20, 30, 40 and 50 eV. These ICSs were derived by extrapolating the respective measured differential cross sections (M J Brunger et al 2000 J. Phys. B: At. Mol. Opt. Phys. 33 783) to 0° and 180° and by performing the appropriate integration. Comparison of the present ICSs with the results of those determined in earlier optical emission measurements, and from theoretical calculations is made. At each incident energy considered, the current ICSs are also summed along with the corresponding elastic and rovibrational excitation ICSs from B Mojarrabi et al (1995 J. Phys. B: At. Mol. Opt. Phys. 28 487) and the ionization cross sections from Rapp and Englander-Golden (1965 J. Chem. Phys. 43 1464), to derive an estimate of the grand total cross sections (GTSs) for e- + NO scattering. The GTSs derived in this manner are compared with the results from independent linear transmission experiments and are found to be entirely consistent with them. The present excited electronic state ICS, and those for elastic and rovibrational excitation from Mojarrabi et al , appear to represent the first set of self-consistent cross sections for electron impact scattering from NO.

Integral elastic, electronic-state, ionization, and total cross sections for electron scattering with furfural

NASA Astrophysics Data System (ADS)

Jones, D. B.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Lima, M. A. P.; Blanco, F.; García, G.; Brunger, M. J.

2016-04-01

We report absolute experimental integral cross sections (ICSs) for electron impact excitation of bands of electronic-states in furfural, for incident electron energies in the range 20-250 eV. Wherever possible, those results are compared to corresponding excitation cross sections in the structurally similar species furan, as previously reported by da Costa et al. [Phys. Rev. A 85, 062706 (2012)] and Regeta and Allan [Phys. Rev. A 91, 012707 (2015)]. Generally, very good agreement is found. In addition, ICSs calculated with our independent atom model (IAM) with screening corrected additivity rule (SCAR) formalism, extended to account for interference (I) terms that arise due to the multi-centre nature of the scattering problem, are also reported. The sum of those ICSs gives the IAM-SCAR+I total cross section for electron-furfural scattering. Where possible, those calculated IAM-SCAR+I ICS results are compared against corresponding results from the present measurements with an acceptable level of accord being obtained. Similarly, but only for the band I and band II excited electronic states, we also present results from our Schwinger multichannel method with pseudopotentials calculations. Those results are found to be in good qualitative accord with the present experimental ICSs. Finally, with a view to assembling a complete cross section data base for furfural, some binary-encounter-Bethe-level total ionization cross sections for this collision system are presented.

Communication: Electron ionization of DNA bases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahman, M. A.; Krishnakumar, E., E-mail: ekkumar@tifr.res.in

2016-04-28

No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve themore » existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.« less

Detection of explosives, nerve agents, and illicit substances by zero-energy electron attachment

NASA Technical Reports Server (NTRS)

Chutjian, A.; Darrach, M. R.

2000-01-01

The Reversal Electron Attachment Detection (READ) method, developed at JPL/Caltech, has been used to detect a variety of substances which have electron-attachment resonances at low and intermediate electron energies. In the case of zero-energy resonances, the cross section (hence attachment probability and instrument sensitivity) is mediated by the so-called s-wave phenomenon, in which the cross sections vary as the inverse of the electron velocity. Hence this is, in the limit of zero electron energy or velocity, one of the rare cases in atomic and molecular physics where one carries out detection via infinite cross sections.

Analysis of Data on the Cross Sections for Electron-Impact Ionization and Excitation of Electronic States of Atomic Hydrogen (Review)

NASA Astrophysics Data System (ADS)

Shakhatov, V. A.; Lebedev, Yu. A.

2018-01-01

A review is given of experimental and theoretical data on the cross sections for ionization, excitation, and deexcitation of atomic hydrogen. The set of the cross sections required to calculate the electron energy distribution function and find the level-to-level rate coefficients needed to solve balance equations for the densities of neutral and charged particles in hydrogen plasma is determined.

Electron impact excitation of the 1{sup 1}{ital S}{r_arrow}3{sup 1}{ital P} transition in helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khakoo, M.A.; Roundy, D.; Rugamas, F.

1995-07-03

In the first direct application of the electron-photon coincidence technique for differential cross-section measurements, experimentally determined ratios of the differential cross sections for the electron impact excitation of the 1{sup 1}{ital S}{r_arrow}2{sup 1}{ital P} to the 1{sup 1}{ital S}{r_arrow}3{sup 1}{ital P} transitions are presented at 30 and 40 eV incident electron energies. Differential cross sections for the 1{sup 1}{ital S}{r_arrow}3{sup 1}{ital P} transitions are derived by normalizing these ratios to available experimental differential cross sections for the 1{sup 1}{ital S}{r_arrow}2{sup 1}{ital P} transition.

Electron-neutrino charged-current quasi-elastic scattering in MINERvA

NASA Astrophysics Data System (ADS)

Wolcott, Jeremy

2014-03-01

The electron-neutrino charged-current quasi-elastic (CCQE) cross-section on nuclei is an important input parameter to appearance-type neutrino oscillation experiments. Current experiments typically work from the muon neutrino CCQE cross-section and apply corrections from theoretical arguments to obtain a prediction for the electron neutrino CCQE cross-section, but to date there has been no precise experimental verification of these estimates at an energy scale appropriate to such experiments. We present the current status of a direct measurement of the electron neutrino CCQE differential cross-section as a function of the squared four-momentum transfer to the nucleus, Q2, in MINERvA. This talk will discuss event selection, background constraints, and the flux prediction used in the calculation.

Integral cross sections for electron impact excitation of the 1Σ+u and 1Πu electronic states in CO2

NASA Astrophysics Data System (ADS)

Kawahara, H.; Kato, H.; Hoshino, M.; Tanaka, H.; Campbell, L.; Brunger, M. J.

2008-04-01

We apply the method of Kim (2007 J. Chem. Phys. 126 064305) in order to derive integral cross sections for the 1Σ+u and 1Πu states of CO2, from our corresponding earlier differential cross section measurements (Green et al 2002 J. Phys. B: At. Mol. Opt. Phys. 35 567). The energy range of this work is 20 200 eV. In addition, the BEf-scaling approach is used to calculate integral cross sections for these same states, from their respective thresholds to 5000 eV. In general, good agreement is found between the experimental integral cross sections and those calculated within the BEf-scaling paradigm, over the entire common energy range. Finally, we employ our calculated integral cross sections to determine the electron energy transfer rates for these states, for a thermal electron energy distribution. Such transfer rates are in principle important for understanding the phenomena in atmospheres where CO2 is a dominant constituent, such as on Mars and Venus.

Electron scattering by highly polar molecules. II - LiF

NASA Technical Reports Server (NTRS)

Vuskovic, L.; Srivastavas, S. K.; Trajmar, S.

1978-01-01

The crossed electron-beam - molecular-beam scattering technique has been used to measure relative values of differential 'elastic' scattering cross sections at electron impact energies of 5.4 and 20 eV for the angular range from 20 to 130 deg. The absolute values of these cross sections have been obtained by normalization to the classical perturbation theory of Dickinson (1977) at a scattering angle of 40 deg. These differential cross sections have then been used to calculate the integral and momentum-transfer cross sections. An energy-loss spectrum at 100 eV electron impact energy and 15 deg scattering angle has also been obtained. Two weak features at the energy losses of 6.74 and 8.82 eV appear. Their energy positions are compared with the recent calculations of Kahn et al. (1974).

Elastic electron scattering from formamide

NASA Astrophysics Data System (ADS)

Buk, M. V.; Bardela, F. P.; da Silva, L. A.; Iga, I.; Homem, M. G. P.

2018-05-01

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.

Production of negative ions by dissociative electron attachment to SO2

NASA Technical Reports Server (NTRS)

Orient, O. J.; Srivastava, S. K.

1983-01-01

Dissociative electron attachment cross section measurements for the production of O(-), S(-), and SO(-) have been performed utilizing a crossed target SO2 molecule beam-electron beam geometry. The relative flow technique is employed to determine the absolute values of cross sections. The attachment energies corresponding to various cross section maxima are: 4.30 and 7.1 eV for O(-)/SO2; 4.0, 7.5, and 8.9 eV for S(-)/SO2, and 4.7 and 7.5 eV for SO(-)/SO2.

Electron Bremsstrahlung Cross Sections at 25 and 50 keV from Xe and Kr

NASA Astrophysics Data System (ADS)

Portillo, Salvador; Quarles, C. A.

2002-05-01

Absolute doubly differential bremsstrahlung cross sections for radiation at 90 from 25 and 50 keV electron bombardment of Kr and Xe of will be presented. The electrons were accelerated by a Cockcroft - Walton accelerator into an Al chamber through a .06" Al collimator. Thick target bremsstrahlung background was minimized by having Al nipples and fixtures and by the addition of a carbon lined nipple placed at 180 to the SiLi detector. A comparison of the doubly differential cross sections will be made with current bremsstrahlung theories. The ratio of the Kr and Xe cross sections will also be compared with the theoretical cross section ratios. The ratio provides a more sensitive test of the contribution, if any, of polarization bremsstrahlung.

Total Electron-Impact Ionization Cross-Sections of CFx and NFx (x = 1 - 3)

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Tarnovsky, Vladimir; Becker, Kurt H.; Kwak, Dochan (Technical Monitor)

2001-01-01

The discrepancy between experimental and theoretical total electron-impact ionization cross sections for a group of fluorides, CFx, and NFx, (x = 1 - 3), is attributed to the inadequacies in previous theoretical models. Cross-sections calculated using a recently developed siBED (simulation Binary-Encounter-Dipole) model that takes into account the shielding of the long-range dipole potential between the scattering electron and target are in agreement with experimentation. The present study also carefully reanalyzed the previously reported experimental data to account for the possibility of incomplete collection of fragment ions and the presence of ion-pair formation channels. For NF3, our experimental and theoretical cross-sections compare well with the total ionization cross-sections recently reported by Haaland et al. in the region below dication formation.

Experimental electron energy-loss spectra and cross sections for the 4/2/S - 4/2/P transition in Zn II

NASA Technical Reports Server (NTRS)

Chutjian, A.; Newell, W. R.

1982-01-01

Electron energy-loss spectra and differential cross sections are reported for inelastic scattering from Zn II. Measurements were carried out in a crossed electron beam-ion beam apparatus, at incident electron energies of 30, 40, 50, 60, 75, 85, and 100 eV, and at a scattering angle of 14 deg. The present results are the first reported measurements of inelastic electron scattering from an ion.

Electron impact scattering study of hypohalous acids HOX (X = F, Cl, Br, I)

NASA Astrophysics Data System (ADS)

Yadav, Hitesh; Bhutadia, Harshad; Prajapati, Dinesh; Desai, Hardik; Vinodkumar, Minaxi; Vinodkumar, P. C.

2018-05-01

In this article we aim to report total cross sections (TCS) QT, total elastic cross sections (Qel), total inelastic cross sections (Qinel) i.e. (total ionizations cross sections (Qion)+total electronic excitation cross sections (Qexc)) from threshold of the target to 5000 eV energy range. We have used a well-defined theoretical methodology Spherical Complex Optical Potential (SCOP) to compute QT, Qel and Qinel and Complex Scattering Potential - ionization contribution (CSP - ic) method to report the (Qion). The cross-sectional data reported here for the Hypohalous Acids is for the first time and the present data can become a guideline for the experimentalist to study these targets.

Electron-impact excitation cross sections for the b /sup 3/. sigma. /sub u//sup +/ state of H/sub 2/

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khakoo, M.A.; Trajmar, S.; McAdams, R.

1987-04-01

Differential and integral cross sections for electron-impact excitation of the b /sup 3/..sigma../sub u//sup +/ state of H/sub 2/ have been determined in the 20--100-eV impact energy region. The calibration of the cross sections was achieved through the H/sub 2/ elastic scattering cross sections, which in turn were normalized to absolute He elastic scattering cross sections. Comparison is made with available experimental data and with theoretical results applying Born-Ochkur-Rudge, distorted-wave, and close-coupling approximations.

Electron-Impact Total Ionization Cross Sections of CH and C2H2

PubMed Central

Kim, Yong-Ki; Ali, M. Asgar; Rudd, M. Eugene

1997-01-01

Electron-impact total ionization cross sections for the CH radical and C2H2 (acetylene) have been calculated using the Binary-Encounter-Bethe (BEB) model. The BEB model combines the Mott cross section and the asymptotic form of the Bethe theory, and has been shown to generate reliable ionization cross sections for a large variety of molecules. The BEB cross sections for CH and C2H2 are in good agreement with the available experimental data from ionization thresholds to hundreds of eV in incident energies. PMID:27805116

Correlation between energy deposition and molecular damage from Auger electrons: A case study of ultra-low energy (5–18 eV) electron interactions with DNA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rezaee, Mohammad, E-mail: Mohammad.Rezaee@USherbrooke.ca; Hunting, Darel J.; Sanche, Léon

2014-07-15

Purpose: The present study introduces a new method to establish a direct correlation between biologically related physical parameters (i.e., stopping and damaging cross sections, respectively) for an Auger-electron emitting radionuclide decaying within a target molecule (e.g., DNA), so as to evaluate the efficacy of the radionuclide at the molecular level. These parameters can be applied to the dosimetry of Auger electrons and the quantification of their biological effects, which are the main criteria to assess the therapeutic efficacy of Auger-electron emitting radionuclides. Methods: Absorbed dose and stopping cross section for the Auger electrons of 5–18 eV emitted by{sup 125}I withinmore » DNA were determined by developing a nanodosimetric model. The molecular damages induced by these Auger electrons were investigated by measuring damaging cross section, including that for the formation of DNA single- and double-strand breaks. Nanoscale films of pure plasmid DNA were prepared via the freeze-drying technique and subsequently irradiated with low-energy electrons at various fluences. The damaging cross sections were determined by employing a molecular survival model to the measured exposure–response curves for induction of DNA strand breaks. Results: For a single decay of{sup 125}I within DNA, the Auger electrons of 5–18 eV deposit the energies of 12.1 and 9.1 eV within a 4.2-nm{sup 3} volume of a hydrated or dry DNA, which results in the absorbed doses of 270 and 210 kGy, respectively. DNA bases have a major contribution to the deposited energies. Ten-electronvolt and high linear energy transfer 100-eV electrons have a similar cross section for the formation of DNA double-strand break, while 100-eV electrons are twice as efficient as 10 eV in the induction of single-strand break. Conclusions: Ultra-low-energy electrons (<18 eV) substantially contribute to the absorbed dose and to the molecular damage from Auger-electron emitting radionuclides; hence, they should be considered in the dosimetry calculation of such radionuclides. Moreover, absorbed dose is not an appropriate physical parameter for nanodosimetry. Instead, stopping cross section, which describes the probability of energy deposition in a target molecule can be an appropriate nanodosimetric parameter. The stopping cross section is correlated with a damaging cross section (e.g., cross section for the double-strand break formation) to quantify the number of each specific lesion in a target molecule for each nuclear decay of a single Auger-electron emitting radionuclide.« less

Correlation between energy deposition and molecular damage from Auger electrons: A case study of ultra-low energy (5–18 eV) electron interactions with DNA

PubMed Central

Rezaee, Mohammad; Hunting, Darel J.; Sanche, Léon

2015-01-01

Purpose The present study introduces a new method to establish a direct correlation between biologically related physical parameters (i.e., stopping and damaging cross sections, respectively) for an Auger-electron emitting radionuclide decaying within a target molecule (e.g., DNA), so as to evaluate the efficacy of the radionuclide at the molecular level. These parameters can be applied to the dosimetry of Auger electrons and the quantification of their biological effects, which are the main criteria to assess the therapeutic efficacy of Auger-electron emitting radionuclides. Methods Absorbed dose and stopping cross section for the Auger electrons of 5–18 eV emitted by 125I within DNA were determined by developing a nanodosimetric model. The molecular damages induced by these Auger electrons were investigated by measuring damaging cross section, including that for the formation of DNA single- and double-strand breaks. Nanoscale films of pure plasmid DNA were prepared via the freeze-drying technique and subsequently irradiated with low-energy electrons at various fluences. The damaging cross sections were determined by employing a molecular survival model to the measured exposure–response curves for induction of DNA strand breaks. Results For a single decay of 125I within DNA, the Auger electrons of 5–18 eV deposit the energies of 12.1 and 9.1 eV within a 4.2-nm3 volume of a hydrated or dry DNA, which results in the absorbed doses of 270 and 210 kGy, respectively. DNA bases have a major contribution to the deposited energies. Ten-electronvolt and high linear energy transfer 100-eV electrons have a similar cross section for the formation of DNA double-strand break, while 100-eV electrons are twice as efficient as 10 eV in the induction of single-strand break. Conclusions Ultra-low-energy electrons (<18 eV) substantially contribute to the absorbed dose and to the molecular damage from Auger-electron emitting radionuclides; hence, they should be considered in the dosimetry calculation of such radionuclides. Moreover, absorbed dose is not an appropriate physical parameter for nanodosimetry. Instead, stopping cross section, which describes the probability of energy deposition in a target molecule can be an appropriate nanodosimetric parameter. The stopping cross section is correlated with a damaging cross section (e.g., cross section for the double-strand break formation) to quantify the number of each specific lesion in a target molecule for each nuclear decay of a single Auger-electron emitting radionuclide. PMID:24989405

Theoretical studies of dissociative recombination

NASA Technical Reports Server (NTRS)

Guberman, S. L.

1985-01-01

The calculation of dissociative recombination rates and cross sections over a wide temperature range by theoretical quantum chemical techniques is described. Model calculations on electron capture by diatomic ions are reported which illustrate the dependence of the rates and cross sections on electron energy, electron temperature, and vibrational temperature for three model crossings of neutral and ionic potential curves. It is shown that cross sections for recombination to the lowest vibrational level of the ion can vary by several orders of magnitude depending upon the position of the neutral and ionic potential curve crossing within the turning points of the v = 1 vibrational level. A new approach for calculating electron capture widths is reported. Ab initio calculations are described for recombination of O2(+) leading to excited O atoms.

Dissociative excitation of the manganese atom quartet levels by collisions e-MnBr2

NASA Astrophysics Data System (ADS)

Smirnov, Yu M.

2017-04-01

Dissociative excitation of quartet levels of the manganese atom was studied in collisions of electrons with manganese dibromide molecules. Eighty-two cross-sections for transitions originating at odd levels and eleven cross-sections for transitions originating at even levels have been measured at an incident electron energy of 100 eV. An optical excitation function has been recorded in the electron energy range of 0-100 eV for transitions originating from 3d 64p z 4 F° levels. For the majority of transitions, a comparison of the resulting cross-section values to cross-sections produced by direct excitation is provided.

Electron transport parameters in NF3

NASA Astrophysics Data System (ADS)

Lisovskiy, V.; Yegorenkov, V.; Ogloblina, P.; Booth, J.-P.; Martins, S.; Landry, K.; Douai, D.; Cassagne, V.

2014-03-01

We present electron transport parameters (the first Townsend coefficient, the dissociative attachment coefficient, the fraction of electron energy lost by collisions with NF3 molecules, the average and characteristic electron energy, the electron mobility and the drift velocity) in NF3 gas calculated from published elastic and inelastic electron-NF3 collision cross-sections using the BOLSIG+ code. Calculations were performed for the combined RB (Rescigno 1995 Phys. Rev. E 52 329, Boesten et al 1996 J. Phys. B: At. Mol. Opt. Phys. 29 5475) momentum-transfer cross-section, as well as for the JB (Joucoski and Bettega 2002 J. Phys. B: At. Mol. Opt. Phys. 35 783) momentum-transfer cross-section. In addition, we have measured the radio frequency (rf) breakdown curves for various inter-electrode gaps and rfs, and from these we have determined the electron drift velocity in NF3 from the location of the turning point in these curves. These drift velocity values are in satisfactory agreement with those calculated by the BOLSIG+ code employing the JB momentum-transfer cross-section.

Electron-neutrino scattering off nuclei from two different theoretical perspectives

NASA Astrophysics Data System (ADS)

Martini, M.; Jachowicz, N.; Ericson, M.; Pandey, V.; Van Cuyck, T.; Van Dessel, N.

2016-07-01

We analyze charged-current electron-neutrino cross sections on carbon. We consider two different theoretical approaches, on one hand the continuum random phase approximation (CRPA) which allows a description of giant resonances and quasielastic excitations, on the other hand the RPA-based calculations which are able to describe multinucleon emission and coherent and incoherent pion production as well as quasielastic excitations. We compare the two approaches in the genuine quasielastic channel, and find a satisfactory agreement between them at large energies while at low energies the collective giant resonances show up only in the CRPA approach. We also compare electron-neutrino cross sections with the corresponding muon-neutrino ones in order to investigate the impact of the different charged-lepton masses. Finally, restricting to the RPA-based approach, we compare the sum of quasielastic, multinucleon emission, coherent, and incoherent one-pion production cross sections (folded with the electron-neutrino T2K flux) with the charged-current inclusive electron-neutrino differential cross sections on carbon measured by T2K. We find a good agreement with the data. The multinucleon component is needed in order to reproduce the T2K electron-neutrino inclusive cross sections.

Theoretical and experimental study on electron interactions with chlorobenzene: Shape resonances and differential cross sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barbosa, Alessandra Souza; Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica; Varella, Márcio T. do N.

2016-08-28

In this work, we report theoretical and experimental cross sections for elastic scattering of electrons by chlorobenzene (ClB). The theoretical integral and differential cross sections (DCSs) were obtained with the Schwinger multichannel method implemented with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR). The calculations with the SMCPP method were done in the static-exchange (SE) approximation, for energies above 12 eV, and in the static-exchange plus polarization approximation, for energies up to 12 eV. The calculations with the IAM-SCAR method covered energies up to 500 eV. The experimental differential cross sections were obtained in themore » high resolution electron energy loss spectrometer VG-SEELS 400, in Lisbon, for electron energies from 8.0 eV to 50 eV and angular range from 7{sup ∘} to 110{sup ∘}. From the present theoretical integral cross section (ICS) we discuss the low-energy shape-resonances present in chlorobenzene and compare our computed resonance spectra with available electron transmission spectroscopy data present in the literature. Since there is no other work in the literature reporting differential cross sections for this molecule, we compare our theoretical and experimental DCSs with experimental data available for the parent molecule benzene.« less

Electron-Impact Cross Sections for Dipole- and Spin-Allowed Excitations of Hydrogen, Helium, and Lithium.

PubMed

Stone, Philip M; Kim, Yong-Ki; Desclaux, J P

2002-01-01

Electron-impact excitation cross sections are presented for the dipole- and spin allowed transitions from the ground states to the np (2)P states for hydrogen and lithium, and to the 1snp (1)P states for helium, n = 2 through 10. Two scaling formulas developed earlier by Kim [Phys. Rev. A 64, 032713 (2001)] for plane-wave Born cross sections are used. The scaled Born cross sections are in excellent agreement with available theoretical and experimental data.

Cross sections for electron impact excitation of the C 1Π and D 1Σ+ electronic states in N2O

NASA Astrophysics Data System (ADS)

Kawahara, H.; Suzuki, D.; Kato, H.; Hoshino, M.; Tanaka, H.; Ingólfsson, O.; Campbell, L.; Brunger, M. J.

2009-09-01

Differential and integral cross sections for electron-impact excitation of the dipole-allowed C Π1 and D Σ1+ electronic states of nitrous oxide have been measured. The differential cross sections were determined by analysis of normalized energy-loss spectra obtained using a crossed-beam apparatus at six electron energies in the range 15-200 eV. Integral cross sections were subsequently derived from these data. The present work was undertaken in order to check both the validity of the only other comprehensive experimental study into these excitation processes [Marinković et al., J. Phys. B 32, 1949 (1998)] and to extend the energy range of those data. Agreement with the earlier data, particularly at the lower common energies, was typically found to be fair. In addition, the BEf-scaling approach [Kim, J. Chem. Phys. 126, 064305 (2007)] is used to calculate integral cross sections for the C Π1 and D Σ1+ states, from their respective thresholds to 5000 eV. In general, good agreement is found between the experimental integral cross sections and those calculated within the BEf-scaling paradigm, the only exception being at the lowest energies of this study. Finally, optical oscillator strengths, also determined as a part of the present investigations, were found to be in fair accordance with previous corresponding determinations.

Electron transport in furfural: dependence of the electron ranges on the cross sections and the energy loss distribution functions

NASA Astrophysics Data System (ADS)

Ellis-Gibbings, L.; Krupa, K.; Colmenares, R.; Blanco, F.; Muńoz, A.; Mendes, M.; Ferreira da Silva, F.; Limá Vieira, P.; Jones, D. B.; Brunger, M. J.; García, G.

2016-09-01

Recent theoretical and experimental studies have provided a complete set of differential and integral electron scattering cross section data from furfural over a broad energy range. The energy loss distribution functions have been determined in this study by averaging electron energy loss spectra for different incident energies and scattering angles. All these data have been used as input parameters for an event by event Monte Carlo simulation procedure to obtain the electron energy deposition patterns and electron ranges in liquid furfural. The dependence of these results on the input cross sections is then analysed to determine the uncertainty of the simulated values.

Electron-impact electronic-state excitation of para-benzoquinone

NASA Astrophysics Data System (ADS)

Jones, D. B.; da Costa, R. F.; Kossoski, F.; Varella, M. T. do N.; Bettega, M. H. F.; Ferreira da Silva, F.; Limão-Vieira, P.; García, G.; Lima, M. A. P.; White, R. D.; Brunger, M. J.

2018-03-01

Angle resolved electron energy loss spectra (EELS) for para-benzoquinone (C6H4O2) have been recorded for incident electron energies of 20, 30, and 40 eV. Measured differential cross sections (DCSs) for electronic band features, composed of a combination of energetically unresolved electronic states, are subsequently derived from those EELS. Where possible, the obtained DCSs are compared with those calculated using the Schwinger multichannel method with pseudopotentials. These calculations were performed using a minimum orbital basis single configuration interaction framework at the static exchange plus polarisation level. Here, quite reasonable agreement between the experimental cross sections and the theoretical cross sections for the summation of unresolved states was observed.

Total Born approximation cross sections for single electron loss by atoms and ions colliding with atoms

NASA Technical Reports Server (NTRS)

Rule, D. W.

1977-01-01

The first born approximation (FBA) is applied to the calculation of single electron loss cross sections for various ions and atoms containing from one to seven electrons. Screened hydrogenic wave functions were used for the states of the electron ejected from the projectile, and Hartree-Fock elastic and incoherent scattering factors were used to describe the target. The effect of the target atom on the scaling of projectile ionization cross sections with respect to the projectile nuclear charge was explored in the case of hydrogen-like ions. Scaling of the cross section with respect to the target nuclear charge for electron loss by Fe (+25) in collision with neutral atoms ranging from H to Fe is also examined. These results were compared to those of the binary encounter approximation and to the FBA for the case of ionization by completely stripped target ions.

A Survey of Electron Impact Cross-Sections for Halogens and Halogen Compounds of Interest to Plasma Processing

NASA Technical Reports Server (NTRS)

Sharma, S. P.; Rao, M. V. V. S.; Arnold, James O. (Technical Monitor)

1998-01-01

Published electron impact cross section data on halogens Cl2, F2, and halogen containing compounds such as Cx Fy, HCl, Cx Cly Fz are reviewed and critically evaluated based on the information provided by various researchers. The present work reports data on electron impact excitation, ionization, dissociation, electron attachment, electron detachment, and photo detachment. Elastic scattering cross sections and data on bulk properties such as diffusion coefficients in various background gases are also evaluated. Since some of the cross sectional data is derived from indirect measurements such as drift velocity, care has been taken to reconcile the differences among the reported data with due attention to the measurement technique. In conclusion, the processes with no or very limited amount of data and questionable set of data are identified and recommendation for further research direction is made.

Measurement of the Inclusive Electron Neutrino Charged Current Cross Section on Carbon with the T2K Near Detector

NASA Astrophysics Data System (ADS)

Abe, K.; Adam, J.; Aihara, H.; Akiri, T.; Andreopoulos, C.; Aoki, S.; Ariga, A.; Assylbekov, S.; Autiero, D.; Barbi, M.; Barker, G. J.; Barr, G.; Bass, M.; Batkiewicz, M.; Bay, F.; Berardi, V.; Berger, B. E.; Berkman, S.; Bhadra, S.; Blaszczyk, F. d. M.; Blondel, A.; Bojechko, C.; Bordoni, S.; Boyd, S. B.; Brailsford, D.; Bravar, A.; Bronner, C.; Buchanan, N.; Calland, R. G.; Caravaca Rodríguez, J.; Cartwright, S. L.; Castillo, R.; Catanesi, M. G.; Cervera, A.; Cherdack, D.; Christodoulou, G.; Clifton, A.; Coleman, J.; Coleman, S. J.; Collazuol, G.; Connolly, K.; Cremonesi, L.; Dabrowska, A.; Danko, I.; Das, R.; Davis, S.; de Perio, P.; De Rosa, G.; Dealtry, T.; Dennis, S. R.; Densham, C.; Dewhurst, D.; Di Lodovico, F.; Di Luise, S.; Drapier, O.; Duboyski, T.; Duffy, K.; Dumarchez, J.; Dytman, S.; Dziewiecki, M.; Emery-Schrenk, S.; Ereditato, A.; Escudero, L.; Finch, A. J.; Friend, M.; Fujii, Y.; Fukuda, Y.; Furmanski, A. P.; Galymov, V.; Giffin, S.; Giganti, C.; Gilje, K.; Goeldi, D.; Golan, T.; Gonin, M.; Grant, N.; Gudin, D.; Hadley, D. R.; Haesler, A.; Haigh, M. D.; Hamilton, P.; Hansen, D.; Hara, T.; Hartz, M.; Hasegawa, T.; Hastings, N. C.; Hayato, Y.; Hearty, C.; Helmer, R. L.; Hierholzer, M.; Hignight, J.; Hillairet, A.; Himmel, A.; Hiraki, T.; Hirota, S.; Holeczek, J.; Horikawa, S.; Huang, K.; Ichikawa, A. K.; Ieki, K.; Ieva, M.; Ikeda, M.; Imber, J.; Insler, J.; Irvine, T. J.; Ishida, T.; Ishii, T.; Iwai, E.; Iwamoto, K.; Iyogi, K.; Izmaylov, A.; Jacob, A.; Jamieson, B.; Johnson, R. A.; Jo, J. H.; Jonsson, P.; Jung, C. K.; Kabirnezhad, M.; Kaboth, A. C.; Kajita, T.; Kakuno, H.; Kameda, J.; Kanazawa, Y.; Karlen, D.; Karpikov, I.; Katori, T.; Kearns, E.; Khabibullin, M.; Khotjantsev, A.; Kielczewska, D.; Kikawa, T.; Kilinski, A.; Kim, J.; Kisiel, J.; Kitching, P.; Kobayashi, T.; Koch, L.; Kolaceke, A.; Konaka, A.; Kormos, L. L.; Korzenev, A.; Koshio, Y.; Kropp, W.; Kubo, H.; Kudenko, Y.; Kurjata, R.; Kutter, T.; Lagoda, J.; Lamont, I.; Larkin, E.; Laveder, M.; Lawe, M.; Lazos, M.; Lindner, T.; Lister, C.; Litchfield, R. P.; Longhin, A.; Ludovici, L.; Magaletti, L.; Mahn, K.; Malek, M.; Manly, S.; Marino, A. D.; Marteau, J.; Martin, J. F.; Martynenko, S.; Maruyama, T.; Matveev, V.; Mavrokoridis, K.; Mazzucato, E.; McCarthy, M.; McCauley, N.; McFarland, K. S.; McGrew, C.; Metelko, C.; Mijakowski, P.; Miller, C. A.; Minamino, A.; Mineev, O.; Missert, A.; Miura, M.; Moriyama, S.; Mueller, Th. A.; Murakami, A.; Murdoch, M.; Murphy, S.; Myslik, J.; Nakadaira, T.; Nakahata, M.; Nakamura, K.; Nakayama, S.; Nakaya, T.; Nakayoshi, K.; Nielsen, C.; Nirkko, M.; Nishikawa, K.; Nishimura, Y.; O'Keeffe, H. M.; Ohta, R.; Okumura, K.; Okusawa, T.; Oryszczak, W.; Oser, S. M.; Owen, R. A.; Oyama, Y.; Palladino, V.; Palomino, J. L.; Paolone, V.; Payne, D.; Perevozchikov, O.; Perkin, J. D.; Petrov, Y.; Pickard, L.; Pinzon Guerra, E. S.; Pistillo, C.; Plonski, P.; Poplawska, E.; Popov, B.; Posiadala, M.; Poutissou, J.-M.; Poutissou, R.; Przewlocki, P.; Quilain, B.; Radicioni, E.; Ratoff, P. N.; Ravonel, M.; Rayner, M. A. M.; Redij, A.; Reeves, M.; Reinherz-Aronis, E.; Rodrigues, P. A.; Rojas, P.; Rondio, E.; Roth, S.; Rubbia, A.; Ruterbories, D.; Sacco, R.; Sakashita, K.; Sánchez, F.; Sato, F.; Scantamburlo, E.; Scholberg, K.; Schoppmann, S.; Schwehr, J.; Scott, M.; Seiya, Y.; Sekiguchi, T.; Sekiya, H.; Sgalaberna, D.; Shiozawa, M.; Short, S.; Shustrov, Y.; Sinclair, P.; Smith, B.; Smy, M.; Sobczyk, J. T.; Sobel, H.; Sorel, M.; Southwell, L.; Stamoulis, P.; Steinmann, J.; Still, B.; Suda, Y.; Suzuki, A.; Suzuki, K.; Suzuki, S. Y.; Suzuki, Y.; Tacik, R.; Tada, M.; Takahashi, S.; Takeda, A.; Takeuchi, Y.; Tanaka, H. K.; Tanaka, H. A.; Tanaka, M. M.; Terhorst, D.; Terri, R.; Thompson, L. F.; Thorley, A.; Tobayama, S.; Toki, W.; Tomura, T.; Totsuka, Y.; Touramanis, C.; Tsukamoto, T.; Tzanov, M.; Uchida, Y.; Vacheret, A.; Vagins, M.; Vasseur, G.; Wachala, T.; Waldron, A. V.; Walter, C. W.; Wark, D.; Wascko, M. O.; Weber, A.; Wendell, R.; Wilkes, R. J.; Wilking, M. J.; Wilkinson, C.; Williamson, Z.; Wilson, J. R.; Wilson, R. J.; Wongjirad, T.; Yamada, Y.; Yamamoto, K.; Yanagisawa, C.; Yano, T.; Yen, S.; Yershov, N.; Yokoyama, M.; Yuan, T.; Yu, M.; Zalewska, A.; Zalipska, J.; Zambelli, L.; Zaremba, K.; Ziembicki, M.; Zimmerman, E. D.; Zito, M.; Żmuda, J.; T2K Collaboration

2014-12-01

The T2K off-axis near detector ND280 is used to make the first differential cross-section measurements of electron neutrino charged current interactions at energies ˜1 GeV as a function of electron momentum, electron scattering angle, and four-momentum transfer of the interaction. The total flux-averaged νe charged current cross section on carbon is measured to be ⟨σ ⟩ϕ =1.11 ±0.10 (stat)±0.18 (syst)×1 0-38 cm2/nucleon . The differential and total cross-section measurements agree with the predictions of two leading neutrino interaction generators, NEUT and GENIE. The NEUT prediction is 1.23 ×1 0-38 cm2/nucleon and the GENIE prediction is 1.08 ×1 0-38 cm2/nucleon . The total νe charged current cross-section result is also in agreement with data from the Gargamelle experiment.

Low-energy electron-impact single ionization of helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colgan, J.; Pindzola, M. S.; Childers, G.

2006-04-15

A study is made of low-energy electron-impact single ionization of ground-state helium. The time-dependent close-coupling method is used to calculate total integral, single differential, double differential, and triple differential ionization cross sections for impact electron energies ranging from 32 to 45 eV. For all quantities, the calculated cross sections are found to be in very good agreement with experiment, and for the triple differential cross sections, good agreement is also found with calculations made using the convergent close-coupling technique.

Cross sections for the production of energetic cations by electron impact on N2 and CO2

NASA Technical Reports Server (NTRS)

Iga, I.; Srivastava, S. K.; Rao, M. V. V. S.; Katayama, D. H.

1995-01-01

Dissociative ionization cross sections for the production of singly charged energetic ions by electron impact on N2 and CO2 have been measured. The ions were divided into two groups: one with energies less than 1 eV and the other with energies greater than 1 eV. The ions detected were N+ from N2 and C+, O+, and CO+ from CO2. The electron impact energy range, and cross section data on ions is given.

Absolute cascade-free cross-sections for the 2S to 2P transition in Zn(+) using electron-energy-loss and merged-beams methods

NASA Technical Reports Server (NTRS)

Smith, Steven J.; Man, K.-F.; Chutjian, A.; Mawhorter, R. J.; Williams, I. D.

1991-01-01

Absolute cascade-free excitation cross-sections in an ion have been measured for the resonance 2S to 2P transition in Zn(+) using electron-energy-loss and merged electron-ion beams methods. Measurements were carried out at electron energies of below threshold to 6 times threshold. Comparisons are made with 2-, 5-, and 15-state close-coupling and distorted-wave theories. There is good agreement between experiment and the 15-state close-coupling cross-sections over the energy range of the calculations.

Integral cross sections for electron impact excitation of electronic states of N2

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.; Nolan, A. M.; Kelly, L. J.; Wedding, A. B.; Harrison, J.; Teubner, P. J. O.; Cartwright, D. C.; McLaughlin, B.

2001-04-01

We report integral cross sections (ICSs) for electron impact excitation of the A 3Σ+u, B 3Πg, W 3Δu, B' 3Σ-u, a' 1Σ-u, a 1Πg, ω1Δu, C 3Πu, E 3Σ+g and a'' 1Σ+g electronic states of N2. The present data, for each state, were derived at five incident electron energies in the range 15-50 eV, from the earlier crossed-beam differential cross section (DCS) measurements of our group. This was facilitated by using a molecular phase shift analysis technique to extrapolate the measured DCSs to 0° and 180°, before performing the integration. A comprehensive comparison of the present ICSs with the results of earlier experimental studies, both crossed beam and electron swarm, and theoretical calculations is provided. This comparison clearly indicates that some of the previous estimates for these excited electronic-state cross sections need to be reassessed. In addition, we have used the present ICSs in a Monte Carlo simulation for modelling the behaviour of an electron swarm in the bulk of a low current N2 discharge. The macroscopic transport parameters determined from this simulation are compared against those measured from independent swarm-based experiments and the self-consistency of our ICSs evaluated.

Integral elastic, electronic-state, ionization, and total cross sections for electron scattering with furfural

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, D. B.; Costa, R. F. da; Departamento de Física, Universidade Federal do Espírito Santo, 29075-910, Vitória, Espírito Santo

We report absolute experimental integral cross sections (ICSs) for electron impact excitation of bands of electronic-states in furfural, for incident electron energies in the range 20–250 eV. Wherever possible, those results are compared to corresponding excitation cross sections in the structurally similar species furan, as previously reported by da Costa et al. [Phys. Rev. A 85, 062706 (2012)] and Regeta and Allan [Phys. Rev. A 91, 012707 (2015)]. Generally, very good agreement is found. In addition, ICSs calculated with our independent atom model (IAM) with screening corrected additivity rule (SCAR) formalism, extended to account for interference (I) terms that arisemore » due to the multi-centre nature of the scattering problem, are also reported. The sum of those ICSs gives the IAM-SCAR+I total cross section for electron–furfural scattering. Where possible, those calculated IAM-SCAR+I ICS results are compared against corresponding results from the present measurements with an acceptable level of accord being obtained. Similarly, but only for the band I and band II excited electronic states, we also present results from our Schwinger multichannel method with pseudopotentials calculations. Those results are found to be in good qualitative accord with the present experimental ICSs. Finally, with a view to assembling a complete cross section data base for furfural, some binary-encounter-Bethe-level total ionization cross sections for this collision system are presented.« less

Atom Optics for Bose-Einstein Condensates (BEC)

DTIC Science & Technology

2012-04-25

Electron Micrograph of the Top View of Test Chip A .......................................29 11. A Scanning Electron Micrograph of the Cross...Sectional View of Test Chip A .....................29 12. A Scanning Electron Micrograph of the Top View of Test Chip B...30 13. A Scanning Electron Micrograph of the Cross Sectional View of Test Chip B .....................30 14. Toner Masks for Etching

s-wave threshold in electron attachment - Results in 2-C4F6 and CFCl3 at ultra-low electron energies

NASA Technical Reports Server (NTRS)

Chutjian, A.; Alajajian, S. H.; Ajello, J. M.; Orient, O. J.

1984-01-01

Electron attachment lineshapes and cross sections are reported for the processes 2-C4F6(-)/2-C4F6 and Cl(-)/CFCl3 at electron energies of 0-120 and 0-140 meV, and at resolutions of 6 and 7 meV (FWHM), respectively. As in previous measurements in CCl4 and SF6, the results show resolution-limited narrow structure in the cross section at electron energies below 15 meV. This structure arises from the divergence of the s-wave cross section in the limit of zero electron energy. Comparisons are given with swarm-measured results, and with collisional ionization (high-Rydberg attachment) data in this energy range.

Use of the Bethe equation for inner-shell ionization by electron impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Cedric J.; Llovet, Xavier; Salvat, Francesc

2016-05-14

We analyzed calculated cross sections for K-, L-, and M-shell ionization by electron impact to determine the energy ranges over which these cross sections are consistent with the Bethe equation for inner-shell ionization. Our analysis was performed with K-shell ionization cross sections for 26 elements, with L-shell ionization cross sections for seven elements, L{sub 3}-subshell ionization cross sections for Xe, and M-shell ionization cross sections for three elements. The validity (or otherwise) of the Bethe equation could be checked with Fano plots based on a linearized form of the Bethe equation. Our Fano plots, which display theoretical cross sections andmore » available measured cross sections, reveal two linear regions as predicted by de Heer and Inokuti [in Electron Impact Ionization, edited by T. D. Märk and G. H. Dunn, (Springer-Verlag, Vienna, 1985), Chap. 7, pp. 232–276]. For each region, we made linear fits and determined values of the two element-specific Bethe parameters. We found systematic variations of these parameters with atomic number for both the low- and the high-energy linear regions of the Fano plots. We also determined the energy ranges over which the Bethe equation can be used.« less

Thickness dependence of scattering cross-sections in quantitative scanning transmission electron microscopy.

PubMed

Martinez, G T; van den Bos, K H W; Alania, M; Nellist, P D; Van Aert, S

2018-04-01

In quantitative scanning transmission electron microscopy (STEM), scattering cross-sections have been shown to be very sensitive to the number of atoms in a column and its composition. They correspond to the integrated intensity over the atomic column and they outperform other measures. As compared to atomic column peak intensities, which saturate at a given thickness, scattering cross-sections increase monotonically. A study of the electron wave propagation is presented to explain the sensitivity of the scattering cross-sections. Based on the multislice algorithm, we analyse the wave propagation inside the crystal and its link to the scattered signal for the different probe positions contained in the scattering cross-section for detector collection in the low-, middle- and high-angle regimes. The influence to the signal from scattering of neighbouring columns is also discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Donor impurity-related photoionization cross section in GaAs cone-like quantum dots under applied electric field

NASA Astrophysics Data System (ADS)

Iqraoun, E.; Sali, A.; Rezzouk, A.; Feddi, E.; Dujardin, F.; Mora-Ramos, M. E.; Duque, C. A.

2017-06-01

The donor impurity-related electron states in GaAs cone-like quantum dots under the influence of an externally applied static electric field are theoretically investigated. Calculations are performed within the effective mass and parabolic band approximations, using the variational procedure to include the electron-impurity correlation effects. The uncorrelated Schrödinger-like electron states are obtained in quasi-analytical form and the entire electron-impurity correlated states are used to calculate the photoionisation cross section. Results for the electron state energies and the photoionisation cross section are reported as functions of the main geometrical parameters of the cone-like structures as well as of the electric field strength.

Vanadium fine-structure K-shell electron impact ionization cross sections for fast-electron diagnostic in laser–solid experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmeri, P., E-mail: patrick.palmeri@umons.ac.be; Quinet, P., E-mail: pascal.quinet@umons.ac.be; IPNAS, Université de Liège, B-4000 Liège

2015-09-15

The K-shell electron impact ionization (EII) cross section, along with the K-shell fluorescence yield, is one of the key atomic parameters for fast-electron diagnostic in laser–solid experiments through the K-shell emission cross section. In addition, in a campaign dedicated to the modeling of the K lines of astrophysical interest (Palmeri et al. (2012)), the K-shell fluorescence yields for the K-vacancy fine-structure atomic levels of all the vanadium isonuclear ions have been calculated. In this study, the K-shell EII cross sections connecting the ground and the metastable levels of the parent vanadium ions to the daughter ions K-vacancy levels considered in Palmerimore » et al. (2012) have been determined. The relativistic distorted-wave (DW) approximation implemented in the FAC atomic code has been used for the incident electron kinetic energies up to 20 times the K-shell threshold energies. Moreover, the resulting DW cross sections have been extrapolated at higher energies using the asymptotic behavior of the modified relativistic binary encounter Bethe model (MRBEB) of Guerra et al. (2012) with the density-effect correction proposed by Davies et al. (2013)« less

Experimental study of low-energy charge transfer in nitrogen

NASA Technical Reports Server (NTRS)

Smith, A.

1979-01-01

Total charge transfer cross sections were obtained for the N2(+)-N2 system with relative translational ion energies between 9 and 441 eV. Data were obtained to examine the dependence of total cross section on ion energy. The effect of ion excitation on the cross sections was studied by varying the electron ionization energy in the mass spectrometer ion source over an electron energy range between 14.5 and 32.1 eV. The dependence of total cross section on the neutralization chamber gas pressure was examined by obtaining data at pressure values from 9.9 to 0.000199 torr. Cross section values obtained were compared with experimental and theoretical results of other investigations.

Electron-impact vibrational excitation of furan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hargreaves, L. R.; Albaridy, R.; Serna, G.

2011-12-15

We report measurements of differential cross sections for the vibrational excitation of furan (C{sub 4}H{sub 4}O), obtaining results for nine features spanning the electron energy loss range from 0 to 0.8 eV, at electron-impact energies of 5, 6, 7.5, 10, and 15 eV and for scattering angles ranging from 10{sup o} to 130{sup o}. The normalization of the differential cross sections was done using elastic differential cross sections for furan determined earlier by our group [Khakoo et al., Phys. Rev A 81, 062716 (2010)].

Electron scattering by molecules. II - Experimental methods and data

NASA Technical Reports Server (NTRS)

Trajmar, S.; Chutjian, A.; Register, D. F.

1983-01-01

Experimental techniques for measuring electron-molecule collision cross sections are briefly summarized. A survey of the available experimental cross section data is presented. The emphasis here is on elastic scattering, rotational, vibrational and electronic excitations, total electron scattering, and momentum transfer in the few eV to few hundred eV impact energy range. Reference is made to works concerned with high energy electron scattering, innershell and multi-electron excitations, conicidence methods and electron scattering in laser fields.

Measurements of the electron and muon inclusive cross-sections in proton–proton collisions at s = 7   TeV with the ATLAS detector

DOE PAGES

Aad, G.; Abbott, B.; Abdallah, J.; ...

2011-12-27

Here, this Letter presents measurements of the differential cross-sections for inclusive electron and muon production in proton–proton collisions at a centre-of-mass energy of √s = 7 TeV, using data collected by the ATLAS detector at the LHC. The muon cross-section is measured as a function of p T in the range 4 < p T < 100 GeV and within pseudorapidity |η| < 2.5. In addition the electron and muon cross-sections are measured in the range 7 < p T < 26 GeV and within |η| < 2.0, excluding 1.37 < |η| < 1.52. Integrated luminosities of 1.3 pb –1more » and 1.4 pb –1 are used for the electron and muon measurements, respectively. After subtraction of the W/Z/γ* contribution, the differential cross-sections are found to be in good agreement with theoretical predictions for heavy-flavour production obtained from Fixed Order NLO calculations with NLL high-p T resummation, and to be sensitive to the effects of NLL resummation.« less

Excitation cross sections for the ns 2S yields np 2P resonance transitions in Mg(+) (n = 3) and Zn(+) (n = 4) using electron-energy-loss and merged-beams methods

NASA Technical Reports Server (NTRS)

Smith, Steven J.; Chutjian, A.; Mitroy, J.; Tayal, S. S.; Henry, Ronald J. W.; Man, K.-F.; Mawhorter, R. J.; Williams, I. D.

1993-01-01

Electron-excitation cross sections are reported for the 3s 2S yields 3p 2P(h, k) resonance transition in Mg(+) at energies from threshold (4.43 eV) to approximately 9 times threshold (40.0 eV). The electron-energy-loss merged-beams technique used in these measurements is described in detail. In addition, the method of separating contributions of the elastically scattered (Coulomb) and the inelastically scattered electrons in the present Mg(+) case and previously reported Zn(+) results is described. Comparisons in the experimental energy range are made for Mg(+) with the two five-state close-coupling theoretical calculations carried out herein, and with other published close-coupling, distorted-wave, and semiempirical calculations. The present Mg(+) cross sections and Zn(+) cross sections from earlier measurements are tabulated.

Quantum Shielding Effects on the Eikonal Collision Cross Section in Strongly Coupled Two-temperature Plasmas

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Jung, Young-Dae

2017-05-01

The influence of nonisothermal and quantum shielding on the electron-ion collision process is investigated in strongly coupled two-temperature plasmas. The eikonal method is employed to obtain the eikonal scattering phase shift and eikonal cross section as functions of the impact parameter, collision energy, electron temperature, ion temperature, Debye length, and de Broglie wavelength. The results show that the quantum effect suppresses the eikonal scattering phase shift for the electron-ion collision in two-temperature dense plasmas. It is also found that the differential eikonal cross section decreases for small impact parameters. However, it increases for large impact parameters with increasing de Broglie wavelength. It is also found that the maximum position of the differential eikonal cross section is receded from the collision center with an increase in the nonisothermal character of the plasma. In addition, it is found that the total eikonal cross sections in isothermal plasmas are always greater than those in two-temperature plasmas. The variations of the eikonal cross section due to the two-temperature and quantum shielding effects are also discussed.

Gas mixtures for gas-filled particle detectors

DOEpatents

Christophorou, Loucas G.; McCorkle, Dennis L.; Maxey, David V.; Carter, James G.

1980-01-01

Improved binary and tertiary gas mixtures for gas-filled particle detectors are provided. The components are chosen on the basis of the principle that the first component is one gas or mixture of two gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a gas (Ar) having a very small cross section at and below aout 0.5 eV, whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electron field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Improved gas mixtures for gas-filled particle detectors

DOEpatents

Christophorou, L.G.; McCorkle, D.L.; Maxey, D.V.; Carter, J.G.

Improved binary and tertiary gas mixture for gas-filled particle detectors are provided. The components are chosen on the basis of the principle that the first component is one gas or mixture of two gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a gas (Ar) having a very small cross section at and below about 0.5 eV; whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electron field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Boltzmann Calculations of Electron Transport in CF4 and CF_4/Ar

NASA Astrophysics Data System (ADS)

Wang, Yicheng; van Brunt, R. J.

1996-10-01

A new set of electron collisional cross sections(L. G. Christophorou, J. K. Olthoff, and M. V. V. S. Rao, J. Phys. Chem. Ref. Data, submitted (May 1996)) for CF4 has been proposed, based primarily upon available experimental measurements. In this paper we present the results of calculations of the drift velocity, ionization coefficient, and attachment coefficient for electrons in CF4 based upon the new cross section set, using a two-term Boltzmann calculation. Comparison of results with experimental determinations of the transport parameters, such as drift velocity, are presented, along with comparison of results obtained using two previously pubished(M. Hyashi, in Swarm Studies and Elastic Electron-Molecule Collisions) (1987); and Y. Nakamura in Gaseous Electronics and Their Applications (1991) electron impact cross section sets for CF_4. Additions and adjustments to the cross section sets required for the model to achieve consitency with transport data are discussed. - Research sponsored in part by the U.S. Air Force Wright Laboratory under contract F33615-96-C-2600 with the University of Tennessee. Also, Department of Physics, The University of Tennessee, Knoxville, TN.

Modification and benchmarking of MCNP for low-energy tungsten spectra.

PubMed

Mercier, J R; Kopp, D T; McDavid, W D; Dove, S B; Lancaster, J L; Tucker, D M

2000-12-01

The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x-ray spectra in the 30-150 kV range. Validating the modified code for coupled electron-photon transport with benchmark spectra was supplemented with independent electron-only and photon-only transport benchmarks. Major revisions to the code included the proper treatment of characteristic K x-ray production and scoring, new impact ionization cross sections, and new bremsstrahlung cross sections. Minor revisions included updated photon cross sections, electron-electron bremsstrahlung production, and K x-ray yield. The modified MCNP code is benchmarked to electron backscatter factors, x-ray spectra production, and primary and scatter photon transport.

Electron impact excitation of H2 - Rydberg band systems and the benchmark dissociative cross section for H Lyman-alpha

NASA Technical Reports Server (NTRS)

Shemansky, D. E.; Hall, D. T.; Ajello, J. M.

1985-01-01

The cross sections sigma R 1 (2p) for excitation of H Ly-alpha emission produced by electron impact on H2 is reexamined. A more accurate estimate for sigma R 1 (2p) is obtained based on Born approximation estimates of the H2 Rydberg system cross sections using measured relative excitation functions. The obtained value is (8.18 + or -1.2) x 10 to the -18th sq cm at 100 eV, a factor of 0.69 below the value universally applied to cross section measurements over the past decade. Cross sections for the H2 Rydberg systems fixed in magnitude by the Born approximation have also been obtained using experimentally determined excitation functions. Accurate analytic expressions for these cross sections allow the direct calculation of rate coefficients.

Measurement of relative cross sections for simultaneous ionization and excitation of the helium 4 2s and 4 2p states

NASA Technical Reports Server (NTRS)

Sutton, J. F.

1972-01-01

The relative cross sections for simultaneous ionization and excitation of helium by 200-eV electrons into the 4 2s and 4 2p states were measured via a fast delayed coincidence technique. Results show good agreement with the relative cross sections for single electron excitation of helium and hydrogen. An application of the results of the measurement to the development of ultraviolet intensity standard is suggested. This technique involves the use of known branching ratios, a visible light flux reference, and the measured relative cross sections.

Molecular processes in a high temperature shock layer

NASA Technical Reports Server (NTRS)

Guberman, S. L.

1985-01-01

The development of techniques for the calculation of electron capture widths, electronic wave functions, cross sections and rates needed for the description of the dissociative recombination (DR) of molecular ions with electrons were described. The cross sections and rates were calculated by using harmonic oscillator wave functions for the ion and a delta function approximation for the continuum vibrational wave function in the repulsive dissociative channel. In order to obtain DR cross sections of quantitative accuracy, a computer program which solves the one dimensional nuclear motion wave equation was revised to calculate the cross sections and rates. The program and the new results are described. Included is a discussion of large windows found in the dissociative recombination cross sections from excited ion vibrational levels. These windows have not been previously reported in the literature. The magnitude of the DR cross sections for several dissociative routes are sensitive to the location of the crossing of the neutral and ion potential curves. Studies of the effects of basis set and CI wave function size on vertical excitation energies are described. Preliminary studies on N2 and O2 using large scale wave functions are also reported.

Cross sections for electron scattering from furan molecules: Measurements and calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szmytkowski, Czeslaw; Mozejko, Pawel; Ptasinska-Denga, Elzbieta

Electron-scattering cross sections have been determined for the furan (C{sub 4}H{sub 4}O) molecule, both experimentally and theoretically. An absolute total cross section (TCS) has been measured over energies from 0.6 to 400 eV using a linear electron-transmission method. The TCS energy function is dominated with a very broad enhancement, between 1.2 and 9 eV; on the low-energy side, some resonant structures are visible. Integral elastic (ECS) and ionization (ICS) cross sections have been also calculated up to 4 keV in the additivity rule approximation and the binary-encounter-Bethe approach, respectively. Their sum, ECS+ICS, is in a very good agreement with themore » measured TCS above 70 eV.« less

Electron capture cross sections by O+ from atomic He

NASA Astrophysics Data System (ADS)

Joseph, Dwayne C.; Saha, Bidhan C.

2009-11-01

The adiabatic representation is used in both the quantal and semi classical molecular orbital close coupling methods (MOCC) to evaluate charge exchange cross sections. Our results show good agreement with experimental cross sections

Production of O(-) from CO2 by dissociative electron attachment

NASA Technical Reports Server (NTRS)

Orient, O. J.; Srivastava, S. K.

1983-01-01

Dissociative electron attachment cross-section measurements for the production of O(-) from CO2 are performed using a crossed target-beam - electron-beam collision geometry and a quadrupole mass spectrometer. The relative flow technique is used in determining the absolute values of the cross sections. The attachment energies corresponding to the five cross-section maxima are given. They are 4.4 + or - 0.1, 8.2 + or - 0.1, 13.0 + or - 0.2, 16.9 + or - 0.2, and 19.4 + or 0.2 eV. Also given are the cross sections at these maxima: 1.43 x 10 to the -19th sq cm, 4.48 x 10 to the -19th sq cm, 8.1 x 10 to the -21st sq cm, 8.1 x 10 to the -21st sq cm, and 1.2 x 10 to the -20th sq cm, respectively.

Electron impact ionization of cycloalkanes, aldehydes, and ketones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Dhanoj; Antony, Bobby, E-mail: bka.ism@gmail.com

The theoretical calculations of electron impact total ionization cross section for cycloalkane, aldehyde, and ketone group molecules are undertaken from ionization threshold to 2 keV. The present calculations are based on the spherical complex optical potential formalism and complex scattering potential ionization contribution method. The results of most of the targets studied compare fairly well with the recent measurements, wherever available and the cross sections for many targets are predicted for the first time. The correlation between the peak of ionization cross sections with number of target electrons and target parameters is also reported. It was found that the crossmore » sections at their maximum depend linearly with the number of target electrons and with other target parameters, confirming the consistency of the values reported here.« less

Electronic stopping in oxides beyond Bragg additivity

NASA Astrophysics Data System (ADS)

Sigmund, P.; Schinner, A.

2018-01-01

We present stopping cross sections calculated by our PASS code for several ions in metal oxides and SiO2 over a wide energy range. Input takes into account changes in the valence structure by assigning two additional electrons to the 2p shell of oxygen and removing the appropriate number of electrons from the outer shells of the metal atom. Results are compared with tabulated experimental values and with two versions of Bragg's additivity rule. Calculated stopping cross sections are applied in testing a recently-proposed scaling rule, which relates the stopping cross section to the number of oxygen atoms per molecule.

Total electron scattering cross sections of some important biomolecules at 0.2-6.0 keV energies

NASA Astrophysics Data System (ADS)

Gurung, Meera Devi; Ariyasinghe, W. M.

2017-12-01

The total electron scattering cross sections (TCS) of five nucleic bases (adenine, cytosine, guanine, thymine and uracil), phosphoric acid, three amino acids (glycine, lysine, and L-histidine), D-glucose, alpha-D-glucose, tetrahydropyran (THP), 3-hydroxytetrahydrofuran and furan have been determined in the energy range 0.2-6.0 keV using a simple model based on the effective atomic total electron scattering cross sections (EATCS). The reliability of the model is confirmed by comparing the determined TCS with the predictions of those by existing theoretical models.

Comparisons of sets of electron-neutral scattering cross sections and calculated swarm parameters in Kr and Xe

NASA Astrophysics Data System (ADS)

Bordage, M. C.; Hagelaar, G. J. M.; Pitchford, L. C.; Biagi, S. F.; Puech, V.

2011-10-01

Xenon is used in a number of application areas ranging from light sources to x-ray detectors for imaging in medicine, border security and high-energy particle physics. There is a correspondingly large body of data available for electron scattering cross sections and swarm parameters in Xe, whereas data for Kr are more limited. In this communication we show intercomparisons of the cross section sets in Xe and Kr presently available on the LXCat site. Swarm parameters calculated using these cross sections sets are compared with experimental data, also available on the LXCat site. As was found for Ar, diffusion coefficients calculated using these cross section data in a 2-term Boltzmann solver are higher than Monte Carlo results by about 30% over a range of E/N from 1 to 100 Td. We find otherwise good agreement in Xe between 2-term and Monte Carlo results and between measured and calculated values of electron mobility, ionization rates and light emission (dimer) at atmospheric pressure. The available cross section data in Kr yield swarm parameters in agreement with the limited experimental data. The cross section compilations and measured swarm parameters used in this work are available on-line at www.lxcat.laplace. univ-tlse.fr.

Electron Collisions in our Atmosphere — How the Microscopic Drives the Macroscopic

NASA Astrophysics Data System (ADS)

Buckman, S. J.; Brunger, M. J.; Campbell, L.; Jelisavcic, M.; Petrovic, Z. Lj.

2005-05-01

Recent measurements of low energy, absolute electron scattering cross sections for vibrational excitation of NO have been used to update the cross set used for modeling atmospheric auroral processes. These new cross sections, which highlight the role that intermediate negative ions (resonances) play at energies below 5 eV in mediating vibrational excitation, also indicate that electron-driven processes play an important role in the infrared (˜5 um) auroral emissions from the NO molecule.

Influence of quantum diffraction and shielding on electron-ion collision in two-component semiclassical plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Woo-Pyo; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791

2015-01-15

The influence of quantum diffraction and shielding on the electron-ion collision process is investigated in two-component semiclassical plasmas. The eikonal method and micropotential taking into account the quantum diffraction and shielding are used to obtain the eikonal scattering phase shift and the eikonal collision cross section as functions of the collision energy, density parameter, Debye length, electron de Broglie wavelength, and the impact parameter. The result shows that the quantum diffraction and shielding effects suppress the eikonal scattering phase shift as well as the differential eikonal collision cross section, especially, in small-impact parameter regions. It is also shown that themore » quantum shielding effect on the eikonal collision cross section is more important in low-collision energies. In addition, it is found that the eikonal collision cross section increases with an increase in the density parameter. The variations of the eikonal cross section due to the quantum diffraction and shielding effects are also discussed.« less

Studies of electron-molecule collisions - Applications to e-H2O

NASA Technical Reports Server (NTRS)

Brescansin, L. M.; Lima, M. A. P.; Gibson, T. L.; Mckoy, V.; Huo, W. M.

1986-01-01

Elastic differential and momentum transfer cross sections for the elastic scattering of electrons by H2O are reported for collision energies from 2 to 20 eV. These fixed-nuclei static-exchange cross sections were obtained using the Schwinger variational approach. In these studies the exchange potential is directly evaluated and not approximated by local models. The calculated differential cross sections, obtained with a basis set expansion of the scattering wave function, agree well with available experimental data at intermediate and larger angles. As used here, the results cannot adequately describe the divergent cross sections at small angles. An interesting feature of the calculated cross sections, particularly at 15 and 20 eV, is their significant backward peaking. This peaking occurs in the experimentally inaccessible region beyond a scattering angle of 120 deg. The implication of this feature for the determination of momentum transfer cross sections is described.

Electron-induced scattering dynamics of Boron, Aluminium and Gallium trihalides in the intermediate energy domain

NASA Astrophysics Data System (ADS)

Verma, Pankaj; Alam, Mohammad Jane; Ahmad, Shabbir; Antony, Bobby

2018-05-01

This article is focused on the calculation of electron-induced ionisation and total scattering cross sections by Boron, Aluminium and Gallium trihalide molecules in the intermediate energy domain. The computational formalism, spherical complex optical potential has been employed for the study of these two scattering cross sections. The ionisation cross section has been derived from the inelastic cross section using a semi-empirical method called complex scattering potential-ionisation contribution (CSP-ic) method. We have also calculated the ionisation cross section using the BEB theory with Hartree-Fock and density functional theory (DFT- ωB97XD) orbitals so that a comparison can be made with the cross sections predicted by CSP-ic method. For this theoretical study, we have also calculated polarisability and bond length of some targets which were not found in literature using DFT/B3LYP in Gaussian 09 software.

Simple method for determining fullerene negative ion formation★

NASA Astrophysics Data System (ADS)

Felfli, Zineb; Msezane, Alfred Z.

2018-04-01

A robust potential wherein is embedded the crucial core-polarization interaction is used in the Regge-pole methodology to calculate low-energy electron elastic scattering total cross section for the C60 fullerene in the electron impact energy range 0.02 ≤ E ≤ 10.0 eV. The energy position of the characteristic dramatically sharp resonance appearing at the second Ramsauer-Townsend minimum of the total cross section representing stable C60 - fullerene negative ion formation agrees excellently with the measured electron affinity of C60 [Huang et al., J. Chem. Phys. 140, 224315 (2014)]. The benchmarked potential and the Regge-pole methodology are then used to calculate electron elastic scattering total cross sections for selected fullerenes, from C54 through C240. The total cross sections are found to be characterized generally by Ramsauer-Townsend minima, shape resonances and dramatically sharp resonances representing long-lived states of fullerene negative ion formation. For the total cross sections of C70, C76, C78, and C84 the agreement between the energy positions of the very sharp resonances and the measured electron affinities is outstanding. Additionally, we compare our extracted energy positions of the resultant fullerene anions from our calculated total cross sections of the C86, C90 and C92 fullerenes with the estimated electron affinities ≥3.0 eV by the experiment [Boltalina et al., Rapid Commun. Mass Spectrom. 7, 1009 (1993)]. Resonance energy positions of other fullerenes, including C180 and C240 are also obtained. Most of the total cross sections presented in this paper are the first and only; our novel approach is general and should be applicable to other fullerenes as well and complex heavy atoms, such as the lanthanide atoms. We conclude with a remark on the catalytic properties of the fullerenes through their negative ions.

Time-of-flight electron scattering from molecular hydrogen: Benchmark cross sections for excitation of the X 1Σg+→b 3Σu+ transition

NASA Astrophysics Data System (ADS)

Zawadzki, M.; Wright, R.; Dolmat, G.; Martin, M. F.; Hargreaves, L.; Fursa, D. V.; Zammit, M. C.; Scarlett, L. H.; Tapley, J. K.; Savage, J. S.; Bray, I.; Khakoo, M. A.

2018-05-01

The electron impact X 1Σg+→b 3Σu+ transition in molecular hydrogen is one of the most important dissociation pathways to forming atomic hydrogen atoms, and is of great importance in modeling astrophysical and industrial plasmas where molecular hydrogen is a substantial constituent. Recently, it has been found that the convergent close-coupling (CCC) cross sections of Zammit et al. [Phys. Rev. A 95, 022708 (2017), 10.1103/PhysRevA.95.022708] are up to a factor of 2 smaller than the currently recommended data. We have determined normalized differential cross sections for excitation of this transition from our experimental ratios of the inelastic to elastic scattering of electrons by molecular hydrogen using a transmission-free time-of-flight electron spectrometer, and find excellent agreement with the CCC calculations. Since there is already excellent agreement for the absolute elastic differential cross sections, we establish benchmark differential and integrated cross sections for the X 1Σg+→b 3Σu+ transition, with theory and experiment being essentially in complete agreement.

Indirect contributions to electron-impact ionization of Li+ (1 s 2 s S31 ) ions: Role of intermediate double-K -vacancy states

NASA Astrophysics Data System (ADS)

Müller, A.; Borovik, A.; Huber, K.; Schippers, S.; Fursa, D. V.; Bray, I.

2018-02-01

Fine details of the cross section for electron-impact ionization of metastable two-electron Li+(1 s 2 s S31) ions are scrutinized by both experiment and theory. Beyond direct knockoff ionization, indirect ionization mechanisms proceeding via formation of intermediate double-K-vacancy (hollow) states either in a Li+ ion or in a neutral lithium atom and subsequent emission of one or two electrons, respectively, can contribute to the net production of Li2 + ions. The partial cross sections for such contributions are less than 4% of the total single-ionization cross section. The characteristic steps, resonances, and interference phenomena in the indirect ionization contribution are measured with an experimental energy spread of less than 0.9 eV and with a statistical relative uncertainty of the order of 1.7%, requiring a level of statistical uncertainty in the total single-ionization cross section of better than 0.05%. The measurements are accompanied by convergent-close-coupling calculations performed on a fine energy grid. Theory and experiment are in remarkable agreement concerning the fine details of the ionization cross section. Comparison with previous R-matrix results is less favorable.

Electron Impact Ionization Cross Sections in Rb and Cs.

NASA Astrophysics Data System (ADS)

Reddish, T. J.; Lukomski, M.; Sutton, S.; Kedzierski, W.; McConkey, J. W.; Bartschat, K.; Bartlett, P. L.; Stelbovics, A. T.; Bray, I.

2006-05-01

We present a new atom trapping technique for determining absolute, total ionisation cross sections (TICS) out of an excited atom. The novel feature of this method is in utilizing Doppler cooling of neutral atoms to determine ionisation cross sections. This fluorescence-monitoring experiment, which is a variant of the `trap loss' technique, has enabled us to obtain the experimental electron impact ionisation cross sections out of the Cs 6^2P3/2 excited state between 7 - 400 eV. New CCC, R-Matrix with Pseudo-States (RMPS), and Born approximation single ionisation cross sections (SICS) are also presented for both the ground and excited states of Cs and Rb, and compared with the available experimental data. The comparison of the results reveals the importance of the autoionisation and multiple ionisation contributions to the TICS. The autoionisation contribution appears to be substantial for ionisation out of the Cs 6^2P and Rb 5^2P excited states; ˜ 3-4 larger than the direct ionisation contribution predicted by CCC at ˜ 30-50 eV. This surprising result shows the importance of multi-electron processes in determining the ionisation cross sections of heavy alkali atoms.

Gas mixtures for gas-filled radiation detectors

DOEpatents

Christophorou, Loucas G.; McCorkle, Dennis L.; Maxey, David V.; Carter, James G.

1982-01-05

Improved binary and ternary gas mixtures for gas-filled radiation detectors are provided. The components are chosen on the basis of the principle that the first component is one molecular gas or mixture of two molecular gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a noble gas having a very small cross section at and below about 1.0 eV, whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electric field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Improved gas mixtures for gas-filled radiation detectors

DOEpatents

Christophorou, L.G.; McCorkle, D.L.; Maxey, D.V.; Carter, J.G.

1980-03-28

Improved binary and ternary gas mixtures for gas-filled radiation detectors are provided. The components are chosen on the basis of the principle that the first component is one molecular gas or mixture of two molecular gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a noble gas having a very small cross section at and below about 1.0 eV, whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electric field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Photodissociation spectroscopy of the dysprosium monochloride molecular ion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunning, Alexander, E-mail: alexander.dunning@gmail.com; Schowalter, Steven J.; Puri, Prateek

2015-09-28

We have performed a combined experimental and theoretical study of the photodissociation cross section of the molecular ion DyCl{sup +}. The photodissociation cross section for the photon energy range 35 500 cm{sup −1} to 47 500 cm{sup −1} is measured using an integrated ion trap and time-of-flight mass spectrometer; we observe a broad, asymmetric profile that is peaked near 43 000 cm{sup −1}. The theoretical cross section is determined from electronic potentials and transition dipole moments calculated using the relativistic configuration-interaction valence-bond and coupled-cluster methods. The electronic structure of DyCl{sup +} is extremely complex due to the presence of multiple open electronic shells,more » including the 4f{sup 10} configuration. The molecule has nine attractive potentials with ionically bonded electrons and 99 repulsive potentials dissociating to a ground state Dy{sup +} ion and Cl atom. We explain the lack of symmetry in the cross section as due to multiple contributions from one-electron-dominated transitions between the vibrational ground state and several resolved repulsive excited states.« less

Dissociative attachment of electrons with Si2H6

NASA Technical Reports Server (NTRS)

Krishnakumar, E.; Srivastava, S. K.; Iga, I.

1991-01-01

Cross-sections for the production of negative ion fragments by electron attachment to Si2H6 and ion pair formation from it have been measured by utilizing the crossed electron beam-molecular beam collision technique. The negative ions are mass-analyzed by employing a quadrupole mass spectrometer. There are serious disagreements between the present and two previously published results. In the present paper cross-section values, appearance potentials, and the various channels of dissociation for the formation of negative monosilane fragments are presented.

Elastic electron scattering from the DNA bases cytosine and thymine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colyer, C. J.; Bellm, S. M.; Lohmann, B.

2011-10-15

Cross-section data for electron scattering from biologically relevant molecules are important for the modeling of energy deposition in living tissue. Relative elastic differential cross sections have been measured for cytosine and thymine using the crossed-beam method. These measurements have been performed for six discrete electron energies between 60 and 500 eV and for detection angles between 15 deg. and 130 deg. Calculations have been performed via the screen-corrected additivity rule method and are in good agreement with the present experiment.

Collision energy-resolved study of the emission cross-section and the Penning ionization cross-section in the reaction of BrCN with He*(2 3S)

NASA Astrophysics Data System (ADS)

Kanda, Kazuhiro; Yamakita, Yoshihiro; Ohno, Koichi

2001-12-01

The dissociative excitation of BrCN producing CN(B 2Σ +) fragment by the collision of He *(2 3S) was investigated by the collision energy-resolved electron and emission spectroscopy using time-of-flight method with a high-intensity He * beam. The Penning electrons ejected from BrCN and the subsequent CN ( B2Σ +- X2Σ +) emission were measured as a function of collision energy in the range of 90-180 meV. The formation of CN ( B2Σ +) is concluded to proceed dominantly via the promotion of an electron from Π-character orbital, by comparison between the collision energy dependence of the partial Penning ionization cross-sections and the CN ( B2Σ +- X2Σ +) emission cross-section.

Accurate Cross Sections for Microanalysis.

PubMed

Rez, Peter

2002-01-01

To calculate the intensity of x-ray emission in electron beam microanalysis requires a knowledge of the energy distribution of the electrons in the solid, the energy variation of the ionization cross section of the relevant subshell, the fraction of ionizations events producing x rays of interest and the absorption coefficient of the x rays on the path to the detector. The theoretical predictions and experimental data available for ionization cross sections are limited mainly to K shells of a few elements. Results of systematic plane wave Born approximation calculations with exchange for K, L, and M shell ionization cross sections over the range of electron energies used in microanalysis are presented. Comparisons are made with experimental measurement for selected K shells and it is shown that the plane wave theory is not appropriate for overvoltages less than 2.5 V.

Cross sections for electron impact excitation of the b 3Sigma(+)u state of H2 - An application of the Schwinger multichannel variational method

NASA Technical Reports Server (NTRS)

Lima, M. A. P.; Gibson, T. L.; Mckoy, V.; Huo, W. M.

1985-01-01

In this and the two accompanying letters, the results of calculations of the cross sections for electron impact excitation of the b 3Sigma(+)u state of H2, for collision energies from near threshold to 30 eV, are presented. These results are obtained using a multichannel extension of the Schwinger variational principle at the two-state level. The quantitative agreement between the integral cross sections of these three studies is very good. Inclusion of correlation terms in the scattering wavefunctions, which relax the orthogonality between bound and continuum orbitals, is seen to affect the cross sections substantially. Although a comparison of these calculated cross sections with available experimental data is encouraging, some seious discrepancies exist.

Low-Energy Elastic Electron Scattering by Atomic Oxygen

NASA Technical Reports Server (NTRS)

Zatsarinny O.; Bartschat, K.; Tayal, S. S.

2006-01-01

The B-spline R-matrix method is employed to investigate the low-energy elastic electron scattering by atomic oxygen. Flexible non-orthogonal sets of radial functions are used to construct the target description and to represent the scattering functions. A detailed investigation regarding the dependence of the predicted partial and total cross sections on the scattering model and the accuracy of the target description is presented. The predicted angle-integrated elastic cross sections are in good agreement with experiment, whereas significant discrepancies are found in the angle-differential elastic cross sections near the forward direction. .The near-threshold results are found to strongly depend on the treatment of inner-core short-range correlation effects in the target description, as well as on a proper account of the target polarizability. A sharp increase in the elastic cross sections below 1 eV found in some earlier calculations is judged to be an artifact of an unbalanced description of correlation in the N-electron target structure and the (N+l)-electron-collision problems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyriakou, Ioanna; Emfietzoglou, Dimitris; Nojeh, Alireza

A systematic study of electron-beam penetration and backscattering in multi-walled carbon nanotube (MWCNT) materials for beam energies of {approx}0.3 to 30 keV is presented based on event-by-event Monte Carlo simulation of electron trajectories using state-of-the-art scattering cross sections. The importance of different analytic approximations for computing the elastic and inelastic electron-scattering cross sections for MWCNTs is emphasized. We offer a simple parameterization for the total and differential elastic-scattering Mott cross section, using appropriate modifications to the Browning formula and the Thomas-Fermi screening parameter. A discrete-energy-loss approach to inelastic scattering based on dielectric theory is adopted using different descriptions of themore » differential cross section. The sensitivity of electron penetration and backscattering parameters to the underlying scattering models is examined. Our simulations confirm the recent experimental backscattering data on MWCNT forests and, in particular, the steep increase of the backscattering yield at sub-keV energies as well as the sidewalls escape effect at high-beam energies.« less

Intermediate energy cross sections for electron-impact vibrational-excitation of pyrimidine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, D. B.; Ellis-Gibbings, L.; García, G.

2015-09-07

We report differential cross sections (DCSs) and integral cross sections (ICSs) for electron-impact vibrational-excitation of pyrimidine, at incident electron energies in the range 15–50 eV. The scattered electron angular range for the DCS measurements was 15°–90°. The measurements at the DCS-level are the first to be reported for vibrational-excitation in pyrimidine via electron impact, while for the ICS we extend the results from the only previous condensed-phase study [P. L. Levesque, M. Michaud, and L. Sanche, J. Chem. Phys. 122, 094701 (2005)], for electron energies ⩽12 eV, to higher energies. Interestingly, the trend in the magnitude of the lower energymore » condensed-phase ICSs is much smaller when compared to the corresponding gas phase results. As there is no evidence for the existence of any shape-resonances, in the available pyrimidine total cross sections [Baek et al., Phys. Rev. A 88, 032702 (2013); Fuss et al., ibid. 88, 042702 (2013)], between 10 and 20 eV, this mismatch in absolute magnitude between the condensed-phase and gas-phase ICSs might be indicative for collective-behaviour effects in the condensed-phase results.« less

Scaled plane-wave Born cross sections for atoms and molecules

NASA Astrophysics Data System (ADS)

Tanaka, H.; Brunger, M. J.; Campbell, L.; Kato, H.; Hoshino, M.; Rau, A. R. P.

2016-04-01

Integral cross sections for optically allowed electronic-state excitations of atoms and molecules by electron impact, by applying scaled plane-wave Born models, are reviewed. Over 40 years ago, Inokuti presented an influential review of charged-particle scattering, based on the theory pioneered by Bethe forty years earlier, which emphasized the importance of reliable cross-section data from low eV energies to high keV energies that are needed in many areas of radiation science with applications to astronomy, plasmas, and medicine. Yet, with a couple of possible exceptions, most computational methods in electron-atom scattering do not, in general, overlap each other's validity range in the region from threshold up to 300 eV and, in particular, in the intermediate region from 30 to 300 eV. This is even more so for electron-molecule scattering. In fact this entire energy range is of great importance and, to bridge the gap between the two regions of low and high energy, scaled plane-wave Born models were developed to provide reliable, comprehensive, and absolute integral cross sections, first for ionization by Kim and Rudd and then extended to optically allowed electronic-state excitation by Kim. These and other scaling models in a broad, general application to electron scattering from atoms and molecules, their theoretical basis, and their results for cross sections along with comparison to experimental measurements are reviewed. Where possible, these data are also compared to results from other computational approaches.

Resonant parametric interference effect in spontaneous bremsstrahlung of an electron in the field of a nucleus and two pulsed laser waves

NASA Astrophysics Data System (ADS)

Lebed', A. A.; Padusenko, E. A.; Roshchupkin, S. P.; Dubov, V. V.

2018-04-01

Electron-nucleus bremsstrahlung in the field of two moderately strong pulsed laser waves in the case of incommensurate frequencies is theoretically studied under resonant conditions. The process is studied in detail in a special kinematic region, where stimulated processes with correlated emission and absorption of photons of the first and second waves become predominant (parametric interference effect). The availability of this region is caused by interference of the first and second laser waves. The correspondence between the emission angle and the final-electron energy is established in this interference kinematic. In this case, the cross-sectional properties are determined by the multiphoton quantum interference parameter, which is proportional to the product of intensities of the first and second waves. The resonant differential cross section of electron-nucleus spontaneous bremsstrahlung with simultaneous registration of both emission angles of the spontaneous photon and the scattered electron can exceed by four or five orders of magnitude the corresponding cross section in the absence of an external field. It was shown for nonrelativistic electrons that the resonant cross section of the studied process in the field of two pulsed laser waves within the interference region in two order of magnitude may exceed corresponding cross sections at other scattering kinematics. The obtained results may be experimentally verified, for example, by scientific facilities at sources of pulsed laser radiation (such as SLAC, FAIR, XFEL, ELI).

Ion charge state distribution effects on elastic X-ray Thomson scattering

NASA Astrophysics Data System (ADS)

Iglesias, Carlos A.

2018-03-01

Analytic models commonly applied in elastic X-ray Thomson scattering cross-section calculations are used to generate results from a discrete ion charge distribution and an average charge description. Comparisons show that interchanging the order of the averaging procedure can appreciably alter the cross-section, especially for plasmas with partially filled K-shell bound electrons. In addition, two common approximations to describe the free electron density around an ion are shown to yield significantly different elastic X-ray Thomson scattering cross-sections.

Electron impact cross-sections and cooling rates for methane. [in thermal balance of electrons in atmospheres and ionospheres of planets and satellites in outer solar system

NASA Technical Reports Server (NTRS)

Gan, L.; Cravens, T. E.

1992-01-01

Energy transfer between electrons and methane gas by collisional processes plays an important role in the thermal balance of electrons in the atmospheres and ionospheres of planets and satellites in the outer solar system. The literature is reviewed for electron impact cross-sections for methane in this paper. Energy transfer rates are calculated for elastic and inelastic processes using a Maxwellian electron distribution. Vibrational, rotational, and electronic excitation and ionization are included. Results are presented for a wide range of electron temperatures and neutral temperatures.

Elastic electron differential cross sections for argon atom in the intermediate energy range from 40 eV to 300 eV

NASA Astrophysics Data System (ADS)

Ranković, Miloš Lj.; Maljković, Jelena B.; Tökési, Károly; Marinković, Bratislav P.

2018-02-01

Measurements and calculations for electron elastic differential cross sections (DCS) of argon atom in the energy range from 40 to 300 eV are presented. DCS have been measured in the crossed beam arrangement of the electron spectrometer with an energy resolution of 0.5 eV and angular resolution of 1.5∘ in the range of scattering angles from 20∘ to 126∘. Both angular behaviour and energy dependence of DCS are obtained in a separate sets of experiments, while the absolute scale is achieved via relative flow method, using helium as a reference gas. All data is corrected for the energy transmission function, changes of primary electron beam current and target pressure, and effective path length (volume correction). DCSs are calculated in relativistic framework by expressing the Mott's cross sections in partial wave expansion. Our results are compared with other available data.

Low-energy and very-low energy total cross sections for electron collisions with N2

NASA Astrophysics Data System (ADS)

Kitajima, Masashi; Kishino, Takaya; Okumura, Takuma; Kobayashi, Naomasa; Sayama, Atsushi; Mori, Yuma; Hosaka, Kouichi; Odagiri, Takeshi; Hoshino, Masamitsu; Tanaka, Hiroshi

2017-06-01

Absolute grand total cross sections for electron scattering from N2 are obtained in the energy range from 20 eV down to 5 meV with very narrow electron energy width of 9 meV using the threshold-photoelectron source. Total cross sections obtained in the present study are compared with the previous experimentally obtained results. At the very-low energy region below 50 meV, the present total cross sections are somewhat smaller than those reported by the Aarhus group [S.V. Hoffmann et al., Rev. Sci. Instrum. 73, 4157 (2002)], which has been the only experimental work that provided the total cross sections in the very-low energy region. The energy positions of the peaks in the total cross sections due to the 2Πg shape resonance are obtained with higher accuracy, due to the improved uncertainty of the energy position in the present measurement compared to the previous works. The resonance structure in the total cross sections due to the Feshbach resonances of N2 at around 11.5 eV are also observed. Analysis of the resonant structure was carried out in order to determine the values of resonance width of Feshbach resonances of N2. Contribution to the Topical Issue: "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

Sequence dependence of electron-induced DNA strand breakage revealed by DNA nanoarrays

PubMed Central

Keller, Adrian; Rackwitz, Jenny; Cauët, Emilie; Liévin, Jacques; Körzdörfer, Thomas; Rotaru, Alexandru; Gothelf, Kurt V.; Besenbacher, Flemming; Bald, Ilko

2014-01-01

The electronic structure of DNA is determined by its nucleotide sequence, which is for instance exploited in molecular electronics. Here we demonstrate that also the DNA strand breakage induced by low-energy electrons (18 eV) depends on the nucleotide sequence. To determine the absolute cross sections for electron induced single strand breaks in specific 13 mer oligonucleotides we used atomic force microscopy analysis of DNA origami based DNA nanoarrays. We investigated the DNA sequences 5′-TT(XYX)3TT with X = A, G, C and Y = T, BrU 5-bromouracil and found absolute strand break cross sections between 2.66 · 10−14 cm2 and 7.06 · 10−14 cm2. The highest cross section was found for 5′-TT(ATA)3TT and 5′-TT(ABrUA)3TT, respectively. BrU is a radiosensitizer, which was discussed to be used in cancer radiation therapy. The replacement of T by BrU into the investigated DNA sequences leads to a slight increase of the absolute strand break cross sections resulting in sequence-dependent enhancement factors between 1.14 and 1.66. Nevertheless, the variation of strand break cross sections due to the specific nucleotide sequence is considerably higher. Thus, the present results suggest the development of targeted radiosensitizers for cancer radiation therapy. PMID:25487346

Measurement of the Charged-Current Quasi-Elastic Cross-Section for Electron Neutrinos on a Hydrocarbon Target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolcott, Jeremy

2016-01-01

Appearance-type neutrino oscillation experiments, which observe the transition from muon neutrinos to electron neutrinos, promise to help answer some of the fundamental questions surrounding physics in the post-Standard-Model era. Because they wish to observe the interactions of electron neutrinos in their detectors, and because the power of current results is typically limited by their systematic uncertainties, these experiments require precise estimates of the cross-section for electron neutrino interactions. Of particular interest is the charged-current quasi-elastic (CCQE) process, which gures signi cantly in the composition of the reactions observed at the far detector. However, no experimental measurements of this crosssection currentlymore » exist for electron neutrinos; instead, current experiments typically work from the abundance of muon neutrino CCQE cross-section data and apply corrections from theoretical arguments to obtain a prediction for electron neutrinos. Veri cation of these predictions is challenging due to the di culty of constructing an electron neutrino beam, but the advent of modern high-intensity muon neutrino beams|together with the percent-level electron neutrino impurity inherent in these beams| nally presents the opportunity to make such a measurement. We report herein the rst-ever measurement of a cross-section for an exclusive state in electron neutrino scattering, which was made using the MINER A detector in the NuMI neutrino beam at Fermilab. We present the electron neutrino CCQE di erential cross-sections, which are averaged over neutrinos of energies 1-10 GeV (with mean energy of about 3 GeV), in terms of various kinematic variables: nal-state electron angle, nal-state electron energy, and the square of the fourmomentum transferred to the nucleus by the neutrino , Q 2. We also provide a total cross-section vs. neutrino energy. While our measurement of this process is found to be in agreement with the predictions of the GENIE event generator, we also report on an unpredicted photon-like process we observe in a similar kinematic regime. The absence of this process from models for neutrino interactions is a potential stumbling block for future on-axis neutrino oscillation experiments. We include kinematic and particle species identi cation characterizations which can be used in building models to help address this shortcoming.« less

Measurement of electron impact collisional excitation cross sections of Ni to Ge-like gold

DOE PAGES

May, M. J.; Beiersdorfer, P.; Jordan, N.; ...

2017-03-01

We have measured the collisional excitation cross sections for the 3d→4f and 3d→5f excitations in Au ions near the Ni-like charge state by using beam plasmas created in the Livermore electron beam ion trap EBIT-I. The cross sections have been experimentally determined at approximately 1, 2 and 3 keV above the threshold energy, ET, for the 3d→4f excitations (ET ~2.5 keV) and at approximately 0.1, 1 and 2 keV above the threshold energy for the 3d→5f excitations (ET ~3.3 keV). The cross section measurements were made possible by using the GSFC x-ray microcalorimeter at the Livermore EBIT facility. The absolutemore » cross sections are determined from the ratio of the intensity of the collisionally excited bound-bound transitions to the intensity of the radiative recombination lines produced in EBIT-I plasmas. The effects of polarization and Auger decay channels are accounted for in the cross section determination. Measured cross sections are compared with those from HULLAC, DWS and FAC calculations. Finally, the measurements demonstrate that some errors exist in the calculated excitation cross sections.« less

Measurement of electron impact collisional excitation cross sections of Ni to Ge-like gold

NASA Astrophysics Data System (ADS)

May, M. J.; Beiersdorfer, P.; Jordan, N.; Scofield, J. H.; Reed, K. J.; Brown, G. V.; Hansen, S. B.; Porter, F. S.; Kelley, R.; Kilbourne, C. A.; Boyce, K. R.

2017-03-01

We have measured the collisional excitation cross sections for the 3d→4f and 3d→5f excitations in Au ions near the Ni-like charge state by using beam plasmas created in the Livermore electron beam ion trap EBIT-I. The cross sections have been experimentally determined at approximately 1, 2 and 3 keV above the threshold energy, ET, for the 3d→4f excitations (ET ˜ 2.5 keV) and at approximately 0.1, 1 and 2 keV above the threshold energy for the 3d→5f excitations (ET ˜ 3.3 keV). The cross section measurements were made possible by using the GSFC x-ray microcalorimeter at the Livermore EBIT facility. The absolute cross sections are determined from the ratio of the intensity of the collisionally excited bound-bound transitions to the intensity of the radiative recombination lines produced in EBIT-I plasmas. The effects of polarization and Auger decay channels are accounted for in the cross section determination. Measured cross sections are compared with those from HULLAC, DWS and FAC calculations. The measurements demonstrate that some errors exist in the calculated excitation cross sections.

Theoretical estimates of supernova-neutrino cross sections for the stable even-even lead isotopes: Charged-current reactions

NASA Astrophysics Data System (ADS)

Almosly, W.; Carlsson, B. G.; Suhonen, J.; Toivanen, J.; Ydrefors, E.

2016-10-01

A detailed study of the charged-current supernova electron neutrino and electron antineutrino scattering off the stable even-mass lead isotopes A =204 , 206, and 208 is reported in this work. The proton-neutron quasiparticle random-phase approximation (pnQRPA) is adopted to construct the nuclear final and initial states. Three different Skyrme interactions are tested for their isospin and spin-isospin properties and then applied to produce (anti)neutrino-nucleus scattering cross sections for (anti)neutrino energies below 80 MeV. Realistic estimates of the nuclear responses to supernova (anti)neutrinos are computed by folding the computed cross sections with a two-parameter Fermi-Dirac distribution of the electron (anti)neutrino energies. The computed cross sections are compared with earlier calculations and the analyses are extended to take into account the effects coming from the neutrino oscillations.

CCC calculated integrated cross sections of electron-H2 scattering

NASA Astrophysics Data System (ADS)

Zammit, Mark; Fursa, Dmitry; Savage, Jeremy; Bray, Igor

2016-09-01

Recently we applied the molecular convergent close-coupling (CCC) method to electron scattering from molecular hydrogen H2. Convergence of the major integrated cross sections has been explicitly demonstrated in the fixed-nuclei approximation by increasing the number of H2 target states in the close-coupling expansion from 9 to 491. The calculations have been performed using a projectile partial wave expansion with maximum orbital angular momentum Lmax = 8 and total orbital angular momentum projections | M | <= 8 . Coupling to the ionization continuum is modeled via a large pseudo state expansion, which we found is required to obtain reliable elastic and excitation cross sections. Here we present benchmark elastic, single-ionization, electronic excitation and total integrated cross sections over a broad energy range (0.1 to 300 eV) and compare with available experiment and previous calculations. Los Alamos National Laboratory and Curtin University.

Electron induced inelastic and ionization cross section for plasma modeling

NASA Astrophysics Data System (ADS)

Verma, Pankaj; Mahato, Dibyendu; Kaur, Jaspreet; Antony, Bobby

2016-09-01

The present paper reports electron impact total inelastic and ionization cross section for silicon, germanium, and tin tetrahalides at energies varying from ionization threshold of the target to 5000 eV. These cross section data over a wide energy domain are very essential to understand the physico-chemical processes involved in various environments such as plasma modeling, semiconductor etching, atmospheric sciences, biological sciences, and radiation physics. However, the cross section data on the above mentioned molecules are scarce. In the present article, we report the computation of total inelastic cross section using spherical complex optical potential formalism and the estimation of ionization cross section through a semi-empirical method. The present ionization cross section result obtained for SiCl4 shows excellent agreement with previous measurements, while other molecules have not yet been investigated experimentally. Present results show more consistent behaviour than previous theoretical estimates. Besides cross sections, we have also studied the correlation of maximum ionization cross section with the square root of the ratio of polarizability to ionization potential for the molecules with known polarizabilities. A linear relation is observed between these quantities. This correlation is used to obtain approximate polarizability volumes for SiBr4, SiI4, GeCl4, GeBr4, and GeI4 molecules.

Ionization cross sections of the Au L subshells by electron impact from the L3 threshold to 100 keV

NASA Astrophysics Data System (ADS)

Barros, Suelen F.; Vanin, Vito R.; Maidana, Nora L.; Martins, Marcos N.; García-Alvarez, Juan A.; Santos, Osvaldo C. B.; Rodrigues, Cleber L.; Koskinas, Marina F.; Fernández-Varea, José M.

2018-01-01

We measured the cross sections for Au Lα, Lβ, Lγ, Lℓ and Lη x-ray production by the impact of electrons with energies from the L3 threshold to 100 keV using a thin Au film whose mass thickness was determined by Rutherford Backscattering Spectrometry. The x-ray spectra were acquired with a Si drift detector, which allowed to separate the components of the Lγ multiplet lines. The measured Lα, Lβ, {{L}}{γ }1, L{γ }{2,3,6}, {{L}}{γ }{4,4\\prime }, {{L}}{γ }5, {{L}}{\\ell } and Lη x-ray production cross sections were then employed to derive Au L1, L2 and L3 subshell ionization cross sections with relative uncertainties of 8%, 7% and 7%, respectively; these figures include the uncertainties in the atomic relaxation parameters. The correction for the increase in electron path length inside the Au film was estimated by means of Monte Carlo simulations. The experimental ionization cross sections are about 10% above the state-of-the-art distorted-wave calculations.

Electron transport in biomolecular gaseous and liquid systems: theory, experiment and self-consistent cross-sections

NASA Astrophysics Data System (ADS)

White, R. D.; Cocks, D.; Boyle, G.; Casey, M.; Garland, N.; Konovalov, D.; Philippa, B.; Stokes, P.; de Urquijo, J.; González-Magaña, O.; McEachran, R. P.; Buckman, S. J.; Brunger, M. J.; Garcia, G.; Dujko, S.; Petrovic, Z. Lj

2018-05-01

Accurate modelling of electron transport in plasmas, plasma-liquid and plasma-tissue interactions requires (i) the existence of accurate and complete sets of cross-sections, and (ii) an accurate treatment of electron transport in these gaseous and soft-condensed phases. In this study we present progress towards the provision of self-consistent electron-biomolecule cross-section sets representative of tissue, including water and THF, by comparison of calculated transport coefficients with those measured using a pulsed-Townsend swarm experiment. Water–argon mixtures are used to assess the self-consistency of the electron-water vapour cross-section set proposed in de Urquijo et al (2014 J. Chem. Phys. 141 014308). Modelling of electron transport in liquids and soft-condensed matter is considered through appropriate generalisations of Boltzmann’s equation to account for spatial-temporal correlations and screening of the electron potential. The ab initio formalism is applied to electron transport in atomic liquids and compared with available experimental swarm data for these noble liquids. Issues on the applicability of the ab initio formalism for krypton are discussed and addressed through consideration of the background energy of the electron in liquid krypton. The presence of self-trapping (into bubble/cluster states/solvation) in some liquids requires a reformulation of the governing Boltzmann equation to account for the combined localised–delocalised nature of the resulting electron transport. A generalised Boltzmann equation is presented which is highlighted to produce dispersive transport observed in some liquid systems.

Following electron impact excitations of Rn, Ra, Th, U and Pu single atom L sub-shells ionization cross section calculations by using Lotz’s equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayinol, M., E-mail: aydinolm@dicle.edu.tr; Aydeniz, D., E-mail: daydeniz@hotmail.com

L shell ionization cross section and L{sub i} subshells ionization cross sections of Rn, Ra, Th, U, Pu atoms calculated. For each of atoms, ten different electron impact energy values (E{sub o}) are used. Calculations carried out by using Lotz equation in Matlab. First, calculations done for non-relativistic case by using non-relativistic Lotz equation then repeated with relativistic Lotz equation. σ{sub L} total and σ{sub Li}(i = 1,2,3) subshells ionisation cross section values obtained for E{sub o} values in the energy range of E{sub Li}

The interaction of low-energy electrons with fructose molecules

NASA Astrophysics Data System (ADS)

Chernyshova, I. V.; Kontrosh, E. E.; Markush, P. P.; Shpenik, O. B.

2017-11-01

Using a hypocycloidal electronic spectrometer, the interactions of low energy electrons (0-8.50 eV) with fructose molecules, namely, electron scattering and dissociative attachment, are studied. The results of these studies showed that the fragmentation of fructose molecules occurs effectively even at an electron energy close to zero. In the total electron-scattering cross section by molecules, resonance features (at energies 3.10 and 5.00 eV) were first observed near the formation thresholds of light ion fragments OH- and H-. The correlation of the features observed in the cross sections of electron scattering and dissociative attachment is analyzed.

a Time-Dependent Many-Electron Approach to Atomic and Molecular Interactions

NASA Astrophysics Data System (ADS)

Runge, Keith

A new methodology is developed for the description of electronic rearrangement in atomic and molecular collisions. Using the eikonal representation of the total wavefunction, time -dependent equations are derived for the electronic densities within the time-dependent Hartree-Fock approximation. An averaged effective potential which ensures time reversal invariance is used to describe the effect of the fast electronic transitions on the slower nuclear motions. Electron translation factors (ETF) are introduced to eliminate spurious asymptotic couplings, and a local ETF is incorporated into a basis of traveling atomic orbitals. A reference density is used to describe local electronic relaxation and to account for the time propagation of fast and slow motions, and is shown to lead to an efficient integration scheme. Expressions for time-dependent electronic populations and polarization parameters are given. Electronic integrals over Gaussians including ETFs are derived to extend electronic state calculations to dynamical phenomena. Results of the method are in good agreement with experimental data for charge transfer integral cross sections over a projectile energy range of three orders of magnitude in the proton-Hydrogen atom system. The more demanding calculations of integral alignment, state-to-state integral cross sections, and differential cross sections are found to agree well with experimental data provided care is taken to include ETFs in the calculation of electronic integrals and to choose the appropriate effective potential. The method is found to be in good agreement with experimental data for the calculation of charge transfer integral cross sections and state-to-state integral cross sections in the one-electron heteronuclear Helium(2+)-Hydrogen atom system and in the two-electron system, Hydrogen atom-Hydrogen atom. Time-dependent electronic populations are seen to oscillate rapidly in the midst of collision event. In particular, multiple exchanges of the electron are seen to occur in the proton-Hydrogen atom system at low collision energies. The concepts and results derived from the approach provide new insight into the dynamics of nuclear screening and electronic rearrangement in atomic collisions.

Differential cross sections for electron impact excitation of the Herzberg pseudocontinuum of molecular oxygen

NASA Astrophysics Data System (ADS)

Green, M. A.; Maddern, T.; Brunger, M. J.; Campbell, L.; Cartwright, D. C.; Newell, W. R.; Teubner, P. J. O.

2002-09-01

We report differential cross sections (DCSs) for electron impact excitation of the sum (c1Σ u- + A'3 Δ u + A3 Σ u+) of the three states that constitute the Herzberg pseudocontinuum in O2. These DCSs were measured at seven incident electron energies in the range 9-20 eV and over the scattered electron angular range 10-90°. We note that this represents a far more detailed study than has hitherto previously been reported. In their review on electron-diatomic molecule scattering systems, Brunger and Buckman (Brunger M J and Buckman S J 2002 Phys. Rep. 357 215) clearly identified gaps in our knowledge for electron impact excitation of the Herzberg electronic states. The present study rectifies this situation and, additionally, seeks to stimulate theoreticians to extend their existing integral cross section calculations, for the c1 Σ u-, A'3 Δ u and A3 Σ u+ states, to the DCS-level.

Electron-impact total ionization cross sections of DNA sugar-phosphate backbone and an additivity principle

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Dateo, Christopher E.

2005-01-01

The improved binary-encounter dipole (iBED) model [W.M. Huo, Phys. Rev. A64, 042719-1 (2001)l is used to study the total ionization cross sections of the DNA sugar-phosphate backbone by electron impact. Calculations using neutral fragments found that the total ionization cross sections of C3' - and C5', -deoxyribose-phospate, two conformers of the sugar-phosphate backbone, are close to each other. Furthermore, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3' - and C5" -deoxyribose-phospate cross sections, differing by less than 10%. The result implies that certain properties of the-DNA, like the total singly ionization cross section, are localized properties and a building-up or additivity principle may apply. This allows us to obtain accurate properties of larger molecular systems built up from the results of smaller subsystem fragments. Calculations are underway using a negatively charged sugar-phosphate backbone with a metal counter-ion.

Ab initio Potential-Energy Surfaces and Electron-Spin-Exchange Cross Sections for H-O2 Interactions

NASA Technical Reports Server (NTRS)

Stallcop, James R.; Partridge, Harry; Levin, Eugene

1996-01-01

Accurate quartet- and doublet-state potential-energy surfaces for the interaction of a hydrogen atom and an oxygen molecule in their ground states have been determined from an ab initio calculation using large-basis sets and the internally contracted multireference configuration interaction method. These potential surfaces have been used to calculate the H-O2 electron-spin-exchange cross section; the square root of the cross section (in a(sub 0)), not taking into account inelastic effects, can be obtained approximately from the expressions 2.390E(sup -1/6) and 5.266-0.708 log10(E) at low and high collision energies E (in E(sub h)), respectively. These functional forms, as well as the oscillatory structure of the cross section found at high energies, are expected from the nature of the interaction energy. The mean cross section (the cross section averaged over a Maxwellian velocity distribution) agrees reasonably well with the results of measurements.

Nucleon Form Factors above 6 GeV

DOE R&D Accomplishments Database

Taylor, R. E.

1967-09-01

This report describes the results from a preliminary analysis of an elastic electron-proton scattering experiment... . We have measured cross sections for e-p scattering in the range of q{sup 2} from 0.7 to 25.0 (GeV/c){sup 2}, providing a large region of overlap with previous measurements. In this experiment we measure the cross section by observing electrons scattered from a beam passing through a liquid hydrogen target. The scattered particles are momentum analyzed by a magnetic spectrometer and identified as electrons in a total absorption shower counter. Data have been obtained with primary electron energies from 4.0 to 17.9 GeV and at scattering angles from 12.5 to 35.0 degrees. In general, only one measurement of a cross section has been made at each momentum transfer.

Total electron scattering cross section from pyridine molecules in the energy range 10-1000 eV

NASA Astrophysics Data System (ADS)

Dubuis, A. Traoré; Costa, F.; da Silva, F. Ferreira; Limão-Vieira, P.; Oller, J. C.; Blanco, F.; García, G.

2018-05-01

We report on experimental total electron scattering cross-section (TCS) from pyridine (C5H5N) for incident electron energies between 10 and 1000 eV, with experimental uncertainties within 5-10%, as measured with a double electrostatic analyser apparatus. The experimental results are compared with our theoretical calculations performed within the independent atom model complemented with a screening corrected additivity rule (IAM-SCAR) procedure which has been updated by including interference effects. A good level of agreement is found between both data sources within the experimental uncertainties. The present TCS results for electron impact energy under study contribute, together with other scattering data available in the literature, to achieve a consistent set of cross section data for modelling purposes.

Scaling of cross sections for K-electron capture by high-energy protons and alpha-particles from the multielectron atoms

NASA Technical Reports Server (NTRS)

Omidvar, K.

1976-01-01

Electron capture by protons from H, He, and the K-shell of Ar, and alpha particles from He are considered. It is shown that when a certain function of the experimental cross sections is plotted versus the inverse of the collision energy, at high energies the function falls on a straight line. At lower energies the function concaves up or down, depending on the charge of the projectile, the effective charge and the ionization potential of the electron that is being captured. The plot can be used to predict cross sections where experimental data are not available, and as a guide in future experiments. High energy scaling formulas for K-electron capture by low-charge projectiles are given.

Exchange and Inelastic OH(+) + H Collisions on the Doublet and Quartet Electronic States.

PubMed

Bulut, Niyazi; Lique, François; Roncero, Octavio

2015-12-17

The exchange and inelastic state-to-state cross sections for the OH(+) + H collisions are computed from wave packet calculations using the doublet and quartet ground electronic potential energy surface (PES) correlating to the open shell reactants, for collision energies in the range of 1 meV to 0.7 eV. The doublet PES presents a deep insertion well, of ≈6 eV, but the exchange reaction has a rather low probability, showing that the mechanism is not statistical. This well is also responsible of a rather high rotational energy transfer, which makes the rigid-rotor approach overestimate the cross section for low Δj transitions and for high collisonal energies. The quartet PES, with a much shallower well, also presents a low exchange reaction cross section, but the inelastic state-to-state cross sections are very well reproduced by rigid-rotor calculations. When the electronic partition is used to obtain the total state-to-state cross section, the contribution of the doublet state becomes small, and the resulting total cross sections become close to those obtained for the quartet state. Thus, the total (quartet and doublet) cross sections for this open shell system can be reproduced rather satisfactorily by those obtained with the rigid-rotor approximation on the quartet state. Finally, we compare the new OH(+)-H cross sections with OH(+)-He ones recently computed. We found significant differences, especially for transitions with large Δj showing that specific OH(+)-H calculations had to be performed to accurately analyze the OH(+) emission from interstellar molecular clouds.

Copper fine-structure K-shell electron impact ionization cross sections for fast-electron diagnostic in laser-solid experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmeri, P., E-mail: patrick.palmeri@umons.ac.be; Quinet, P., E-mail: pascal.quinet@umons.ac.be; IPNAS, Université de Liège, B-4000 Liège

2015-03-15

The K-shell electron impact ionization (EII) cross section, along with the K-shell fluorescence yield, is one of the key atomic parameters for fast-electron diagnostic in laser-solid experiments through the K-shell emission cross section. In addition, copper is a material that has been often used in those experiments because it has a maximum total K-shell emission yield. Furthermore, in a campaign dedicated to the modeling of the K lines of astrophysical interest (Palmeri et al., 2012), the K-shell fluorescence yields for the K-vacancy fine-structure atomic levels of all the copper isonuclear ions have been calculated. In this study, the K-shell EII crossmore » sections connecting the ground and the metastable levels of the parent copper ions to the daughter ions K-vacancy levels considered in Palmeri et al. (2012) have been determined. The relativistic distorted-wave (DW) approximation implemented in the FAC atomic code has been used for the incident electron kinetic energies up to 10 times the K-shell threshold energies. Moreover, the resulting DW cross sections have been extrapolated at higher energies using the asymptotic form proposed by Davies et al. (2013)« less

Study of scattering cross section of a plasma column using Green's function volume integral equation method

NASA Astrophysics Data System (ADS)

Soltanmoradi, Elmira; Shokri, Babak

2017-05-01

In this article, the electromagnetic wave scattering from plasma columns with inhomogeneous electron density distribution is studied by the Green's function volume integral equation method. Due to the ready production of such plasmas in the laboratories and their practical application in various technological fields, this study tries to find the effects of plasma parameters such as the electron density, radius, and pressure on the scattering cross-section of a plasma column. Moreover, the incident wave frequency influence of the scattering pattern is demonstrated. Furthermore, the scattering cross-section of a plasma column with an inhomogeneous collision frequency profile is calculated and the effect of this inhomogeneity is discussed first in this article. These results are especially used to determine the appropriate conditions for radar cross-section reduction purposes. It is shown that the radar cross-section of a plasma column reduces more for a larger collision frequency, for a relatively lower plasma frequency, and also for a smaller radius. Furthermore, it is found that the effect of the electron density on the scattering cross-section is more obvious in comparison with the effect of other plasma parameters. Also, the plasma column with homogenous collision frequency can be used as a better shielding in contrast to its inhomogeneous counterpart.

Study of electron impact inelastic scattering of chlorine molecule (Cl2)

NASA Astrophysics Data System (ADS)

Yadav, Hitesh; Vinodkumar, Minaxi; Limbachiya, Chetan; Vinodkumar, P. C.

2018-02-01

A theoretical study is carried out for electron interactions with the chlorine molecule (Cl2) for incident energies ranging from 0.01 to 5000 eV. This wide range of energy has allowed us to investigate a variety of processes and report data on symmetric excitation energies, dissociative electron attachment (DEA), total excitation cross sections, and ionization cross section (Q ion) along with total inelastic cross sections (Q inel). The present study is important since Cl2 is a prominent gas for plasma etching and its anionic atoms are important in the etching of semiconductor wafers. In order to compute the total inelastic cross sections, we have employed the ab initio R-matrix method (0.01 to 15 eV) together with the spherical complex optical potential method (∼15 to 5000 eV). The R-matrix calculations are performed using a close coupling method, and we have used DEA estimator via Quantemol-N to calculate the DEA fragmentation and cross sections. The present study finds overall good agreement with the available experimental data. Total excitation and inelastic cross sections of e-{{{Cl}}}2 scattering for a wide energy range (0.01 to 5 keV) are reported for the first time, to the best of our knowledge.

The electron-furfural scattering dynamics for 63 energetically open electronic states

NASA Astrophysics Data System (ADS)

da Costa, Romarly F.; do N. Varella, Márcio T.; Bettega, Márcio H. F.; Neves, Rafael F. C.; Lopes, Maria Cristina A.; Blanco, Francisco; García, Gustavo; Jones, Darryl B.; Brunger, Michael J.; Lima, Marco A. P.

2016-03-01

We report on integral-, momentum transfer- and differential cross sections for elastic and electronically inelastic electron collisions with furfural (C5H4O2). The calculations were performed with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (Nopen) at either the static-exchange (Nopen ch-SE) or the static-exchange-plus-polarisation (Nopen ch-SEP) approximation was employed to calculate the scattering amplitudes at impact energies lying between 5 eV and 50 eV, using a channel coupling scheme that ranges from the 1ch-SEP up to the 63ch-SE level of approximation depending on the energy considered. For elastic scattering, we found very good overall agreement at higher energies among our SMCPP cross sections, our IAM-SCAR+I cross sections and the experimental data for furan (a molecule that differs from furfural only by the substitution of a hydrogen atom in furan with an aldehyde functional group). This is a good indication that our elastic cross sections are converged with respect to the multichannel coupling effect for most of the investigated intermediate energies. However, although the present application represents the most sophisticated calculation performed with the SMCPP method thus far, the inelastic cross sections, even for the low lying energy states, are still not completely converged for intermediate and higher energies. We discuss possible reasons leading to this discrepancy and point out what further steps need to be undertaken in order to improve the agreement between the calculated and measured cross sections.

The electron-furfural scattering dynamics for 63 energetically open electronic states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costa, Romarly F. da; Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, São Paulo 09210-580; Varella, Márcio T. do N

We report on integral-, momentum transfer- and differential cross sections for elastic and electronically inelastic electron collisions with furfural (C{sub 5}H{sub 4}O{sub 2}). The calculations were performed with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (N{sub open}) at either the static-exchange (N{sub open} ch-SE) or the static-exchange-plus-polarisation (N{sub open} ch-SEP) approximation was employed to calculate the scattering amplitudes at impact energies lying between 5 eV and 50 eV, using a channelmore » coupling scheme that ranges from the 1ch-SEP up to the 63ch-SE level of approximation depending on the energy considered. For elastic scattering, we found very good overall agreement at higher energies among our SMCPP cross sections, our IAM-SCAR+I cross sections and the experimental data for furan (a molecule that differs from furfural only by the substitution of a hydrogen atom in furan with an aldehyde functional group). This is a good indication that our elastic cross sections are converged with respect to the multichannel coupling effect for most of the investigated intermediate energies. However, although the present application represents the most sophisticated calculation performed with the SMCPP method thus far, the inelastic cross sections, even for the low lying energy states, are still not completely converged for intermediate and higher energies. We discuss possible reasons leading to this discrepancy and point out what further steps need to be undertaken in order to improve the agreement between the calculated and measured cross sections.« less

Photoionization of Li2

NASA Astrophysics Data System (ADS)

Li, Y.; Pindzola, M. S.; Ballance, C. P.; Colgan, J.

2014-05-01

Single and double photoionization cross sections for Li2 are calculated using a time-dependent close-coupling method. The correlation between the outer two electrons of Li2 is obtained by relaxation of the close-coupled equations in imaginary time. Propagation of the close-coupled equations in real time yields single and double photoionization cross sections for Li2. The two active electron cross sections are compared with one active electron distorted-wave and close-coupling results for both Li and Li2. This work was supported in part by grants from NSF and US DoE. Computational work was carried out at NERSC in Oakland, California, NICS in Knoxville, Tennessee, and OLCF in Oak Ridge, Tennessee.

CCC calculated differential cross sections of electron-H2 scattering

NASA Astrophysics Data System (ADS)

Fursa, Dmitry; Zammit, Mark; Savage, Jeremy; Bray, Igor

2016-09-01

Recently we applied the molecular convergent close-coupling (CCC) method to electron scattering from molecular hydrogen H2. Convergence of the major differential cross sections has been explicitly demonstrated in the fixed-nuclei approximation. A large close-coupling expansion that coupled highly excited states and ionization channels proved to be important to obtain convergent results. Here we present benchmark elastic and electronic excitation differential cross sections for b3Σu+ , a3Σg+ , c3Πu , B1Σu+ , EF1Σg+ , C1Πu , and e3Σu+ states and compare with available experiment and previous calculations. Work supported by Los Alamos National Laboratory and Curtin University.

Electron-impact excitation of the 1{sup 1}{ital S}{r_arrow}3{sup 1}{ital P} and 1{sup 1}{ital S}{r_arrow}4{sup 1}{ital P} transitions in helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khakoo, M.A.; Roundy, D.; Rugamas, F.

1996-11-01

The method of electron-photon coincidence is used to {open_quote}{open_quote}resolve{close_quote}{close_quote} the electron-impact excitation of the {ital n}{sup 1}{ital P} levels ({ital n}=3 and 4) from nearby levels. Experimentally determined ratios of the differential cross sections for the electron-impact excitation of 1{sup 1}{ital S}{r_arrow}2{sup 1}{ital P}, to 1{sup 1}{ital S}{r_arrow}3{sup 1}{ital P}, and 4{sup 1}{ital P} transitions are presented at 30-, 40-, and 80-eV incident electron energies. Differential cross sections for the 1{sup 1}{ital S}{r_arrow}3{sup 1}{ital P} and 1{sup 1}{ital S}{r_arrow}4{sup 1}{ital P} transitions are derived by normalizing these ratios to available experimental differential cross sections for the 1{sup 1}{ital S}{r_arrow}2{sup 1}{italmore » P} transition. The ratios and differential cross sections are compared to available theoretical and semiempirical data. {copyright} {ital 1996 The American Physical Society.}« less

Note on measuring electronic stopping of slow ions

NASA Astrophysics Data System (ADS)

Sigmund, P.; Schinner, A.

2017-11-01

Extracting stopping cross sections from energy-loss measurements requires careful consideration of the experimental geometry. Standard procedures for separating nuclear from electronic stopping treat electronic energy loss as a friction force, ignoring its dependence on impact parameter. In the present study we find that incorporating this dependence has a major effect on measured stopping cross sections, in particular for light ions at low beam energies. Calculations have been made for transmission geometry, nuclear interactions being quantified by Bohr-Williams theory of multiple scattering on the basis of a Thomas-Fermi-Molière potential, whereas electronic interactions are characterized by Firsov theory or PASS code. Differences between the full and the restricted stopping cross section depend on target thickness and opening angle of the detector and need to be taken into account in comparisons with theory as well as in applications of stopping data. It follows that the reciprocity principle can be violated when checked on restricted instead of full electronic stopping cross sections. Finally, we assert that a seeming gas-solid difference in stopping of low-energy ions is actually a metal-insulator difference. In comparisons with experimental results we mostly consider proton data, where nuclear stopping is only a minor perturbation.

State-resolved Photodissociation and Radiative Association Data for the Molecular Hydrogen Ion

NASA Astrophysics Data System (ADS)

Zammit, Mark C.; Savage, Jeremy S.; Colgan, James; Fursa, Dmitry V.; Kilcrease, David P.; Bray, Igor; Fontes, Christopher J.; Hakel, Peter; Timmermans, Eddy

2017-12-01

We present state-resolved (electronic, vibrational, and rotational) cross sections and rate coefficients for the photodissociation (PD) of {{{H}}}2+ and radiative association (RA) of H–H+. We developed a fully quantum mechanical approach within the nonrelativistic Born–Oppenheimer approximation to describe {{{H}}}2+ and calculate the data for transitions between the ground electronic state 1s{σ }g and the 2p{σ }u, 2p{π }u, 3p{σ }u, 3p{π }u, 4p{σ }u, 4f{σ }u, 4f{π }u, and 4p{π }u electronic states (i.e., up to {{{H}}}2+ n = 4). Tables of the dipole-matrix elements and energies needed to calculate state-resolved cross sections and rate coefficients will be made publicly available. These data could be important in astrophysical models when dealing with photon wavelengths (or radiation temperature distributions that are weighted toward such wavelengths) around 100 nm. For example, at these wavelengths and a material temperature of 8400 K, the LTE-averaged PD cross section via the (second electronically excited) 2p{π }u state is over three times larger than the PD cross section via the (first electronically excited) 2p{σ }u state.

Positronium collisions with atoms and molecules

NASA Astrophysics Data System (ADS)

Fabrikant, I. I.; Gribakin, G. F.; Wilde, R. S.

2017-11-01

We review recent theoretical efforts to explain observed similarities between electron-atom and positronium(Ps)-atom scattering which also extends to molecular targets. In the range of the projectile velocities above the threshold for Ps ionization (break-up) this similarity can be explained in terms of quasi-free electron scattering and impulse approximation. However, for lower Ps velocities more sophisticated methods should be developed. Our calculations of Ps scattering by heavy noble-gas atoms agree well with experiments at Ps velocities above the Ps ionization threshold. However, in contrast to electron scattering cross sections, at lower velocities they exhibit maxima whereas the experimental cross sections tend to decrease toward lower velocities indicating the same similarity with electron scattering cross section observed above the threshold. Our preliminary results for Ps-N2 scattering confirm experimental observation of a resonance similar to the ∏ g resonance in electron-N2 scattering.

Laser Assisted Free-Free Transition in Electron - Atom Collision

NASA Technical Reports Server (NTRS)

Sinha, C.; Bhatia, A. K.

2011-01-01

Free-free transition is studied for electron-Hydrogen atom system in ground state at very low incident energies in presence of an external homogeneous, monochromatic and linearly polarized laser field. The incident electron is considered to be dressed by the laser in a non perturbative manner by choosing the Volkov solutions in both the channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron exchange, short range as well as of the long range interactions. Laser assisted differential as well as elastic total cross sections are calculated for single photon absorption/emission in the soft photon limit, the laser intensity being much less than the atomic field intensity. A strong suppression is noted in the laser assisted cross sections as compared to the field free situations. Significant difference is noted in the singlet and the triplet cross sections.

Triple differential cross sections for the electron-impact ionization of H{sub 2} molecules for equal and unequal outgoing electron energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colgan, J.; Al-Hagan, O.; Madison, D. H.

A comprehensive theoretical and experimental investigation of the triple differential cross sections arising from the electron-impact ionization of molecular hydrogen is made, at an incident electron energy of 35.4 eV, for cases where the outgoing electrons have equal and unequal energies, and for a range of experimental geometries. Generally, good agreement is found between two theoretical approaches and experiment, with the best agreement arising for intermediate geometries with large gun angles and for the perpendicular geometry.

Application of the BEf-scaling approach to electron impact excitation of diople-allowed electronic states in molecules

NASA Astrophysics Data System (ADS)

Brunger, M. J.; Thorn, P. A.; Campbell, L.; Kato, H.; Kawahara, H.; Hoshino, M.; Tanaka, H.; Kim, Y.-K.

2008-05-01

We consider the efficacy of the BEf-scaling approach, in calculating reliable integral cross sections for electron impact excitation of dipole-allowed electronic states in molecules. We will demonstrate, using specific examples in H2, CO and H2O, that this relatively simple procedure can generate quite accurate integral cross sections which compare well with available experimental data. Finally, we will briefly consider the ramifications of this to atmospheric and other types of modelling studies.

Calculation of SF6-/SF6 and Cl-/CFCl3 electron attachment cross sections in the energy range 0-100 meV

NASA Technical Reports Server (NTRS)

Chutjian, A.

1982-01-01

Electron attachment cross sections for the processes SF6-/SF6 and Cl-/CFCl3 are calculated in a local theory using a model in which diatomic-like potential energy curves for the normal modes are constructed from available spectroscopic data. Thermally populated vibrational and rotational levels are included. Good agreement is found with experimental cross sections in the energy range 5-100 meV for a particular choice of potential energy curve parameters.

Double Photoionization Near Threshold

NASA Technical Reports Server (NTRS)

Wehlitz, Ralf

2007-01-01

The threshold region of the double-photoionization cross section is of particular interest because both ejected electrons move slowly in the Coulomb field of the residual ion. Near threshold both electrons have time to interact with each other and with the residual ion. Also, different theoretical models compete to describe the double-photoionization cross section in the threshold region. We have investigated that cross section for lithium and beryllium and have analyzed our data with respect to the latest results in the Coulomb-dipole theory. We find that our data support the idea of a Coulomb-dipole interaction.

Effect of nuclear shielding in collision of positive charged helium ions with helium atoms

NASA Astrophysics Data System (ADS)

Ghavaminia, Hoda; Ghavaminia, Shirin

2018-03-01

Differential in angle and absolute cross sections in energy of the scattered particles are obtained for single charge exchange in ^3He^+-^4He collisions by means of the four body boundary-corrected first Born approximation (CB1-4B). The quantum-mechanical post and prior transition amplitudes are derived in terms of two-dimensional real integrals in the case of the prior form and five-dimensional quadratures for the post form. The effect of the dynamic electron correlation through the complete perturbation potential and the nuclear-screening influence of the passive electrons on the electron capture process is investigated. The results obtained in the CB1-4B method are compared with the available experimental data. For differential cross sections, the present results are in better agreement with experimental data than other theoretical data at extreme forward scattering angles. The integral cross sections are in excellent agreement with the experiment. Also, total cross sections for single electron capture, has been investigated using the classical trajectory Monte Carlo method. The present calculated results are found to be in an excellent agreement with the experimental data.

An R-matrix study of electron induced processes in BF3 plasma

NASA Astrophysics Data System (ADS)

Gupta, Dhanoj; Chakrabarti, Kalyan; Yoon, Jung-Sik; Song, Mi-Young

2017-12-01

An R-matrix formalism is used to study electron collision with the BF3 molecule using Quantemol-N, a computational system for electron molecule collisions which uses the molecular R-matrix method. Several target models are tested for BF3 in its equilibrium geometry, and the results are presented for the best model. Scattering calculations are then performed to yield resonance parameters, elastic, differential, excitation, and momentum transfer cross sections. The results for all the cross sections are compared with the experimental and theoretical data, and a good agreement is obtained. The resonances have been detected at 3.79 and 13.58 eV, with the ionization threshold being 15.7 eV. We have also estimated the absolute dissociative electron attachment (DEA) cross section for the F- ion production from BF3, which is a maiden attempt. The peak of the DEA is at around 13.5 eV, which is well supported by the resonance detected at 13.58 eV. The cross sections reported here find a variety of applications in the plasma technology.

Spin-dependence of the electron scattering cross section by a magnetic layer system and the magneto-resistance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J.T.; Tang, F.; Brown, W.D.

1998-12-20

The authors present a theoretical model for calculating the spin-dependent cross section of the scattering of electrons by a magnetic layer system. The model demonstrates that the cross sections of the scattering are different for spin up and spin down electrons. The model assumes that the electrical resistivity in a conductor is proportional to the scattering cross section of the electron in it. It is believed to support the two channel mechanism in interpreting magneto-resistance (MR). Based on the model without considering the scattering due to the interfacial roughness and the spin flipping scattering, the authors have established a relationshipmore » between MR and the square of the magnetic moment in the bulk sample without considering the scattering due to the interfacial roughness and the spin flipping scattering. It can also qualitatively explain the MR difference between the current in plane (CIP) and current perpendicular to the plane (CPP) configurations. The predictions by the model agree well with the experimental findings.« less

Electron collisions with phenol: Total, integral, differential, and momentum transfer cross sections and the role of multichannel coupling effects on the elastic channel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costa, Romarly F. da; Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-580 Santo André, São Paulo; Oliveira, Eliane M. de

2015-03-14

We report theoretical and experimental total cross sections for electron scattering by phenol (C{sub 6}H{sub 5}OH). The experimental data were obtained with an apparatus based in Madrid and the calculated cross sections with two different methodologies, the independent atom method with screening corrected additivity rule (IAM-SCAR), and the Schwinger multichannel method with pseudopotentials (SMCPP). The SMCPP method in the N{sub open}-channel coupling scheme, at the static-exchange-plus-polarization approximation, is employed to calculate the scattering amplitudes at impact energies ranging from 5.0 eV to 50 eV. We discuss the multichannel coupling effects in the calculated cross sections, in particular how the numbermore » of excited states included in the open-channel space impacts upon the convergence of the elastic cross sections at higher collision energies. The IAM-SCAR approach was also used to obtain the elastic differential cross sections (DCSs) and for correcting the experimental total cross sections for the so-called forward angle scattering effect. We found a very good agreement between our SMCPP theoretical differential, integral, and momentum transfer cross sections and experimental data for benzene (a molecule differing from phenol by replacing a hydrogen atom in benzene with a hydroxyl group). Although some discrepancies were found for lower energies, the agreement between the SMCPP data and the DCSs obtained with the IAM-SCAR method improves, as expected, as the impact energy increases. We also have a good agreement among the present SMCPP calculated total cross section (which includes elastic, 32 inelastic electronic excitation processes and ionization contributions, the latter estimated with the binary-encounter-Bethe model), the IAM-SCAR total cross section, and the experimental data when the latter is corrected for the forward angle scattering effect [Fuss et al., Phys. Rev. A 88, 042702 (2013)].« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aydinol, M., E-mail: aydinolm@dicle.edu.tr; Aydeniz, D., E-mail: daydeniz@hotmail.com

L shell ionization cross section and {sub Li} subshells ionization cross sections of Os, Pt, Hg, Pb, Po atoms calculated. For each atom, ten different electron impacty energy values E{sub oi} used. Calculations carried out by using nonrelativistic Lotz equation in Matlab. Ionization cross section values obtained for Eoi values in the energy range of E{sub Li} ≤E{sub oi}≤4E{sub Li} for each atom. Starting allmost from E{sub oi} = E{sub Li} (i = 1,2,3) values of the each subshell ionization threshold energy, ionization cross section are increasing rapidly with E{sub oi}. For a fixed E{sub oi} = 3. E{sub Li}more » values, while Z increases from Z = 76 to Z = 84, ionization cross section are decrease. These results help to understand some results which obtained from other electron-sigle atom impact studies on σ{sub Li} subshells.« less

Characteristics of Polarisation in the Ramsauer-Townsend Minima in Strongly Coupled Semiclassic Plasmas

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Jung, Young-Dae

2017-10-01

The influence of quantum shielding on the Ramsauer-Townsend phenomena for the total electron-atom polarisation collision cross-section is investigated in partially ionised strongly coupled semiclassic plasmas. The result shows that the quantum shielding effect changes the position of the Ramsauer energy in partially ionised strongly coupled plasmas. It is also found that the quantum shielding effect enhances the total electron-atom collision cross-section when the collision energy is greater than the Ramsauer energy; however, it suppresses the collision cross-section when the collision energy is smaller than the Ramsauer energy. In addition, it is shown that the plasma screening effect significantly changes the position of the Ramsauer energy and the influence of plasma screening on the magnitude of the collision cross-section is more significant near the Ramsauer energy domain. The variations of the Ramsauer energy and the collision cross-section due to the quantum shielding effect are also discussed.

Energy and angular distributions of electron emission from diatomic molecules by bare ion impact

NASA Astrophysics Data System (ADS)

Mondal, A.; Mandal, C. R.; Purkait, M.

2015-06-01

The three-Coulomb wave model has been used extensively to study the energy and angular distributions of double-differential cross sections (DDCS) of electron emissions from hydrogen and nitrogen molecules by bare ion impact at intermediate and high energies. In the present model, we have expressed the molecular triple differential cross section in terms of the corresponding atomic triple differential cross section multiplied by the occupation number and the average Rayleigh interference factor, which accounts for the two-center interference effect. Here we have used an active electron approximation of the molecule as a whole in the initial channel. To account for the effect of passive electrons, we have constructed a model potential that satisfies the initial conditions and the corresponding wavefunction has been calculated from the model Hamiltonian of the active electron in the target. In the final channel, we have used a hydrogenic model with an effective nuclear charge that is calculated from its binding energy. In this model, the correlated motion of the particles in the exit channel of the reaction is considered by an adequate product of three-Coulomb functions. The emitted electron, the incident projectile ion and the residual ion are considered to be in same plane. The obtained results are compared with other recent theoretical and experimental findings. There is an overall agreement of the calculations with the experimental data for electron emission cross sections.

A New Scaling Law of Resonance in Total Scattering Cross Section in Gases

NASA Astrophysics Data System (ADS)

Raju, Gorur Govinda

2009-10-01

Electrical discharges in gases continue to be an active area of research because of industrial applications such as power systems, environmental clean up, laser technology, semiconductor fabrication etc. A fundamental knowledge of electron-gas neutral interaction is indispensable and, the total scattering cross section is one of the quantities that have been measured extensively. The energy dependence of the total cross sections shows peaks or resonance processes that are operative in the collision process. These peaks and the energies at which they occur are shown to satisfy a broad relationship involving the polarizability and the dipole moment of the target particle. Data on 62 target particles belonging to the following species are analyzed. (Eq 1) Rare gas atoms (Eq 2) Di-atomic molecules with combinations of polar, non-polar, attaching, and non-attaching properties Poly-atomic molecules with combinations of polar, non-polar, attaching, and non-attaching properties. Methods of improving the newly identified scaling law and possible application have been identified. 1 INTRODUCTION: Data on electron-neutral interactions are one of the most fundamental in the study of gaseous electronics and an immense literature, both experimental and theoretical, has become available since about the year 1920. [1-5]. In view of the central role which these data play in all facets of gas discharges and plasma science, it is felt that a critical review of available data is timely, mainly for the community of high voltage engineers and industries connected with plasma science in general. The electron-neutral interaction, often referred to as scattering in the scientific literature, is quantified by using the quantity called the total scattering cross section (QT, m^2). In the literature on cross section, total cross section and total scattering cross section are terms used synonymously and we follow the same practice. A definition may be found in reference [1]. This paper concerns scaling of total cross section of gases at resonance energy and the electron energy at which resonance occurs. The meaning of resonance is briefly explained in the following section. Here, we use the term scaling to relate the two quantities mentioned, namely, the resonance energy and the total cross section at that energy. Consistent with the definition of scaling, if the law proposed holds, one of the two quantities mentioned above may be calculated if the other is known. Such a method is very useful in gas discharge modeling and calculation of breakdown voltages, as more fully explained in the later section of the paper. 2 DESCRIPTION OF RESONANCE: A brief description of resonance phenomena in several types of target particles, viz., atomic, poly atomic, polar, non-polar phenomena are presented. 3 PREVIOUS SCALING LAWS: A common representation of a given characteristic with as few adjustable parameters as possible is generally known as the scaling law. The Paschen curve for breakdown voltage is such a familiar scaling law. With reference to cross sections several attempts have been made to obtain a scaling law, with varying degree of success. If the cross section-energy curve is qualitatively similar without having sharp peaks and oscillations, moderately successful scaling laws may be devised. For example, the ionization cross section- energy curves for most gases follow a general pattern. Several published scaling laws are discussed. 4 A NEW SCALING LAW AND DISCUSSION: In this work the author has compiled the resonance details for more than 60 gasest hat include the range from simple atoms to complex molecules that are polyatomic, dipolar, electron-attaching and isomers. The target particles exhibit a number of distinct features, as far as their total cross section variation with electron energy is concerned as already explained.

Inelastic scattering of electrons at real metal surfaces

NASA Astrophysics Data System (ADS)

Ding, Z.-J.

1997-04-01

A theory is presented to calculate the electron inelastic scattering cross section for a moving electron near the surface region at an arbitrary takeoff angle. The theory is based on using a bulk plasmon-pole approximation to derive the numerically computable expression of the electron self-energy in the random-phase approximation for a surface system, through the use of experimental optical constants. It is shown that the wave-vector-dependent surface dielectric function satisfies the surface sum rules in this scheme. The theory provides a detailed knowledge of electron self-energy depending on the kinetic energy, distance from surface, and velocity vector of an electron moving in any metal of a known dielectric constant, accommodating the formulation to practical situation in surface electron spectroscopies. Numerical computations of the energy-loss cross section have been made for Si and Au. The contribution to the total differential scattering cross section from each component is analyzed. The depth dependence informs us in detail how the bulk excitation mode changes to a surface excitation mode with an electron approaching the surface from the interior of a medium.

Asymptotic form for the cross section for the Coulomb interacting rearrangement collisions.

NASA Technical Reports Server (NTRS)

Omidvar, K.

1973-01-01

It is shown that in a rearrangement collision leading to the formation of highly excited hydrogenlike states the cross section at high energies behaves as 1/n-squared, with n the principal quantum number, thus invalidating the Brinkman-Kramers approximation for large n. Similarly, in high-energy inelastic electron-hydrogenlike-atom collisions the exchange cross section for sufficiently large n dominates the direct excitation cross section.

Electron-impact excitation heating rates in the atmosphere of Titan

NASA Astrophysics Data System (ADS)

Campbell, L.; Kato, H.; Brunger, M. J.; Bradshaw, M. D.

2010-09-01

A previous study of various heating rates in the atmosphere of Titan included electron-impact excitation of molecular nitrogen as one component. This work examines this component in more detail, using a statistical equilibrium calculation to avoid approximations made in the earlier work. The sensitivity of the results to different cross-section sets is investigated. It is found that using recent and more physical cross sections for vibrational excitation produces a significant increase in the heating rate. On the other hand, using more accurate cross sections for the electronic states had little apparent effect on the heating rates when used within the approximations made in the previous model. However, the inclusion of more transitions in this study produces a significant increase in the electronic state heating rates, as states that were originally neglected are now accounted for here.

EXCITATION OF LEVELS IN Li$sup 7$ BY INELASTIC ELECTRON SCATTERING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernheim, M; Bishop, G R

1963-07-15

Cross sections for the excitation of some levels in Li/sup 7/ up to 8- Mev excitation energy were measured by the iiielastic scattering of electrons for a variety of incident electron energies and scatiering angles. The cross section calculated in first Dorn approximation is expected to be valid for this nucleus. The calculated angular distribution is given for different spin and parity and for different levels of excitation. (R.E.U.)

Inelastic collisions of positrons with one-valence-electron targets

NASA Technical Reports Server (NTRS)

Abdel-Raouf, Mohamed Assad

1990-01-01

The total elastic and positronium formation cross sections of the inelastic collisions between positrons and various one-valence-electron atoms, (namely hydrogen, lithium, sodium, potassium and rubidium), and one-valence-electron ions, (namely hydrogen-like, lithium-like and alkaline-earth positive ions) are determined using an elaborate modified coupled-static approximation. Special attention is devoted to the behavior of the Ps cross sections at the energy regions lying above the Ps formation thresholds.

Elastic electron scattering by ethyl vinyl ether

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khakoo, M. A.; Hong, L.; Kim, B.

2010-02-15

We report measured and calculated results for elastic scattering of low-energy electrons by ethyl vinyl ether (ethoxyethene), a prototype system for studying indirect dissociative attachment processes that may play a role in DNA damage. The integral cross section displays the expected {pi}{sup *} shape resonance. The agreement between the calculated and measured cross sections is generally good.

Electron and positron scattering from CF 3I molecules below 600 eV: a comparison with CF 3H

NASA Astrophysics Data System (ADS)

Kawada, Michihito K.; Sueoka, Osamu; Kimura, Mineo

2000-11-01

The total cross-sections (TCSs) for electron and positron scattering from CF 3I molecules have been studied experimentally. A theoretical analysis based on the continuum multiple-scattering (CMS) method has been performed to understand the origin of resonances and the elastic cross-sections. The present TCS for electron scattering is found to be larger by about 20% than that of T. Underwood-Lemons, D.C. Winkler, J.A. Tossel, J.H. Moore [J. Chem. Phys. 100 (1994) 9117] although the general shape agrees well in the entire energy studied. The difference in the cross-sections for CF 3I and CF 3H is explained by the sizes and the dipole moments of these molecules.

Double differential cross sections of ethane molecule

NASA Astrophysics Data System (ADS)

Kumar, Rajeev

2018-05-01

Partial and total double differential cross sections corresponding to various cations C2H6+, C2H4+, C2H5+, C2H3+, C2H2+, CH3+, H+, CH2+, C2H+, H2+, CH+, H3+, C2+ and C+ produced during the direct and dissociative electron ionization of Ethane (C2H6) molecule have been calculated at fixed impinging electron energies 200 and 500eV by using modified Jain-Khare semi empirical approach. The calculation for double differential cross sections is made as a function of energy loss suffered by primary electron and angle of incident. To the best of my knowledge no other data is available for the comparison.

Angle-Differential Cross Sections for Radiative Recombination and the Photoelectric Effect in the K, L, and M Shells of One-Electron Systems Calculated Within AN Exact Relativistic Description

NASA Astrophysics Data System (ADS)

Ichihara, Akira; Eichler, Jörg

2001-11-01

An extensive tabulation of angle-differential cross sections for radiative recombination and, consequently, for the photoelectric effect of hydrogen-like ions with representative charge numbers Z=18, 36, 54, 66, 79, 82, and 92 is presented for the K, L, and M shells and electron energies ranging from 1.0 keV to 1.5 MeV. The cross sections, accurate to three digits, are based on fully relativistic calculations including the effects of the finite nuclear size and all multipole orders of the photon field. In order to provide a good overview, the following procedure has been adopted: For the charge numbers 18, 54, and 92, the differential cross sections are presented in figures for all subshells and for representative energies. Furthermore, as a sample of the calculations, we present a complete table for the case of Z=79. The full tabulation for all charge numbers mentioned above is provided in electronic form (http://www.idealibrary.com/links/doi/10.1006/adnd.2001.0868/dat). By simple scaling, the dependence on the projectile energy in MeV/u can be derived for accelerator experiments, and, by using elementary formulas, the differential cross section for the photoelectric effect as a function of the electron emission angle can also be obtained.

Dissociative recombination of HCl+

NASA Astrophysics Data System (ADS)

Larson, Åsa; Fonseca dos Santos, Samantha; E. Orel, Ann

2017-08-01

The dissociative recombination of HCl+, including both the direct and indirect mechanisms, is studied. For the direct process, the relevant electronic states are calculated ab initio by combining electron scattering calculations to obtain resonance positions and autoionization widths with multi-reference configuration interaction calculations of the ion and Rydberg states. The cross section for the direct dissociation along electronic resonant states is computed by solution of the time-dependent Schrödinger equation. For the indirect process, an upper bound value for the cross section is obtained using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Vibrational excitations of the ionic core from the ground vibrational state, v = 0 , to the first three excited vibrational states, v = 1 , v = 2 , and v = 3 , are considered. Autoionization is neglected and the effect of the spin-orbit splitting of the ionic potential energy upon the indirect dissociative recombination cross section is considered. The calculated cross sections are compared to measurements.

Electron Scattering from MERCURY-198 and Mercury -204.

NASA Astrophysics Data System (ADS)

Laksanaboonsong, Jarungsaeng

This experiment is the first electron scattering study on mercury isotopes. Electron scattering from ^{198}Hg and ^{204 }Hg has been performed at the NIKHEF-K Medium Energy Accelerator. Measured cross sections cover an effective momentum transfer range from 0.4 to 2.9 fm^ {-1}. Elastic cross sections were determined for scattering from both isotopes. Cross section for inelastic excitations in ^{198}Hg below 3 MeV were also determined. Measured cross sections were fit using DWBA phase shift codes to determine coefficients for Fourier-Bessel expansions of ground state and transition charge densities. Differences between the ground state charge densities of the two isotopes reveal the effect of the polarization of the proton core in response to the addition of neutrons. Spin and parity of several excited states of ^{198}Hg were determined. Extracted transition densities of these states show their predominantly collective nature. Charge densities for members of the ground state rotational band were compared with axially symmetric Hartree-Fock and geometrical model predictions.

Dissociative recombination of HCl.

PubMed

Larson, Åsa; Fonseca Dos Santos, Samantha; E Orel, Ann

2017-08-28

The dissociative recombination of HCl + , including both the direct and indirect mechanisms, is studied. For the direct process, the relevant electronic states are calculated ab initio by combining electron scattering calculations to obtain resonance positions and autoionization widths with multi-reference configuration interaction calculations of the ion and Rydberg states. The cross section for the direct dissociation along electronic resonant states is computed by solution of the time-dependent Schrödinger equation. For the indirect process, an upper bound value for the cross section is obtained using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Vibrational excitations of the ionic core from the ground vibrational state, v = 0, to the first three excited vibrational states, v = 1, v = 2, and  v = 3, are considered. Autoionization is neglected and the effect of the spin-orbit splitting of the ionic potential energy upon the indirect dissociative recombination cross section is considered. The calculated cross sections are compared to measurements.

Measurements of inclusive W and Z cross sections in pp collisions at sqrt(s)=7 TeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khachatryan, V.; et al.,

2011-01-01

Measurements of inclusive W and Z boson production cross sections in pp collisions at sqrt(s)=7 TeV are presented, based on 2.9 inverse picobarns of data recorded by the CMS detector at the LHC. The measurements, performed in the electron and muon decay channels, are combined to give sigma(pp to WX) times B(W to muon or electron + neutrino) = 9.95 \\pm 0.07(stat.) \\pm 0.28(syst.) \\pm 1.09(lumi.) nb and sigma(pp to ZX) times B(Z to oppositely charged muon or electron pairs) = 0.931 \\pm 0.026(stat.) \\pm 0.023(syst.) \\pm 0.102(lumi.) nb. Theoretical predictions, calculated at the next-to-next-to-leading order in QCD using recentmore » parton distribution functions, are in agreement with the measured cross sections. Ratios of cross sections, which incur an experimental systematic uncertainty of less than 4%, are also reported.« less

Collisions of low-energy electrons with isopropanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bettega, M. H. F.; Winstead, C.; McKoy, V.

2011-10-15

We report measured and calculated cross sections for elastic scattering of low-energy electrons by isopropanol (propan-2-ol). The experimental data were obtained using the relative flow technique with helium as the standard gas and a thin aperture as the collimating target gas source, which permits use of this method without the restrictions imposed by the relative flow pressure conditions on helium and the unknown gas. The differential cross sections were measured at energies of 1.5, 2, 3, 5, 6, 8, 10, 15, 20, and 30 eV and for scattering angles from 10 deg. to 130 deg. The cross sections were computedmore » over the same energy range employing the Schwinger multichannel method in the static-exchange plus polarization approximation. Agreement between theory and experiment is very good. The present data are compared with previously calculated and measured results for n-propanol, the other isomer of C{sub 3}H{sub 7}OH. Although the integral and momentum transfer cross sections for the isomers are very similar, the differential cross sections show a strong isomeric effect: In contrast to the f-wave behavior seen in scattering by n-propanol, d-wave behavior is observed in the cross sections of isopropanol. These results corroborate our previous observations in electron collisions with isomers of C{sub 4}H{sub 9}OH.« less

The hydrogen molecule under the reaction microscope: single photon double ionization at maximum cross section and threshold (doubly differential cross sections)

DOE PAGES

Weber, Thorsten; Foucar, Lutz; Jahnke, Till; ...

2017-07-07

In this paper, we studied the photo double ionization of hydrogen molecules in the threshold region (50 eV) and the complete photo fragmentation of deuterium molecules at maximum cross section (75 eV) with single photons (linearly polarized) from the Advanced Light Source, using the reaction microscope imaging technique. The 3D-momentum vectors of two recoiling ions and up to two electrons were measured in coincidence. We present the kinetic energy sharing between the electrons and ions, the relative electron momenta, the azimuthal and polar angular distributions of the electrons in the body-fixed frame. We also present the dependency of the kineticmore » energy release in the Coulomb explosion of the two nuclei on the electron emission patterns. We find that the electronic emission in the body-fixed frame is strongly influenced by the orientation of the molecular axis to the polarization vector and the internuclear distance as well as the electronic energy sharing. Finally, traces of a possible breakdown of the Born–Oppenheimer approximation are observed near threshold.« less

The hydrogen molecule under the reaction microscope: single photon double ionization at maximum cross section and threshold (doubly differential cross sections)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weber, Thorsten; Foucar, Lutz; Jahnke, Till

In this paper, we studied the photo double ionization of hydrogen molecules in the threshold region (50 eV) and the complete photo fragmentation of deuterium molecules at maximum cross section (75 eV) with single photons (linearly polarized) from the Advanced Light Source, using the reaction microscope imaging technique. The 3D-momentum vectors of two recoiling ions and up to two electrons were measured in coincidence. We present the kinetic energy sharing between the electrons and ions, the relative electron momenta, the azimuthal and polar angular distributions of the electrons in the body-fixed frame. We also present the dependency of the kineticmore » energy release in the Coulomb explosion of the two nuclei on the electron emission patterns. We find that the electronic emission in the body-fixed frame is strongly influenced by the orientation of the molecular axis to the polarization vector and the internuclear distance as well as the electronic energy sharing. Finally, traces of a possible breakdown of the Born–Oppenheimer approximation are observed near threshold.« less

Low-Energy Electron-Induced Strand Breaks in Telomere-Derived DNA Sequences-Influence of DNA Sequence and Topology.

PubMed

Rackwitz, Jenny; Bald, Ilko

2018-03-26

During cancer radiation therapy high-energy radiation is used to reduce tumour tissue. The irradiation produces a shower of secondary low-energy (<20 eV) electrons, which are able to damage DNA very efficiently by dissociative electron attachment. Recently, it was suggested that low-energy electron-induced DNA strand breaks strongly depend on the specific DNA sequence with a high sensitivity of G-rich sequences. Here, we use DNA origami platforms to expose G-rich telomere sequences to low-energy (8.8 eV) electrons to determine absolute cross sections for strand breakage and to study the influence of sequence modifications and topology of telomeric DNA on the strand breakage. We find that the telomeric DNA 5'-(TTA GGG) 2 is more sensitive to low-energy electrons than an intermixed sequence 5'-(TGT GTG A) 2 confirming the unique electronic properties resulting from G-stacking. With increasing length of the oligonucleotide (i.e., going from 5'-(GGG ATT) 2 to 5'-(GGG ATT) 4 ), both the variety of topology and the electron-induced strand break cross sections increase. Addition of K + ions decreases the strand break cross section for all sequences that are able to fold G-quadruplexes or G-intermediates, whereas the strand break cross section for the intermixed sequence remains unchanged. These results indicate that telomeric DNA is rather sensitive towards low-energy electron-induced strand breakage suggesting significant telomere shortening that can also occur during cancer radiation therapy. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

EDDIX--a database of ionisation double differential cross sections.

PubMed

MacGibbon, J H; Emerson, S; Liamsuwan, T; Nikjoo, H

2011-02-01

The use of Monte Carlo track structure is a choice method in biophysical modelling and calculations. To precisely model 3D and 4D tracks, the cross section for the ionisation by an incoming ion, double differential in the outgoing electron energy and angle, is required. However, the double differential cross section cannot be theoretically modelled over the full range of parameters. To address this issue, a database of all available experimental data has been constructed. Currently, the database of Experimental Double Differential Ionisation Cross sections (EDDIX) contains over 1200 digitalised experimentally measured datasets from the 1960s to present date, covering all available ion species (hydrogen to uranium) and all available target species. Double differential cross sections are also presented with the aid of an eight parameter functions fitted to the cross sections. The parameters include projectile species and charge, target nuclear charge and atomic mass, projectile atomic mass and energy, electron energy and deflection angle. It is planned to freely distribute EDDIX and make it available to the radiation research community for use in the analytical and numerical modelling of track structure.

Asymptotic form for the cross section for the Coulomb interacting rearrangement collisions

NASA Technical Reports Server (NTRS)

Omidvar, K.

1973-01-01

It is shown that in a rearrangement collision leading to the formation of the highly excited hydrogenlike states the cross section in all orders of the Born approximation behaves as 1/n sq, with n the principal quantum number, thus invalidating the Brinkman-Kramers approximation for large n. Similarly, in high energy inelastic electron-hydrogenlike atom collisions the exchange cross section for sufficiently large n dominates the direct excitation cross section.

Electron removal from H and He atoms in collisions with C q+ , O q+ ions

NASA Astrophysics Data System (ADS)

Janev, R. K.; McDowell, M. R. C.

1984-06-01

Cross sections for electron capture and ionisation in collision of partially and completely stripped C q+ , N q+ and O q+ ions with hydrogen and helium atoms have been calculated at selected energies. The classical trajectory Monte Carlo method was used with a variable-charge pseudopotential to describe the interaction of the active electron with the projectile ion. A scalling relationship has been derived for the electron removal (capture and ionisation) cross section which allows a unifield representation of the data.

Electron-impact ionization and electron attachment cross sections of radicals important in transient gaseous discharges

NASA Technical Reports Server (NTRS)

Lee, Long C.; Srivastava, Santosh K.

1990-01-01

Electron-impact ionization and electron attachment cross sections of radicals and excited molecules were measured using an apparatus that consists of an electron beam, a molecular beam and a laser beam. The information obtained is needed for the pulse power applications in the areas of high power gaseous discharge switches, high energy lasers, particle beam experiments, and electromagnetic pulse systems. The basic data needed for the development of optically-controlled discharge switches were also investigated. Transient current pulses induced by laser irradiation of discharge media were observed and applied for the study of electron-molecule reaction kinetics in gaseous discharges.

Electron-impact excitation of the a-italic /sup 3/. sigma. /sub g//sup +/, B-italic /sup 1/. sigma. /sub u//sup +/, c-italic /sup 3/Pi/sub u/, and C-italic /sup 1/Pi/sub u/ states of H/sub 2/

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khakoo, M.A.; Trajmar, S.

1986-07-01

Normalized differential and integral cross sections for electron-impact excitation of the dipole-allowed B-italic /sup 1/..sigma../sub u//sup +/,C-italic /sup 1/Pi/sub u/ and dipole-forbidden a-italic /sup 3/..sigma../sub g//sup +/,c-italic /sup 3/Pi/sub u/ states of molecular hydrogen have been determined by analysis of energy-loss spectra obtained with a crossed-beam apparatus at electron-impact energies of 20, 30, 40, and 60 eV and scattering angles ranging from 10/sup 0/ to 120/sup 0/. Normalization of the data was achieved by utilizing the elastic differential cross sections measured previously by us (preceding article). The cross sections are compared with other available theoretical and experimental data.

Influence of renormalization shielding on the electron-impact ionization process in dense partially ionized plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Mi-Young; Yoon, Jung-Sik; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

2015-04-15

The renormalization shielding effects on the electron-impact ionization of hydrogen atom are investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it ismore » found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed.« less

New calculations and measurements of the Coulomb cross-section for the production of direct electron pairs by high energy nuclei

NASA Technical Reports Server (NTRS)

Derrickson, J. H.; Dake, S.; Dong, B. L.; Eby, P. B.; Fountain, W. F.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Iyono, A.; King, D. T.

1989-01-01

Recently, new calculations were made of the direct Coulomb pair cross section that rely less in arbitrary parameters. More accurate calculations of the cross section down to low pair energies were made. New measurements of the total direct electron pair yield, and the energy and angular distribution of the electron pairs in emulsion were made for O-16 at 60 and 200 GeV/amu at S-32 at 200 GeV/amu which give satisfactory agreement with the new calculations. These calculations and measurements are presented along with previous accelerator measurements made of this effect during the last 40 years. The microscope scanning criteria used to identify the direct electron pairs is described. Prospects for application of the pair method to cosmic ray energy measurements in the region 10 (exp 13) to 10 (exp 15) eV/amu are discussed.

Cascades from nu_E above 1020 eV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, Spencer R.

2004-12-21

At very high energies, the Landau-Pomeranchuk-Migdal effect reduces the cross sections for electron bremsstrahlung and photon e{sup +}e{sup -} pair production. The fractional electron energy loss and pair production cross sections drop as the energy increases. In contrast, the cross sections for photonuclear interactions grow with energy. In solids and liquids, at energies above 10{sup 20} eV, photonuclear reactions dominate, and showers that originate as photons or electrons quickly become hadronic showers. These electron-initiated hadronic showers are much shorter (due to the absence of the LPM effect), but wider than purely electromagnetic showers would be. This change in shape altersmore » the spectrum of the electromagnetic and acoustic radiation emitted from the shower. These alterations have important implications for existing and planned searches for radiation from u{sub e} induced showers above 10{sup 20} eV, and some existing limits should be reevaluated.« less

Photoionization and electron-impact ionization of Ar5+

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J.C.; Lu, M.; Esteves, D.

2007-02-27

Absolute cross sections for photoionization andelectron-impact Photionization of Ar5+ have been measuredusing twodifferent interacting-beams setups. The spectra consist of measurementsof the yield of products dueto single ionization as a function ofelectron or photon energy. In addition, absolute photoionization andelectron-impact ionization cross sections were measured to normalize themeasured Ar6+ product-ion yield spectra. In the energy range from 90 to111 eV, both electron-impact ionization and photoionization of Ar5+aredominated by indirect 3s subshell excitation-autoionization. In theenergy range from 270 to 285 eV, resonances due to 2p-3dexcitation-autoionization are prominent in the photoionization spectrum.In the range from 225 to 335 eV, an enhancement due tomore » 2p-nl (n>2>excitations are evident in the electron-impactionization cross section.The electron and photon impact data show some features due to excitationof the same intermediate autoionizing states.« less

Total reaction cross sections of electronic state-specified transition metal cations: V + +C2H6, C3H8, and C2H4 at 0.2 eV

NASA Astrophysics Data System (ADS)

Sanders, Lary; Hanton, Scott D.; Weisshaar, James C.

1990-03-01

We describe a crossed beam experiment which measures total cross sections for reaction of electronic state-specified V+ with small hydrocarbons at well-defined collision energy E=0.2 eV. The V+ state distribution created at each ionizing wavelength is directly measured by angle-integrated photoelectron spectroscopy (preceding paper). Reactant and product ions are collected and analyzed by pulsed time-of-flight mass spectrometry following a reaction time of 6 μs. Tests of the performance of the apparatus are described in detail. Our experiment defines the reactant V+ electronic state distribution and the collision energy much more precisely than previous work. For all three hydrocarbons C2H6, C3H8, and C2H4, H2 elimination products dominate at 0.2 eV. We observe a dramatic dependence of cross section on the V+ electronic term. The second excited term 3d34s(3F) is more reactive than either lower energy quintet term 3d4(5D) or 3d34s(5F) by a factor of ≥270, 80, and ≥6 for the C2H6, C3H8, and C2H4 reactions, respectively. The 3d34s(3F) reaction cross sections at 0.2 eV are 20±11 Å2, 37±19 Å2, and 2.7±1.6 Å2, respectively, compared with Langevin cross sections of ˜80 Å2. For the C2H6 and C3H8 reactions, cross sections are independent of initial spin-orbit level J within the 3F term to the limits of our accuracy. Comparison with earlier work by Armentrout and co-workers shows that electronic excitation to d3s(3F) is far more effective at promoting H2 elimination than addition of the same total kinetic energy to reactants. Electron spin is clearly a key determinant of V+ reactivity with small hydrocarbons. We suggest that triplet V+ reacts much more efficiently than quintet V+ because of its ability to conserve total electron spin along paths to insertion in a C-H bond of the hydrocarbon.

Projectile-charge dependence of the differential cross section for the ionization of argon atoms at 1 keV

NASA Astrophysics Data System (ADS)

Purohit, G.; Kato, D.

2017-10-01

The single ionization triple differential cross sections (TDCS) of the Ar (3 p ) atoms are reported for the positron and electron impact at 1 keV. The calculated cross sections have been obtained using distorted wave Born approximation (DWBA) approach for the average ejected electron energies 13 and 26 eV at different momentum transfer conditions. The present attempt is helpful to probe the information on the TDCS trends for the particle-matter and antiparticle-matter interactions and to analyze the recent measurements [Phy. Rev. A 95, 062703 (2017), 10.1103/PhysRevA.95.062703]. The binary electron emission is enhanced while the recoil emission is decreased for the positron impact relative to the electron impact in the DWBA calculation results. Systematic shift of peaks, shifting away from the momentum transfer direction for positron impact and shifting towards each other for electron impact, is observed with increasing momentum transfer.

Coherent electron emission from O2 in collisions with fast electrons

NASA Astrophysics Data System (ADS)

Chowdhury, Madhusree Roy; Stia, Carlos R.; Tachino, Carmen A.; Fojón, Omar A.; Rivarola, Roberto D.; Tribedi, Lokesh C.

2017-08-01

Absolute double differential cross sections (DDCS) of secondary electrons emitted in ionization of O2 by fast electrons have been measured for different emission angles. Theoretical calculations of atomic DDCS were obtained using the first Born approximation with an asymptotic charge of Z T = 1. The measured molecular DDCS were divided by twice the theoretical atomic DDCS to detect the presence of interference effects which was the aim of the experiment. The experimental to theoretical DDCS ratios showed clear signature of first order interference oscillation for all emission angles. The ratios were fitted by a first order Cohen-Fano type model. The variation of the oscillation amplitudes as a function of the electron emission angle showed a parabolic behaviour which goes through a minimum at 90°. The single differential and total ionization cross sections have also been deduced, besides the KLL Auger cross sections. In order to make a comparative study, we have discussed these results along with our recent experimental data obtained for N2 molecule.

Parametrization of electron impact ionization cross sections for CO, CO2, NH3 and SO2

NASA Technical Reports Server (NTRS)

Srivastava, Santosh K.; Nguyen, Hung P.

1987-01-01

The electron impact ionization and dissociative ionization cross section data of CO, CO2, CH4, NH3, and SO2, measured in the laboratory, were parameterized utilizing an empirical formula based on the Born approximation. For this purpose an chi squared minimization technique was employed which provided an excellent fit to the experimental data.

Theoretical and experimental quantification of doubly and singly differential cross sections for electron-induced ionization of isolated tetrahydrofuran molecules

DOE PAGES

Champion, Christophe; Quinto, Michele A.; Bug, Marion U.; ...

2014-07-29

Electron-induced ionization of the commonly used surrogate of the DNA sugar-phosphate backbone, namely, the tetrahydrofuran molecule, is here theoretically described within the 1 st Born approximation by means of quantum-mechanical approach. Comparisons between theory and recent experiments are reported in terms of doubly and singly differential cross sections.

Energy and angular distribution of electrons ejected from water by the impact of fast O8+ ion beams

NASA Astrophysics Data System (ADS)

Bhattacharjee, Shamik; Bagdia, Chandan; Chowdhury, Madhusree Roy; Monti, Juan M.; Rivarola, Roberto D.; Tribedi, Lokesh C.

2018-01-01

Double differential cross sections (DDCS) of electrons emitted from vapor water molecules (in vapor phase) by 2.0 MeV/u and 3.75 MeV/u bare oxygen ion impact have been measured by continuum electron spectroscopy technique. The ejected electrons were detected by an electrostatic hemispherical deflection analyzer over an energy range of 1-600 eV and emission angles from 20∘ to 160∘. The DDCS data has been compared with the continuum-distorted-wave-eikonal-initial state (CDW-EIS) approximation and a reasonable agreement was found with both version of the models i.e. post and prior version. By numerical integration of the DDCS data, the single differential cross section (SDCS) and total ionization cross section (TCS) were obtained. The obtained TCS results were compared with other available TCS results for water target within the same energy range. The total ionization cross sections values are seen to saturate as the projectile charge state ( q p ) increases, which is in contrast to the first-Born predicted q p 2 dependence. This is also in contrast to the prediction of the CDW-EIS models.

Electron impact excitation of methane

NASA Technical Reports Server (NTRS)

Vuskovic, L.; Trajmar, S.

1983-01-01

A crossed molecular beam-electron beam apparatus was employed to examine the excitation cross-sections of CH4. Attention was given to 20, 30, and 200 eV impact energies at angles from 8-130 deg. Spectra were obtained in the elastic and inelastic realms as well as in the ionization continuum in the 12.99-15.0 eV energy-loss range. Differential cross-sections were also determined. The results are useful for modeling the behavior of CH4 in planetary atmospheres.

Benchmarking electronic-state excitation cross sections for electron-N{sub 2} collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kato, Hidetoshi; Suzuki, Daisuke; Ohkawa, Mizuha

2010-04-15

We report differential cross sections for electron impact excitation of the a {sup 1{Pi}}{sub g}, C {sup 3{Pi}}{sub u}, E {sup 3{Sigma}}{sub g}{sup +}, a{sup ''} {sup 1{Sigma}}{sub g}{sup +}, b {sup 1{Pi}}{sub u}, c{sub 3} {sup 1{Pi}}{sub u}, o{sub 3} {sup 1{Pi}}{sub u}, b{sup '} {sup 1{Sigma}}{sub u}{sup +}, c{sub 4}{sup '} {sup 1{Sigma}}{sub u}{sup +}, G {sup 3{Pi}}{sub u}, and F {sup 3{Pi}}{sub u} electronic states in N{sub 2}. The incident electron energies are 20, 30, and 40 eV, while the scattered electron angles are 10 deg. and 20 deg. These kinematic conditions were specifically targeted in ordermore » to try and shed new light on the worrying discrepancies that exist in the literature for the a {sup 1{Pi}}{sub g}, C {sup 3{Pi}}{sub u}, E {sup 3{Sigma}}{sub g}{sup +}, and a{sup ''} {sup 1{Sigma}}{sub g}{sup +} cross sections, and in general the present measurements confirm that those from the more recent results of the University of California, Fullerton, and the Jet Propulsion Laboratory [M. A. Khakoo, P. V. Johnson, I. Ozkay, P. Yan, S. Trajmar, and I. Kanik, Phys. Rev. A 71, 062703 (2005); C. P. Malone, P. V. Johnson, I. Kanik, B. Ajdari, and M. A. Khakoo, Phys. Rev. A 79, 032704 (2009)] are reliable. In addition, we provide a rigorous cross-check for the remaining seven electronic states, where the only recent comprehensive study is from Khakoo and colleagues [Phys. Rev. A 77, 012704 (2008)]. Here, however, some of those cross sections are confirmed and others are not, suggesting that further work is still needed.« less

Absorption effects in electron-sulfur-dioxide collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Machado, L. E.; Sugohara, R. T.; Santos, A. S. dos

2011-09-15

A joint experimental-theoretical study on electron-SO{sub 2} collisions in the low and intermediate energy range is reported. More specifically, experimental elastic differential, integral, and momentum transfer cross sections in absolute scale are measured in the 100-1000 eV energy range using the relative-flow technique. Calculated elastic differential, integral, and momentum transfer cross sections as well as grand-total and total absorption cross sections are also presented in the 1-1000 eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics, whereas the Schwinger variational iterative method combined with the distorted-wave approximation is used to solve the scattering equations.more » Comparison of the present results is made with the theoretical and experimental results available in the literature.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darling, Christopher Lynn

By determining the production cross sections for heavy flavor hadrons, we test the theoretical predictions from perturhative quantum chroma-dynamics (QCD). In the case of pion induced beauty production, the few published results do not resolve the issue of the applicability of perturbative QCD. This analysis is undertaken in order to help resolve this situation. We determine the total beauty and charm production cross sections using an analysis of single electron decay products. We extract the cross sections per nucleon from the two-dimensional distribution of electron p versus impact parameter ( d) to the primary vertex. We place an upper limit on the beauty production cross section of σ bmore » $$\\bar{b}$$ < 105 nb at the 90% confidence level, where the limit includes both statistical and systematic errors. The charm production cross section is determined to be σ cc = 13.9$$+2.4/atop{-2.3}$$ (stat) ± 1.8 (syst) μ.b, which is in good agreement with next-to-leading order QCD predictions and other measurements.« less

Measurement of the Z → τ τ cross section with the ATLAS detector

DOE PAGES

Aad, G.; Abbott, B.; Abdallah, J.; ...

2011-12-14

Here, the Z → ττ cross section is measured with the ATLAS experiment at the LHC in four different final states determined by the decay modes of the τ leptons: muon-hadron, electron-hadron, electron-muon, and muon-muon. The analysis is based on a data sample corresponding to an integrated luminosity of 36 pb –1, at a proton-proton center-of-mass energy of √s = 7 TeV. Cross sections are measured separately for each final state in fiducial regions of high detector acceptance, as well as in the full phase space, over the mass region 66–116 GeV. The individual cross sections are combined and themore » product of the total Z production cross section and Z→ττ branching fraction is measured to be 0.97 ± 0.07(stat) ± 0.06(syst) ± 0.03(lumi) nb, in agreement with next-to-next-to-leading order calculations.« less

New electron-energy transfer rates for vibrational excitation of O2

NASA Astrophysics Data System (ADS)

Jones, D. B.; Campbell, L.; Bottema, M. J.; Brunger, M. J.

2003-09-01

We report on our computation of electron-energy transfer rates for vibrational excitation of O2. This work was necessitated by inadequacies in the electron-impact cross section databases employed in previous studies and, in one case, an inaccurate approximate formulation to the rate equation. Both these inadequacies led to incorrect energy transfer rates being published in the literature. We also demonstrate the importance of using cross sections that encompass an energy range that is extended enough to appropriately describe the environment under investigation.

Low energy electron transport in furfural

NASA Astrophysics Data System (ADS)

Lozano, Ana I.; Krupa, Kateryna; Ferreira da Silva, Filipe; Limão-Vieira, Paulo; Blanco, Francisco; Muñoz, Antonio; Jones, Darryl B.; Brunger, Michael J.; García, Gustavo

2017-09-01

We report on an initial investigation into the transport of electrons through a gas cell containing 1 mTorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulation, our preferred energy loss distribution function is presented and discussed.

Photoionization and pseudopotentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costa, Romarly F. da; Lima, Marco A.P.; Ferreira, Luiz G.

2003-05-01

Transferability of norm-conserving pseudopotentials to low-energy electron-molecule scattering processes has been very successful [Bettega et al., Phys. Rev. A 47, 1111 (1993)]. In this paper we discuss the possibility of using effective potentials in calculations of valence electrons photoionization cross sections. Through atomic targets, we illustrate that pseudopotentials can be optimized to give cross sections in good agreement with all-electron calculations. The present work represents a first step towards more elaborate computer programs for photoionization of molecular targets containing heavy atoms.

Cross sections for electron collision with difluoroacetylene

NASA Astrophysics Data System (ADS)

Gupta, Dhanoj; Choi, Heechol; Kwon, Deuk-Chul; Yoon, Jung-Sik; Antony, Bobby; Song, Mi-Young

2017-04-01

We report a detailed calculation of total elastic, differential elastic, momentum transfer and electronic excitation for electron impact on difluoroacetylene (C2F2) molecules using the R-matrix method at low energies. After testing many target models, the final results are reported for the target model that gave the best target properties and predicted the lowest value of the shape resonance. The shape resonance is detected at 5.86 eV and 6.49 eV with the close-coupling and static exchange models due to 2Πg (2B2g, 2B3g) states. We observed that the effect of polarization becomes prominent at low energies below 4 eV, decreasing the magnitude of the elastic cross section systematically as it increases for C2F2. We have also computed elastic cross sections for C2H2, C2F4 and C2H4 with a similar model and compared with the experimental data for these molecules along with C2F2. General agreement is found in terms of the shape and nature of the cross section. Such a comparison shows the reliability of the present method for obtaining the cross section for C2F2. The calculation of elastic scattering cross section is extended to higher energies up to 5 keV using the spherical complex optical potential method. The two methods are found to be consistent, merging at around 12 eV for the elastic scattering cross section. Finally we report the total ionization cross section using the binary encounter Bethe method for C2F2. The perfluorination effect in the shape and magnitude of the elastic, momentum transfer and ionization cross sections when compared with C2H2 showed a similar trend to that in the C2H4-C2F4 and C6H6-C6F6 systems. The cross-section data reported in this article could be an important input for the development of a C2F2 plasma model for selective etching of Si/SiO2 in the semiconductor industry.

Accurate electron gun-positioning mechanism for electron beam-mapping of large cross-section magnetic surfaces

NASA Astrophysics Data System (ADS)

Anderson, F. S. B.; Middleton, F.; Colchin, R. J.; Million, D.

1989-04-01

A method of accurately supporting and positioning an electron source inside a large cross-sectional area magnetic field which provides very low electron beam occlusion is reported. The application of electrical discharge machining to the fabrication of a 1-m truss support structure has provided an extremely long, rigid and mechanically strong electron gun support. Reproducible electron gun positioning to within 1 mm has been achieved at any location within a 1×0.6-m2 area. The extremely thin sections of the support truss (≤1.5 mm) have kept the electron beam occlusion to less than 3 mm. The support and drive mechanism have been designed and fabricated at the University of Wisconsin for application to the mapping of the magnetic surface structure of the Advanced Toroidal Facility torsatron1 at the Oak Ridge National Laboratory.

Electron-impact-ionization dynamics of S F6

NASA Astrophysics Data System (ADS)

Bull, James N.; Lee, Jason W. L.; Vallance, Claire

2017-10-01

A detailed understanding of the dissociative electron ionization dynamics of S F6 is important in the modeling and tuning of dry-etching plasmas used in the semiconductor manufacture industry. This paper reports a crossed-beam electron ionization velocity-map imaging study on the dissociative ionization of cold S F6 molecules, providing complete, unbiased kinetic energy distributions for all significant product ions. Analysis of these distributions suggests that fragmentation following single ionization proceeds via formation of S F5 + or S F3 + ions that then dissociate in a statistical manner through loss of F atoms or F2, until most internal energy has been liberated. Similarly, formation of stable dications is consistent with initial formation of S F4 2 + ions, which then dissociate on a longer time scale. These data allow a comparison between electron ionization and photoionization dynamics, revealing similar dynamical behavior. In parallel with the ion kinetic energy distributions, the velocity-map imaging approach provides a set of partial ionization cross sections for all detected ionic fragments over an electron energy range of 50-100 eV, providing partial cross sections for S2 +, and enables the cross sections for S F4 2 + from S F+ to be resolved.

Measurement of exclusive γγ → l +l – production in proton–proton collisions at √s = 7 TeV with the ATLAS detector

DOE PAGES

Aad, G.

2015-07-31

This Letter reports a measurement of the exclusive γγ → l +l – (l = e, μ) cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV by the ATLAS experiment at the LHC, based on an integrated luminosity of 4.6 fb –1. For the electron or muon pairs satisfying exclusive selection criteria, a fit to the dilepton acoplanarity distribution is used to extract the fiducial cross-sections. The cross-section in the electron channel is determined to be σ excl. γγ → e+e– = 0.428 ± 0.035 (stat.) ± 0.018 (syst.) pbfor a phase-space region with invariant mass of themore » electron pairs greater than 24GeV, in which both electrons have transverse momentum p T > 12 GeV and pseudorapidity |η| < 2.4. For muon pairs with invariant mass greater than 20GeV, muon transverse momentum p T > 10 GeV and pseudorapidity |η| < 2.4, the cross-section is determined to be σ excl. γγ → μ+μ– = 0.628 ± 0.032(stat.) ± 0.021 (syst.) pb. As a result, when proton absorptive effects due to the finite size of the proton are taken into account in the theory calculation, the measured cross-sections are found to be consistent with the theory prediction.« less

Differential cross sections for electron-impact excitation of the electronic states of pyrimidine

NASA Astrophysics Data System (ADS)

Brunger, Michael; Jones, Darryl; Bellm, Susan

2012-06-01

Pyrimidine (C4N2H4) is an important molecule, as it forms the basis of larger biomolecules, such as the DNA bases thymine, cytosine and uracil. There is a pressing demand for low-energy electron scattering data from such biological analogs in order to model radiation induced damage [1]. We therefore present the first measurements for absolute differential cross section data for low-energy electron-impact excitation of the electronic states of pyrimidine. The present measurements were performed using a crossed-beam apparatus [2] for incident electron energies ranging between 15 to 50eV while covering a 10 to 90^o angular range. Here the absolute scale has been determined through a normalisation to the recently measured elastic scattering differential cross section data for pyrimidine [3]. [1] F. Ferreira da Silva, D. Almeida, G. Martins, A. R. Milosavljevic, B. P. Marinkovic, S. V. Hoffmann, N. J. Mason, Y. Nunes, G. Garcia and P. Limao-Vieira, Phys Chem Chem Phys 12, 6717 (2010). [2] M. J. Brunger and P. J. O. Teubner, Phys Rev A 41, 1413 (1990). [3] P. Palihawadana, J. Sullivan, M. Brunger, C. Winstead, V. McKoy, G. Garcia, F. Blanco and S. Buckman, Phys Rev A 84, 062702 (2011).

Electron impact ionisation cross sections of iron oxides

NASA Astrophysics Data System (ADS)

Huber, Stefan E.; Mauracher, Andreas; Sukuba, Ivan; Urban, Jan; Maihom, Thana; Probst, Michael

2017-12-01

We report electron impact ionisation cross sections (EICSs) of iron oxide molecules, FexOx and FexOx+1 with x = 1, 2, 3, from the ionisation threshold to 10 keV, obtained with the Deutsch-Märk (DM) and binary-encounter-Bethe (BEB) methods. The maxima of the EICSs range from 3.10 to 9 . 96 × 10-16 cm2 located at 59-72 eV and 5.06 to 14.32 × 10-16 cm2 located at 85-108 eV for the DM and BEB approaches, respectively. The orbital and kinetic energies required for the BEB method are obtained by employing effective core potentials for the inner core electrons in the quantum chemical calculations. The BEB cross sections are 1.4-1.7 times larger than the DM cross sections which can be related to the decreasing population of the Fe 4s orbitals upon addition of oxygen atoms, together with the different methodological foundations of the two methods. Both the DM and BEB cross sections can be fitted excellently to a simple analytical expression used in modelling and simulation codes employed in the framework of nuclear fusion research. Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjd/e2017-80308-2.

Low-energy electron collisions with C{sub 4}H{sub 6} isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopes, A.R.; Bettega, M.H.F.; Lima, M.A.P.

2004-01-01

We report integral, differential, and momentum-transfer cross sections for elastic scattering of low-energy electrons by C{sub 4}H{sub 6} isomers, namely, 1,3-butadiene, 2-butyne, and cyclobutene. We use the Schwinger multichannel method with pseudopotentials [M. H. F. Bettega, L. G. Ferreira, and M. A. P. Lima, Phys. Rev. A 47, 1111 (1993)] at the static-exchange approximation to compute the cross sections for energies from 10 to 60 eV. In particular, we discuss the isomer effect, reported by experimental studies for isomers of C{sub 3}H{sub 4} and C{sub 4}H{sub 6}. We also calculate the total ionization cross section using the binary-encounter-Bethe model formore » 2-butyne and 1,3-butadiene, and estimate the inelastic cross section for these two isomers.« less

Hartree-Fock calculation of the differential photoionization cross sections of small Li clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galitskiy, S. A.; Artemyev, A. N.; Jänkälä, K.

2015-01-21

Cross sections and angular distribution parameters for the single-photon ionization of all electron orbitals of Li{sub 2−8} are systematically computed in a broad interval of the photoelectron kinetic energies for the energetically most stable geometry of each cluster. Calculations of the partial photoelectron continuum waves in clusters are carried out by the single center method within the Hartree-Fock approximation. We study photoionization cross sections per one electron and analyze in some details general trends in the photoionization of inner and outer shells with respect to the size and geometry of a cluster. The present differential cross sections computed for Li{submore » 2} are in a good agreement with the available theoretical data, whereas those computed for Li{sub 3−8} clusters can be considered as theoretical predictions.« less

Magnetically confined electron beam system for high resolution electron transmission-beam experiments

NASA Astrophysics Data System (ADS)

Lozano, A. I.; Oller, J. C.; Krupa, K.; Ferreira da Silva, F.; Limão-Vieira, P.; Blanco, F.; Muñoz, A.; Colmenares, R.; García, G.

2018-06-01

A novel experimental setup has been implemented to provide accurate electron scattering cross sections from molecules at low and intermediate impact energies (1-300 eV) by measuring the attenuation of a magnetically confined linear electron beam from a molecular target. High-resolution electron energy is achieved through confinement in a magnetic gas trap where electrons are cooled by successive collisions with N2. Additionally, we developed and present a method to correct systematic errors arising from energy and angular resolution limitations. The accuracy of the entire measurement procedure is validated by comparing the N2 total scattering cross section in the considered energy range with benchmark values available in the literature.

Emmision cross section of OI (135.6nm) at 100 eV resulting from electron-inpact dissociative excitation of O-2

NASA Technical Reports Server (NTRS)

Noren, C.; Kanik, I.; Ajello, J.; McCartney, P.; Makarov, O.; McClintock, W.; Drake, V.

2001-01-01

In this Letter, we report for the first time, the ratio of the O I (135.6 nm)/O I (130.4 nm) absolute emission cross sections from electron-impact dissociative excitation of O-2 at 100 eV using facilities located at the University of Colorado, Laboratory for Atmospheric and Space Physics (LASP).

Application of the Schwinger multichannel formulation to electron-impact excitation of the B 1Sigma(+)u state of H2

NASA Technical Reports Server (NTRS)

Gibson, Thomas L.; Lima, Marco A. P.; Mckoy, Vincent; Huo, Winifred M.

1987-01-01

The paper reports cross sections for electron-impact excitation of the X 1Sigma(+)g - BISigma(+)u transition in H2 for collision energies of 15, 20, and 30 eV. For this dipole-allowed transition with its associated long-range potential, the contributions of the more strongly scattered low-angular-momentum partial waves to the cross section were obtained from a two-state Schwinger multichannel calculation, and a modified Born-closure scheme was used to include the contributions from the remaining weakly scattered partial waves. Agreement between the calculated differential cross sections and available experimental data is encouraging.

Studies of electron-polyatomic-molecule collisions Applications to e-CH4

NASA Technical Reports Server (NTRS)

Lima, M. A. P.; Gibson, T. L.; Mckoy, V.; Huo, W. M.

1985-01-01

The first application of the Schwinger multichannel formulation to low-energy electron collisions with a nonlinear polyatomic target is reported. Integral and differential cross sections are obtained for e-CH4 collisions from 3 to 20 eV at the static-plus-exchange interaction level. In these studies, the exchange potential is directly evaluated and not approximated by local models. An interesting feature of the small-angle differential cross section is ascribed to polarization effects and not reproduced at the static-plus-exchange level. These differential cross sections are found to be in reasonable agreement with existing measurements at 7.5 eV and higher energies.

Investigating the sensitivity of nitric oxide infrared emissions to electron impact

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.; Allan, M.

2008-05-01

Integral cross sections for low energy electron excitation of the 0→1, 0→2 and 0→3 vibrational modes in nitric oxide have quite recently become available [Trevisan et al. PRA 71, 052714 (2005)]. In this study we adapt our recent work [Campbell and Brunger GRL, in press (2007)], to look at the effect of these new cross sections on the production of nitric oxide infrared radiation. Predictions from our model are compared with measurements from Espy et al. [Planet. Space Sci. 36, 543 (1988)], with the inclusion of the new cross sections improving the agreement of the shape of the spectrum with the measurements.

Vibrational excitation and vibrationally resolved electronic excitation cross sections of positron-H2 scattering

NASA Astrophysics Data System (ADS)

Zammit, Mark; Fursa, Dmitry; Savage, Jeremy; Bray, Igor

2016-09-01

Vibrational excitation and vibrationally resolved electronic excitation cross sections of positron-H2 scattering have been calculated using the single-centre molecular convergent close-coupling (CCC) method. The adiabatic-nuclei approximation was utilized to model the above scattering processes and obtain the vibrationally resolved positron-H2 scattering length. As previously demonstrated, the CCC results are converged and accurately account for virtual and physical positronium formation by coupling basis functions with large orbital angular momentum. Here vibrationally resolved integrated and differential cross sections are presented over a wide energy range and compared with previous calculations and available experiments. Los Alamos National Laboratory and Curtin University.

Dissociative excitation of vacuum ultraviolet emission features by electron impact on molecular gases. 3: CO2

NASA Technical Reports Server (NTRS)

Mumma, M. J.; Borst, W. L.; Zipf, E. C.

1972-01-01

Vacuum ultraviolet multiplets of C I, C II, and O I were produced by electron impact of CO2. Absolute emission cross sections for these multiplets were measured from threshold to 350 eV. The electrostatically focussed electron gun used in this series of experiments is described in detail. The atomic multiplets which were produced by dissociative excitation of CO2 and the cross sections at 100 eV are given. The dependence of the excitation functions on electron energy shows that these multiplets are produced by electric-dipole-allowed transitions in CO2.

A coincidence study of electron and positron impact ionization of Ar (3p) at 1 keV

NASA Astrophysics Data System (ADS)

Campeanu, Radu I.; Walters, James H. R.; Whelan, Colm T.

2015-10-01

Distorted-wave calculations of the triple differential cross section (TDCS) are presented for electron and positron impact ionization of Ar(3p) in coplanar asymmetric geometry at an impact energy of 1 keV and are compared with a recent experiment. The experiment indicates that the positron TDCS is generally larger than the equivalent electron TDCS. It is shown that the magnitude of the TDCS is extremely sensitive to the energy of the ejected electron and that only when the cross section is averaged over energy do we get a reasonable agreement with experiment.

Integral cross sections for the direct excitation of the A 3 (sigma) u +, B 3 (pi) g, W 3 (delta) u, B' 3 (sigma) u -, a' 1 (sigma) u -, a 1 (pi) g, w 1 (delta) u, and C 3 (pi) u electronic states in

NASA Technical Reports Server (NTRS)

Johnson, P. V.; Malone, C. P.; Kanik, I.

2005-01-01

Integral cross sections for electron impact excitation out of the ground state (X 1(sigma)g +) to the A 3(sigma)u +, B 3(pi)g, W 3(delta)u, B' 3(sigma)u -, a' 1(sigma)u -, a 1(pi)g, w 1(delta)u, and states in N2 are reported at incident energies ranging between 10 and 100 eV. These data have been derived by integrating differential cross sections previously reported by this group. New differential cross section measurements for the a 1(pi)g state at 200 eV are also presented to extend the range of the reported integral cross sections for this state, which is responsible for the emissions of the Lyman-Birge-Hopfield band system (a 1(pi)g (rightwards arrow) X 1(sigma)g +). The present results are compared and critically evaluated against existing cross sec In general, the present cross sections are smaller than previous results at low impact energies from threshold through the excitation function peak regions. These lower cross sections have potentially significant implications on our understanding of UV emissions in the atmospheres of Earth and Titan.

Correction of the near threshold behavior of electron collisional excitation cross-sections in the plane-wave Born approximation

NASA Astrophysics Data System (ADS)

Kilcrease, D. P.; Brookes, S.

2013-12-01

The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. A simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure for the Born cross-sections that employs the Elwert-Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. We also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations.

Excitation of the 6p7s {sup 3}P{sub 0,1} states of Pb atoms by electron impact: Differential and integrated cross sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milisavljevic, S.; Rabasovic, M. S.; Sevic, D.

2007-08-15

Experimental measurements of electron impact excitation of the 6p7s {sup 3}P{sub 0,1} states of Pb atoms have been made at incident electron energies E{sub 0}=10, 20, 40, 60, 80, and 100 eV and scattering angles from 10 deg. to 150 deg. In addition, relativistic distorted-wave calculations have been carried out at these energies. The data obtained include the differential (DCS), integral (Q{sub I}), momentum transfer (Q{sub M}), and viscosity (Q{sub V}) cross sections. Absolute values for the differential cross sections have been obtained by normalizing the relative DCSs at 10 deg. to the experimental DCS values of [S. Milisavljevic, M.more » S. Rabasovic, D. Sevic, V. Pejcev, D. M. Filipovic, L. Sharma, R. Srivastava, A. D. Stauffer, and B. P. Marinkovic, Phys. Rev. A 75, 052713 (2007)]. The integrated cross sections were determined by numerical integration of the absolute DCSs. The experimental results have been compared with the corresponding calculations and good agreement is obtained.« less

Improved surface-roughness scattering and mobility models for multi-gate FETs with arbitrary cross-section and biasing scheme

NASA Astrophysics Data System (ADS)

Lizzit, D.; Badami, O.; Specogna, R.; Esseni, D.

2017-06-01

We present a new model for surface roughness (SR) scattering in n-type multi-gate FETs (MuGFETs) and gate-all-around nanowire FETs with fairly arbitrary cross-sections, its implementation in a complete device simulator, and the validation against experimental electron mobility data. The model describes the SR scattering matrix elements as non-linear transformations of interface fluctuations, which strongly influences the root mean square value of the roughness required to reproduce experimental mobility data. Mobility simulations are performed via the deterministic solution of the Boltzmann transport equation for a 1D-electron gas and including the most relevant scattering mechanisms for electronic transport, such as acoustic, polar, and non-polar optical phonon scattering, Coulomb scattering, and SR scattering. Simulation results show the importance of accounting for arbitrary cross-sections and biasing conditions when compared to experimental data. We also discuss how mobility is affected by the shape of the cross-section as well as by its area in gate-all-around and tri-gate MuGFETs.

Low-energy electron collisions with proline and pyrrolidine: A comparative study

NASA Astrophysics Data System (ADS)

Barbosa, Alessandra Souza; Freitas, Thiago Corrêa; Bettega, M. H. F.

2018-02-01

We present a comparative study on the calculated cross sections obtained for the elastic collisions of low-energy electrons with the amino acid proline (C5H9NO2) and its building block pyrrolidine (C4H9N). We employed the Schwinger multichannel method implemented with pseudopotentials to compute integral, differential, and momentum transfer cross sections in the static-exchange plus polarization approximation, for energies up to 15 eV. We report three shape resonances for proline at around 1.7 eV, 6.8 eV, and 10 eV and two shape resonances for pyrrolidine centered at 7 eV and 10.2 eV. The present resonance energies are compared with available experimental data on vertical attachment energies and dissociative electron attachment, where a good agreement is found. From the comparison of the present results with available calculated cross sections for the simplest carboxylic acid, formic acid (HCOOH), and from electronic structure calculations, we found that the first resonance of proline, at 1.7 eV, is due the presence of the carboxylic group, whereas the other two structures, at 6.8 eV and 10 eV, clearly arise from the pyrrolidine ring. A comparison between the differential cross sections for proline and pyrrolidine at some selected energies of the incident electron is also reported in this paper.

Electron impact ionization cross sections of beryllium-tungsten clusters*

NASA Astrophysics Data System (ADS)

Sukuba, Ivan; Kaiser, Alexander; Huber, Stefan E.; Urban, Jan; Probst, Michael

2016-01-01

We report calculated electron impact ionization cross sections (EICSs) of beryllium-tungsten clusters, BenW with n = 1,...,12, from the ionization threshold to 10 keV using the Deutsch-Märk (DM) and the binary-encounter-Bethe (BEB) formalisms. The positions of the maxima of DM and BEB cross sections are mostly close to each other. The DM cross sections are more sensitive with respect to the cluster size. For the clusters smaller than Be4W they yield smaller cross sections than BEB and vice versa larger cross sections than BEB for clusters larger than Be6W. The maximum cross section values for the singlet-spin groundstate clusters range from 7.0 × 10-16 cm2 at 28 eV (BeW) to 54.2 × 10-16 cm2 at 43 eV (Be12W) for the DM cross sections and from 13.5 × 10-16 cm2 at 43 eV (BeW) to 38.9 × 10-16 cm2 at 43 eV (Be12W) for the BEB cross sections. Differences of the EICSs in different isomers and between singlet and triplet states are also explored. Both the DM and BEB cross sections could be fitted perfectly to a simple expression used in modeling and simulation codes in the framework of nuclear fusion research. Contribution to the Topical Issue "Atomic Cluster Collisions (7th International Symposium)", edited by Gerardo Delgado Barrio, Andrey Solov'Yov, Pablo Villarreal, Rita Prosmiti.Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2015-60583-7

Electron Collision Processes with Carbon Dioxide: Resolving Long-Standing Paradoxes

NASA Astrophysics Data System (ADS)

Rescigno, T. N.; Haxton, D. J.; McCurdy, C. W.

2012-10-01

The principal features of low-energy electron-CO2 collisions have been known and studied for over forty years. The scattering is characterized by a rapid rise in the total cross section below 1 eV, anomalous threshold behavior for excitation of symmetric stretch and bending vibrational modes, resonant vibrational excitation near 4 eV with weak ``boomerang'' structure in the excitation cross sections and dissociative electron attachment cross sections leading to CO + O^- which peak near 4 eV and 8 eV and have angular distributions which show large deviations from axial recoil. The nuclear dynamics associated with all these features is intrinsically polyatomic in nature and cannot be described with one-dimensional models. The present study provides a consistent description of all these phenomena and resolves a number long-standing paradoxes and misconceptions found in the extant literature.

Prompt Electron Production in Electron-Positron Annihilations at 29 GEV.

NASA Astrophysics Data System (ADS)

Koop, Dale E.

We have studied the production of prompt electrons in high statistics sample (118 pb('-1)) of multihadron events produced in electron positron annihilations at 29 Gev. The experiment was performed using the DELCO facility on the PEP storage ring at SLAC. Electron identification was done primarily with a large acceptance threshold Cerenkov counter. Both the momentum and the transverse momentum spectra are measured in terms of a differential cross section for electrons having momenta in the range 0.5 < P < 5.5 Gev/c. We measure the inclusive cross section in this momentum range to be 35.8 (+OR-) 3.1 pb. The final distribution of candidates in the P - P(,(PERP)) plane are fit well using a Monte Carlo having a combination of bottom and charm quark decays with the semielectronic branching ratios of (15.0 (+OR-) 2.9)% and (8.9 (+OR-) 1.4)%. We observe no evidence of electron production from new sources and determine a cross section upper limit of 11.6 pb (90% CL) for this process. We find that the fragmentation functions are hard for both b and c quarks, characterized by the values < z(,b) > = 0.77 + 0.05 and < z(,c) > = 0.68 (+OR -) 0.06, where z is the fraction of the heavy quark's energy that is retained by the primary hadron containing the heavy quark. The fragmentation function is fit well by the form. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). Finally, we observe events having two electrons with an inclusive cross section of 2.8 (+OR-) 1.3 pb for this process, which is consistent with the rate expected from the measured semielectronic rates.

Total Hadron Cross Section, New Particles, and Muon Electron Events in e{sup +}e{sup -} Annihilation at SPEAR

DOE R&D Accomplishments Database

Richter, B.

1976-01-01

The review of total hadron electroproduction cross sections, the new states, and the muon--electron events includes large amount of information on hadron structure, nine states with width ranging from 10's of keV to many MeV, the principal decay modes and quantum numbers of some of the states, and limits on charm particle production. 13 references. (JFP)

In-flight calibration of mesospheric rocket plasma probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Havnes, Ove; University Studies Svalbard; Hartquist, Thomas W.

Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effectivemore » cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes.« less

In-flight calibration of mesospheric rocket plasma probes.

PubMed

Havnes, Ove; Hartquist, Thomas W; Kassa, Meseret; Morfill, Gregor E

2011-07-01

Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effective cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes.

Vibrational excitation of water by electron impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khakoo, M. A.; Winstead, C.; McKoy, V.

2009-05-15

Experimental and calculated differential cross sections (DCSs) for electron-impact excitation of the (010) bending mode and unresolved (100) symmetric and (001) antisymmetric stretching modes of water are presented. Measurements are reported at incident energies of 1-100 eV and scattering angles of 10 deg. - 130 deg. and are normalized to the elastic-scattering DCSs for water determined earlier by our group. The calculated cross sections are obtained in the adiabatic approximation from fixed-nuclei, electronically elastic scattering calculations using the Schwinger multichannel method. The present results are compared to available experimental and theoretical data.

LETTER TO THE EDITOR: Integral cross sections for electron impact excitation of the Herzberg pseudocontinuum of molecular oxygen

NASA Astrophysics Data System (ADS)

Green, M. A.; Teubner, P. J. O.; Brunger, M. J.; Cartwright, D. C.; Campbell, L.

2001-03-01

We report integral cross sections (ICSs) for electron impact excitation of the sum (c 1Σ-u + A' 3Δu + A 3Σ+u) of the three states that constitute the Herzberg pseudocontinuum in O2. These ICSs were measured at seven incident electron energies in the range 9-20 eV in order to investigate for the existence of the strong resonance feature predicted by earlier R-matrix calculations. No such structure was observed in this letter.

Alternative forms of the Spencer-Fano equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inokuti, M.; Kowari, K.

We point out a relation between the electron degradation spectra determined by two differing cross-section sets but subject to the same source. The relation takes a form of the Fredholm integral equation of the second kind and may be viewed as an alternative form of the Spencer-Fano equation. The relation leads to a precise definition of the partial degradation spectra of electrons of successive generations. It also provides a basis for the perturbation theory by which one calculates effects of small changes of cross-section data upon the electron degradation spectrum.

Near-threshold electron-impact doubly differential cross sections for the ionization of argon and krypton

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yates, Brent R.; Khakoo, Murtadha A.

2011-04-15

We present normalized doubly differential cross sections (DDCS's) for the near-threshold, electron-impact single ionization of argon and krypton, similar to those taken earlier for Ne and Xe [Yates et al., J. Phys. B 42, 095206 (2009)]. The Ar measurements were taken at incident energies of 17, 18, 20, and 30 eV while the Kr measurements were taken at 15, 16, 17.5, and 20 eV. The DDCS scattering angles range from 15 deg. to 120 deg. The differential data are initially normalized to available experimental cross sections for excitation of the ground np{sup 6} to the np{sup 5}(n+1)s excited states ofmore » the noble gas and, after integration, to well-established experimental total ionization cross sections of Rapp and Englander-Golden [J. Chem. Phys. 43, 1464 (1965)].« less

Formation of negative hydrogen ion: polarization electron capture and nonthermal shielding.

PubMed

Ki, Dae-Han; Jung, Young-Dae

2012-09-07

The influence of the nonthermal shielding on the formation of the negative hydrogen ion (H(-)) by the polarization electron capture are investigated in partially ionized generalized Lorentzian plasmas. The Bohr-Lindhard method has been applied to obtain the negative hydrogen formation radius and cross section as functions of the collision energy, de Broglie wave length, Debye length, impact parameter, and spectral index of the plasma. The result shows that the nonthermal character of the plasma enhances the formation radius of the negative hydrogen, especially, for small Debye radii. It is found that the nonthermal effect increases the formation cross section of the negative hydrogen. It is also found that the maximum position of the formation cross section approaches to the collision center with an increase of the spectral index. In addition, it is found that the formation cross section significantly decreases with an increase of the Debye length, especially, for small spectral indices.

Electron-impact ionization cross sections out of the ground and 6P2 excited states of cesium

NASA Astrophysics Data System (ADS)

Łukomski, M.; Sutton, S.; Kedzierski, W.; Reddish, T. J.; Bartschat, K.; Bartlett, P. L.; Bray, I.; Stelbovics, A. T.; McConkey, J. W.

2006-09-01

An atom trapping technique for determining absolute, total ionization cross sections (TICS) out of an excited atom is presented. The unique feature of our method is in utilizing Doppler cooling of neutral atoms to determine ionization cross sections. This fluorescence-monitoring experiment, which is a variant of the “trap loss” technique, has enabled us to obtain the experimental electron impact ionization cross sections out of the Cs 6P3/22 state between 7eV and 400eV . CCC, RMPS, and Born theoretical results are also presented for both the ground and excited states of cesium and rubidium. In the low energy region (<11eV) where best agreement between these excited state measurements and theory might be expected, a discrepancy of approximately a factor of five is observed. Above this energy there are significant contributions to the TICS from both autoionization and multiple ionization.

Exclusive ϱ0 production in deep inelastic electron-proton scattering at HERA

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Mikunas, D.; Musgrave, B.; Repond, J.; Stanek, R.; Talaga, R. L.; Zhang, H.; Ayad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Cara Romeo, G.; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Contin, A.; Corradi, M.; Gialas, I.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Zamora Garcia, Y.; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Eckert, M.; Feld, L.; Frey, A.; Geerts, M.; Grothe, M.; Hartmann, H.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mari, S. M.; Mengel, S.; Mollen, J.; Paul, E.; Pfeiffer, M.; Rembser, Ch.; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Llewellyn, T. J.; Morgado, C. J. S.; Norman, D. J. P.; O'Mara, J. A.; Tapper, R. J.; Wilson, S. S.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Capua, M.; Garfagnini, A.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Cartiglia, N.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Zhu, Q.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Beier, H.; Bienlein, J. K.; Coldewey, C.; Deppe, O.; Desler, K.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Glasman, C.; Göttlicher, P.; Große-Knetter, J.; Gutjahr, B.; Haas, T.; Hain, W.; Hasell, D.; Heßling, H.; Iga, Y.; Johnson, K.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mainusch, J.; Mańczak, O.; Monteiro, T.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schulz, W.; Selonke, F.; Stiliaris, E.; Surrow, B.; Voß, T.; Westphal, D.; Wolf, G.; Youngman, C.; Zeuner, W.; Zhou, J. F.; Grabosch, H. J.; Kharchilava, A.; Leich, A.; Mattingly, M. C. K.; Meyer, A.; Schlenstedt, S.; Wulff, N.; Barbagli, G.; Pelfer, P.; Anzivino, G.; Maccarrone, G.; De Pasquale, S.; Votano, L.; Bamberger, A.; Eisenhardt, S.; Freidhof, A.; Söldner-Rembold, S.; Schroeder, J.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Fleck, J. I.; Saxon, D. H.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Hagge, L.; Lohrmann, E.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Zetsche, F.; Bacon, T. C.; Bruemmer, N.; Butterworth, I.; Gallo, E.; Harris, V. L.; Hung, B. Y. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Nam, S. W.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Fernandez, J. P.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; Martinez, M.; del Peso, J.; Puga, J.; Terron, J.; de Trocóniz, J. F.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; St. Laurent, M.; Ullmann, R.; Zacek, G.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Yu. A.; Kobrin, V. D.; Korzhavina, I. A.; Kurzhavina, V. A.; Kuzmin, V. A.; Lukina, O. Yu.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Botje, M.; Chlebana, F.; Dake, A.; Engelen, J.; de Kamps, M.; Kooijman, P.; Kruse, A.; Tiecke, H.; Verkerke, W.; Veeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Bailey, D. S.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Lindemann, L.; McFall, J. D.; Nath, C.; Noyes, V. A.; Quadt, A.; Tickner, J. R.; Uijterwaal, H.; Walczak, R.; Waters, D. S.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; De Giorgi, M.; Dosselli, U.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Feild, R. G.; Oh, B. Y.; Whitmore, J. J.; D'Agostini, G.; Marini, G.; Nigro, A.; Tassi, E.; Hart, J. C.; McCubbin, N. A.; Prytz, K.; Shah, T. P.; Short, T. L.; Barberis, E.; Dubbs, T.; Heusch, C.; Van Hook, M.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Williams, D. C.; Biltzinger, J.; Seifert, R. J.; Schwarzer, O.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nakamitsu, Y.; Yamauchi, K.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Polenz, S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Blankenship, K.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchuła, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Karshon, U.; Revel, D.; Zer-Zion, D.; Ali, I.; Badgett, W. F.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Vaiciulis, A.; Wodarczyk, M.; Tsurugai, T.; Bhadra, S.; Cardy, M. L.; Fagerstroem, C.-P.; Frisken, W. R.; Furutani, K. M.; Khakzad, M.; Schmidke, W. B.; ZEUS Collaboration

1995-02-01

The exclusive production of ϱ0 mesons in deep inelastic electron-proton scattering has been studied using the ZEUS detector. Cross sections have been measured in the range 7 < Q2 < 25 GeV 2 for λ ∗p centre of mass (c.m.) energies 40 to 130 GeV. The λ ∗p → ϱ 0p cross section exhibits a Q-(4.2±0.8 -0.5+1.4) dependence and both longitudinally and transversely polarised ϱ0's are observed. The λ ∗p → ϱ 0p cross section rises strongly with increasing c.m. energy, when compared with NMC data at lower energy, which cannot be explained by production through soft pomeron exchange. The data are compared with perturbative QCD calculations where the rise in the cross section reflects the increase in the gluon density at low x.

Absolute total and partial dissociative cross sections of pyrimidine at electron and proton intermediate impact velocities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolff, Wania, E-mail: wania@if.ufrj.br; Luna, Hugo; Sigaud, Lucas

Absolute total non-dissociative and partial dissociative cross sections of pyrimidine were measured for electron impact energies ranging from 70 to 400 eV and for proton impact energies from 125 up to 2500 keV. MOs ionization induced by coulomb interaction were studied by measuring both ionization and partial dissociative cross sections through time of flight mass spectrometry and by obtaining the branching ratios for fragment formation via a model calculation based on the Born approximation. The partial yields and the absolute cross sections measured as a function of the energy combined with the model calculation proved to be a useful toolmore » to determine the vacancy population of the valence MOs from which several sets of fragment ions are produced. It was also a key point to distinguish the dissociation regimes induced by both particles. A comparison with previous experimental results is also presented.« less

Dissociative-ionization cross sections for 12-keV-electron impact on CO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatt, Pragya; Singh, Raj; Yadav, Namita

The dissociative ionization of a CO{sub 2} molecule is studied at an electron energy of 12 keV using the multiple ion coincidence imaging technique. The absolute partial ionization cross sections and the precursor-specific absolute partial ionization cross sections of resulting fragment ions are obtained and reported. It is found that {approx}75% of single ionization, 22% of double ionization, and {approx}2% of triple ionization of the parent molecule contribute to the total fragment ion yield; quadruple ionization of CO{sub 2} is found to make a negligibly small contribution. Furthermore, the absolute partial ionization cross sections for ion-pair and ion-triple formation aremore » measured for nine dissociative ionization channels of up to a quadruply ionized CO{sub 2} molecule. In addition, the branching ratios for single-ion, ion-pair, and ion-triple formation are also determined.« less

A Semiempirical Formula for Single-Electron-Capture Cross Sections of Multiply Charged Ions Colliding with H, H2 and He

NASA Astrophysics Data System (ADS)

Nakai, Yohta; Shirai, Toshizo; Tabata, Tatsuo; Ito, Rinsuke

1989-01-01

A universal analytic formula is given for the total cross sections of single-electron capture by multiply-charged ions colliding with H, H2 or He. Values of constants in the formula have been determined by least-squares fit to experimental data collected from the literature. The formula is applicable to ions of almost all atomic species with charge q greater than 4 (for the H and H2 targets) or 5 (for the He target) in the energy region from about 1 to 107 eV amu-1. The root-mean-square deviation of the data from the formula is 29%. The formula shows that the cross sections are proportional to q1.07 at low energies and to q2.86 at high energies. Other trends of the cross sections that can be derived from the formula are also discussed.

Temperature dependence of the cross section for the fragmentation of thymine via dissociative electron attachment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kopyra, Janina; Abdoul-Carime, Hassan, E-mail: hcarime@ipnl.in2p3.fr

Providing experimental values for absolute Dissociative Electron Attachment (DEA) cross sections for nucleobases at realistic biological conditions is a considerable challenge. In this work, we provide the temperature dependence of the cross section, σ, of the dehydrogenated thymine anion (T − H){sup −} produced via DEA. Within the 393-443 K temperature range, it is observed that σ varies by one order of magnitude. By extrapolating to a temperature of 313 K, the relative DEA cross section for the production of the dehydrogenated thymine anion at an incident energy of 1 eV decreases by 2 orders of magnitude and the absolutemore » value reaches approximately 6 × 10{sup −19} cm{sup 2}. These quantitative measurements provide a benchmark for theoretical prediction and also a contribution to a more accurate description of the effects of ionizing radiation on molecular medium.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, X.; Senftleben, A.; Pflueger, T.

Absolutely normalized (e,2e) measurements for H{sub 2} and He covering the full solid angle of one ejected electron are presented for 16 eV sum energy of both final state continuum electrons. For both targets rich cross-section structures in addition to the binary and recoil lobes are identified and studied as a function of the fixed electron's emission angle and the energy sharing among both electrons. For H{sub 2} their behavior is consistent with multiple scattering of the projectile as discussed before [Al-Hagan et al., Nature Phys. 5, 59 (2009)]. For He the binary and recoil lobes are significantly larger thanmore » for H{sub 2} and partly cover the multiple scattering structures. To highlight these patterns we propose a alternative representation of the triply differential cross section. Nonperturbative calculations are in good agreement with the He results and show discrepancies for H{sub 2} in the recoil peak region. For H{sub 2} a perturbative approach reasonably reproduces the cross-section shape but deviates in absolute magnitude.« less

Electron- and positron-impact atomic scattering calculations using propagating exterior complex scaling

NASA Astrophysics Data System (ADS)

Bartlett, P. L.; Stelbovics, A. T.; Rescigno, T. N.; McCurdy, C. W.

2007-11-01

Calculations are reported for four-body electron-helium collisions and positron-hydrogen collisions, in the S-wave model, using the time-independent propagating exterior complex scaling (PECS) method. The PECS S-wave calculations for three-body processes in electron-helium collisions compare favourably with previous convergent close-coupling (CCC) and time-dependent exterior complex scaling (ECS) calculations, and exhibit smooth cross section profiles. The PECS four-body double-excitation cross sections are significantly different from CCC calculations and highlight the need for an accurate representation of the resonant helium final-state wave functions when undertaking these calculations. Results are also presented for positron-hydrogen collisions in an S-wave model using an electron-positron potential of V12 = - (8 + (r1 - r2)2)-1/2. This model is representative of the full problem, and the results demonstrate that ECS-based methods can accurately calculate scattering, ionization and positronium formation cross sections in this three-body rearrangement collision.

Quantum-mechanical predictions of electron-induced ionization cross sections of DNA components

NASA Astrophysics Data System (ADS)

Champion, Christophe

2013-05-01

Ionization of biomolecules remains still today rarely investigated on both the experimental and the theoretical sides. In this context, the present work appears as one of the first quantum mechanical approaches providing a multi-differential description of the electron-induced ionization process of the main DNA components for impact energies ranging from the target ionization threshold up to about 10 keV. The cross section calculations are here performed within the 1st Born approximation framework in which the ejected electron is described by a Coulomb wave whereas the incident and the scattered electrons are both described by a plane wave. The biological targets of interest, namely, the DNA nucleobases and the sugar-phosphate backbone, are here described by means of the GAUSSIAN 09 system using the restricted Hartree-Fock method with geometry optimization. The theoretical predictions also obtained have shown a reasonable agreement with the experimental total ionization cross sections while huge discrepancies have been pointed out with existing theoretical models, mainly developed within a semi-classical framework.

Electronic excitation of Na due to low-energy He collisions

NASA Astrophysics Data System (ADS)

Lin, C. Y.; Liebermann, H. P.

2005-05-01

In warm astrophysical environments electron collisions are the primary mechanism for thermalizing the internal energy of ambient atoms and molecules. However, in cool stellar and planetary atmospheres, the electron abundance is extremely low so that thermalization is only possible through collisions of the dominant neutral species, H2, He, and H. Typically, the neutral cross sections are much smaller than those due to electrons, so that the level populations of the atmospheric constituents may display departures from equilibrium. Unfortunately, these cross sections are generally not available for collision energies typical of stellar/planetary environments. In this work, we investigate the electronic excitation of Na due to collisions with He for energies near and just above threshold. The calculations are performed with the quantum-mechanical molecular-orbital close-coupling method utilizing ab initio adiabatic potential curves and nonadiabatic radial and rotational coupling matrix elements obtained from multireference single- and double- excitation configuration interaction approach. State-to-state cross sections and rate coefficients will be presented and compared with other theoretical and experimental data where available.

Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

NASA Astrophysics Data System (ADS)

Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R. P.; Arrington, J.; Brooks, W. K.; Adhikari, K. P.; Afanasev, A. V.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Burkert, V. D.; Carman, D. S.; Careccia, S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dodge, G. E.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Fradi, A.; Garillon, B.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S. M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jenkins, D.; Jiang, H.; Jo, H. S.; Joo, K.; Joosten, S.; Kalantarians, N.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mattione, P.; Mayer, M.; McKinnon, B.; Mestayer, M. D.; Meyer, C. A.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moody, C. I.; Moutarde, H.; Movsisyan, A.; Camacho, C. Munoz; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Peña, C.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Sharabian, Y. G.; Simonyan, A.; Skorodumina, I.; Smith, E. S.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Trivedi, A.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Wei, X.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.; CLAS Collaboration

2015-02-01

There is a significant discrepancy between the values of the proton electric form factor, GEp, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GEp from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ɛ ) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ɛ at Q2=1.45 GeV2 . This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2 - 3 GeV2 .

Low-energy electron scattering from atomic hydrogen. II. Elastic and inelastic scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

James, K.E. Jr.; Childers, J.G.; Khakoo, M.A.

2004-02-01

We present measurements of differential cross sections for elastic electron scattering from atomic hydrogen at 20 eV and 40 eV incident electron energies and ratios of differential cross sections for electron-impact excitation of atomic hydrogen to the n=2, 3, and 4 levels at incident electron energies of 14.6 eV, 15.6 eV, 17.6 eV, 20 eV, 25 eV, and 40 eV with scattering angles ranging from 10 deg. to 130 deg. We compare our results to available experimental measurements and recent convergent close-coupling calculations. Our results resolve significant discrepancies that existed between theory and past experiments.

Carbon dioxide electron cooling rates in the atmospheres of Mars and Venus

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.; Rescigno, T. N.

2008-08-01

The cooling of electrons in collisions with carbon dioxide in the atmospheres of Venus and Mars is investigated. Calculations are performed with both previously accepted electron energy transfer rates and with new ones determined using more recent theoretical and experimental cross sections for electron impact on CO2. Emulation of a previous model for Venus confirms the validity of the current model and shows that use of the updated cross sections leads to cooling rates that are lower by one third. Application of the same model to the atmosphere of Mars gives more than double the previous cooling rates at altitudes where the electron temperature is very low.

Influence of electron correlation on the cross section and linear polarization of radiation emitted by electron-impact excitation of Ca+ and Ba+ ions

NASA Astrophysics Data System (ADS)

Chen, Zhan-Bin

2018-04-01

Calculations of the electron-impact excitation (EIE) of singly charged Ca+ and Ba+ ions and subsequent de-excitation process are performed using a fully relativistic distorted wave (RDW) method. To resolve the discrepancy between previous theory and experiment, careful consideration is given to the generation of the target state wave-functions through the systematic inclusion of electron correlations. It is found that the electron correlation effects play a significant role on the cross section, while the effects on the linear polarization of the emitted radiation are relatively small. Good agreement between our result and experiment is obtained.

Development and Application of Low Energy X-Ray and Electron Physics.

DTIC Science & Technology

1981-01-01

measured and theoretical photoionization cross section data (including those measured in this laboratory). In 1975, a detailed set of tables of these...available reported (to 1980) experimental and theoretical photoionization cross section data have been compiled and reviewed particularly for the low energy...orbital dimensions, the current theoretical partial photoionization cross section calculations have been applied to yield oscillator densities which permit

Double Electron Processes in Collisions of Partially Stripped Ions Cq+(q = 1-4) with Helium

NASA Astrophysics Data System (ADS)

Ding, Bao-Wei; Chen, Xi-Meng; Yu, De-Yang; Fu, Hong-Bin; Liu, Zhao-Yuan; Sun, Guang-Zhi; Liu, Yu-Wen; Lu, Yan-Xia; Xie, Jiang-Shan; Du, Juan; Gao, Zhi-Min; Chen, Lin; Cui, Ying; Shao, Jian-Xiong; He, Zi-Feng; Cai, Xiao-Hong

2007-01-01

The multi-electron processes are investigated for 17.9-120 keV/u C1+, 30-323 keV/u C2+, 120-438 keV/u C3+, 287-480 keV/u C4+ incident on a helium target. The cross-section ratios of double electron (DE) process to the total of the single electron (SE) and the double electron process (i.e. SE+DE), the direct double electron (DDI) to the direct single ionization (DSI) as well as the contributions of DDI to DE and of TI to DE are measured using coincidence techniques. The energy and charge state dependences of the measured cross-section ratios are studied and discussed.

Effects of quantum interference between radiative and dielectronic recombination on photorecombination cross-section profiles for the He-like ions Ar{sup 16+} and Fe{sup 24+}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Behar, Ehud; Jacobs, Verne L.; Oreg, Joseph

Total cross sections for electron-ion photorecombination (PR) processes are calculated using a projection-operator and resolvent-operator approach. This approach provides a unified quantum-mechanical description of the combined electron-ion PR process, including radiative and dielectronic recombination as coherent, interfering components. An especially adapted version of the Hebrew-University Lawrence-Livermore Atomic Code HULLAC is developed and employed for the calculations. In particular, PR cross sections for He-like argon and iron ions are calculated for incident-electron energies in the vicinity of the 1s2l2l{sup '} and 1s2l3l{sup '} doubly-excited, autoionizing levels of the Li-like ions. Significant effects of quantum interference between radiative and dielectronic recombination, inmore » the form of asymmetric PR cross-section profiles, are predicted, especially for weak transitions. The general behavior of the interference effect, as a function of the ion charge q and as a function of the principal quantum number n{sup '} of the outer electron in the autoionizing state, is investigated using a hydrogenic-scaling analysis. It is found that the degree of asymmetry in the PR cross-section profile can be substantial for close-to-neutral ions and also for very highly-charged ions. In the intermediate-charge regime, on the other hand, the asymmetry is anticipated to be less prominent. The dependence of the quantum-interference effect on n{sup '} is predicted to be much weaker.« less

Partial wave analysis for folded differential cross sections

NASA Astrophysics Data System (ADS)

Machacek, J. R.; McEachran, R. P.

2018-03-01

The value of modified effective range theory (MERT) and the connection between differential cross sections and phase shifts in low-energy electron scattering has long been recognized. Recent experimental techniques involving magnetically confined beams have introduced the concept of folded differential cross sections (FDCS) where the forward (θ ≤ π/2) and backward scattered (θ ≥ π/2) projectiles are unresolved, that is the value measured at the angle θ is the sum of the signal for particles scattered into the angles θ and π - θ. We have developed an alternative approach to MERT in order to analyse low-energy folded differential cross sections for positrons and electrons. This results in a simplified expression for the FDCS when it is expressed in terms of partial waves and thereby enables one to extract the first few phase shifts from a fit to an experimental FDCS at low energies. Thus, this method predicts forward and backward angle scattering (0 to π) using only experimental FDCS data and can be used to determine the total elastic cross section solely from experimental results at low-energy, which are limited in angular range.

Application of PIXE in the determination of the production cross section of a radionuclide decaying by electron capture

NASA Astrophysics Data System (ADS)

Morales, J. R.; Chesta, M. A.; Cancino, S. A.; Miranda, P. A.; Dinator, M. I.; Avila, M. J.

2005-01-01

Proton induced X-ray emission (PIXE) has been applied to the measurement of the production cross section of a radionuclide decaying by electron capture. By performing a PIXE type experiment on the daughter nuclide important advantages are obtained. The determination of some factors with usually large uncertainties, like solid angle and detector efficiency were avoided. The method was applied to the determination of cross section of the reaction 63Cu(d, p)64Cu at 2.4 MeV for 64Cu production. This result is in full agreement with that obtained through the decay of the 1346 keV gamma ray of 64Cu.

Cross sections for electron scattering by carbon disulfide in the low- and intermediate-energy range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brescansin, L. M.; Iga, I.; Lee, M.-T.

2010-01-15

In this work, we report a theoretical study on e{sup -}-CS{sub 2} collisions in the low- and intermediate-energy ranges. Elastic differential, integral, and momentum-transfer cross sections, as well as grand total (elastic + inelastic) and absorption cross sections, are reported in the 1-1000 eV range. A recently proposed complex optical potential composed of static, exchange, and correlation-polarization plus absorption contributions is used to describe the electron-molecule interaction. The Schwinger variational iterative method combined with the distorted-wave approximation is applied to calculate the scattering amplitudes. The comparison between our calculated results and the existing experimental and/or theoretical results is encouraging.

Electron capture from circular Rydberg atoms

NASA Astrophysics Data System (ADS)

Lundsgaard, M. F. V.; Chen, Z.; Lin, C. D.; Toshima, N.

1995-02-01

Electron capture cross sections from circular Rydberg states as a function of the angle cphi between the ion velocity and the angular momentum of the circular orbital have been reported recently by Hansen et al. [Phys. Rev. Lett. 71, 1522 (1993)]. We show that the observed cphi dependence can be explained in terms of the propensity rule that governs the dependence of electron capture cross sections on the magnetic quantum numbers of the initial excited states. We also carried out close-coupling calculations to show that electron capture from the circular H(3d,4f,5g) states by protons at the same scaled velocity has nearly the same cphi dependence.

Calculated stopping powers of low-energy electrons in some materials of interest in radiation protection.

PubMed

Akande, W

1993-03-01

Stopping powers of low-energy (< 10 keV) electrons in aluminum, copper, cesium, barium, lead, lithium, and uranium were calculated using an analytic method. The interaction of the electrons with the materials were characterized in terms of three cross sections for total ionization and total scattering. Experimental cross section data were collated, where available, for the materials. The expressions were then fitted to the data to obtain the values of the relevant constants in the expressions. This enabled the basic equation of stopping powers of electrons to be evaluated for the materials. Comparison of the results obtained with those of other workers was affected.

Electron impact excitation of tin

NASA Astrophysics Data System (ADS)

Sharma, Lalita; Bharti, Swati; Srivastava, Rajesh

2017-05-01

We study the electron impact excitation of the fine-structure levels of the ground state configuration 5p2 to the excited states of the configuration 5p6s in tin atom. These calculations have been carried out in the jj coupling scheme using the relativistic distorted-wave method. Results for differential cross section are reported at incident electron energies 20, 50, 80 and 100 eV while integrated cross sections are presented in the incident electron energy range of 5 to 100 eV. Contribution to the Topical Issue: "Low-Energy Interactions related to Atmospheric and Extreme Conditions", edited by S. Ptasinska, M. Smialek-Telega, A. Milosavljevic and B. Sivaraman.

Electron Stark Broadening Database for Atomic N, O, and C Lines

NASA Technical Reports Server (NTRS)

Liu, Yen; Yao, Winifred M.; Wray, Alan A.; Carbon, Duane F.

2012-01-01

A database for efficiently computing the electron Stark broadening line widths for atomic N, O, and C lines is constructed. The line width is expressed in terms of the electron number density and electronatom scattering cross sections based on the Baranger impact theory. The state-to-state cross sections are computed using the semiclassical approximation, in which the atom is treated quantum mechanically whereas the motion of the free electron follows a classical trajectory. These state-to-state cross sections are calculated based on newly compiled line lists. Each atomic line list consists of a careful merger of NIST, Vanderbilt, and TOPbase line datasets from wavelength 50 nm to 50 micrometers covering the VUV to IR spectral regions. There are over 10,000 lines in each atomic line list. The widths for each line are computed at 13 electron temperatures between 1,000 K 50,000 K. A linear least squares method using a four-term fractional power series is then employed to obtain an analytical fit for each line-width variation as a function of the electron temperature. The maximum L2 error of the analytic fits for all lines in our line lists is about 5%.

An experimental and theoretical investigation into the electronically excited states of para-benzoquinone

NASA Astrophysics Data System (ADS)

Jones, D. B.; Limão-Vieira, P.; Mendes, M.; Jones, N. C.; Hoffmann, S. V.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Blanco, F.; García, G.; Ingólfsson, O.; Lima, M. A. P.; Brunger, M. J.

2017-05-01

We report on a combination of experimental and theoretical investigations into the structure of electronically excited para-benzoquinone (pBQ). Here synchrotron photoabsorption measurements are reported over the 4.0-10.8 eV range. The higher resolution obtained reveals previously unresolved pBQ spectral features. Time-dependent density functional theory calculations are used to interpret the spectrum and resolve discrepancies relating to the interpretation of the Rydberg progressions. Electron-impact energy loss experiments are also reported. These are combined with elastic electron scattering cross section calculations performed within the framework of the independent atom model-screening corrected additivity rule plus interference (IAM-SCAR + I) method to derive differential cross sections for electronic excitation of key spectral bands. A generalized oscillator strength analysis is also performed, with the obtained results demonstrating that a cohesive and reliable quantum chemical structure and cross section framework has been established. Within this context, we also discuss some issues associated with the development of a minimal orbital basis for the single configuration interaction strategy to be used for our high-level low-energy electron scattering calculations that will be carried out as a subsequent step in this joint experimental and theoretical investigation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, J.; Richard, P.; Gray, T.J.

The systematics of single and double K-shell-vacancy production in titanium has been investigated in the limit of zero target thickness (approx.1 ..mu..g/cm/sup 2/) for incident C, N, O, F, Mg, Al, Si, S, and Cl ions over a maximum energy range of 0.5 to 6.5 MeV/amu. This corresponds to collision systems with 0.27< or =Z/sub 1//Z/sub 2/< or =0.77 and 0.24< or =v/sub 1//vK< or =0.85, where v/sub 1/ is the projectile nuclear velocity and vK is the mean velocity of an electron in the target K shell. The present work is divided into four major sections. (1) Single K-shell-vacancymore » production has been investigated by measuring K..cap alpha.. and K..beta.. p satellite x-ray-production cross sections for projectiles incident with no K-shell vacancies. For incident ions with Z/sub 1/> or =9, the contribution due to electron-transfer processes from the target K shell to outer shells of the projectile has also been noted. (2) Single K-shell--to--K-shell electron-transfer cross sections have been obtained indirectly by the measuring of the enhancement in the Ti K x-ray production cross section for bare incident projectiles over ions incident with no initial K-shell vacancies. (3) Double K-vacancy production has been investigated by measuring the K..cap alpha.. hypersatellite intensity in ratio to the total K..cap alpha.. intensity. (4) Double K-shell--to--K-shell electron-transfer cross sections have been obtained indirectly with the use of a procedure similar to that used for single K to K transfer. The measured cross sections have been compared to theoretical models for direct Coulomb ionization and inner-shell electron transfer and have been used to investigate the relative importance of these mechanisms for K-vacancy production in heavy-ion--atom collisions.« less

Strong-potential Born calculations for 1s-1s electron capture from atoms by protons

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGuire, J.H.; Kletke, R.E.; Sil, N.C.

1985-08-01

The strong-potential Born (SPB) approximation is examined by comparing various SPB calculations of high-velocity 1s-1s electron capture cross sections with one another and with experimental data. Above about 1 MeV, calculations using the SPB method of McGuire and Sil (SPMS) (Phys. Rev. A 28, 3679 (1983)) are in good agreement with total-cross-section observations for protons on H, He, C, Ne, and Ar as expected. For p+H and p+He, the SPB full-peaking (SPB-FP) approximation of Macek and Alston (Phys. Rev. A 26, 250 (1982)) and the SPB transverse-peaking (SPB-TP) approximation of Alston (Phys. Rev. A 27, 2342 (1982)) differ from ourmore » SPMS total cross sections by typically a factor of 2, as expected from general validity criteria. However, the differential cross sections at very forward angles (well within the Thomas angle) are the same in SPMS, SPB-FP, and SPB-TP methods in all cases. Below 1 MeV, cross sections obtained with use of various SPB methods differ considerably from one another, placing a limit of validity for these SPB calculations. We also suggest that in the gap between those energies where continuum intermediate states simply dominate, and above those energies where bound intermediate states simply dominate, detailed conceptual understanding of electron capture is incomplete.« less

Excitation and Ionization Cross Sections for Electron-Beam Energy Deposition in High Temperature Air

DTIC Science & Technology

1987-07-09

are given and compared to existing experimental results or other theoretical approaches. This information can readily be used as input for a deposition...of the doubly-differential, singly- differential and total ionization cross sections which subsequently served to guide theoretical calculations on...coworkers have been leaders in developing a theoretical base for studying electron production and energy deposition in atmospheric gases such as He, N2

Low-energy electron-impact ionization of helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schow, E.; Hazlett, K.; Childers, J. G.

2005-12-15

Normalized doubly differential cross sections for the electron-impact ionization of helium at low energies are presented. The data are taken at the incident electron energies of 26.3, 28.3, 30.3, 32.5, 34.3, 36.5, and 40.7 eV and for scattering angles of 10 deg. -130 deg. The measurements involve the use of the moveable target method developed at California State University Fullerton to accurately determine the continuum background in the energy-loss spectra. Normalization of experimental data is made on a relative scale to well-established experimental differential cross sections for excitation of the n=2 manifold of helium and then on an absolute scalemore » to the well-established total ionization cross sections of Shah et al. [J. Phys. B 21, 2751 (1988)]. Comparisons are made with available experimental data and the results of the convergent close-coupling theory.« less

Cross-section and rate formulas for electron-impact ionization, excitation, deexcitation, and total depopulation of excited atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vriens, L.; Smeets, A.H.M.

1980-09-01

For electron-induced ionization, excitation, and de-excitation, mainly from excited atomic states, a detailed analysis is presented of the dependence of the cross sections and rate coefficients on electron energy and temperature, and on atomic parameters. A wide energy range is covered, including sudden as well as adiabatic collisions. By combining the available experimental and theoretical information, a set of simple analytical formulas is constructed for the cross sections and rate coefficients of the processes mentioned, for the total depopulation, and for three-body recombination. The formulas account for large deviations from classical and semiclassical scaling, as found for excitation. They agreemore » with experimental data and with the theories in their respective ranges of validity, but have a wider range of validity than the separate theories. The simple analytical form further facilitates the application in plasma modeling.« less

Born distorted-wave approximation applied to the H+ + He collisions at intermediate and high energies

NASA Astrophysics Data System (ADS)

Rahmanian, M.; Fathi, R.; Shojaei, F.

2017-11-01

The single-charge transfer process in collision of protons with helium atoms in their ground states is investigated. The model utilizes the second-order three-body Born distorted-wave approximation (BDW-3B) with correct Coulomb boundary conditions to calculate the differential and total cross sections at intermediate and high energies. The role of the passive electrons and electron-electron correlations are studied by comparing our results and the BDW-4B calculations with the complete perturbation potential. The present results are also compared with other theories, and the Thomas scattering mechanism is investigated. The obtained results are also compared with the recent experimental measurements. For the prior differential cross sections, the comparisons show better agreement with the experiments at smaller scattering angles. The agreement between the total cross sections and the BDW-4B results as well as the experimental data is good at higher impact energies.

Multiple double cross-section transmission electron microscope sample preparation of specific sub-10 nm diameter Si nanowire devices.

PubMed

Gignac, Lynne M; Mittal, Surbhi; Bangsaruntip, Sarunya; Cohen, Guy M; Sleight, Jeffrey W

2011-12-01

The ability to prepare multiple cross-section transmission electron microscope (XTEM) samples from one XTEM sample of specific sub-10 nm features was demonstrated. Sub-10 nm diameter Si nanowire (NW) devices were initially cross-sectioned using a dual-beam focused ion beam system in a direction running parallel to the device channel. From this XTEM sample, both low- and high-resolution transmission electron microscope (TEM) images were obtained from six separate, specific site Si NW devices. The XTEM sample was then re-sectioned in four separate locations in a direction perpendicular to the device channel: 90° from the original XTEM sample direction. Three of the four XTEM samples were successfully sectioned in the gate region of the device. From these three samples, low- and high-resolution TEM images of the Si NW were taken and measurements of the NW diameters were obtained. This technique demonstrated the ability to obtain high-resolution TEM images in directions 90° from one another of multiple, specific sub-10 nm features that were spaced 1.1 μm apart.

Absolute cross sections for electronic excitation of condensed tetrahydrofuran (THF) by 11-16 eV electrons.

PubMed

Lemelin, V; Bass, A D; Cloutier, P; Sanche, L

2016-11-07

Absolute cross section (CS) data on the interaction of low energy electrons with DNA and its molecular constituents are required as input parameters in Monte-Carlo type simulations, for several radiobiological applications. Previously [V. Lemelin et al., J. Chem. Phys. 144, 074701 (2016)], we measured absolute vibrational CSs for low-energy electron scattering from condensed tetrahydrofuran, a convenient surrogate for the deoxyribose. Here we report absolute electronic CSs for energy losses of between 6 and 11.5 eV, by electrons with energies between 11 and 16 eV. The variation of these CSs with incident electron energy shows no evidence of transient anion states, consistent with theoretical and other experimental results, indicating that initial electron capture leading to DNA strand breaks occurs primarily on DNA bases or the phosphate group.

Differential Cross Sections for the Electron Impact Excitation of the A(sup 3)(Sigma)(sub u)(sup +), B(sup 3)Pi(sub g), W(sup 3)(Delta)(sub u), B'(sup 3)(Sigma)(sub u)(sup -), a'(sup 1)Sigma(sub u)(sup -), a(sup 1)Pi(sub g), w(sup 1)Delta(sub u), and C(sup 3)Pi(sub u) States of N(sub 2)

NASA Technical Reports Server (NTRS)

Khakoo, M. A.; Johnson, P. V.; Ozkay, I.; Yan, P.; Trajmar, S.; Kanik, I.

2005-01-01

Measurements of differential cross sections for the electron-impact excitation of molecular nitrogen from the ground X(sup 1)(Sigma)(sub g)(sup +)(v''=0)level to the A(sup 3)(Sigma)(sub u)(sup +)(v'), B(sup 3)Pi(sub g)(v'), W(sup 3)(Delta)(sub u)(v'),B'(sup 3)(Sigma)(sub u)(sup -)(v'), a(sup 1)(Pi)(sub g)(v'), w(sup 1)(Delta)(sub u)(v'), and C(sup 3)(Pi)(sub u)(v') levels are presented. The data are obtained at the incident energies of 10, 12.5, 15, 17.5, 20, 30, 50, and 100 eV over the angular range of 5(deg)-130(deg) in 5(deg) intervals. The individual electronic state excitation differential cross sections are obtained by unfolding electron energy-loss spectra of molecular nitrogen using available semiempirical Frank-Condon factors. The data are compared to previous measurements and to available theory. We also make several important suggestions regarding future work that, like the present, relies on the unfolding of electron energy-loss spectra for obtaining differential cross sections.

The multistate impact parameter method for molecular charge exchange in nitrogen

NASA Technical Reports Server (NTRS)

Ioup, J. W.

1980-01-01

The multistate impact parameter method is applied to the calculation of total cross sections for low energy change transfer between nitrogen ions and nitrogen molecules. Experimental data showing the relationships between total cross section and ion energy for various pressures and electron ionization energies were obtained. Calculated and experimental cross section values from the work are compared with the experimental and theoretical results of other investigators.

Lithography Radiation Effects Study.

DTIC Science & Technology

1984-11-01

Electronic Industries, 7317 South Washinqton Avenue, Edina, Minnesota 5;435, 1972) A- 2-8 15. J. H. Scofield , Theoretical Photoionization Cross Sections...exci- tation of a qiven shell is proportional to the photoionization cross-section * of the shell. Theoretical photoionization cross-sections as a...Ti (Ka = 4.51 keV), 500 A and for Cr (K. = 5.41 keV), 580 A. Comparison of these data with existing theoretical models were not carried out. The

Slow-electron collisions with CO molecules in an exact-exchange plus parameter-free polarization model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jain, A.; Norcross, D.W.

1992-02-01

We report low-energy (0.001--10-eV) electron-CO scattering cross sections obtained using an exact-exchange (via a separable-exchange formulation) plus a parameter-free correlation-polarization model in the fixed-nuclei approximation (FNA). The differential, total, and momentum-transfer cross sections are reported for rotationally elastic, inelastic, and summed processes. To remove the limitations of the FNA with respect to the convergence of total and differential cross sections, the multipole-extracted-adiabatic-nuclei approximation is used. The position and width of the well-known {sup 2}{Pi} shape-resonance structure in the cross section around 2 eV are reproduced quite well; however, some discrepancy between theory and experiment in the magnitude of the totalmore » cross section in the resonance region exists. We also present results for {sup 2}{Pi} shape-resonance parameters as a function of internuclear separation. Differential-cross-section results agree well with the measurements of Tanaka, Srivastava, and Chutjian (J. Chem. Phys. 69, 5329 (1978)) but are about a factor of 2 larger than the results obtained by Jung {ital et} {ital al}. (J. Phys. B 15, 3535 (1982)) in the vicinity of the {sup 2}{Pi} resonance.« less

Simulation of multistatic and backscattering cross sections for airborne radar

NASA Astrophysics Data System (ADS)

Biggs, Albert W.

1986-07-01

In order to determine susceptibilities of airborne radar to electronic countermeasures and electronic counter-countermeasures simulations of multistatic and backscattering cross sections were developed as digital modules in the form of algorithms. Cross section algorithms are described for prolate (cigar shape) and oblate (disk shape) spheroids. Backscattering cross section algorithms are also described for different categories of terrain. Backscattering cross section computer programs were written for terrain categorized as vegetation, sea ice, glacial ice, geological (rocks, sand, hills, etc.), oceans, man-made structures, and water bodies. PROGRAM SIGTERRA is a file for backscattering cross section modules of terrain (TERRA) such as vegetation (AGCROP), oceans (OCEAN), Arctic sea ice (SEAICE), glacial snow (GLASNO), geological structures (GEOL), man-made structures (MAMMAD), or water bodies (WATER). AGCROP describes agricultural crops, trees or forests, prairies or grassland, and shrubs or bush cover. OCEAN has the SLAR or SAR looking downwind, upwind, and crosswind at the ocean surface. SEAICE looks at winter ice and old or polar ice. GLASNO is divided into a glacial ice and snow or snowfields. MANMAD includes buildings, houses, roads, railroad tracks, airfields and hangars, telephone and power lines, barges, trucks, trains, and automobiles. WATER has lakes, rivers, canals, and swamps. PROGRAM SIGAIR is a similar file for airborne targets such as prolate and oblate spheroids.

Correction of the near threshold behavior of electron collisional excitation cross-sections in the plane-wave Born approximation

DOE PAGES

Kilcrease, D. P.; Brookes, S.

2013-08-19

The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. Additionally, a simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure formore » the Born cross-sections that employs the Elwert–Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. Furthermore, we also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations.« less

Low-energy elastic electron scattering from furan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khakoo, M. A.; Muse, J.; Ralphs, K.

We report normalized experimental and theoretical differential cross sections for elastic electron scattering by C{sub 4}H{sub 4}O (furan) molecules from a collaborative project between several Brazilian theoretical groups and an experimental group at California State Fullerton, USA. The measurements are obtained by using the relative flow method with helium as the standard gas and a thin aperture target gas collimating source. The relative flow method is applied without the restriction imposed by the relative flow pressure condition on helium and the unknown gas. The experimental data were taken at incident electron energies of 1, 1.5, 1.73, 2, 2.7, 3, 5,more » 7, 10, 20, 30, and 50 eV and covered the angular range between 10 deg. and 130 deg. The measurements verify observed {pi}* shape resonances at 1.65{+-}0.05eV and 3.10{+-}0.05 eV scattering energies, in good agreement with the transmission electron data of Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004)]. Furthermore, the present results also indicated both resonances dominantly in the d-wave channel. The differential cross sections are integrated in the standard way to obtain integral elastic cross sections and momentum transfer cross sections. The calculations employed the Schwinger multichannel method with pseudopotentials and were performed in the static-exchange and in the static-exchange plus polarization approximations. The calculated integral and momentum transfer cross sections clearly revealed the presence of two shape resonances located at 1.95 and 3.56 eV and ascribed to the B{sub 1} and A{sub 2} symmetries of the C{sub 2v} point group, respectively, in very good agreement with the experimental findings. Overall agreement between theory and experiment regarding the differential, momentum transfer, and integral cross sections is very good, especially for energies below 10 eV.« less

Low-energy elastic electron scattering from furan

NASA Astrophysics Data System (ADS)

Khakoo, M. A.; Muse, J.; Ralphs, K.; da Costa, R. F.; Bettega, M. H. F.; Lima, M. A. P.

2010-06-01

We report normalized experimental and theoretical differential cross sections for elastic electron scattering by C4H4O (furan) molecules from a collaborative project between several Brazilian theoretical groups and an experimental group at California State Fullerton, USA. The measurements are obtained by using the relative flow method with helium as the standard gas and a thin aperture target gas collimating source. The relative flow method is applied without the restriction imposed by the relative flow pressure condition on helium and the unknown gas. The experimental data were taken at incident electron energies of 1, 1.5, 1.73, 2, 2.7, 3, 5, 7, 10, 20, 30, and 50 eV and covered the angular range between 10° and 130°. The measurements verify observed π* shape resonances at 1.65±0.05eV and 3.10±0.05 eV scattering energies, in good agreement with the transmission electron data of Modelli and Burrow [J. Phys. Chem. AJPCAFH 1089-563910.1021/jp048759a 108, 5721 (2004)]. Furthermore, the present results also indicated both resonances dominantly in the d-wave channel. The differential cross sections are integrated in the standard way to obtain integral elastic cross sections and momentum transfer cross sections. The calculations employed the Schwinger multichannel method with pseudopotentials and were performed in the static-exchange and in the static-exchange plus polarization approximations. The calculated integral and momentum transfer cross sections clearly revealed the presence of two shape resonances located at 1.95 and 3.56 eV and ascribed to the B1 and A2 symmetries of the C2v point group, respectively, in very good agreement with the experimental findings. Overall agreement between theory and experiment regarding the differential, momentum transfer, and integral cross sections is very good, especially for energies below 10 eV.

Variation in Differential and Total Cross Sections Due to Different Radial Wave Functions

ERIC Educational Resources Information Center

Williamson, W., Jr.; Greene, T.

1976-01-01

Three sets of analytical wave functions are used to calculate the Na (3s---3p) transition differential and total electron excitation cross sections by Born approximations. Results show expected large variations in values. (Author/CP)

Fast calculator for X-ray emission due to Radiative Recombination and Radiative Electron Capture in relativistic heavy-ion atom collisions

NASA Astrophysics Data System (ADS)

Herdrich, M. O.; Weber, G.; Gumberidze, A.; Wu, Z. W.; Stöhlker, Th.

2017-10-01

In experiments with highly charged, fast heavy ions the Radiative Recombination (RR) and Radiative Electron Capture (REC) processes have significant cross sections in an energy range of up to a few GeV / u . They are some of the most important charge changing processes in collisions of heavy ions with atoms and electrons, leading to the emission of a photon along with the formation of the ground and excited atomic states. Hence, for the understanding and planning of experiments, in particular for X-ray spectroscopy studies, at accelerator ring facilities, such as FAIR, it is crucial to have a good knowledge of these cross sections and the associated radiation characteristics. In the frame of this work a fast calculator, named RECAL, for the RR and REC process is presented and its capabilities are demonstrated with the analysis of a recently conducted experiment at the Experimental Storage Ring (ESR) at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany. A method is presented to determine unknown X-ray emission cross sections via normalization of the recorded spectra to REC cross sections calculated by RECAL.

Excitation energies, photoionization cross sections, and asymmetry parameters of the methyl and silyl radicals.

PubMed

Velasco, A M; Lavín, C; Dolgounitcheva, O; Ortiz, J V

2014-08-21

Vertical excitation energies of the methyl and silyl radicals were inferred from ab initio electron propagator calculations on the electron affinities of CH3(+) and SiH3(+). Photoionization cross sections and angular distribution of photoelectrons for the outermost orbitals of both CH3 and SiH3 radicals have been obtained with the Molecular Quantum Defect Orbital method. The individual ionization cross sections corresponding to the Rydberg channels to which the excitation of the ground state's outermost electron gives rise are reported. Despite the relevance of methyl radical in atmospheric chemistry and combustion processes, only data for the photon energy range of 10-11 eV seem to be available. Good agreement has been found with experiment for photoionization cross section of this radical. To our knowledge, predictions of the above mentioned photoionization parameters on silyl radical are made here for the first time, and we are not aware of any reported experimental measurements. An analysis of our results reveals the presence of a Cooper minimum in the photoionization of the silyl radical. The adequacy of the two theoretical procedures employed in the present work is discussed.

Excitation energies, photoionization cross sections, and asymmetry parameters of the methyl and silyl radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velasco, A. M.; Lavín, C., E-mail: clavin@qf.uva.es; Dolgounitcheva, O.

2014-08-21

Vertical excitation energies of the methyl and silyl radicals were inferred from ab initio electron propagator calculations on the electron affinities of CH{sub 3}{sup +} and SiH{sub 3}{sup +}. Photoionization cross sections and angular distribution of photoelectrons for the outermost orbitals of both CH{sub 3} and SiH{sub 3} radicals have been obtained with the Molecular Quantum Defect Orbital method. The individual ionization cross sections corresponding to the Rydberg channels to which the excitation of the ground state's outermost electron gives rise are reported. Despite the relevance of methyl radical in atmospheric chemistry and combustion processes, only data for the photonmore » energy range of 10–11 eV seem to be available. Good agreement has been found with experiment for photoionization cross section of this radical. To our knowledge, predictions of the above mentioned photoionization parameters on silyl radical are made here for the first time, and we are not aware of any reported experimental measurements. An analysis of our results reveals the presence of a Cooper minimum in the photoionization of the silyl radical. The adequacy of the two theoretical procedures employed in the present work is discussed.« less

Low-Energy Electron Interactions with CF_4

NASA Astrophysics Data System (ADS)

Christophorou, Loucas G.; Olthoff, James K.; Rao, M. V. V. S.

1996-10-01

Carbon tetrafluoride is one of the most widely used components of feed gas mixtures employed for a variety of plasma assisted materials processing applications. In this presentation, we synthesize and assess the available information on the cross sections and rate coefficients of collisional interations of CF4 with electrons.(L. G. Christophorou, J. K. Olthoff, and M.V. V. S. Rao, J. Phys. Chem. Ref. Data, submitted (May 1996)) A ``recommended'' data set is presented, based upon available data for: (i) cross sections for electron scattering (total, elastic, momentum, differential, inelastic), electron impact ionization (total and partial), electron impact dissociation, and electron attachment; and (ii) coefficients for electron transport, electron attachment, and electron impact ionization. -Research sponsored in part by the U.S. Air Force Wright Laboratory under contract F33615-96-C-2600 with the University of Tennessee. Also, Department of Physics, The University of Tennessee, Knoxville, TN.

Absolute cross section for electron-impact ionization of He (1 s 2 s 3S)

NASA Astrophysics Data System (ADS)

Génévriez, Matthieu; Jureta, Jozo J.; Defrance, Pierre; Urbain, Xavier

2017-07-01

We present an experimental determination of the electron-impact ionization cross section of the 1 s 2 s 3S state of helium, for which there is a serious long-lasting discrepancy between theory and experiment. A technique for the production of a fast, intense beam of helium in the 1 s 2 s 3S state only has been developed for this purpose, based on photodetachment of the He- anion. The cross section is measured using the animated crossed beam technique. The present results are much lower than the experimental data of Dixon et al. [J. Phys. B 9, 2617 (1976), 10.1088/0022-3700/9/15/013] and are in excellent agreement with the calculation of Fursa and Bray [J. Phys. B 36, 1663 (2003), 10.1088/0953-4075/36/8/317].

Electronic Excitation of Furan by Low Energy Electrons

NASA Astrophysics Data System (ADS)

Hargreaves, Leigh R.; Khakoo, Murtadha A.; Lopes, Maria Cristina A.; da Costa, Romarly; Bettega, Marcio H. F.; Lima, Marco A. P.

2011-10-01

We present absolute differential cross section (DCS) measurements and calculations of electron impact excitation of the lowest lying triplet 3B2 and 3A1 electronic states of furan. The incident electron energy range of the present study was 5-15eV. The experimental data were normalized to the elastic DCS data of. The cross sections were determined by unfolding electron energy loss spectra, using an open source data analysis package and the spectroscopic assignments of. The calculations employ a Multichannel Schwinger method with a 9-state closed coupling CI configuration including polarized pseudo-potentials. The preliminary theoretical results show reasonable agreement with experiment below 10eV, but differ at higher energies. Funded by the US NSF and the Brazilian funding agencies CNPq, CAPES and FAPESP.

Differential cross sections for the electron impact ionization of Ar (3 p) atoms for equal energy final state electrons

NASA Astrophysics Data System (ADS)

Purohit, Ghanshyam; Singh, Prithvi

2017-06-01

The electron-impact ionization of inert gases for asymmetric final state energy sharing conditions has been studied in detail. However, there have been relatively few studies examining equal energy final state electrons. We report in this communication the results of triple differential cross sections (TDCSs) for electron impact ionization of Ar (3 p) for equal energy sharing of the outgoing electrons. We calculate TDCS in the modified distorted wave Born approximation (DWBA) formalism including post collision interaction (PCI) and polarization potential. We compare the results of our calculation with available measurements [Phys. Rev. A 87, 022712 (2013)]. We study the effect of PCI, target polarization on the trends of TDCS for the single ionization of Ar (3 p) targets.

On the Asymmetric Focusing of Low-Emittance Electron Bunches via Active Lensing by Using Capillary Discharges

NASA Astrophysics Data System (ADS)

Bulanov, Stepan; Bagdasarov, Gennadiy; Bobrova, Nadezhda; Boldarev, Alexey; Olkhovskaya, Olga; Sasorov, Pavel; Gasilov, Vladimir; Barber, Samuel; Gonsalves, Anthony; Schroeder, Carl; van Tilborg, Jeroen; Esarey, Eric; Leemans, Wim; Levato, Tadzio; Margarone, Daniele; Korn, Georg; Kando, Masaki; Bulanov, Sergei

2017-10-01

A novel method for asymmetric focusing of electron beams is proposed. The scheme is based on the active lensing technique, which takes advantage of the strong inhomogeneous magnetic field generated inside the capillary discharge plasma to focus the ultrarelativistic electrons. The plasma and magnetic field parameters inside a capillary discharge are described theoretically and modeled with dissipative MHD simulations to enable analysis of capillaries of oblong rectangle cross-sections implying that large aspect ratio rectangular capillaries can be used to form flat electron bunches. The effect of the capillary cross-section on the electron beam focusing properties were studied using the analytical methods and simulation- derived magnetic field map showing the range of the capillary discharge parameters required for producing the high quality flat electron beams.

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations.

PubMed

Ferreira da Silva, F; Lange, E; Limão-Vieira, P; Jones, N C; Hoffmann, S V; Hubin-Franskin, M-J; Delwiche, J; Brunger, M J; Neves, R F C; Lopes, M C A; de Oliveira, E M; da Costa, R F; Varella, M T do N; Bettega, M H F; Blanco, F; García, G; Lima, M A P; Jones, D B

2015-10-14

The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5-10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range.

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

NASA Astrophysics Data System (ADS)

Ferreira da Silva, F.; Lange, E.; Limão-Vieira, P.; Jones, N. C.; Hoffmann, S. V.; Hubin-Franskin, M.-J.; Delwiche, J.; Brunger, M. J.; Neves, R. F. C.; Lopes, M. C. A.; de Oliveira, E. M.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Blanco, F.; García, G.; Lima, M. A. P.; Jones, D. B.

2015-10-01

The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5-10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range.

Comment on “Single-inclusive jet production in electron–nucleon collisions through next-to-next-to-leading order in perturbative QCD” [Phys. Lett. B 763 (2016) 52–59

DOE PAGES

Bodwin, Geoffrey T.; Braaten, Eric

2017-03-22

In the cross section for single-inclusive jet production in electron nucleon collisions, the distribution of a quark in an electron appears at next-to-next-to-leading order. The numerical calculations in Ref. [1] were carried out using a perturbative approximation for the distribution of a quark in an electron. We point out that that distribution receives nonperturbative QCD contributions that invalidate the perturbative approximation. Here, those nonperturbative effects enter into cross sections for hard-scattering processes through resolved-electron contributions and can be taken into account by determining the distribution of a quark in an electron phenomenologically.

Comment on “Single-inclusive jet production in electron–nucleon collisions through next-to-next-to-leading order in perturbative QCD” [Phys. Lett. B 763 (2016) 52–59

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bodwin, Geoffrey T.; Braaten, Eric

In the cross section for single-inclusive jet production in electron nucleon collisions, the distribution of a quark in an electron appears at next-to-next-to-leading order. The numerical calculations in Ref. [1] were carried out using a perturbative approximation for the distribution of a quark in an electron. We point out that that distribution receives nonperturbative QCD contributions that invalidate the perturbative approximation. Here, those nonperturbative effects enter into cross sections for hard-scattering processes through resolved-electron contributions and can be taken into account by determining the distribution of a quark in an electron phenomenologically.

Electron-electron interaction in ion-atom collisions studied by projectile state-resolved Auger-electron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dohyung Lee.

This dissertation addresses the problem of dynamic electron-electron interactions in fast ion-atom collisions using projectile Auger electron spectroscopy. The study was carried out by measuring high-resolution projectile KKL Auger electron spectra as a function of projectile energy for the various collision systems of 0.25-2 MeV/u O{sup q+} and F{sup q+} incident on H{sub 2} and He targets. The electrons were detected in the beam direction, where the kinematic broadening is minimized. A zero-degree tandem electron spectrometer system, was developed and showed the versatility of zero-degree measurements of collisionally-produced atomic states. The zero-degree binary encounter electrons (BEe), quasifree target electrons ionizedmore » by the projectiles in head-on collisions, were observed as a strong background in the KLL Auger electron spectrum. They were studied by treating the target ionization as 180{degree} Rutherford elastic scattering in the projectile frame, and resulted in a validity test of the impulse approximation (IA) and a way to determine the spectrometer efficiency. An anomalous q-dependence, in which the zero-degree BEe yields increase with decreasing projectile charge state (q), was observed. State-resolved KLL Auger cross sections were determined by using the BEe normalization and thus the cross section of the electron-electron interactions such as resonant transfer-excitation (RTE), electron-electron excitation (eeE), and electron-electron ionization (eeI) were determined. Projectile 2l capture with 1s {yields} 2p excitation by the captured target electron was observed as an RTE process with Li-like and He-like projectiles and the measured RTEA (RTE followed by Auger decay) cross sections showed good agreement with an RTE-IA treatment and RTE alignment theory.« less

Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

NASA Technical Reports Server (NTRS)

James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Bray, I.; Dziczek, D.; Kanik, I.; Ajello, J. M.

1997-01-01

The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range.

Dispersive effects from a comparison of electron and positron scattering from

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul Gueye; M. Bernheim; J. F. Danel

1998-05-01

Dispersive effects have been investigated by comparing elastic scattering of electrons and positrons from {sup 12}C at the Saclay Linear Accelerator. The results demonstrate that dispersive effects at energies of 262 MeV and 450 MeV are less than 2% below the first diffraction minimum [0.95 < q{sub eff} (fm{sup -1}) < 1.66] in agreement with the prediction of Friar and Rosen. At the position of this minimum (q{sub eff} = 1.84 fm{sup -1}), the deviation between the positron scattering cross section and the cross section derived from the electron results is -44% {+-} 30%.

The value of swarm data for practical modeling of plasma devices

NASA Astrophysics Data System (ADS)

Napartovich, A. P.; Kochetov, I. V.

2011-04-01

The non-thermal plasma is a key component in gas lasers, waste gas cleaners, ozone generators, plasma igniters, flame holders, flow control in high-speed aerodynamics and other applications. The specific feature of the non-thermal plasma is its high sensitivity to variations in governing parameters (gas composition, pressure, pulse duration, E/N parameter). The reactivity of the plasma is due to the appearance of atoms and chemical radicals. For the efficient production of chemically active species high average electron energy is required, which is controlled by the balance of gain from the electric field and loss in inelastic collisions. In low-ionized plasma the electron energy distribution function is far from Maxwellian and must be found numerically for specified conditions. Numerical modeling of processes in plasma technologies requires vast databases on electron scattering cross sections to be available. The only reliable criterion for evaluations of validity of a set of cross sections for a particular species is a correct prediction of electron transport and kinetic coefficients measured in swarm experiments. This criterion is used traditionally to improve experimentally measured cross sections, as was suggested earlier by Phelps. The set of cross sections subjected to this procedure is called a self-consistent set. Nowadays, such reliable self-consistent sets are known for many species. Problems encountered in implementation of the fitting procedure and examples of its successful applications are described in the paper. .

Silicon nanowire device and method for its manufacture

DOEpatents

Okandan, Murat; Draper, Bruce L.; Resnick, Paul J.

2017-01-03

There is provided an electronic device and a method for its manufacture. The device comprises an elongate silicon nanowire less than 0.5 .mu.m in cross-sectional dimensions and having a hexagonal cross-sectional shape due to annealing-induced energy relaxation.

Evidence for unnatural-parity contributions to electron-impact ionization of laser-aligned atoms

DOE PAGES

Armstrong, Gregory S. J.; Colgan, James Patrick; Pindzola, M. S.; ...

2015-09-11

Recent measurements have examined the electron-impact ionization of excited-state laser-aligned Mg atoms. In this paper we show that the ionization cross section arising from the geometry where the aligned atom is perpendicular to the scattering plane directly probes the unnatural parity contributions to the ionization amplitude. The contributions from natural parity partial waves cancel exactly in this geometry. Our calculations resolve the discrepancy between the nonzero measured cross sections in this plane and the zero cross section predicted by distorted-wave approaches. Finally, we demonstrate that this is a general feature of ionization from p-state targets by additional studies of ionizationmore » from excited Ca and Na atoms.« less

Electronically cloaked nanoparticles

NASA Astrophysics Data System (ADS)

Shen, Wenqing

The concept of electronic cloaking is to design objects invisible to conduction electrons. The approach of electronic cloaking has been recently suggested to design invisible nanoparticle dopants with electronic scattering cross section smaller than 1% of the physical cross section (pi a2), and therefore to enhance the carrier mobility of bulk materials. The proposed nanoparticles have core-shell structures. The dopants are incorporated inside the core, while the shell layer serves both as a spacer to separate the charge carriers from their parent atoms and as a cloaking shell to minimize the scattering cross section of the electrons from the ionized nanoparticles. Thermoelectric materials are usually highly doped to have enough carrier density. Using invisible dopants could achieve larger thermoelectric power factors by enhancing the electronic mobility. Core-shell nanoparticles show an advantage over one-layer nanoparticles, which are proposed in three-dimensional modulation doping. However designing such nanoparticles is not easy as there are too many parameters to be considered. This thesis first shows an approach to design hollow nanoparticles by applying constrains on variables. In the second part, a simple mapping approach is introduced where one can identify possible core-shell particles by comparing the dimensionless parameters of chosen materials with provided maps. In both parts of this work, several designs with realistic materials were made and proven to achieve electronic cloaking. Improvement in the thermoelectric power factor compared to the traditional impurity doping method was demonstrated in several cases.

Charge exchange cross sections in slow collisions of Si3+ with Hydrogen atom

NASA Astrophysics Data System (ADS)

Joseph, Dwayne; Quashie, Edwin; Saha, Bidhan

2011-05-01

In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. Work supported by NSF CREST project (grant #0630370).

Comparison of local exchange potentials of electron-N2 scattering

NASA Astrophysics Data System (ADS)

Rumble, J. R., Jr.; Truhlar, D. G.

1980-05-01

Vibrationally and electronically elastic electron scattering by N2 at 2-30 eV impact energy is considered. Static, static-exchange, and static-exchange-plus-polarization potentials, Cade-Sales-Wahl and INDO/1s wave functions, and semiclassical exchange and Hara free-electron-gas exchange potentials are examined. It is shown that the semiclassical exchange approximation is too attractive at low energy for N2. It is also shown quantitatively by consideration of partial and total integral cross sections how the effects of approximations to exchange become smaller as the incident energy is increased until the differences are about 8% for the total integral cross section at 30 eV.

Low energy e-Ar momentum transfer cross-section

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brennan, M.J.

1992-12-01

Recent work has shown that solutions of the Boltzmann equation which use the so called {open_quotes}two-term{close_quotes} approximation provide an inadequate description of the transverse diffusion of electrons in argon gas at low values of E/N, contrary to earlier evidence. Previous determinations of the momentum transfer cross section for argon from the analysis of transport data have used two-term codes in good faith. Progress towards the determination of a new cross section in the energy range O - 4 eV, including an analysis of the energy dependence of the uncertainty in the derived cross section is reported.

Determining partial differential cross sections for low-energy electron photodetachment involving conical intersections using the solution of a Lippmann-Schwinger equation constructed with standard electronic structure techniques.

PubMed

Han, Seungsuk; Yarkony, David R

2011-05-07

A method for obtaining partial differential cross sections for low energy electron photodetachment in which the electronic states of the residual molecule are strongly coupled by conical intersections is reported. The method is based on the iterative solution to a Lippmann-Schwinger equation, using a zeroth order Hamiltonian consisting of the bound nonadiabatically coupled residual molecule and a free electron. The solution to the Lippmann-Schwinger equation involves only standard electronic structure techniques and a standard three-dimensional free particle Green's function quadrature for which fast techniques exist. The transition dipole moment for electron photodetachment, is a sum of matrix elements each involving one nonorthogonal orbital obtained from the solution to the Lippmann-Schwinger equation. An expression for the electron photodetachment transition dipole matrix element in terms of Dyson orbitals, which does not make the usual orthogonality assumptions, is derived.

Oscillator strengths and integral cross sections for the valence-shell excitations of nitric oxide studied by fast electron impact.

PubMed

Xu, Xin; Xu, Long-Quan; Xiong, Tao; Chen, Tao; Liu, Ya-Wei; Zhu, Lin-Fan

2018-01-28

The generalized oscillator strengths for the valence-shell excitations of A 2 Σ + , C 2 Π, and D 2 Σ + electronic-states of nitric oxide have been determined at an incident electron energy of 1500 eV with an energy resolution of 70 meV. The optical oscillator strengths for these transitions have been obtained by extrapolating the generalized oscillator strengths to the limit that the squared momentum transfer approaches to zero, which give an independent cross-check to the previous experimental and theoretical results. The integral cross sections for the valence-shell excitations of nitric oxide have been determined systematically from the threshold to 2500 eV with the aid of the newly developed BE-scaling method for the first time. The present optical oscillator strengths and integral cross sections of the valence-shell excitations of nitric oxide play an important role in understanding many physics and chemistry of the Earth's upper atmosphere such as the radiative cooling, ozone destruction, day glow, aurora, and so on.

Influence of Electron Molecule Resonant Vibrational Collisions over the Symmetric Mode and Direct Excitation-Dissociation Cross Sections of CO2 on the Electron Energy Distribution Function and Dissociation Mechanisms in Cold Pure CO2 Plasmas.

PubMed

Pietanza, L D; Colonna, G; Laporta, V; Celiberto, R; D'Ammando, G; Laricchiuta, A; Capitelli, M

2016-05-05

A new set of electron-vibrational (e-V) processes linking the first 10 vibrational levels of the symmetric mode of CO2 is derived by using a decoupled vibrational model and inserted in the Boltzmann equation for the electron energy distribution function (eedf). The new eedf and dissociation rates are in satisfactory agreement with the corresponding ones obtained by using the e-V cross sections reported in the database of Hake and Phelps (H-P). Large differences are, on the contrary, found when the experimental dissociation cross sections of Cosby and Helm are inserted in the Boltzman equation. Comparison of the corresponding rates with those obtained by using the low-energy threshold energy, reported in the H-P database, shows differences up to orders of magnitude, which decrease with the increasing of the reduced electric field. In all cases, we show the importance of superelastic vibrational collisions in affecting eedf and dissociation rates either in the direct electron impact mechanism or in the pure vibrational mechanism.

Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adikaram, D.; Rimal, D.; Weinstein, L. B.

There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentummore » transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.« less

Observation of two-center interference effects for electron impact ionization of N2

NASA Astrophysics Data System (ADS)

Chaluvadi, Hari; Nur Ozer, Zehra; Dogan, Mevlut; Ning, Chuangang; Colgan, James; Madison, Don

2015-08-01

In 1966, Cohen and Fano (1966 Phys. Rev. 150 30) suggested that one should be able to observe the equivalent of Young’s double slit interference if the double slits were replaced by a diatomic molecule. This suggestion inspired many experimental and theoretical studies searching for double slit interference effects both for photon and particle ionization of diatomic molecules. These effects turned out to be so small for particle ionization that this work proceeded slowly and evidence for interference effects were only found by looking at cross section ratios. Most of the early particle work concentrated on double differential cross sections for heavy particle scattering and the first evidence for two-center interference for electron-impact triple differential cross section (TDCS) did not appear until 2006 for ionization of H2. Subsequent work has now firmly established that two-center interference effects can be seen in the TDCS for electron-impact ionization of H2. However, in spite of several experimental and theoretical studies, similar effects have not been found for electron-impact ionization of N2. Here we report the first evidence for two-center interference for electron-impact ionization of N2.

Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

DOE PAGES

Adikaram, D.; Rimal, D.; Weinstein, L. B.; ...

2015-02-10

There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentummore » transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.« less

Towards a resolution of the proton form factor problem: new electron and positron scattering data.

PubMed

Adikaram, D; Rimal, D; Weinstein, L B; Raue, B; Khetarpal, P; Bennett, R P; Arrington, J; Brooks, W K; Adhikari, K P; Afanasev, A V; Amaryan, M J; Anderson, M D; Anefalos Pereira, S; Avakian, H; Ball, J; Battaglieri, M; Bedlinskiy, I; Biselli, A S; Bono, J; Boiarinov, S; Briscoe, W J; Burkert, V D; Carman, D S; Careccia, S; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L; Contalbrigo, M; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dodge, G E; Dupre, R; Egiyan, H; El Alaoui, A; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A; Fradi, A; Garillon, B; Gilfoyle, G P; Giovanetti, K L; Girod, F X; Goetz, J T; Gohn, W; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Harrison, N; Hattawy, M; Hicks, K; Holtrop, M; Hughes, S M; Hyde, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Jenkins, D; Jiang, H; Jo, H S; Joo, K; Joosten, S; Kalantarians, N; Keller, D; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J; Koirala, S; Kubarovsky, V; Kuhn, S E; Livingston, K; Lu, H Y; MacGregor, I J D; Markov, N; Mattione, P; Mayer, M; McKinnon, B; Mestayer, M D; Meyer, C A; Mirazita, M; Mokeev, V; Montgomery, R A; Moody, C I; Moutarde, H; Movsisyan, A; Camacho, C Munoz; Nadel-Turonski, P; Niccolai, S; Niculescu, G; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Peña, C; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Puckett, A J R; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatié, F; Salgado, C; Schott, D; Schumacher, R A; Seder, E; Sharabian, Y G; Simonyan, A; Skorodumina, I; Smith, E S; Smith, G D; Sober, D I; Sokhan, D; Sparveris, N; Stepanyan, S; Stoler, P; Strauch, S; Sytnik, V; Taiuti, M; Tian, Ye; Trivedi, A; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K; Watts, D P; Wei, X; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zhao, Z W; Zonta, I

2015-02-13

There is a significant discrepancy between the values of the proton electric form factor, G(E)(p), extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G(E)(p) from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ϵ) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ϵ at Q(2)=1.45  GeV(2). This measurement is consistent with the size of the form factor discrepancy at Q(2)≈1.75  GeV(2) and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2-3  GeV(2).

Density functional calculations of multiphonon capture cross sections at defects in semiconductors

NASA Astrophysics Data System (ADS)

Barmparis, Georgios D.; Puzyrev, Yevgeniy S.; Zhang, X.-G.; Pantelides, Sokrates T.

2014-03-01

The theory of electron capture cross sections by multiphonon processes in semiconductors has a long and controversial history. Here we present a comprehensive theory and describe its implementation for realistic calculations. The Born-Oppenheimer and the Frank-Condon approximations are employed. The transition probability of an incoming electron is written as a product of an instantaneous electronic transition in the initial defect configuration and the line shape function (LSF) that describes the multiphonon processes that lead to lattice relaxation. The electronic matrix elements are calculated using the Projector Augmented Wave (PAW) method which yields the true wave functions while still employing a plane-wave basis. The LSF is calculated by employing a Monte Carlo method and the real phonon modes of the defect, calculated using density functional theory in the PAW scheme. Initial results of the capture cross section for a prototype system, namely a triply hydrogenated vacancy in Si are presented. The results are relevant for modeling device degradation by hot electron effects. This work is supported in part by the Samsung Advanced Institute of Technology (SAIT)'s Global Research Outreach (GRO) Program and by the LDRD program at ORNL.

Absolute cross section measurements for the scattering of low- and intermediate-energy electrons from PF3. I. Elastic scattering

NASA Astrophysics Data System (ADS)

Hishiyama, N.; Hoshino, M.; Blanco, F.; García, G.; Tanaka, H.

2017-12-01

We report absolute elastic differential cross sections (DCSs) for electron collisions with phosphorus trifluoride, PF3, molecules (e- + PF3) in the impact energy range of 2.0-200 eV and over a scattering angle range of 10°-150°. Measured angular distributions of scattered electron intensities were normalized by reference to the elastic DCSs of He. Corresponding integral and momentum-transfer cross sections were derived by extrapolating the angular range from 0° to 180° with the help of a modified phase-shift analysis. In addition, due to the large dipole moment of the considered molecule, the dipole-Born correction for the forward scattering angles has also been applied. As a part of this study, independent atom model calculations in combination with screening corrected additivity rule were also performed for elastic and inelastic (electronic excitation plus ionization) scattering using a complex optical potential method. Rotational excitation cross sections have been estimated with a dipole-Born approximation procedure. Vibrational excitations are not considered in this calculation. Theoretical data, at the differential and integral levels, were found to reasonably agree with the present experimental results. Furthermore, we explore the systematics of the elastic DCSs for the four-atomic trifluoride molecules of XF3 (X = B, N, and P) and central P-atom in PF3, showing that, owing to the comparatively small effect of the F-atoms, the present angular distributions of elastic DCSs are essentially dominated by the characteristic of the central P-atom at lower impact energies. Finally, these quantitative results for e- - PF3 collisions were compiled together with the previous data available in the literature in order to obtain a cross section dataset for modeling purposes. To comprehensively describe such a considerable amount of data, we proceed by first discussing, in this paper, the vibrationally elastic scattering processes whereas vibrational and electronic excitation shall be the subject of our following paper devoted to inelastic collisions.

Electron-helium S-wave model benchmark calculations. I. Single ionization and single excitation

NASA Astrophysics Data System (ADS)

Bartlett, Philip L.; Stelbovics, Andris T.

2010-02-01

A full four-body implementation of the propagating exterior complex scaling (PECS) method [J. Phys. B 37, L69 (2004)] is developed and applied to the electron-impact of helium in an S-wave model. Time-independent solutions to the Schrödinger equation are found numerically in coordinate space over a wide range of energies and used to evaluate total and differential cross sections for a complete set of three- and four-body processes with benchmark precision. With this model we demonstrate the suitability of the PECS method for the complete solution of the full electron-helium system. Here we detail the theoretical and computational development of the four-body PECS method and present results for three-body channels: single excitation and single ionization. Four-body cross sections are presented in the sequel to this article [Phys. Rev. A 81, 022716 (2010)]. The calculations reveal structure in the total and energy-differential single-ionization cross sections for excited-state targets that is due to interference from autoionization channels and is evident over a wide range of incident electron energies.

Low-energy-electron scattering by CH3CN

NASA Astrophysics Data System (ADS)

Maioli, Leticia S.; Bettega, Márcio H. F.

2017-12-01

We report integral and differential cross sections for the elastic scattering of low-energy electrons by methyl cyanide (CH3CN), also known as acetonitrile. The cross sections were computed using the Schwinger multichannel method implemented with pseudopotentials. The fixed-nuclei scattering calculations were performed in the static-exchange and static-exchange plus polarization approximations for energies up to 15 eV. In our calculations with polarization effects, we found a π* shape resonance at around 2.22 eV and a broad structure associated to a σ* shape resonance at around 7 eV. The low-lying resonance was assigned to the electron capture by the two-fold degenerate π* orbital of the E symmetry of C3v group; the second was assigned to a σ* shape resonance in the A1 symmetry. We compared our cross sections with theoretical results and experimental data available in the literature, and in general we found good agreement for the positions of the two resonances. Contribution to the Topical Issue: "Low Energy Positron and Electron Interactions", edited by James Sullivan, Ron White, Michael Bromley, Ilya Fabrikant, and David Cassidy.

Measurements and calculations of the Coulomb cross section for the production of direct electron pairs by energetic heavy nuclei in nuclear track emulsion

NASA Technical Reports Server (NTRS)

Derrickson, J. H.; Eby, P. B.; Fountain, W. F.; Parnell, T. A.; Dong, B. L.; Gregory, J. C.; Takahashi, Y.; King, D. T.

1988-01-01

Measurements and theoretical predictions of the Coulomb cross section for the production of direct electron pairs by heavy ions in emulsion have been performed. Nuclear track emulsions were exposed to the 1.8 GeV/amu Fe-56 beam at the Lawrence Berkeley Laboratory bevalac and to the 60 and 200 GeV/amu O-16 and the 200 GeV/amu S-32 beam at the European Center for Nuclear Research Super Proton Synchrotron modified to accelerate heavy ions. The calculations combine the Weizsacker-Williams virtual quanta method applicable to the low-energy transfers and the Kelner-Kotov relativistic treatment for the high-energy transfers. Comparison of the measured total electron pair yield, the energy transfer distribution, and the emission angle distribution with theoretical predictions revealed a discrepancy in the frequency of occurrence of the low-energy pairs (less than or = 10 MeV). The microscope scanning criteria used to identify the direct electron pairs is described and efforts to improve the calculation of the cross section for pair production are also discussed.

Following electron impact excitation of single (N, O, F, Ne, Na, Mg, Al, Si) atom L subshells ionization cross section calculations by using Lotz's equation

NASA Astrophysics Data System (ADS)

Aydinol, Mahmut

2017-02-01

L shell and L subshells ionization cross sections σL and σLi (i = 1, 2, 3) following electron impact on (N,O, F, Ne, Na, Mg, Al, Si) atoms calculated. By using Lotz' equation for nonrelativistic cases in Matlab σL and σLi cross section values obtained for ten electron impact(Eo) values in the range of ELi

Two-photon absorption cross sections within equation-of-motion coupled-cluster formalism using resolution-of-the-identity and Cholesky decomposition representations: Theory, implementation, and benchmarks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nanda, Kaushik D.; Krylov, Anna I.

The equation-of-motion coupled-cluster (EOM-CC) methods provide a robust description of electronically excited states and their properties. Here, we present a formalism for two-photon absorption (2PA) cross sections for the equation-of-motion for excitation energies CC with single and double substitutions (EOM-CC for electronically excited states with single and double substitutions) wave functions. Rather than the response theory formulation, we employ the expectation-value approach which is commonly used within EOM-CC, configuration interaction, and algebraic diagrammatic construction frameworks. In addition to canonical implementation, we also exploit resolution-of-the-identity (RI) and Cholesky decomposition (CD) for the electron-repulsion integrals to reduce memory requirements and to increasemore » parallel efficiency. The new methods are benchmarked against the CCSD and CC3 response theories for several small molecules. We found that the expectation-value 2PA cross sections are within 5% from the quadratic response CCSD values. The RI and CD approximations lead to small errors relative to the canonical implementation (less than 4%) while affording computational savings. RI/CD successfully address the well-known issue of large basis set requirements for 2PA cross sections calculations. The capabilities of the new code are illustrated by calculations of the 2PA cross sections for model chromophores of the photoactive yellow and green fluorescent proteins.« less

Material dependence of 2H(d,p)3H cross section at the very low energies

NASA Astrophysics Data System (ADS)

Kılıç, Ali İhsan; Czerski, Konrad; Kuştan-Kılıç, Fadime; Targosz-Sleczka, Natalia; Weissbach, Daniel; Huke, Armin; Ruprecht, Götz

2017-09-01

Calculations of the material dependence of 2H(d,p)3H cross section and neutron-to-proton branching ratio of d+d reactions have been performed including a concept of the 0+ threshold single particle resonance. The resonance has been assumed to explain the enhanced electron screening effect observed in the d+d reaction for different metallic targets. Here, we have included interference effects between the flat and resonance part of the cross section, which allowed us to enlighten observed suppression of the neutron channel in some metals such as Sr and Li. Since the position of the resonance depends on the screening energy that strongly depends on the local electron density. The resonance width, observed for the d+d reactions in the very hygroscopic metals (Sr and Li) and therefore probably contaminated by oxides, should be much larger than for other metals. Thus, the interference term of the cross section depending on the total resonance width provides the material dependences.

Molecular photoionization processes of astrophysical and aeronomical interest

NASA Technical Reports Server (NTRS)

Langhoff, P. W.

1985-01-01

An account is given of aspects of photoionization processes in molecules, with particular reference to recent theoretical and experimental studies of partial cross sections for production of specific final electronic states and of parent and fragment ions. Such cross sections help provide a basis for specifying the state of excitation of the ionized medium, are useful for estimating the kinetic energy distributions of photoejected electrons and fragment ions, provide parent-and fragment-ion yields, and clarify the possible origins of neutral fragments in highly excited rovibronic states. A descriptive account is given of photoionization phenomena, including tabulation of valence- and inner-shell potentials for some molecules of astrophysical and aeronomical interest. Cross sectional expressions are given. Various approximations currently employed in computational studies are described briefly, threshold laws and high-energy limits are indicated, and distinction is drawn between resonant and direct photoionization phenomena. Recent experimental and theoretical studies of partial photoionization cross sections in selected compounds of astrophysical and aeronomical relevance are described and discussed.

Free-Free Transitions of the e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident-Electron Energies

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Sinha, C.

2012-01-01

The free-free transition is studied for an electron-hydrogen atom in ground state when a low-energy electron (external) is injected into hydrogenic plasma in the presence of an external homogenous, monochromatic, and linearly polarized laser field. The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption or emission and no-photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

Calculation on spectrum of direct DNA damage induced by low-energy electrons including dissociative electron attachment.

PubMed

Liu, Wei; Tan, Zhenyu; Zhang, Liming; Champion, Christophe

2017-03-01

In this work, direct DNA damage induced by low-energy electrons (sub-keV) is simulated using a Monte Carlo method. The characteristics of the present simulation are to consider the new mechanism of DNA damage due to dissociative electron attachment (DEA) and to allow determining damage to specific bases (i.e., adenine, thymine, guanine, or cytosine). The electron track structure in liquid water is generated, based on the dielectric response model for describing electron inelastic scattering and on a free-parameter theoretical model and the NIST database for calculating electron elastic scattering. Ionization cross sections of DNA bases are used to generate base radicals, and available DEA cross sections of DNA components are applied for determining DNA-strand breaks and base damage induced by sub-ionization electrons. The electron elastic scattering from DNA components is simulated using cross sections from different theoretical calculations. The resulting yields of various strand breaks and base damage in cellular environment are given. Especially, the contributions of sub-ionization electrons to various strand breaks and base damage are quantitatively presented, and the correlation between complex clustered DNA damage and the corresponding damaged bases is explored. This work shows that the contribution of sub-ionization electrons to strand breaks is substantial, up to about 40-70%, and this contribution is mainly focused on single-strand break. In addition, the base damage induced by sub-ionization electrons contributes to about 20-40% of the total base damage, and there is an evident correlation between single-strand break and damaged base pair A-T.

Recent measurements concerning uranium hexafluoride-electron collision processes

NASA Technical Reports Server (NTRS)

Trajmar, S.; Chutjian, A.; Srivastava, S.; Williams, W.; Cartwright, D. C.

1976-01-01

Scattering of electrons by UF6 molecules was studied at impact energies ranging from 5 to 100 eV and momentum transfer, elastic and inelastic scattering cross sections were determined. The measurements also yielded spectroscopic information which made possible to extend the optical absorption cross sections from 2000 angstroms to 435 angstroms. It was found that UF6 is a very strong absorber in the vacuum UV region. No transitions were found to lie below the onset of the optically detected 3.0 eV feature.

Absorption of infrared radiation by electrons in the field of a neutral hydrogen atom

NASA Technical Reports Server (NTRS)

Stallcop, J. R.

1974-01-01

An analytical expression for the absorption coefficient is developed from a relationship between the cross-section for inverse bremsstrahlung absorption and the cross-section for electron-atom momentum transfer; it is accurate for those photon frequencies v and temperatures such that hv/kT is small. The determination of the absorption of infrared radiation by free-free transitions of the negative hydrogen ion has been extended to higher temperatures. A simple analytical expression for the absorption coefficient has been derived.

Negative ion productions in high velocity collision between small carbon clusters and Helium atom target

NASA Astrophysics Data System (ADS)

M, Chabot; K, Béroff; T, Pino; G, Féraud; N, Dothi; Padellec A, Le; G, Martinet; S, Bouneau; Y, Carpentier

2012-11-01

We measured absolute double capture cross section of Cn+ ions (n=1,5) colliding, at 2.3 and 2.6 a.u velocities, with an Helium target atom and the branching ratios of fragmentation of the so formed electronically excited anions Cn-*. We also measured absolute cross section for the electronic attachment on neutral Cn clusters colliding at same velocities with He atom. This is to our knowledge the first measurement of neutral-neutral charge exchange in high velocity collision.

Structure of junctions of multiwalled carbon nanotubes with tetragonal cross section and flattened nanotubes revealed by electron-beam tomography

NASA Astrophysics Data System (ADS)

Nagano, Yuta; Kohno, Hideo

2017-11-01

Multiwalled carbon nanotubes with tetragonal cross section frequently form junctions with flattened multi-walled carbon nanotubes, a kind of carbon nanoribbon. The three-dimensional structure of the junctions is revealed by transmission-electron-microscopy-based tomography. Two types of junction, parallel and diagonal, are found. The formation mechanism of these two types of junction is discussed in terms of the origami mechanism that was previously proposed to explain the formation of carbon nanoribbons and nanotetrahedra.

Absolute emission cross sections for electron capture reactions of C2+, N3+, N4+ and O3+ ions in collisions with Li(2s) atoms

NASA Astrophysics Data System (ADS)

Rieger, G.; Pinnington, E. H.; Ciubotariu, C.

2000-12-01

Absolute photon emission cross sections following electron capture reactions have been measured for C2+, N3+, N4+ and O3+ ions colliding with Li(2s) atoms at keV energies. The results are compared with calculations using the extended classical over-the-barrier model by Niehaus. We explore the limits of our experimental method and present a detailed discussion of experimental errors.

Differential cross sections for the electron impact excitation of the A {sup 3}{sigma}{sub u}{sup +}, B {sup 3}{pi}{sub g}, W {sup 3}{delta}{sub u}, B{sup '} {sup 3}{sigma}{sub u}{sup -}, a{sup '} {sup 1}{sigma}{sub u}{sup -}, a {sup 1}{pi}{sub g}, w {sup 1}{delta}{sub u}, and C {sup 3}{pi}{sub u} states of N{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khakoo, M.A.; Ozkay, I.; Johnson, P.V.

2005-06-15

Measurements of differential cross sections for the electron-impact excitation of molecular nitrogen from the ground X {sup 1}{sigma}{sub g}{sup +}(v{sup ''}=0) level to the A {sup 3}{sigma}{sub u}{sup +}(v{sup '}), B {sup 3}{pi}{sub g}(v{sup '}), W {sup 3}{delta}{sub u}(v{sup '}), B{sup '} {sup 3}{sigma}{sub u}{sup -}(v{sup '}), a{sup '} {sup 1}{sigma}{sub u}{sup -}(v{sup '}), a {sup 1}{pi}{sub g}(v{sup '}), w {sup 1}{delta}{sub u}(v{sup '}), and C {sup 3}{pi}{sub u}(v{sup '}) levels are presented. The data are obtained at the incident energies of 10, 12.5, 15, 17.5, 20, 30, 50, and 100 eV over the angular range of 5 deg. -130more » deg. in 5 deg. intervals. The individual electronic state excitation differential cross sections are obtained by unfolding electron energy-loss spectra of molecular nitrogen using available semiempirical Frank-Condon factors. The data are compared to previous measurements and to available theory. We also make several important suggestions regarding future work that, like the present, relies on the unfolding of electron energy-loss spectra for obtaining differential cross sections.« less

Electron Spectroscopic Studies of Surfaces and Interfaces for Adhesive Bonding.

DTIC Science & Technology

1980-01-01

published theoretical cross-sections for photoionization . These concentrations are listed in Table 5. There is very good agreement between the surface...and using Scofield cross sections for the is levels. Before adsorption, the carbon to oxygen ratio was 1.3, on exposure to methanol at room temperature...the surface region. Cross sections were taken from the data of Scofield ’, and the results are listed in Tables 3 and 4. 46 TABLE 2 MEASURED FULL WID)THS

Molecular Data for a Biochemical Model of DNA Radiation Damage: Electron Impact Ionization and Dissociative Ionization of DNA Bases and Sugar-Phosphate Backbone

NASA Technical Reports Server (NTRS)

Dateo, Christopher E.; Fletcher, Graham D.

2004-01-01

As part of the database for building up a biochemical model of DNA radiation damage, electron impact ionization cross sections of sugar-phosphate backbone and DNA bases have been calculated using the improved binary-encounter dipole (iBED) model. It is found that the total ionization cross sections of C3'- and C5'-deoxyribose-phospate, two conformers of the sugar-phosphate backbone, are close to each other. Furthermore, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3'- and C5'-deoxyribose-phospate cross sections, differing by less than 10%. Of the four DNA bases, the ionization cross section of guanine is the largest, then in decreasing order, adenine, thymine, and cytosine. The order is in accordance with the known propensity of oxidation of the bases by ionizing radiation. Dissociative ionization (DI), a process that both ionizes and dissociates a molecule, is investigated for cytosine. The DI cross section for the formation of H and (cytosine-Hl)(+), with the cytosine ion losing H at the 1 position, is also reported. The threshold of this process is calculated to be 17.1 eV. Detailed analysis of ionization products such as in DI is important to trace the sequential steps in the biochemical process of DNA damage.

Signatures of the atomic nucleus in laser-assisted single ionization of one-electron atoms

NASA Astrophysics Data System (ADS)

Ajana, Imane; Khalil, Driss; Makhoute, Abdelkader

2018-03-01

The dynamics of the electron-impact single ionization of hydrogenic targets in the presence of a laser field (e, 2e) has been studied for different residual ion charges Z = 1, 2, 3 and 4. The state of fast electron in the laser field is described by the Volkov state, while the dressed state of the ejected slow electron and atomic target is treated perturbatively to the first-order perturbation theory. We calculate the triple differential cross section in the Ehrhardt asymmetric coplanar geometry. We have compared and analyzed the triple differential cross sections from one-electron atoms by varying the charge state of the residual ion, and evaluating the interplay between the laser influence and the role of scattering from the residual ion.

Absolute differential cross sections for electron impact excitation of the 10.8-11.5 eV energy-loss states of CO2

NASA Astrophysics Data System (ADS)

Green, M. A.; Teubner, P. J. O.; Campbell, L.; Brunger, M. J.; Hoshino, M.; Ishikawa, T.; Kitajima, M.; Tanaka, H.; Itikawa, Y.; Kimura, M.; Buenker, R. J.

2002-02-01

Absolute differential cross sections (DCSs) for electron impact excitation of electronic states of CO2 in the 10.8-11.5 eV energy-loss range are reported. These data were obtained at the incident electron energies 20,30,60,100 and 200 eV and over the scattered electron angular range 3.5°-90°. The accuracy of our experimental methods has been established independently by using several different normalization techniques at both Sophia and Flinders Universities. Generalized oscillator strengths were derived from our measured DCSs and then extrapolated to zero momentum transfer, in order to determine the optical oscillator strengths. These optical oscillator strengths, where possible, are compared with the results from previous measurements and calculations.

Measurement of inclusive jet cross sections in photoproduction at HERA

NASA Astrophysics Data System (ADS)

H1 Collaboration; Abt, I.; Ahmed, T.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Bärwolff, H.; Bán, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bergstein, H.; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Biddulph, P.; Binder, E.; Bischoff, A.; Bizot, J. C.; Blobel, V.; Borras, K.; Bosetti, P. C.; Boudry, V.; Bourdarios, C.; Brasse, F.; Braun, U.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Clarke, D.; Clegg, A. B.; Colombo, M.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Danilov, M.; Dann, A. W. E.; Dau, W. D.; David, M.; Deffur, E.; Delcourt, B.; del Buono, L.; Devel, M.; de Roeck, A.; Dingus, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Drescher, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebbinghaus, R.; Eberle, M.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellis, N. N.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Fensome, I. F.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Flauger, W.; Fleischer, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Fuhrmann, P.; Gabathuler, E.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gellrich, A.; Gennis, M.; Genzel, H.; Gerhards, R.; Godfrey, L.; Goerlach, U.; Goerlich, L.; Goldberg, M.; Goodall, A. M.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Greif, H.; Grindhammer, G.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Handschuh, D.; Hanlon, E. M.; Hapke, M.; Harjes, J.; Haydar, R.; Haynes, W. J.; Heatherington, J.; Hedberg, V.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herma, R.; Herynek, I.; Hildesheim, W.; Hill, P.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Huet, Ph.; Hufnagel, H.; Huot, N.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Jansen, T.; Jönsson, L.; Johannsen, K.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kasarian, S.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Kaufmann, H. H.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Langkau, R.; Lanius, P.; Laporte, J. F.; Lebedev, A.; Leuschner, A.; Leverenz, C.; Levonian, S.; Lewin, D.; Ley, Ch.; Lindner, A.; Lindström, G.; Linsel, F.; Lipinski, J.; Loch, P.; Lohmander, H.; Lopez, G. C.; Lüers, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, A.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Mikocki, S.; Milone, V.; Monnier, E.; Moreau, F.; Moreels, J.; Morris, J. V.; Müller, K.; Murín, P.; Murray, S. A.; Nagovizin, V.; Naroska, B.; Naumann, Th.; Newton, D.; Neyret, D.; Nguyen, H. K.; Niebergall, F.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Orenstein, S.; Ould-Saada, F.; Pascaud, C.; Patel, G. D.; Peppel, E.; Peters, S.; Phillips, H. T.; Phillips, J. C.; Pichler, Ch.; Pilgram, W.; Pitzl, D.; Prell, S.; Prosi, R.; Rädel, G.; Raupach, F.; Rauschnabel, K.; Reimer, P.; Ribarics, P.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Robertson, S. M.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Royon, C.; Rudowicz, M.; Ruffer, M.; Rusakov, S.; Rybicki, K.; Sahlmann, N.; Sanchez, E.; Sankey, D. P. C.; Savitsky, M.; Schacht, P.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmitz, W.; Schröder, V.; Schulz, M.; Schwind, A.; Scobel, W.; Seehausen, U.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Smolik, L.; Soloviev, Y.; Spitzer, H.; Staroba, P.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stösslein, U.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Taylor, R. E.; Tchernyshov, V.; Thiebaux, C.; Thompson, G.; Tichomirov, I.; Truöl, P.; Turnau, J.; Tutas, J.; Urban, L.; Usik, A.; Valkar, S.; Valkarova, A.; Vallée, C.; van Esch, P.; Vartapetian, A.; Vazdik, Y.; Vecko, M.; Verrecchia, P.; Vick, R.; Villet, G.; Vogel, E.; Wacker, K.; Walker, I. W.; Walther, A.; Weber, G.; Wegener, D.; Wegner, A.; Wellisch, H. P.; Willard, S.; Winde, M.; Winter, G.-G.; Wolff, Th.; Womersley, L. A.; Wright, A. E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Závada, P.; Zeitnitz, C.; Ziaeepour, H.; Zimmer, M.; Zimmermann, W.; Zomer, F.

1993-09-01

The inclusive jet cross section in photoproduction has been measured as a function of transverse energy and pseudorapidity using the H 1 detector at the HERA electron-proton collider. The results are compared with leading order QCD calculations. Supported by the Swiss National Science Foundation.

Electron attachment to the SF{sub 6} molecule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, B. M., E-mail: bmsmirnov@gmail.com; Kosarim, A. V.

Various models for transition between electron and nuclear subsystems are compared in the case of electron attachment to the SF{sub 6} molecule. Experimental data, including the cross section of electron attachment to this molecule as a function of the electron energy and vibrational temperature, the rate constants of this process in swarm experiments, and the rates of the chemionization process involving Rydberg atoms and the SF{sub 6} molecule, are collected and treated. Based on the data and on the resonant character of electron capture into an autodetachment ion state in accordance with the Breit–Wigner formula, we find that intersection ofmore » the molecule and negative ion electron terms proceeds above the potential well bottom of the molecule with the barrier height 0.05–0.1 eV, and the transition between these electron terms has both the tunnel and abovebarrier character. The limit of small electron energies e for the electron attachment cross section at room vibrational temperature takes place at ε ≪ 2 meV, while in the range 2 meV ≪ ε ≪ 80 meV, the cross section is inversely proportional to ε. In considering the attachment process as a result of the interaction between the electron and vibrational degrees of freedom, we find the coupling factor f between them to be f = aT at low vibrational temperatures T with a ≈ 3 × 10{sup −4} K{sup −1}. The coupling factor is independent of the temperature at T > 400 K.« less

Elastic scattering of low-energy electrons by nitromethane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopes, A. R.; D'A Sanchez, S.; Bettega, M. H. F.

2011-06-15

In this work, we present integral, differential, and momentum transfer cross sections for elastic scattering of low-energy electrons by nitromethane, for energies up to 10 eV. We calculated the cross sections using the Schwinger multichannel method with pseudopotentials, in the static-exchange and in the static-exchange plus polarization approximations. The computed integral cross sections show a {pi}* shape resonance at 0.70 eV in the static-exchange-polarization approximation, which is in reasonable agreement with experimental data. We also found a {sigma}* shape resonance at 4.8 eV in the static-exchange-polarization approximation, which has not been previously characterized by the experiment. We also discuss howmore » these resonances may play a role in the dissociation process of this molecule.« less

Elastic scattering of low-energy electrons by C{sub 3}H{sub 4} isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopes, A.R.; Bettega, M.H.F.

2003-03-01

We report integral, differential, and momentum-transfer cross sections for elastic scattering of low-energy electrons by the C{sub 3}H{sub 4} isomers allene, propyne, and cyclopropene, which belong to the D{sub 2d}, C{sub 3v}, and C{sub 2v} groups, respectively. We use the Schwinger multichannel method with pseudopotentials [Bettega et al., Phys. Rev. A 47, 1111 (1993)] at the static-exchange approximation to compute the cross sections for energies up to 40 eV. We compare our results with available experimental results and find very good agreement. Our results confirm the existence of the shape resonances in the cross sections of allene and propyne, andmore » the isomer effect, both reported by the experimental studies.« less

Comparative study for elastic electron collisions on C{sub 2}N{sub 2} isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michelin, S. E.; Falck, A. S.; Mazon, K. T.

2006-08-15

In this work, we present a theoretical study on elastic electron collisions with the four C{sub 2}N{sub 2} isomers. More specifically, calculated differential, integral, and momentum transfer cross sections are reported in the 1-100 eV energy range. Calculations are performed at both the static-exchange-absorption and the static-exchange-polarization-absorption levels. The iterative Schwinger variational method combined with the distorted wave approximation is used to solve the scattering equations. Our study reveals an interesting trend of the calculated cross sections for the four isomers. In particular, strong isomer effect is seen at low incident energies. Also, we have identified a shape resonance whichmore » leads to a depression in the calculated partial integral cross section.« less

Atomic Processes and Diagnostics of Low Pressure Krypton Plasma

NASA Astrophysics Data System (ADS)

Srivastava, Rajesh; Goyal, Dipti; Gangwar, Reetesh; Stafford, Luc

2015-03-01

Optical emission spectroscopy along with suitable collisional-radiative (CR) model is used in plasma diagnostics. Importance of reliable cross-sections for various atomic processes is shown for low pressure argon plasma. In the present work, radially-averaged Kr emission lines from the 2pi --> 1sj were recorded as a function of pressure from 1 to 50mTorr. We have developed a CR model using our fine-structure relativistic-distorted wave cross sections. The various processes considered are electron-impact excitation, ionization and their reverse processes. The required rate coefficients have been calculated from these cross-sections assuming Maxwellian energy distribution. Electron temperature obtained from the CR model is found to be in good agreement with the probe measurements. Work is supported by IAEA Vienna, DAE-BRNS Mumbai and CSIR, New Delhi.

Electron Impact K-shell Ionization Cross Sections at high energies

NASA Astrophysics Data System (ADS)

Haque, A. K. F.; Sarker, M. S. I.; Patoary, M. A. R.; Shahjahan, M.; Ismail Hossain, M.; Alfaz Uddin, M.; Basak, A. K.; Saha, Bidhan

2008-10-01

A simple modification of the empirical model of Deutsh et. al. [1] by incorporating both the ionic [2] and relativistic corrections [3] is proposed for evaluating the electron impact K -shell ionization cross sections of neutral atomic targets. Present results for 30 atomic targets with atomic number Z=1 -- 92 for incident energies up to E=2 GeV, agree well with available experimental cross sections. Comparisons with other theoretical findings will also be presented at the conference. [1] H. Deutsh, K. Becker, T. D. Mark, Int. J. Mass Spect. 177, 47 (1998). [2] M. A. Uddin, A. K. F. Haque, M. M. Billah, A. K. Basak, K. R. Karim, B. C. Saha, Phys. Rev. A 71, 032715 (2005).; Phys. Rev. A 73, 012708 (2006). [3] M. Gryzinski, Phys. Rev 138, 336 (1965).

Importance of Thomas single-electron transfer in fast p-He collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, D.; Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1 D-69126; Gudmundsson, M.

We report experimental angular differential cross sections for nonradiative single-electron capture in p-He collisions (p+ He -> H + He{sup +}) with a separate peak at the 0.47 mrad Thomas scattering angle for energies in the 1.3-12.5 MeV range. We find that the intensity of this peak scales with the projectile velocity as v{sub P}{sup -11}. This constitutes the first experimental test of the prediction from 1927 by L. H. Thomas [Proc. R. Soc. 114, 561 (1927)]. At our highest energy, the peak at the Thomas angle contributes with 13.5% to the total integrated nonradiative single-electron capture cross section.

Detection of New Dissociative Electron Attachment Channels in NO

NASA Technical Reports Server (NTRS)

Orient, O. J.; Chutjian, A.

1995-01-01

Three dissociative electron attachment channels have been detected and identified in NO via measurement of the O minus (exp 2)P fragment energy. In addition to the known N((exp 2 D(exp 0)) + O minus (exp 2)P channel, two new channels N((exp 1 S(exp 0)) + 0 (2 P) and N(exp 2)P(exp 0) + O(exp 2)P were detected. Cross sections for each of the channels are reported by normalizing the scattering intensities to previously measured total cross sections. The experimental approach uses solenoidal magnetic confinement of the electrons and ions, and trochoidal energy analysis of the low-energy ions.

Photodissociation of CS from Excited Rovibrational Levels

NASA Astrophysics Data System (ADS)

Pattillo, R. J.; Cieszewski, R.; Stancil, P. C.; Forrey, R. C.; Babb, J. F.; McCann, J. F.; McLaughlin, B. M.

2018-05-01

Accurate photodissociation cross sections have been computed for transitions from the X 1Σ+ ground electronic state of CS to six low-lying excited electronic states. New ab initio potential curves and transition dipole moment functions have been obtained for these computations using the multi-reference configuration interaction approach with the Davidson correction (MRCI+Q) and aug-cc-pV6Z basis sets. State-resolved cross sections have been computed for transitions from nearly the full range of rovibrational levels of the X 1Σ+ state and for photon wavelengths ranging from 500 Å to threshold. Destruction of CS via predissociation in highly excited electronic states originating from the rovibrational ground state is found to be unimportant. Photodissociation cross sections are presented for temperatures in the range between 1000 and 10,000 K, where a Boltzmann distribution of initial rovibrational levels is assumed. Applications of the current computations to various astrophysical environments are briefly discussed focusing on photodissociation rates due to the standard interstellar and blackbody radiation fields.

Polarization Dependent Bulk-sensitive Valence Band Photoemission Spectroscopy and Density Functional Theory Calculations: Part I. 3d Transition Metals

NASA Astrophysics Data System (ADS)

Ueda, Shigenori; Hamada, Ikutaro

2017-12-01

The X-ray polarization dependent valence band HAXPES spectra of 3d transition metals (TMs) of Ti-Zn were measured to investigate the orbital resolved electronic structures by utilizing that the fact the photoionization cross-section of the atomic orbitals strongly depends on the experimental geometry. We have calculated the HAXPES spectra, which correspond to the cross-section weighted densities of states (CSW-DOSs), where the DOSs were obtained by the density functional theory calculations, and we have determined the relative photoionization cross-sections of the 4s and 4p orbitals to the 3d orbital in the 3d TMs. The experimentally obtained bulk-sensitive 3d and 4s DOSs were good agreement with the calculated DOSs in Ti, V, Cr, and Cu. In contrast, the deviations between the experimental and calculated 3d DOSs for Mn, Fe, Co, Ni were found, suggesting that the electron correlation plays an important role in the electronic structures for these materials.

A new time of flight mass spectrometer for absolute dissociative electron attachment cross-section measurements in gas phase

NASA Astrophysics Data System (ADS)

Chakraborty, Dipayan; Nag, Pamir; Nandi, Dhananjay

2018-02-01

A new time of flight mass spectrometer (TOFMS) has been developed to study the absolute dissociative electron attachment (DEA) cross section using a relative flow technique of a wide variety of molecules in gas phase, ranging from simple diatomic to complex biomolecules. Unlike the Wiley-McLaren type TOFMS, here the total ion collection condition has been achieved without compromising the mass resolution by introducing a field free drift region after the lensing arrangement. The field free interaction region is provided for low energy electron molecule collision studies. The spectrometer can be used to study a wide range of masses (H- ion to few hundreds atomic mass unit). The mass resolution capability of the spectrometer has been checked experimentally by measuring the mass spectra of fragment anions arising from DEA to methanol. Overall performance of the spectrometer has been tested by measuring the absolute DEA cross section of the ground state SO2 molecule, and the results are satisfactory.

Electron scattering on molecules: search for semi-empirical indications

NASA Astrophysics Data System (ADS)

Fedus, Kamil; Karwasz, Grzegorz P.

2017-06-01

Reliable cross-sections for electron-molecule collisions are urgently needed for numerical modeling of various processes important from technological point of view. Unfortunately, a significant progress in theory and experiment over the last decade is not usually accompanied by the convergence of cross-sections measured at different laboratories and calculated with different methods. Moreover the most advanced contemporary theories involve such large basis sets and complicated equations that they are not easily applied to each specific molecule for which data are needed. For these reasons the search for semi-empirical indications in angular and energy dependencies of scattering cross-section becomes important. In this paper we make a brief review of the applicability of the Born-dipole approximation for elastic, rotational, vibrational and ionization processes that can occur during electron-molecule collisions. We take into account the most recent experimental findings as the reference points. Contribution to the Topical Issue "Atomic and Molecular Data and Their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, and Grzegorz Karwasz.

Importance of projectile-target interactions in the triple differential cross sections for Low energy (e,2e) ionization of aligned H2

NASA Astrophysics Data System (ADS)

Ali, Esam; Madison, Don; Ren, X.; Dorn, A.; Ning, Chuangang

2014-10-01

Experimental and theoretical Triple Differential Cross Sections (TDCS) are presented for electron impact ionization-excitation of the 2 sσg state of H2 in the perpendicular plane. The excited 2 sσg state immediately dissociates and the alignment of the molecule is determined by detecting one of the fragments. Results are presented for three different alignments in the xy-plane (scattering plane is xz)-alignment along y-axis, x-axis, and 45° between the x- and y-axes for incident electron energies of 4, 10, and 25 eV and different scattered electron angles of 20° and 30° in the perpendicular plane. Theoretical M4DW (molecular 4-body distorted wave) results are compared to experimental data, and overall we found reasonably good agreement between experiment and theory. The Results show that (e,2e) cross sections for excitation-ionization depend strongly on the orientation of the H2 molecule.

Cross sections for elastic scattering of electrons by CF3Cl, CF2Cl2, and CFCl3

NASA Astrophysics Data System (ADS)

Hoshino, M.; Horie, M.; Kato, H.; Blanco, F.; García, G.; Limão-Vieira, P.; Sullivan, J. P.; Brunger, M. J.; Tanaka, H.

2013-06-01

Differential, integral, and momentum transfer cross sections have been determined for the elastic scattering of electrons from the molecules CF3Cl, CF2Cl2, and CFCl3.With the help of a crossed electron beam-molecular beam apparatus using the relative flow technique, the ratios of the elastic differential cross sections (DCSs) of CF3Cl, CF2Cl2, and CFCl3 to those of He were measured in the energy region from 1.5 to 100 eV and at scattering angles in the range 15° to 130°. From those ratios, the absolute DCSs were determined by utilizing the known DCS of He. For CF3Cl and CF2Cl2, at the common energies of measurement, we find generally good agreement with the results from the independent experiments of Mann and Linder [J. Phys. B 25, 1621 (1992), 10.1088/0953-4075/25/7/030; Mann and Linder J. Phys. B 25, 1633 (1992), 10.1088/0953-4075/25/7/031]. In addition, as a result of progressively substituting a Cl-atom, undulations in the angular distributions have been found to vary in a largely systematic manner in going from CF4 to CF3Cl to CF2Cl2 to CFCl3 and to CCl4. These observed features suggest that the elastic scattering process is, in an independently additive manner, dominated by the atomic-Cl atoms of the molecules. The present independent atom method calculation typically supports the experimental evidence, within the screened additivity rule formulation, for each species and for energies greater than about 10-20 eV. Integral elastic and momentum transfer cross sections were also derived from the measured DCSs, and are compared to the other available theoretical and experimental results. The elastic integral cross sections are also evaluated as a part of their contribution to the total cross section.

The formation of excited atoms during charge exchange between hydrogen ions and alkali atoms. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Nieman, R. A.

1971-01-01

The charge exchange cross sections for protons and various alkali atoms are calculated using the classical approximation of Gryzinski. It is assumed that the hydrogen atoms resulting from charge exchange exist in all possible excited states. Charge transfer collisions between protons and potassium as well as protons and sodium atoms are studied. The energy range investigated is between 4 and 30 keV. The theoretical calculations of the capture cross section and the cross section for the creation of metastable 2S hydrogen are compared to experimental values. Good quantitative agreement is found for the capture cross section but only qualitative agreement for the metastable cross section. Analysis of the Lyman alpha window in molecular oxygen suggests that measured values of the metastable cross section may be in error. Thick alkali target data are also presented. This allows the determination of the total electron loss cross section. Finally, some work was done with H2(+).

Electron-helium S-wave model benchmark calculations. II. Double ionization, single ionization with excitation, and double excitation

NASA Astrophysics Data System (ADS)

Bartlett, Philip L.; Stelbovics, Andris T.

2010-02-01

The propagating exterior complex scaling (PECS) method is extended to all four-body processes in electron impact on helium in an S-wave model. Total and energy-differential cross sections are presented with benchmark accuracy for double ionization, single ionization with excitation, and double excitation (to autoionizing states) for incident-electron energies from threshold to 500 eV. While the PECS three-body cross sections for this model given in the preceding article [Phys. Rev. A 81, 022715 (2010)] are in good agreement with other methods, there are considerable discrepancies for these four-body processes. With this model we demonstrate the suitability of the PECS method for the complete solution of the electron-helium system.

Experimental and theoretical double differential cross sections for electron impact ionization of methane

NASA Astrophysics Data System (ADS)

Yavuz, Murat; Ozer, Zehra Nur; Ulu, Melike; Champion, Christophe; Dogan, Mevlut

2016-04-01

Experimental and theoretical double differential cross sections (DDCSs) for electron-induced ionization of methane (CH4) are here reported for primary energies ranging from 50 eV to 350 eV and ejection angles between 25° and 130°. Experimental DDCSs are compared with theoretical predictions performed within the first Born approximation Coulomb wave. In this model, the initial molecular state is described by using single center wave functions, the incident (scattered) electron being described by a plane wave, while a Coulomb wave function is used for modeling the secondary ejected electron. A fairly good agreement may be observed between theory and experiment with nevertheless an expected systematic overestimation of the theory at low-ejection energies (<50 eV).

Cross-Sectional Transport Imaging in a Multijunction Solar Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haegel, Nancy M.; Ke, Chi-Wen; Taha, Hesham

2015-06-14

Combining highly localized electron-beam excitation at a point with the spatial resolution capability of optical near-field imaging, we have imaged carrier transport in a cross-sectioned multijunction (GaInP/GaInAs/Ge) solar cell. We image energy transport associated with carrier diffusion throughout the full width of the middle (GaInAs) cell and luminescent coupling from point excitation in the top cell GaInP to the middle cell. Supporting cathodoluminescence and near-field photoluminescence measurements demonstrate excitation-dependent Fermi level splitting effects that influence cross-sectioned spectroscopy results as well as transport limitations on the spatial resolution of cross-sectional measurements.

Comparison of direct DNA strand breaks induced by low energy electrons with different inelastic cross sections

NASA Astrophysics Data System (ADS)

Li, Jun-Li; Li, Chun-Yan; Qiu, Rui; Yan, Cong-Chong; Xie, Wen-Zhang; Zeng, Zhi; Tung, Chuan-Jong

2013-09-01

In order to study the influence of inelastic cross sections on the simulation of direct DNA strand breaks induced by low energy electrons, six different sets of inelastic cross section data were calculated and loaded into the Geant4-DNA code to calculate the DNA strand break yields under the same conditions. The six sets of the inelastic cross sections were calculated by applying the dielectric function method of Emfietzoglou's optical-data treatments, with two different optical datasets and three different dispersion models, using the same Born corrections. Results show that the inelastic cross sections have a notable influence on the direct DNA strand break yields. The yields simulated with the inelastic cross sections based on Hayashi's optical data are greater than those based on Heller's optical data. The discrepancies are about 30-45% for the single strand break yields and 45-80% for the double strand break yields. Among the yields simulated with cross sections of the three different dispersion models, generally the greatest are those of the extended-Drude dispersion model, the second are those of the extended-oscillator-Drude dispersion model, and the last are those of the Ashley's δ-oscillator dispersion model. For the single strand break yields, the differences between the first two are very little and the differences between the last two are about 6-57%. For the double strand break yields, the biggest difference between the first two can be about 90% and the differences between the last two are about 17-70%.

Photo-neutron reaction cross-sections for natMo in the bremsstrahlung end-point energies of 12-16 and 45-70 MeV

NASA Astrophysics Data System (ADS)

Naik, H.; Kim, G. N.; Kapote Noy, R.; Schwengner, R.; Kim, K.; Zaman, M.; Shin, S. G.; Gey, Y.; Massarczyk, R.; John, R.; Junghans, A.; Wagner, A.; Cho, M.-H.

2016-07-01

The natMo( γ, xn)90, 91, 99Mo reaction cross-sections were experimentally determined for the bremsstrahlung end-point energies of 12, 14, 16, 45, 50, 55, 60 and 70MeV by activation and off-line γ -ray spectrometric technique and using the 20MeV electron linac (ELBE) at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany, and the 100MeV electron linac at the Pohang Accelerator Laboratory (PAL), Pohang, Korea. The natMo( γ, xn)88, 89, 90, 91, 99Mo reaction cross-sections as a function of photon energy were also calculated using the computer code TALYS 1.6. The flux-weighted average cross-sections were obtained from the literature data and the calculated values of TALYS based on mono-energetic photons and are found to be in general agreement with the present results. The flux-weighted average experimental and theoretical cross-sections for the natMo( γ, xn)88, 89, 90, 91, 99Mo reactions increase with the bremsstrahlung end-point energy, which indicates the role of excitation energy. After a certain energy, the individual natMo( γ, xn) reaction cross-sections decrease with the increase of bremsstrahlung energy due to opening of other reactions, which indicates sharing of energy in different reaction channels. The 100Mo( γ, n) reaction cross-section is important for the production of 99Mo , which is a probable alternative to the 98Mo(n, γ) and 235U(n, f ) reactions.

Absolute cross sections for the ionization-excitation of helium by electron impact

NASA Astrophysics Data System (ADS)

Bellm, S.; Lower, J.; Weigold, E.; Bray, I.; Fursa, D. V.; Bartschat, K.; Harris, A. L.; Madison, D. H.

2008-09-01

In a recent publication we presented detailed experimental and theoretical results for the electron-impact-induced ionization of ground-state helium atoms. The purpose of that work was to refine theoretical approaches and provide further insight into the Coulomb four-body problem. Cross section ratios were presented for transitions leading to excited states, relative to those leading to the ground state, of the helium ion. We now build on that study by presenting individual relative triple-differential ionization cross sections (TDCSs) for an additional body of experimental data measured at lower values of scattered-electron energies. This has been facilitated through the development of new electron-gun optics which enables us to accurately characterize the spectrometer transmission at low energies. The experimental results are compared to calculations resulting from a number of different approaches. For ionization leading to He+(1s2)1S , cross sections are calculated by the highly accurate convergent close-coupling (CCC) method. The CCC data are used to place the relative experimental data on to an absolute scale. TDCSs describing transitions to the excited states are calculated through three different approaches, namely, through a hybrid distorted- wave+R -matrix (close-coupling) model, through the recently developed four-body distorted-wave model, and by a first Born approximation calculation. Comparison of the first- and second-order theories with experiment allows for the accuracy of the different theoretical approaches to be assessed and gives insight into which physical aspects of the problem are most important to accurately model.

The calculation of radial dose from heavy ions: predictions of biological action cross sections

NASA Technical Reports Server (NTRS)

Katz, R.; Cucinotta, F. A.; Zhang, C. X.; Wilson, J. W. (Principal Investigator)

1996-01-01

The track structure model of heavy ion cross sections was developed by Katz and co-workers in the 1960s. In this model the action cross section is evaluated by mapping the dose-response of a detector to gamma rays (modeled from biological target theory) onto the radial dose distribution from delta rays about the path of the ion. This is taken to yield the radial distribution of probability for a "hit" (an interaction leading to an observable end-point). Radial integration of the probability yields the cross section. When different response from ions of different Z having the same stopping power is observed this model may be indicated. Since the 1960s there have been several developments in the computation of the radial dose distribution, in the measurement of these distributions, and in new radiobiological data against which to test the model. The earliest model, by Butts and Katz made use of simplified delta ray distribution functions, of simplified electron range-energy relations, and neglected angular distributions. Nevertheless it made possible the calculation of cross sections for the inactivation of enzymes and viruses, and allowed extension to tracks in nuclear emulsions and other detectors and to biological cells. It set the pattern for models of observable effects in the matter through which the ion passed. Here we outline subsequent calculations of radial dose which make use of improved knowledge of the electron emission spectrum, the electron range-energy relation, the angular distribution, and some considerations of molecular excitation, of particular interest both close to the path of the ion and the outer limits of electron penetration. These are applied to the modeling of action cross sections for the inactivation of several strains of E-coli and B. subtilis spores where extensive measurements in the "thin-down" region have been made with heavy ion beams. Such calculations serve to test the radial dose calculations at the outer limit of electron penetration. We lack data from which to test these calculations in regions close to the path of the ion aside from our earliest work on latent tracks in plastics, though it appears that the criterion then suggested for the threshold of track formation, of a minimal dose at a minimal distance (of about 20 angstroms, in plastics), remains valid.

Propensity for distinguishing two free electrons with equal energies in electron-impact ionization of helium

NASA Astrophysics Data System (ADS)

Ren, Xueguang; Senftleben, Arne; Pflüger, Thomas; Bartschat, Klaus; Zatsarinny, Oleg; Berakdar, Jamal; Colgan, James; Pindzola, Michael S.; Bray, Igor; Fursa, Dmitry V.; Dorn, Alexander

2015-11-01

We report a combined experimental and theoretical study on the electron-impact ionization of helium at E0=70.6 eV and equal energy sharing of the two outgoing electrons (E1=E2=23 eV ), where a double-peak or dip structure in the binary region of the triple differential cross section is observed. The experimental cross sections are compared with results from convergent close-coupling (CCC), B -spline R-matrix-with-pseudostates (BSR), and time-dependent close-coupling (TDCC) calculations, as well as predictions from the dynamic screening three-Coulomb (DS3C) theory. Excellent agreement is obtained between experiment and the nonperturbative CCC, BSR, and TDCC theories, and good agreement is also found for the DS3C model. The data are further analyzed regarding contributions in particular coupling schemes for the spins of either the two outgoing electrons or one of the outgoing electrons and the 1 s electron remaining in the residual ion. While both coupling schemes can be used to explain the observed double-peak structure in the cross section, the second one allows for the isolation of the exchange contribution between the incident projectile and the target. For different observation angles of the two outgoing electrons, we interpret the results as a propensity for distinguishing these two electrons—one being more likely the incident projectile and the other one being more likely ejected from the target.

Image charge effects on electron capture by dust grains in dusty plasmas.

PubMed

Jung, Y D; Tawara, H

2001-07-01

Electron-capture processes by negatively charged dust grains from hydrogenic ions in dusty plasmas are investigated in accordance with the classical Bohr-Lindhard model. The attractive interaction between the electron in a hydrogenic ion and its own image charge inside the dust grain is included to obtain the total interaction energy between the electron and the dust grain. The electron-capture radius is determined by the total interaction energy and the kinetic energy of the released electron in the frame of the projectile dust grain. The classical straight-line trajectory approximation is applied to the motion of the ion in order to visualize the electron-capture cross section as a function of the impact parameter, kinetic energy of the projectile ion, and dust charge. It is found that the image charge inside the dust grain plays a significant role in the electron-capture process near the surface of the dust grain. The electron-capture cross section is found to be quite sensitive to the collision energy and dust charge.

Microsecond Electron Beam Source with Electron Energy Up to 400 Kev and Plasma Anode

NASA Astrophysics Data System (ADS)

Abdullin, É. N.; Basov, G. F.; Shershnev, S.

2017-12-01

A new high-power source of electrons with plasma anode for producing high-current microsecond electron beams with electron energy up to 400 keV has been developed, manufactured, and put in operation. To increase the cross section and pulse current duration of the beam, a multipoint explosive emission cathode is used in the electron beam source, and the beam is formed in an applied external guiding magnetic field. The Marx generator with vacuum insulation is used as a high-voltage source. Electron beams with electron energy up to 300-400 keV, current of 5-15 kA, duration of 1.5-3 μs, energy up to 4 kJ, and cross section up to 150 cm2 have been produced. The operating modes of the electron beam source are realized in which the applied voltage is influenced weakly on the current. The possibility of source application for melting of metal surfaces is demonstrated.

Electron-Impact Total Ionization Cross Sections of Fluorine Compounds

NASA Astrophysics Data System (ADS)

Kim, Y.-K.; Ali, M. A.; Rudd, M. E.

1997-10-01

A theoretical method called the Binary-Encounter-Bethe (BEB) model(M. A. Ali, Y.-K. Kim, H. Hwang, N. M. Weinberger, and M. E. Rudd, J. Chem. Phys. 106), 9602 (1997), and references therein. that combines the Mott cross section at low incident energies T and the Bethe cross section at high T was applied to fluorine compounds of interest to plasma processing of semiconductors (CF_4, CHF_3, C_2F_6, C_4F_8, etc.). The theory provides total ioniztion cross sections in an analytic form from the threshold to a few keV in T, making it convenient to use the theory for modeling. The theory is particularly effective for closed-shell molecules. The theoretical cross sections are compared to available experimental data.

Electron-impact ionization of atomic hydrogen at incident electron energies of 15.6, 17.6, 25, and 40 eV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Childers, J. G.; James, K. E.; Hughes, M.

2003-09-01

Absolute doubly differential cross sections for the electron-impact ionization of atomic hydrogen have been measured from near threshold to intermediate energies. The measurements are calibrated to the well-established, accurate differential cross section for electron-impact excitation of the atomic hydrogen transition H(1{sup 2}S{yields}2{sup 2}S+2{sup 2}P). In these experiments background secondary electrons are suppressed by moving the atomic hydrogen target source to and from the collision region. Measurements cover the incident electron energy range of 14.6-40 eV, for scattering angles of 10 degree sign -120 degree sign and are found to be in very good agreement with the results of the mostmore » advanced theoretical models--the convergent close-coupling model and the exterior complex scaling model.« less

First measurement of the ratio of central-electron to forward-electron W partial cross sections in pp[over] collisions at (square root)s =1.96 TeV.

PubMed

Abulencia, A; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Aurisano, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Beauchemin, P-H; Bedeschi, F; Behari, S; Bellettini, G; Bellinger, J; Belloni, A; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Bizjak, I; Blair, R E; Blocker, C; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Boveia, A; Brau, B; Brigliadori, L; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Buzatu, A; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carillo, S; Carlsmith, D; Carosi, R; Carron, S; Casal, B; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chou, J P; Choudalakis, G; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Cilijak, M; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Coca, M; Compostella, G; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Crescioli, F; Almenar, C Cuenca; Cuevas, J; Culbertson, R; Cully, J C; DaRonco, S; Datta, M; D'Auria, S; Davies, T; Dagenhart, D; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; De Lorenzo, G; Dell'Orso, M; Delli Paoli, F; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Giovanni, G P Di; Dionisi, C; Di Ruzza, B; Dittmann, J R; D'Onofrio, M; Dörr, C; Donati, S; Dong, P; Donini, J; Dorigo, T; Dube, S; Efron, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, I; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Forrest, R; Forrester, S; Franklin, M; Freeman, J C; Furic, I; Gallinaro, M; Galyardt, J; Garcia, J E; Garberson, F; Garfinkel, A F; Gay, C; Gerberich, H; Gerdes, D; Giagu, S; Giannetti, P; Gibson, K; Gimmell, J L; Ginsburg, C; Giokaris, N; Giordani, M; Giromini, P; Giunta, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, J; Golossanov, A; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Goulianos, K; Gresele, A; Grinstein, S; Grosso-Pilcher, C; Grundler, U; Guimaraes da Costa, J; Gunay-Unalan, Z; Haber, C; Hahn, K; Hahn, S R; Halkiadakis, E; Hamilton, A; Han, B-Y; Han, J Y; Handler, R; Happacher, F; Hara, K; Hare, D; Hare, M; Harper, S; Harr, R F; Harris, R M; Hartz, M; Hatakeyama, K; Hauser, J; Hays, C; Heck, M; Heijboer, A; Heinemann, B; Heinrich, J; Henderson, C; Herndon, M; Heuser, J; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Holloway, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Husemann, U; Huston, J; Incandela, J; Introzzi, G; Iori, M; Ivanov, A; Iyutin, B; James, E; Jang, D; Jayatilaka, B; Jeans, D; Jeon, E J; Jindariani, S; Johnson, W; Jones, M; Joo, K K; Jun, S Y; Jung, J E; Junk, T R; Kamon, T; Karchin, P E; Kato, Y; Kemp, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kimura, N; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Kondo, K; Kong, D J; Konigsberg, J; Korytov, A; Kotwal, A V; Kraan, A C; Kraus, J; Kreps, M; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kubo, T; Kuhlmann, S E; Kuhr, T; Kulkarni, N P; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; LeCompte, T; Lee, J; Lee, J; Lee, Y J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Lin, C; Lin, C S; Lindgren, M; Lipeles, E; Lister, A; Litvintsev, D O; Liu, T; Lockyer, N S; Loginov, A; Loreti, M; Lu, R-S; Lucchesi, D; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; MacQueen, D; Madrak, R; Maeshima, K; Makhoul, K; Maki, T; Maksimovic, P; Malde, S; Malik, S; Manca, G; Manousakis, A; Margaroli, F; Marginean, R; Marino, C; Marino, C P; Martin, A; Martin, M; Martin, V; Martínez, M; Martínez-Ballarín, R; Maruyama, T; Mastrandrea, P; Masubuchi, T; Matsunaga, H; Mattson, M E; Mazini, R; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Mehtala, P; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; Miao, T; Miladinovic, N; Miles, J; Miller, R; Mills, C; Milnik, M; Mitra, A; Mitselmakher, G; Miyamoto, A; Moed, S; Moggi, N; Mohr, B; Moon, C S; Moore, R; Morello, M; Fernandez, P Movilla; Mülmenstädt, J; Mukherjee, A; Muller, Th; Mumford, R; Murat, P; Mussini, M; Nachtman, J; Nagano, A; Naganoma, J; Nakamura, K; Nakano, I; Napier, A; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nodulman, L; Norniella, O; Nurse, E; Oh, S H; Oh, Y D; Oksuzian, I; Okusawa, T; Oldeman, R; Orava, R; Osterberg, K; Pagliarone, C; Palencia, E; Papadimitriou, V; 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Wang, S M; Warburton, A; Waters, D; Weinberger, M; Wester, W C; Whitehouse, B; Whiteson, D; Wicklund, A B; Wicklund, E; Williams, G; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, C; Wright, T; Wu, X; Wynne, S M; Yagil, A; Yamamoto, K; Yamaoka, J; Yamashita, T; Yang, C; Yang, U K; Yang, Y C; Yao, W M; Yeh, G P; Yoh, J; Yorita, K; Yoshida, T; Yu, G B; Yu, I; Yu, S S; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zhang, X; Zhou, J; Zucchelli, S

2007-06-22

We present a measurement of sigma(pp[over] --> W) x B(W --> e nu) at (square root)s = 1.96 TeV, using electrons identified in the forward region (1.2 < |eta| < 2.8) of the CDF II detector, in 223 pb(-1) of data. We measure sigma x B = 2796 +/- 13(stat)(-90)(+95)(syst) +/- 162(lum) pb. Combining this result with a previous CDF measurement obtained using electrons in the central region (|eta| approximately < 1), we present the first measurement of the ratio of central-electron to forward-electron W partial cross sections R(exp) = 0.925 +/- 0.006(stat) +/- 0.032(syst), consistent with theoretical predictions using Coordinated Theoretical-Experimental Project on QCD (CTEQ) and Martin-Roberts-Stirling-Thorne (MRST) parton distribution functions.

DBCC Software as Database for Collisional Cross-Sections

NASA Astrophysics Data System (ADS)

Moroz, Daniel; Moroz, Paul

2014-10-01

Interactions of species, such as atoms, radicals, molecules, electrons, and photons, in plasmas used for materials processing could be very complex, and many of them could be described in terms of collisional cross-sections. Researchers involved in plasma simulations must select reasonable cross-sections for collisional processes for implementing them into their simulation codes to be able to correctly simulate plasmas. However, collisional cross-section data are difficult to obtain, and, for some collisional processes, the cross-sections are still not known. Data on collisional cross-sections can be obtained from numerous sources including numerical calculations, experiments, journal articles, conference proceedings, scientific reports, various universities' websites, national labs and centers specifically devoted to collecting data on cross-sections. The cross-sections data received from different sources could be partial, corresponding to limited energy ranges, or could even not be in agreement. The DBCC software package was designed to help researchers in collecting, comparing, and selecting cross-sections, some of which could be constructed from others or chosen as defaults. This is important as different researchers may place trust in different cross-sections or in different sources. We will discuss the details of DBCC and demonstrate how it works and why it is beneficial to researchers working on plasma simulations.

ROVIBRATIONALLY RESOLVED DIRECT PHOTODISSOCIATION THROUGH THE LYMAN AND WERNER TRANSITIONS OF H{sub 2} FOR FUV/X-RAY-IRRADIATED ENVIRONMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gay, C. D.; Porter, R. L.; Stancil, P. C.

Using ab initio potential curves and dipole transition moments, cross-section calculations were performed for the direct continuum photodissociation of H{sub 2} through the B{sup 1}{Sigma}{sup +}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Lyman) and C{sup 1}{Pi}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Werner) transitions. Partial cross-sections were obtained for wavelengths from 100 A to the dissociation threshold between the upper electronic state and each of the 301 bound rovibrational levels v''J'' within the ground electronic state. The resulting cross-sections are incorporated into three representative classes of interstellar gas models: diffuse clouds, photon-dominated regions, and X-ray-dominated regions (XDRs). The models, whichmore » used the CLOUDY plasma/molecular spectra simulation code, demonstrate that direct photodissociation is comparable to fluorescent dissociation (or spontaneous radiative dissociation, the Solomon process) as an H{sub 2} destruction mechanism in intense far-ultraviolet or X-ray-irradiated gas. In particular, changes in H{sub 2} rotational column densities are found to be as large as 20% in the XDR model with the inclusion of direct photodissociation. The photodestruction rate from some high-lying rovibrational levels can be enhanced by pumping from H Ly{beta} due to a wavelength coincidence with cross-section resonances resulting from quasi-bound levels of the upper electronic states. Given the relatively large size of the photodissociation data set, a strategy is described to create truncated, but reliable, cross-section data consistent with the wavelength resolving power of typical observations.« less

The electronic states of cyclopropane studied by VUV absorption and electron energy-loss spectroscopies

NASA Astrophysics Data System (ADS)

Gingell, M.; Mason, N. J.; Walker, I. C.; Marston, G.; Zhao, H.; Siggel, M. R. F.

1999-06-01

Absolute optical (VUV) absorption cross sections for cyclopropane have been measured from 5.0 to 11.2 and 20-40 eV using synchrotron radiation. Also, electron energy-loss (EEL) spectra have been obtained using incident electrons of (a) 150 eV energy scattered through small angles (energy loss 5.0-15 eV) and (b) near-threshold energies scattered through large angles (energy loss 0-10.5 eV). Taken together these confirm that the low-lying excited electronic states of cyclopropane are of Rydberg type and, although spectral bands are diffuse, a known Rydberg series has been extended. Recent computations (Galasso V 1996 Chem. Phys. 206 289) appear to give a good account of the experimental spectrum from threshold to about 11 eV, but these must be extended if valence-excited states are to be characterized. Particular attention has been directed at the evaluation of absolute optical cross sections. These are now believed to be established over the energy ranges 5-15 and 20-40 eV. In the gap region (15-20 eV) second-order radiation may affect the optical measurements. From consideration of second-order effects, and comparison of the present studies with earlier measurements, we propose a best-estimate cross section in this energy region also.

Upper-limit charge exchange cross sections for mercury (plus) on molybdenum and cesium (plus) on aluminum

NASA Technical Reports Server (NTRS)

Dugan, J. V., Jr.

1972-01-01

Upper-limit charge exchange cross sections are calculated for Hg(+) on Mo and Cs(+) on Al. The cross sections are calculated from the polarization interaction at low ion energies (1 to 500 eV) and by assuming favorable curve crossings with a hard-core reaction radius at higher energies (500 eV to 10 keV). The cross sections for Hg(+) on Mo becomes greater than corresponding Hg Hg(+) resonance values at ion energies below 2 eV, whereas the Cs(+) Al values remain considerably lower than the Cs(+)Cs resonance value at all ion energies. It is also shown that charge exchange of slow Hg(+) with Mo may be important for spacecraft with electron bombardment thrusters.

Analysis of density effects in plasmas and their influence on electron-impact cross sections

NASA Astrophysics Data System (ADS)

Belkhiri, M.; Poirier, M.

2014-12-01

Density effects in plasmas are analyzed using a Thomas-Fermi approach for free electrons. First, scaling properties are determined for the free-electron potential and density. For hydrogen-like ions, the first two terms of an analytical expansion of this potential as a function of the plasma coupling parameter are obtained. In such ions, from these properties and numerical calculations, a simple analytical fit is proposed for the plasma potential, which holds for any electron density, temperature, and atomic number, at least assuming that Maxwell-Boltzmann statistics is applicable. This allows one to analyze perturbatively the influence of the plasma potential on energies, wave functions, transition rates, and electron-impact collision rates for single-electron ions. Second, plasmas with an arbitrary charge state are considered, using a modified version of the Flexible Atomic Code (FAC) package with a plasma potential based on a Thomas-Fermi approach. Various methods for the collision cross-section calculations are reviewed. The influence of plasma density on these cross sections is analyzed in detail. Moreover, it is demonstrated that, in a given transition, the radiative and collisional-excitation rates are differently affected by the plasma density. Some analytical expressions are proposed for hydrogen-like ions in the limit where the Born or Lotz approximation applies and are compared to the numerical results from the FAC.

Electron capture in collisions of Al2+ ions with He atoms at intermediate energies

NASA Astrophysics Data System (ADS)

Watanabe, A.; Sato, H.; Gu, J. P.; Hirsch, G.; Buenker, R. J.; Kimura, M.

2001-09-01

Electron capture resulting from collisions of Al2+ ions with He atoms from 0.15 to 1000 keV/u is investigated using a molecular-orbital representation within a semiclassical frame. Molecular electronic states and corresponding couplings are determined by the ALCHEMY program. Sixteen molecular states all connecting to single-electron-capture processes are included, and hence radial and rotational couplings among these channels are fully considered. The trajectory effect arising from the straight-line, Coulomb, and ground-state potential trajectories for electron-capture and excitation processes is carefully assessed. The electron-capture cross section by ground-state Al2+(2S) ions slowly increases before it reaches a maximum of 1.3×10-16 cm2 at 100 keV/u. Those for metastable Al2+(2P) ions sharply increase with increasing energy, and reach a peak at 1 keV/u with a value of 1.5×10-16 cm2. The earlier experimental data are found to be larger by an order of magnitude although their energy dependence is in good accord with the present result. Excitation cross sections for both the ground and metastable states are found to be much larger by a factor of 2-3 than corresponding capture cross sections above 1 keV/u although they become comparable below this energy.

Adsorption on Nanopores of Different Cross Sections Made by Electron Beam Nanolithography.

PubMed

Bruschi, Lorenzo; Mistura, Giampaolo; Prasetyo, Luisa; Do, Duong D; Dipalo, Michele; De Angelis, Francesco

2018-01-09

Adsorption on nanoporous matrices is characterized by a pronounced hysteresis loop in the adsorption isotherm, when the substrate is loaded and unloaded with adsorbate, the origin of which is a matter of immense debate in the literature. In this work, we report a study of argon adsorption at 85 K on nonconnecting nanopores with one end closed to the surrounding where the effects of different pore cross sections fabricated by electron beam lithography (EBL) are investigated. A polymethylmethacrylate (PMMA) resist is deposited on the electrodes of a sensitive quartz crystal microbalance without degradation of the resonance quality factor or the long-term and short-term stabilities of the device even at cryogenic temperatures. Four different pores' cross sections: circular, square, rectangular, and triangular, are produced from EBL, and the isotherms for these pore shapes exhibit pronounced hysteresis loops whose adsorption and desorption branches are nearly vertical and have almost the same slopes. No difference is observed in the hysteresis loops of the isotherms for the pores with triangular and square cross sections, whereas the hysteresis loop for the pore with circular cross sections is much narrower, suggesting that they are more regular than the other pores. All of these observations suggest that the hysteresis behavior resulted mainly from microscopic geometric irregularities present in these porous matrices.

Impact of geometric, thermal and tunneling effects on nano-transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Langhua; Chen, Duan, E-mail: dchen10@uncc.edu; Wei, Guo-Wei

Electronic transistors are fundamental building blocks of large scale integrated circuits in modern advanced electronic equipments, and their sizes have been down-scaled to nanometers. Modeling and simulations in the framework of quantum dynamics have emerged as important tools to study functional characteristics of these nano-devices. This work explores the effects of geometric shapes of semiconductor–insulator interfaces, phonon–electron interactions, and quantum tunneling of three-dimensional (3D) nano-transistors. First, we propose a two-scale energy functional to describe the electron dynamics in a dielectric continuum of device material. Coupled governing equations, i.e., Poisson–Kohn–Sham (PKS) equations, are derived by the variational principle. Additionally, it ismore » found that at a given channel cross section area and gate voltage, the geometry that has the smallest perimeter of the channel cross section offers the largest channel current, which indicates that ultra-thin nanotransistors may not be very efficient in practical applications. Moreover, we introduce a new method to evaluate quantum tunneling effects in nanotransistors without invoking the comparison of classical and quantum predictions. It is found that at a given channel cross section area and gate voltage, the geometry that has the smallest perimeter of the channel cross section has the smallest quantum tunneling ratio, which indicates that geometric defects can lead to higher geometric confinement and larger quantum tunneling effect. Furthermore, although an increase in the phonon–electron interaction strength reduces channel current, it does not have much impact to the quantum tunneling ratio. Finally, advanced numerical techniques, including second order elliptic interface methods, have been applied to ensure computational accuracy and reliability of the present PKS simulation.« less

Production of vibrationally excited N 2 by electron impact

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.; Cartwright, D. C.; Teubner, P. J. O.

2004-08-01

Energy transfer from electrons to neutral gases and ions is one of the dominant electron cooling processes in the ionosphere, and the role of vibrationally excited N 2 in this is particularly significant. We report here the results from a new calculation of electron energy transfer rates ( Q) for vibrational excitation of N 2, as a function of the electron temperature Te. The present study was motivated by the development of a new cross-section compilation for vibrational excitation processes in N 2 which supercedes those used in the earlier calculations of the electron energy transfer rates. We show that the energy dependence and magnitude of these cross sections, particularly in the region of the well-known 2Π g resonance in N 2, significantly affect the calculated values of Q. A detailed comparison between the current and previous calculated electron energy transfer rates is made and coefficients are provided so that these rates for transitions from level 0 to levels 1-10 can be calculated for electron temperatures less than 6000 K.

Confined states of individual type-II GaSb/GaAs quantum rings studied by cross-sectional scanning tunneling spectroscopy.

PubMed

Timm, Rainer; Eisele, Holger; Lenz, Andrea; Ivanova, Lena; Vossebürger, Vivien; Warming, Till; Bimberg, Dieter; Farrer, Ian; Ritchie, David A; Dähne, Mario

2010-10-13

Combined cross-sectional scanning tunneling microscopy and spectroscopy results reveal the interplay between the atomic structure of ring-shaped GaSb quantum dots in GaAs and the corresponding electronic properties. Hole confinement energies between 0.2 and 0.3 eV and a type-II conduction band offset of 0.1 eV are directly obtained from the data. Additionally, the hole occupancy of quantum dot states and spatially separated Coulomb-bound electron states are observed in the tunneling spectra.

Radiative corrections to elastic proton-electron scattering measured in coincidence

NASA Astrophysics Data System (ADS)

Gakh, G. I.; Konchatnij, M. I.; Merenkov, N. P.; Tomasi-Gustafsson, E.

2017-05-01

The differential cross section for elastic scattering of protons on electrons at rest is calculated, taking into account the QED radiative corrections to the leptonic part of interaction. These model-independent radiative corrections arise due to emission of the virtual and real soft and hard photons as well as to vacuum polarization. We analyze an experimental setup when both the final particles are recorded in coincidence and their energies are determined within some uncertainties. The kinematics, the cross section, and the radiative corrections are calculated and numerical results are presented.

The Trojan Horse Method in nuclear astrophysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spitaleri, C., E-mail: spitaleri@lns.infn.it; Mukhamedzhanov, A. M.; Blokhintsev, L. D.

2011-12-15

The study of energy production and nucleosynthesis in stars requires an increasingly precise knowledge of the nuclear reaction rates at the energies of interest. To overcome the experimental difficulties arising from the small cross sections at those energies and from the presence of the electron screening, the Trojan Horse Method has been introduced. The method provides a valid alternative path to measure unscreened low-energy cross sections of reactions between charged particles, and to retrieve information on the electron screening potential when ultra-low energy direct measurements are available.

Kuang's Semi-Classical Formalism for Calculating Electron Capture Cross Sections: A Space- Physics Application

NASA Technical Reports Server (NTRS)

Barghouty, A. F.

2014-01-01

Accurate estimates of electroncapture cross sections at energies relevant to the modeling of the transport, acceleration, and interaction of energetic neutral atoms (ENA) in space (approximately few MeV per nucleon) and especially for multi-electron ions must rely on detailed, but computationally expensive, quantum-mechanical description of the collision process. Kuang's semi-classical approach is an elegant and efficient way to arrive at these estimates. Motivated by ENA modeling efforts for apace applications, we shall briefly present this approach along with sample applications and report on current progress.

Electron collisions with F2CO molecules

NASA Astrophysics Data System (ADS)

Freitas, Thiago Corrêa; Barbosa, Alessandra Souza; Bettega, Márcio Henrique Franco

2017-07-01

In this paper we present elastic differential, integral, and momentum-transfer cross sections for electron collisions with carbonyl fluoride (F2CO ) molecules for the incident electron's energy from 0.5 eV to 20 eV. The Schwinger multichannel method with pseudopotentials was employed to obtain the cross sections in the static-exchange and static-exchange plus polarization approximations. The present results were compared with the available data in the literature, in particular, with the results of Kaur, Mason, and Antony [Phys. Rev. A 92, 052702 (2015), 10.1103/PhysRevA.92.052702] for the differential, total, and momentum-transfer cross sections. We have found a π* shape resonance centered at 2.6 eV in the B1 symmetry and other resonance, in the B2 symmetry, located at around 9.7 eV. A systematic study of the inclusion of polarization effects was performed in order to have a well balanced description of this negative-ion transient state. The effects of the long-range electric dipole potential were included by the Born closure scheme. Electronic structure calculations were also performed to help in the interpretation of the scattering results, and associate the transient states to the unoccupied orbitals.

Absolute electron-impact total ionization cross sections of chlorofluoromethanes

NASA Astrophysics Data System (ADS)

Martínez, Roberto; Sierra, Borja; Redondo, Carolina; Rayo, María N. Sánchez; Castaño, Fernando

2004-12-01

An experimental study is reported on the electron-impact total ionization cross sections (TICSs) of CCl4, CCl3F, CCl2F2, and CClF3 molecules. The kinetic energy of the colliding electrons was in the 10-85 eV range. TICSs were obtained as the sum of the partial ionization cross sections of all fragment ions, measured and identified in a linear double focusing time-of-flight mass spectrometer. The resulting TICS profiles—as a function of the electron-impact energy—have been compared both with those computed by ab initio and (semi)empirical methods and with the available experimental data. The computational methods used include the binary-encounter-Bethe (BEB) modified to include atoms with principal quantum numbers n⩾3, the Deutsch and Märk (DM) formalism, and the modified additivity rule (MAR). It is concluded that both modified BEB and DM methods fit the experimental TICS for (CF4), CClF3, CCl2F2, CCl3F, and CCl4 to a high accuracy, in contrast with the poor accord of the MAR method. A discussion on the factors influencing the discrepancies of the fittings is presented.

Radiative recombination data for tungsten ions: II. W{sup 47+}–W{sup 71+}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trzhaskovskaya, M.B., E-mail: Trzhask@MT5605.spb.edu; Nikulin, V.K.

2014-07-15

New radiative recombination and photoionization cross sections, radiative recombination rate coefficients, and radiated power loss rate coefficients are presented for 23 tungsten impurity ions in plasmas. We consider ions from W{sup 47+} to W{sup 71+} that are of importance to fusion studies for ITER and for experiments using electron beam ion traps. The calculations are fully relativistic and all significant multipoles of the radiative field are taken into account. The Dirac–Fock method is used to compute the electron wavefunctions. Radiative recombination rates and radiated power loss rates are found using the relativistic Maxwell–Jüttner distribution of the continuum electron velocity. Themore » total radiative recombination cross sections are given in the electron energy range from 1 eV to ∼80keV. Partial cross sections for ground and excited states are approximated by an analytical expression involving five fit parameters. Radiative recombination rates and radiated power loss rates are calculated in the temperature range from 10{sup 4}K to 10{sup 9}K. The total radiative recombination rates are approximated by another analytical expression with four fit parameters.« less

Application of relativistic electrons for the quantitative analysis of trace elements

NASA Astrophysics Data System (ADS)

Hoffmann, D. H. H.; Brendel, C.; Genz, H.; Löw, W.; Richter, A.

1984-04-01

Particle induced X-ray emission methods (PIXE) have been extended to relativistic electrons to induce X-ray emission (REIXE) for quantitative trace-element analysis. The electron beam (20 ≤ E0≤ 70 MeV) was supplied by the Darmstadt electron linear accelerator DALINAC. Systematic measurements of absolute K-, L- and M-shell ionization cross sections revealed a scaling behaviour of inner-shell ionization cross sections from which X-ray production cross sections can be deduced for any element of interest for a quantitative sample investigation. Using a multielemental mineral monazite sample from Malaysia the sensitivity of REIXE is compared to well established methods of trace-element analysis like proton- and X-ray-induced X-ray fluorescence analysis. The achievable detection limit for very heavy elements amounts to about 100 ppm for the REIXE method. As an example of an application the investigation of a sample prepared from manganese nodules — picked up from the Pacific deep sea — is discussed, which showed the expected high mineral content of Fe, Ni, Cu and Ti, although the search for aliquots of Pt did not show any measurable content within an upper limit of 250 ppm.

STORAGE RING CROSS SECTION MEASUREMENTS FOR ELECTRON IMPACT IONIZATION OF Fe{sup 7+}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hahn, M.; Novotný, O.; Savin, D. W.

2015-11-01

We have measured electron impact ionization for Fe{sup 7+} from the ionization threshold up to 1200 eV. The measurements were performed using the TSR heavy ion storage ring. The ions were stored long enough prior to measurements to remove most metastables, resulting in a beam of 94% ground-level ions. Comparing with the previously recommended atomic data, we find that the Arnaud and Raymond cross section is up to about 40% larger than our measurement, with the largest discrepancies below about 400 eV. The cross section of Dere agrees to within 10%, which is about the magnitude of the experimental uncertainties.more » The remaining discrepancies between our measurement and the Dere calculations are likely due to shortcomings in the theoretical treatment of the excitation-autoionization contribution.« less

Applications of the Trojan Horse method in nuclear astrophysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spitaleri, Claudio, E-mail: spitaleri@lns.infn.it

2015-02-24

The study of the energy production in stars and related nucleosyntesis processes requires increasingly precise knowledge of the nuclear reaction cross section and reaction rates at interaction energy. In order to overcome the experimental difficulties, arising from small cross-sections involved in charge particle induced reactions at astrophysical energies, and from the presence of electron screening, it was necessary to introduce indirect methods. Trough these methods it is possible to measure cross sections at very small energies and retrieve information on electron screening effect when ultra-low energy direct measurements are available. The Trojan Horse Method (THM) represents the indirect technique tomore » determine the bare nucleus astrophysical S-factor for reactions between charged particles at astrophysical energies. The basic theory of the THM is discussed in the case of non-resonant.« less

Erratum: Measurement of the $$t \\bar{t}$$ production cross section in the dilepton channel in pp collisions at $$\\sqrt{s}$$ = 8 TeV

DOE PAGES

Chatrchyan, Serguei

2014-02-05

In this study, the top-antitop quark (tt¯) production cross section is measured in proton-proton collisions at √s = 8 TeV with the CMS experiment at the LHC, using a data sample corresponding to an integrated luminosity of 5.3 fb –1. The measurement is performed by analysing events with a pair of electrons or muons, or one electron and one muon, and at least two jets, one of which is identified as originating from hadronisation of a bottom quark. The measured cross section is 239±2 (stat.)±11 (syst.)±6 (lum.) pb, for an assumed top-quark mass of 172.5 GeV, in agreement with themore » prediction of the standard model.« less

Measurement of the tt¯ production cross section in pp collisions at √s=7 TeV in dilepton final states containing a τ

DOE PAGES

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; ...

2012-06-19

The top quark pair production cross section is measured in dilepton events with one electron or muon, and one hadronically decaying τ lepton from the decay tt¯→(lν l)(τ hν τ)bb¯, (l=e,μ). The data sample corresponds to an integrated luminosity of 2.0 fb⁻¹ for the electron channel and 2.2 fb⁻¹ for the muon channel, collected by the CMS detector at the LHC. This is the first measurement of the tt¯ cross section explicitly including τ leptons in proton-proton collisions at √s=7 TeV. The measured value σ tt¯=143±14(stat)±22(syst)±3(lumi) pb is consistent with the standard model predictions.

A screened independent atom model for the description of ion collisions from atomic and molecular clusters

NASA Astrophysics Data System (ADS)

Lüdde, Hans Jürgen; Horbatsch, Marko; Kirchner, Tom

2018-05-01

We apply a recently introduced model for an independent-atom-like calculation of ion-impact electron transfer and ionization cross sections to proton collisions from water, neon, and carbon clusters. The model is based on a geometrical interpretation of the cluster cross section as an effective area composed of overlapping circular disks that are representative of the atomic contributions. The latter are calculated using a time-dependent density-functional-theory-based single-particle description with accurate exchange-only ground-state potentials. We find that the net capture and ionization cross sections in p-X n collisions are proportional to n α with 2/3 ≤ α ≤ 1. For capture from water clusters at 100 keV impact energy α is close to one, which is substantially different from the value α = 2/3 predicted by a previous theoretical work based on the simplest-level electron nuclear dynamics method. For ionization at 100 keV and for capture at lower energies we find smaller α values than for capture at 100 keV. This can be understood by considering the magnitude of the atomic cross sections and the resulting overlaps of the circular disks that make up the cluster cross section in our model. Results for neon and carbon clusters confirm these trends. Simple parametrizations are found which fit the cross sections remarkably well and suggest that they depend on the relevant bond lengths.

Specific formation of negative ions from leucine and isoleucine molecules

NASA Astrophysics Data System (ADS)

Papp, Peter; Shchukin, Pavel; Matejčík, Štefan

2010-01-01

Dissociative electron attachment (DEA) to gas phase leucine (Leu) and isoleucine (Ile) molecules was studied using experimental and quantum-chemical methods. The relative partial cross sections for DEA have been measured using crossed electron/molecular beams technique. Supporting ab initio calculations of the structure, energies of neutral molecules, fragments, and negative ions have been carried out at G3MP2 and B3LYP levels in order to interpret the experimental data. Leu and Ile exhibit several common features. The negative ionic fragments from both molecules are formed in the electron energy range from 0 to approximately 14 eV via three resonances (1.2, 5.5, and 8 eV). The relative partial cross sections for DEA Leu and Ile are very similar. The dominant negative ions formed were closed shell negative ions (M-H)- (m/z=130) formed preferentially via low electron energy resonance of 1.23 eV. Additional negative ions with m/z=115, 114, 113, 112, 84, 82, 74, 45, 26, and 17 have been detected.

Use of Relativistic Effective Core Potentials in the Calculation of Electron-Impact Ionization Cross Sections

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Kim, Yong-Ki

1999-01-01

Based on the Binary-Encounter-Bethe (BEB) model, the advantage of using relativistic effective core potentials (RECP) in the calculation of total ionization cross sections of heavy atoms or molecules containing heavy atoms is discussed. Numerical examples for Ar, Kr, Xe, and WF6 are presented.

On the direct and dissociative excitation of the O(3s 3S0) state by electron impact on atomic and molecular oxygen

NASA Technical Reports Server (NTRS)

Zipf, E. C.

1986-01-01

The ratio of the cross sections for the direct and dissociative excitation of the OI(3s 3S0-2p 3P; 1304 A wavelength) transition, sigma A/sigma D, are accurately determined, and the sigma A/sigma D ratio is directly normalized to the ratio of the O(+) and O2(+) ionization cross sections using a high-density diffuse gas source, an electrostatically focused electron gun, a vacuum-ultraviolet monochromater, and a quadrupole mass spectrometer for simultaneous optical and composition measurements. Using revised sigma A(1304 A) values calculated with new calibration standards, the shape of the cross section for the excitation of the O(3s 3S0) state agrees well with previous results, though the absolute magnitude of sigma A(1304 A) is smaller than the results of Stone and Zipf (1974) by a factor of 2.8. The revised cross sections agree well with recent quantum calculations when cascade excitation of the 3s 3S0 state is taken into account.

Electron-ion continuum-continuum mixing in dissociative recombination

NASA Technical Reports Server (NTRS)

Guberman, Steven L.

1993-01-01

In recent calculations on the dissociative recombination (DR) of the v=1 vibrational level of the ground state of N2(+), N2(+)(v=1) + e(-) yields N + N, we have observed an important continuun-continuum mixing process involving the open channels on both sides of N2(+)(v=1) + e(-) yields N2(+)(v=0) + e(-). In vibrational relaxation by electron impact (immediately above) the magnitude of the cross section depends upon the strength of the interaction between these continua. In DR of the v=1 ion level, these continua can also interact in the entrance channel, and the mixing can have a profound effect upon the DR cross section from v=1, as we illustrate in this paper. In our theoretical calculations of N2(+) DR using multichannel quantum defect theory (MQDT), the reactants and products in the two above equations are described simultaneously. This allows us to calculate vibrational relaxation and excitation cross sections as well as DR cross sections. In order to understand the mixing described above, we first present a brief review of the prior results for DR of the v=0 level of N2(+).

Electrophilic dark matter with dark photon: From DAMPE to direct detection

NASA Astrophysics Data System (ADS)

Gu, Pei-Hong; He, Xiao-Gang

2018-03-01

The electron-positron excess reported by the DAMPE collaboration recently may be explained by an electrophilic dark matter (DM). A standard model singlet fermion may play the role of such a DM when it is stabilized by some symmetries, such as a dark U(1)X gauge symmetry, and dominantly annihilates into the electron-positron pairs through the exchange of a scalar mediator. The model, with appropriate Yukawa couplings, can well interpret the DAMPE excess. Naively one expects that in this type of models the DM-nucleon cross section should be small since there is no tree-level DM-quark interactions. We however find that at one-loop level, a testable DM-nucleon cross section can be induced for providing ways to test the electrophilic model. We also find that a U (1) kinetic mixing can generate a sizable DM-nucleon cross section although the U(1)X dark photon only has a negligible contribution to the DM annihilation. Depending on the signs of the mixing parameter, the dark photon can enhance/reduce the one-loop induced DM-nucleon cross section.

Resonant vibrational-excitation cross sections and rate constants for low-energy electron scattering by molecular oxygen

NASA Astrophysics Data System (ADS)

Laporta, V.; Celiberto, R.; Tennyson, J.

2013-04-01

Resonant vibrational-excitation cross sections and rate constants for electron scattering by molecular oxygen are presented. Transitions between all 42 vibrational levels of O_2({X}\\, ^3\\Sigma_g^{-}) are considered. Molecular rotations are parametrized by the rotational quantum number J, which is considered in the range 1-151. The lowest four resonant states of O_2^- , 2Πg, 2Πu, ^4\\Sigma_u^- and ^2\\Sigma_u^- are taken into account. The calculations are performed using the fixed-nuclei R-matrix approach to determine the resonance positions and widths, and the boomerang model to characterize the nuclei motion. Two energy regions below and above 4 eV are investigated: the first one is characterized by sharp structures in the cross section and the second by a broad resonance peaked at 10 eV. The computed cross sections are compared with theoretical and experimental results available in the literature for both energy regions, and are made available for use by modelers. The effect of including rotational motion is found to be non-negligible.

Comparative study of elastic electron collisions on the isoelectronic SiN{sub 2}, SiCO, and CSiO radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujimoto, M. M.; Michelin, S. E.; Mazon, K. T.

2007-07-15

We report a theoretical study of elastic electron collisions on three isoelectronic free radicals, namely, SiNN, SiCO, and CSiO. More specifically, differential, integral, and momentum-transfer cross sections are calculated and reported in the (1-100) eV energy range. Calculations are performed at the static-exchange-polarization-absorption level of approximation. A combination of the iterative Schwinger variational method and the distorted-wave approximation is used to solve the scattering equations. Our study reveals that the calculated cross sections for the e{sup -}-SiNN and e{sup -}-SiCO collisions are very similar even at incident energies as low as 3 eV. Strong isomeric effects are also observed inmore » the calculated cross sections for e{sup -}-CSiO and e{sup -}-SiCO collisions, particularly at incident energies below 20 eV. It is believed that the position of the silicon atom being at the center or extremity of the molecules may exert important influence on the calculated cross sections.« less

A parameterization scheme for the x-ray linear attenuation coefficient and energy absorption coefficient.

PubMed

Midgley, S M

2004-01-21

A novel parameterization of x-ray interaction cross-sections is developed, and employed to describe the x-ray linear attenuation coefficient and mass energy absorption coefficient for both elements and mixtures. The new parameterization scheme addresses the Z-dependence of elemental cross-sections (per electron) using a simple function of atomic number, Z. This obviates the need for a complicated mathematical formalism. Energy dependent coefficients describe the Z-direction curvature of the cross-sections. The composition dependent quantities are the electron density and statistical moments describing the elemental distribution. We show that it is possible to describe elemental cross-sections for the entire periodic table and at energies above the K-edge (from 6 keV to 125 MeV), with an accuracy of better than 2% using a parameterization containing not more than five coefficients. For the biologically important elements 1 < or = Z < or = 20, and the energy range 30-150 keV, the parameterization utilizes four coefficients. At higher energies, the parameterization uses fewer coefficients with only two coefficients needed at megavoltage energies.

Electron capture to the continuum manifestation in fully differential cross sections for ion impact single ionization

NASA Astrophysics Data System (ADS)

Ciappina, M. F.; Fojón, O. A.; Rivarola, R. D.

2018-04-01

We present theoretical calculations of single ionization of He atoms by protons and multiply charged ions. The kinematical conditions are deliberately chosen in such a way that the ejected electron velocity matches the projectile impact velocity. The computed fully differential cross sections (FDCS) in the scattering plane using the continuum-distorted wave-eikonal initial state show a distinct peaked structure for a polar electron emission angle θ k = 0°. This element is absent when a first order theory is employed. Consequently, we can argue that this peak is a clear manifestation of a three-body effect, not observed before in FDCS. We discuss a possible interpretation of this new feature.

Photoexcitation and ionization in carbon dioxide - Theoretical studies in the separated-channel static-exchange approximation

NASA Technical Reports Server (NTRS)

Padial, N.; Csanak, G.; Mckoy, B. V.; Langhoff, P. W.

1981-01-01

Vertical-electronic static-exchange photoexcitation and ionization cross sections are reported which provide a first approximation to the complete dipole spectrum of CO2. Separated-channel static-exchange calculations of vertical-electronic transition energies and oscillator strengths, and Stieltjes-Chebyshev moment methods were used in the development. Detailed comparisons were made of the static-exchange excitation and ionization spectra with photoabsorption, electron-impact excitation, and quantum-defect estimates of discrete transition energies and intensities, and with partial-channel photoionization cross sections obtained from fluorescence measurements and from tunable-source and (e, 2e) photoelectron spectroscopy. Results show that the separate-channel static-exchange approximation is generally satisfactory in CO2.

Electron impact excitation of argon in the extreme vacuum ultraviolet

NASA Technical Reports Server (NTRS)

Mentall, J. E.; Morgan, H. D.

1976-01-01

Polarization-free excitation cross sections in the extreme vacuum ultraviolet have been measured for electron impact on Ar. Observed spectral features were those lines of Ar I and Ar II which lie between 700 and 1100 A. Excitation functions were measured for the Ar I resonance line at 1048 A and the Ar II resonance line at 920 A. Peak cross sections for these two lines were found to be (39.4 plus or minus 7.9) x 10 to the -18th and (6.9 plus or minus 1.4) x 10 to the -18th, respectively. At low energies, excitation of the Ar II resonance line is dominated by an electron exchange transition.

VUV dissociative excitation cross sections of H2O, NH3, and CH4 by electron impact. [Vacuum Ultra-Violet

NASA Technical Reports Server (NTRS)

Morgan, H. D.; Mentall, J. E.

1974-01-01

Absolute excitation functions for excited fragments resulting from electron bombardment of H2O, NH3, and CH4 by low-energy electrons (0 to 300 eV) have been measured in the vacuum ultraviolet (1100 to 1950 A). The predominant emission for each molecule was the H Lyman-alpha line, while the O I, N I, C I, and C II emissions were at least an order of magnitude weaker. Absolute cross sections at 100 eV are given along with the appearance potential of the various processes and the possible dissociative-excitation channels through which such processes proceed.

Absolute vibrational excitation cross sections for 1-18 eV electron scattering from condensed dimethyl phosphate (DMP)

NASA Astrophysics Data System (ADS)

Lemelin, V.; Bass, A. D.; Wagner, J. R.; Sanche, L.

2017-12-01

Absolute cross sections (CSs) for vibrational excitation by 1-18 eV electrons incident on condensed dimethyl phosphate (DMP) were measured with a high-resolution electron energy loss (EEL) spectrometer. Absolute CSs were extracted from EEL spectra of DMP condensed on multilayer film of Ar held at about 20 K under ultra-high vacuum (˜1 × 10-11 Torr). Structures observed in the energy dependence of the CSs around 2, 4, 7, and 12 eV were compared with previous results of gas- and solid-phase experiments and with theoretical studies on dimethyl phosphate and related molecules. These structures were attributed to the formation of shape resonances.

Triple differential cross section measurements for the outer valence molecular orbitals (1t2) of a methane molecule at 250 eV electron impact

NASA Astrophysics Data System (ADS)

Işık, N.; Doğan, M.; Bahçeli, S.

2016-03-01

In this study, detailed experimental research of triple differential cross section (TDCS) measurements is performed to investigate single ionization dynamics for the 1t2 orbital of methane molecule by 250 eV electron impact. In our experiments, the outgoing electrons are simultaneously measured in coincidence in a coplanar asymmetric geometry with the scattering angles of 10° and 20°. Therefore, TDCS measurements are performed for two different values of momentum transfer (K ≈ 0.9 au and 1.5 au). A detailed analysis of the dependence of the TDCS versus the momentum transfer is reported here.

Double Photoionization of helium atom using Screening Potential Approach

NASA Astrophysics Data System (ADS)

Saha, Haripada

2014-05-01

The triple differential cross section for double Photoionization of helium atom will be investigated using our recently extended MCHF method. It is well known that electron correlation effects in both the initial and the final states are very important. To incorporate these effects we will use the multi-configuration Hartree-Fock method to account for electron correlation in the initial state. The electron correlation in the final state will be taken into account using the angle-dependent screening potential approximation. The triple differential cross section (TDCS) will be calculated for 20 eV photon energy, which has experimental results. Our results will be compared with available experimental and the theoretical observations.

Total cross sections for electron scattering by 1-propanol at impact energies in the range 40-500 eV

NASA Astrophysics Data System (ADS)

da Silva, D. G. M.; Gomes, M.; Ghosh, S.; Silva, I. F. L.; Pires, W. A. D.; Jones, D. B.; Blanco, F.; Garcia, G.; Buckman, S. J.; Brunger, M. J.; Lopes, M. C. A.

2017-11-01

Absolute total cross section (TCS) measurements for electron scattering from 1-propanol molecules are reported for impact energies from 40 to 500 eV. These measurements were obtained using a new apparatus developed at Juiz de Fora Federal University—Brazil, which is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the molecules to be studied at a given pressure. Besides these experimental measurements, we have also calculated TCS using the Independent-Atom Model with Screening Corrected Additivity Rule and Interference (IAM-SCAR+I) approach with the level of agreement between them being typically found to be very good.

Electron- and proton-induced ionization of pyrimidine

DOE PAGES

Champion, Christophe; Quinto, Michele; Weck, Philippe F

2015-03-27

This present work describes a quantum-mechanically based model of the electron- and proton-induced ionization of isolated pyrimidine molecules. The impact energies range from the target ionization threshold up to ~1 keV for electrons and from 10 keV up to 10 MeV for protons. The cross-section calculations are performed within the 1st Born approximation in which the ejected electron is described by a Coulomb wave whereas the incident and the scattered projectiles are both described by plane waves. The pyrimidine target is described using the Gaussian 09 software package. Furthermore, our theoretical predictions obtained are in good agreement with experimental absolutemore » total cross sections, while large discrepancies are observed between existing semi-empirical models and the present calculations.« less

Photodetachment of electrons from amide and arsenide ions - The electron affinities of NH2., and AsH2.

NASA Technical Reports Server (NTRS)

Smyth, K. C.; Brauman, J. I.

1972-01-01

The relative cross section for the gas-phase photodetachment of electrons has been determined for NH2(-) in the wavelength region of 1195 to 1695 nm and for AsH2(-) in the region from 620 to 1010 nm. An ion cyclotron resonance spectrometer was used to generate, trap, and detect negative ions. A 1000-W xenon arc lamp with a grating monochromator was used as the light source, except for one series of experiments in which a tunable laser was employed. Single sharp thresholds were observed in both cross sections, and the following electron affinity values were determined: 0.744 (plus or minus 0.022) eV for NH2. and 1.27 (plus or minus 0.03) eV for AsH2.

Coupled-Sturmian and perturbative treatments of electron transfer and ionization in high-energy p-He+ collisions

NASA Astrophysics Data System (ADS)

Winter, Thomas G.; Alston, Steven G.

1992-02-01

Cross sections have been determined for electron transfer and ionization in collisions between protons and He+ ions at proton energies from several hundred kilo-electron-volts to 2 MeV. A coupled-Sturmian approach is taken, extending the work of Winter [Phys. Rev. A 35, 3799 (1987)] and Stodden et al. [Phys. Rev. A 41, 1281 (1990)] to high energies where perturbative approaches are expected to be valid. An explicit connection is made with the first-order Born approximation for ionization and the impulse version of the distorted, strong-potential Born approximation for electron transfer. The capture cross section is shown to be affected by the presence of target basis functions of positive energy near v2/2, corresponding to the Thomas mechanism.

Photoabsorption cross section of acetylene in the EUV region

NASA Technical Reports Server (NTRS)

Wu, C. Y. R.; Judge, D. L.

1985-01-01

The measurement of the absolute photoabsorption cross sections of C2H2 in the 175-740 A region by means of a double ionization chamber is reported. The continuum background source is the synchrotron radiation emitted by the Wisconsin 240 MeV electron storage ring. It is found that the cross sections range from 2 to a maximum of 36 Mb. Two new Rydberg series are identified and the cross section data are applied in the analysis of various sum rules. From the rules, it is shown that the data of C2H2 in the 580-1088 A range may be too low, while the measured ionization transition moment may be too high.

Calculations of Total Classical Cross Sections for a Central Field

NASA Astrophysics Data System (ADS)

Tsyganov, D. L.

2018-07-01

In order to find the total collision cross-section a direct method of the effective potential (EPM) in the framework of classical mechanics was proposed. EPM allows to over come both the direct scattering problem (calculation of the total collision cross-section) and the inverse scattering problem (reconstruction of the scattering potential) quickly and effectively. A general analytical expression was proposed for the generalized Lennard-Jones potentials: (6-3), (9-3), (12-3), (6-4), (8-4), (12-4), (8-6), (12-6), (18-6). The values for the scattering potential of the total cross section for pairs such as electron-N2, N-N, and O-O2 were obtained in a good approximation.

Electron interaction in matter

NASA Technical Reports Server (NTRS)

Dance, W. E.; Rainwater, W. J.; Rester, D. H.

1969-01-01

Data on the scattering of 1-MeV electrons in aluminum for the case of non-normal incidence, electron-bremsstrahlung cross-sections in thin targets, and the production of bremstrahlung by electron interaction in thick targets, are presented both in tabular and graphic form. These results may interest physicists and radiologists.

Electromagnetic Dissociation and Spacecraft Electronics Damage

NASA Technical Reports Server (NTRS)

Norbury, John W.

2016-01-01

When protons or heavy ions from galactic cosmic rays (GCR) or solar particle events (SPE) interact with target nuclei in spacecraft, there can be two different types of interactions. The more familiar strong nuclear interaction often dominates and is responsible for nuclear fragmentation in either the GCR or SPE projectile nucleus or the spacecraft target nucleus. (Of course, the proton does not break up, except possibly to produce pions or other hadrons.) The less familiar, second type of interaction is due to the very strong electromagnetic fields that exist when two charged nuclei pass very close to each other. This process is called electromagnetic dissociation (EMD) and primarily results in the emission of neutrons, protons and light ions (isotopes of hydrogen and helium). The cross section for particle production is approximately defined as the number of particles produced in nucleus-nucleus collisions or other types of reactions. (There are various kinematic and other factors which multiply the particle number to arrive at the cross section.) Strong, nuclear interactions usually dominate the nuclear reactions of most interest that occur between GCR and target nuclei. However, for heavy nuclei (near Fe and beyond) at high energy the EMD cross section can be much larger than the strong nuclear interaction cross section. This paper poses a question: Are there projectile or target nuclei combinations in the interaction of GCR or SPE where the EMD reaction cross section plays a dominant role? If the answer is affirmative, then EMD mechanisms should be an integral part of codes that are used to predict damage to spacecraft electronics. The question can become more fine-tuned and one can ask about total reaction cross sections as compared to double differential cross sections. These issues will be addressed in the present paper.

Compton Scattering Cross Sections in Strong Magnetic Fields: Advances for Neutron Star Applications

NASA Astrophysics Data System (ADS)

Ickes, Jesse; Gonthier, Peter L.; Eiles, Matthew; Baring, Matthew G.; Wadiasingh, Zorawar

2014-08-01

Various telescopes including RXTE, INTEGRAL, Suzaku and Fermi have detected steady non-thermal X-ray emission in the 10 ~ 200 keV band from strongly magnetic neutron stars known as magnetars. Magnetic inverse Compton scattering is believed to be a leading candidate for the production of this intense X-ray radiation. Generated by electrons possessing ultra-relativistic energies, this leads to attractive simplifications of the magnetic Compton cross section. We have recently addressed such a case by developing compact analytic expressions using correct spin-dependent widths acquired through the implementation of Sokolov & Ternov (ST) basis states, focusing specifically on ground state-to-ground state scattering. Such scattering in magnetar magnetospheres can cool electrons down to mildly-relativistic energies. Moreover, soft gamma-ray flaring in magnetars may well involve strong Comptonization in expanding clouds of mildly-relativistic pairs. These situations necessitate the development of more general magnetic scattering cross sections, where the incoming photons acquire substantial incident angles relative to the field in the rest frame of the electron, and the intermediate state can be excited to arbitrary Landau levels. Here, we highlight results from such a generalization using ST formalism. The cross sections treat the plethora of harmonic resonances associated with various cyclotron transitions between Landau states. Polarization dependence of the cross section for the four scattering modes is illustrated and compared with the non-relativistic Thompson cross section with classical widths. Results will find application to various neutron star problems, including computation of Eddington luminosities and polarization mode-switching rates in transient magnetar fireballs.We express our gratitude for the generous support of Michigan Space Grant Consortium, the National Science Foundation (grants AST-0607651, AST-1009725, AST-1009731 and PHY/DMR-1004811), and the NASA Astrophysics Theory Program through grants NNX06AI32G, NNX09AQ71G and NNX10AC59A.

Influence of cross-sectional geometry on the sensitivity and hysteresis of liquid-phase electronic pressure sensors

NASA Astrophysics Data System (ADS)

Park, Yong-Lae; Tepayotl-Ramirez, Daniel; Wood, Robert J.; Majidi, Carmel

2012-11-01

Cross-sectional geometry influences the pressure-controlled conductivity of liquid-phase metal channels embedded in an elastomer film. These soft microfluidic films may function as hyperelastic electric wiring or sensors that register the intensity of surface pressure. As pressure is applied to the elastomer, the cross-section of the embedded channel deforms, and the electrical resistance of the channel increases. In an effort to improve sensitivity and reduce sensor nonlinearity and hysteresis, we compare the electrical response of 0.25 mm2 channels with different cross-sectional geometries. We demonstrate that channels with a triangular or concave cross-section exhibit the least nonlinearity and hysteresis over pressures ranging from 0 to 70 kPa. These experimental results are in reasonable agreement with predictions made by theoretical calculations that we derive from elasticity and Ohm's Law.

High-Energy Electron-Induced SEUs and Jovian Environment Impact

NASA Astrophysics Data System (ADS)

Tali, Maris; Alía, Rubén García; Brugger, Markus; Ferlet-Cavrois, Veronique; Corsini, Roberto; Farabolini, Wilfrid; Mohammadzadeh, Ali; Santin, Giovanni; Virtanen, Ari

2017-08-01

We present experimental evidence of electron-induced upsets in a reference European Space Agency (ESA) single event upset (SEU) monitor, induced by a 200-MeV electron beam at the Very energetic Electronic facility for Space Planetary Exploration in harsh Radiation environments facility at CERN. Comparison of experimental cross sections and simulated cross sections is shown and the differences are analyzed. Possible secondary contributions to the upset rate by neutrons, flash effects, and cumulative dose effects are discussed, showing that electronuclear reactions are the expected SEU mechanism. The ESA Jupiter Icy Moons Explorer mission, to be launched in 2022, presents a challenging radiation environment due to the intense high-energy electron flux in the trapped radiation belts. Insight is given to the possible contribution of electrons to the overall upset rates in the Jovian radiation environment. Relative contributions of both typical electron and proton spectra created when the environmental spectra are transported through a typical spacecraft shielding are shown and the different mission phases are discussed.

The Electronic-Vibrational Behaviour of O2 in the Upper Atmosphere under Night-time Auroral Conditions

NASA Astrophysics Data System (ADS)

Jones, D. B.; Cartwright, D. C.; Campbell, L.; Teubner, P. J. O.; Brunger, M. J.; Bottema, M. J.

2004-09-01

We report on the extension of our Statistical Equlibrium Code (SEC) to determine the electronic-vibrational behaviour of O2 in the thermosphere, under night-time auroral conditions. This work was necessitated by the inadequacies in previous studies where the electron-impact cross section data bases employed have been superceeded, and/or direct excitation of states via electron impact has been neglected. Here we use the latest electron-impact cross section data bases to present the first electron-impact excitation rates for the 8 lowest lying electronic states of O_2. We then use these rates in conjunction with the most accurately available Franck-Condon factors, transition probabilities and quenching rates to determine the excited state populations. Note that predissociation, which is important for O_2, is also included in our model. We present radiative rates for various transitions and compare these results with those from other models and experimental rocket measurements.

Electron-Impact Ionization and Dissociative Ionization of Biomolecules

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Chaban, Galina M.; Dateo, Christopher E.

2006-01-01

It is well recognized that secondary electrons play an important role in radiation damage to humans. Particularly important is the damage of DNA by electrons, potentially leading to mutagenesis. Molecular-level study of electron interaction with DNA provides information on the damage pathways and dominant mechanisms. Our study of electron-impact ionization of DNA fragments uses the improved binary-encounter dipole model and covers DNA bases, sugar phosphate backbone, and nucleotides. An additivity principle is observed. For example, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3(sup prime)- and C5 (sup prime)-deoxyribose-phospate cross sections, differing by less than 5%. Investigation of tandem double lesion initiated by electron-impact dissociative ionization of guanine, followed by proton reaction with the cytosine in the Watson-Crick pair, is currently being studied to see if tandem double lesion can be initiated by electron impact. Up to now only OH-induced tandem double lesion has been studied.

Experimental and theoretical triple differential cross sections for electron-impact ionization of Ar (3p) for equal energy final state electrons

NASA Astrophysics Data System (ADS)

Amami, Sadek; Ozer, Zehra N.; Dogan, Mevlut; Yavuz, Murat; Varol, Onur; Madison, Don

2016-09-01

There have been several studies of electron-impact ionization of inert gases for asymmetric final state energy sharing and normally one electron has an energy significantly higher than the other. However, there have been relatively few studies examining equal energy final state electrons. Here we report experimental and theoretical triple differential cross sections for electron impact ionization of Ar (3p) for equal energy sharing of the outgoing electrons. Previous experimental results combined with some new measurements are compared with distorted wave born approximation (DWBA) results, DWBA results using the Ward-Macek (WM) approximation for the post collision interaction (PCI), and three-body distorted wave (3DW) which includes PCI without approximation. The results show that it is crucially important to include PCI in the calculation particularly for lower energies and that the WM approximation is valid only for high energies. The 3DW, on the other hand, is in reasonably good agreement with data down to fairly low energies.

Investigations of the valence-shell excitations of molecular ethane by high-energy electron scattering

NASA Astrophysics Data System (ADS)

Xu, Wei-Qing; Xu, Long-Quan; Qi, De-Guang; Chen, Tao; Liu, Ya-Wei; Zhu, Lin-Fan

2018-04-01

The differential cross sections and generalized oscillator strengths for the low-lying excitations of the valence-shell 1eg orbital electron in ethane have been measured for the first time at a high incident electron energy of 1500 eV and a scattering angular range of 1.5°-10°. A weak feature, termed X here, with a band center of about 7.5 eV has been observed, which was also announced by the previous experimental and theoretical studies. The dynamic behaviors of the generalized oscillator strengths for the 3s (8.7 eV), 3s+3p (9.31 eV, 9.41 eV), and X (˜7.5 eV) transitions on the momentum transfer squared have been obtained. The integral cross sections of these transitions from their thresholds to 5000 eV have been obtained with the aid of the BE-scaling (B is the binding energy and E is the excitation energy) method. The optical oscillator strengths of the above transitions determined by extrapolating their generalized oscillator strengths to the limit of the squared momentum transfer K2 → 0 are in good agreement with the ones from the photoabsorption spectrum [J. W. Au et al., Chem. Phys. 173, 209 (1993)], which indicates that the present differential cross sections, generalized oscillator strengths, and integral cross sections can serve as benchmark data.

Average-atom treatment of relaxation time in x-ray Thomson scattering from warm dense matter.

PubMed

Johnson, W R; Nilsen, J

2016-03-01

The influence of finite relaxation times on Thomson scattering from warm dense plasmas is examined within the framework of the average-atom approximation. Presently most calculations use the collision-free Lindhard dielectric function to evaluate the free-electron contribution to the Thomson cross section. In this work, we use the Mermin dielectric function, which includes relaxation time explicitly. The relaxation time is evaluated by treating the average atom as an impurity in a uniform electron gas and depends critically on the transport cross section. The calculated relaxation rates agree well with values inferred from the Ziman formula for the static conductivity and also with rates inferred from a fit to the frequency-dependent conductivity. Transport cross sections determined by the phase-shift analysis in the average-atom potential are compared with those evaluated in the commonly used Born approximation. The Born approximation converges to the exact cross sections at high energies; however, differences that occur at low energies lead to corresponding differences in relaxation rates. The relative importance of including relaxation time when modeling x-ray Thomson scattering spectra is examined by comparing calculations of the free-electron dynamic structure function for Thomson scattering using Lindhard and Mermin dielectric functions. Applications are given to warm dense Be plasmas, with temperatures ranging from 2 to 32 eV and densities ranging from 2 to 64 g/cc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, W. R.; Nilsen, J.

Here, the influence of finite relaxation times on Thomson scattering from warm dense plasmas is examined within the framework of the average-atom approximation. Presently most calculations use the collision-free Lindhard dielectric function to evaluate the free-electron contribution to the Thomson cross section. In this work, we use the Mermin dielectric function, which includes relaxation time explicitly. The relaxation time is evaluated by treating the average atom as an impurity in a uniform electron gas and depends critically on the transport cross section. The calculated relaxation rates agree well with values inferred from the Ziman formula for the static conductivity andmore » also with rates inferred from a fit to the frequency-dependent conductivity. Transport cross sections determined by the phase-shift analysis in the average-atom potential are compared with those evaluated in the commonly used Born approximation. The Born approximation converges to the exact cross sections at high energies; however, differences that occur at low energies lead to corresponding differences in relaxation rates. The relative importance of including relaxation time when modeling x-ray Thomson scattering spectra is examined by comparing calculations of the free-electron dynamic structure function for Thomson scattering using Lindhard and Mermin dielectric functions. Applications are given to warm dense Be plasmas, with temperatures ranging from 2 to 32 eV and densities ranging from 2 to 64 g/cc.« less

Average-atom treatment of relaxation time in x-ray Thomson scattering from warm dense matter

DOE PAGES

Johnson, W. R.; Nilsen, J.

2016-03-14

Here, the influence of finite relaxation times on Thomson scattering from warm dense plasmas is examined within the framework of the average-atom approximation. Presently most calculations use the collision-free Lindhard dielectric function to evaluate the free-electron contribution to the Thomson cross section. In this work, we use the Mermin dielectric function, which includes relaxation time explicitly. The relaxation time is evaluated by treating the average atom as an impurity in a uniform electron gas and depends critically on the transport cross section. The calculated relaxation rates agree well with values inferred from the Ziman formula for the static conductivity andmore » also with rates inferred from a fit to the frequency-dependent conductivity. Transport cross sections determined by the phase-shift analysis in the average-atom potential are compared with those evaluated in the commonly used Born approximation. The Born approximation converges to the exact cross sections at high energies; however, differences that occur at low energies lead to corresponding differences in relaxation rates. The relative importance of including relaxation time when modeling x-ray Thomson scattering spectra is examined by comparing calculations of the free-electron dynamic structure function for Thomson scattering using Lindhard and Mermin dielectric functions. Applications are given to warm dense Be plasmas, with temperatures ranging from 2 to 32 eV and densities ranging from 2 to 64 g/cc.« less

Implementation of new physics models for low energy electrons in liquid water in Geant4-DNA.

PubMed

Bordage, M C; Bordes, J; Edel, S; Terrissol, M; Franceries, X; Bardiès, M; Lampe, N; Incerti, S

2016-12-01

A new alternative set of elastic and inelastic cross sections has been added to the very low energy extension of the Geant4 Monte Carlo simulation toolkit, Geant4-DNA, for the simulation of electron interactions in liquid water. These cross sections have been obtained from the CPA100 Monte Carlo track structure code, which has been a reference in the microdosimetry community for many years. They are compared to the default Geant4-DNA cross sections and show better agreement with published data. In order to verify the correct implementation of the CPA100 cross section models in Geant4-DNA, simulations of the number of interactions and ranges were performed using Geant4-DNA with this new set of models, and the results were compared with corresponding results from the original CPA100 code. Good agreement is observed between the implementations, with relative differences lower than 1% regardless of the incident electron energy. Useful quantities related to the deposited energy at the scale of the cell or the organ of interest for internal dosimetry, like dose point kernels, are also calculated using these new physics models. They are compared with results obtained using the well-known Penelope Monte Carlo code. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Electron ionization cross-section calculations for liquid water at high impact energies

NASA Astrophysics Data System (ADS)

Bousis, C.; Emfietzoglou, D.; Hadjidoukas, P.; Nikjoo, H.; Pathak, A.

2008-04-01

Cross-sections for the ionization of liquid water is perhaps the most essential set of data needed for modeling electron transport in biological matter. The complexity of ab initio calculations for any multi-electron target has led to largely heuristic semi-empirical models which take advantage elements of the Bethe, dielectric and binary collision theories. In this work we present various theoretical models for calculating total ionization cross-sections (TICSs) for liquid water over the 10 keV-1 MeV electron energy range. In particular, we extend our recent dielectric model calculations for liquid water to relativistic energies using both the appropriate kinematic corrections and the transverse part. Comparisons are made with widely used atomic and molecular TICS models such as those of Khare and co-workers, Kim-Rudd, Deutsch-Märk, Vriens and Gryzinski. The required dipole oscillator strength was provided by our recent optical-data model which is based on the latest experimental data for liquid water. The TICSs computed by the above models differ by up to 40% from the dielectric results. The best agreement (to within ∼10%) was obtained by Khare's original model and an approximate form of Gryzinski's model. In contrast, the binary-encounter-dipole (BED) models of both Kim-Rudd and Khare and co-workers resulted in ∼10-20% higher TICS values, while discrepancies increased to ∼30-40% when their simpler binary-encounter-Bethe (BEB) versions were used. Finally, we discuss to what extent the accuracy of the TICS is indicative of the reliability of the underlying differential cross-sections.

Probing photoelectron multiple interferences via Fourier spectroscopy in energetic photoionization of Xe@C60

NASA Astrophysics Data System (ADS)

Potter, Andrea; McCune, Matthew A.; de, Ruma; Madjet, Mohamed E.; Chakraborty, Himadri S.

2010-09-01

Considering the photoionization of the Xe@C60 endohedral compound, we study in detail the ionization cross sections of various levels of the system at energies higher than the plasmon resonance region. Five classes of single-electron levels are identified depending on their spectral character. Each class engenders distinct oscillations in the cross section, emerging from the interference between active ionization modes specific to that class. Analysis of the cross sections based on their Fourier transforms unravels oscillation frequencies that carry unique fingerprints of the emitting level.

Dissociative excitation of the N(+)(5S) state by electron impact on N2 - Excitation function and quenching

NASA Technical Reports Server (NTRS)

Erdman, P. W.; Zipf, E. C.

1986-01-01

Metastable N(+)(5S) ions were produced in the laboratory by dissociative excitation of N2 with energetic electrons. The resulting radiative decay of the N(+)(5S) state was observed with sufficient resolution to completely resolve the doublet from the nearby N2 molecular radiation. The excitation function was measured from threshold to 500 eV. The cross section peaks at a high electron energy and also exhibits a high threshold energy both of which are typical of dissociative excitation-ionization processes. This finding complicates the explanation of electron impact on N2 as the mechanism for the source of the 2145 A 'auroral mystery feature' by further increasing the required peak cross section. It is suggested that the apparent N(+)(5S) quenching in auroras may be an artifact due to the softening of the electron energy spectrum in the auroral E region.

Electron impact excitation of the electronic states of N2. III - Transitions in the 12.5-14.2-eV energy-loss region at incident energies of 40 and 60 eV

NASA Technical Reports Server (NTRS)

Chutjian, A.; Trajmar, S.; Cartwright, D. C.

1977-01-01

Analysis of electron energy-loss data at incident electron energies of 40 and 60 eV has led to the determination of normalized absolute differential cross sections for electron-impact excitation of five optically-allowed singlet states, two known triplet states, and two unknown triplet-like states of N2, lying in the energy-loss range 12.5-14.2 eV. The range of scattering angles was 5 to 138 deg. The optically allowed transitions and the known triplet excitations are identified. Cross sections for excitation to two unidentified triplet-like states at 13.155 and 13.395 eV were also obtained. The relationship of the generalized oscillator strength for the dipole-allowed states obtained from the described data to known optical oscillator strengths is discussed.

Photodissociation of anisole and absolute photoionization cross-section of the phenoxy radical.

PubMed

Xu, Hong; Pratt, S T

2013-11-21

We have studied the photodissociation dynamics of anisole (C6H5OCH3) at 193 nm and determined the absolute photoionization cross-section of the phenoxy radical at 118.2 nm (10.486 eV) relative to the known cross-section of the methyl radical. Even at this energy, there is extensive fragmentation of the phenoxy radical upon photoionization, which is attributed to ionizing transitions that populate low-lying excited electronic states of the cation. For phenoxy radicals with less than ∼1 eV of internal energy, we find a cross-section for the production of the phenoxy cation of 14.8 ± 3.8 Mb. For radicals with higher internal energy, dissociative ionization is the dominant process, and for internal energies of ∼2.7-3.7 eV, we find a total cross-section (photoionization plus dissociative ionization) of 22.3 ± 4.1 Mb. The results are discussed relative to the recently reported photoionization cross-section of phenol.

Population inversion calculations using near resonant charge exchange as a pumping mechanism

NASA Technical Reports Server (NTRS)

Chubb, D. L.; Rose, J. R.

1972-01-01

Near resonance charge exchange between ions of a large ionization potential gas such as helium or neon and vapors of metals such as zinc, cadmium, selenium, or tellurium has produced laser action in the metal ion gas. The possibility of obtaining population inversions in near resonant charge exchange systems (Xe-Ca, Xe-Mg, Xe-Sr, Xe-Ba, Ar-Mg, N-Ca) was investigated. The analysis is an initial value problem that utilizes rate equations for the densities of relevant levels of the laser gas (Ca, Ba, Mg, or Sr) and an electron energy equation. Electron excitation rates are calculated using the Bohr-Thomson approximation for the cross section. Approximations to experimental values of the electron ionization cross section and the ion-atom charge exchange cross section are used. Preliminary results have been obtained for the Ca-Xe system and show that it is possible to obtain gains greater than 10 to the 14th power/m with inversion times up to 8x10 to the minus 7th power second. A possible charge exchange laser system using a MPD arc plasma accelerator is also described.

LETTER TO THE EDITOR: Iteratively-coupled propagating exterior complex scaling method for electron hydrogen collisions

NASA Astrophysics Data System (ADS)

Bartlett, Philip L.; Stelbovics, Andris T.; Bray, Igor

2004-02-01

A newly-derived iterative coupling procedure for the propagating exterior complex scaling (PECS) method is used to efficiently calculate the electron-impact wavefunctions for atomic hydrogen. An overview of this method is given along with methods for extracting scattering cross sections. Differential scattering cross sections at 30 eV are presented for the electron-impact excitation to the n = 1, 2, 3 and 4 final states, for both PECS and convergent close coupling (CCC), which are in excellent agreement with each other and with experiment. PECS results are presented at 27.2 eV and 30 eV for symmetric and asymmetric energy-sharing triple differential cross sections, which are in excellent agreement with CCC and exterior complex scaling calculations, and with experimental data. At these intermediate energies, the efficiency of the PECS method with iterative coupling has allowed highly accurate partial-wave solutions of the full Schrödinger equation, for L les 50 and a large number of coupled angular momentum states, to be obtained with minimal computing resources.

Calculations of total electron-impact ionization cross sections for Fluoroketone C5F10O and Fluoronitrile C4F7N using modified Deutsch-Märk formula

NASA Astrophysics Data System (ADS)

Xiong, Jiayu; Li, Xingwen; Wu, Jian; Guo, Xiaoxue; Zhao, Hu

2017-11-01

Both fluoroketone C5F10O and fluoronitrile C4F7N are promising substitute gases for SF6. The electron-impact ionization cross sections for these two gases are calculated using the Deutsch-Märk (DM) formula and its modified method. The necessary molecular geometry optimization and electron population were determined by ab initio calculation, which was performed with quantum chemistry code. The level of calculation, including the theoretical method and basis-set, are carefully determined. To eliminate the drawbacks of the DM formula, a modified DM formula is set in this paper. The modified DM formula, of which the weighting factors are changed, has a better agreement with the experimental data on both the peak and shape of the cross-section curves. The results calculated by DM formula and modified DM formula are given as references to fill in gaps in further research into C5F10O and C4F7N.

Evaluation of computational models and cross sections used by MCNP6 for simulation of characteristic X-ray emission from thick targets bombarded by kiloelectronvolt electrons

NASA Astrophysics Data System (ADS)

Poškus, A.

2016-09-01

This paper evaluates the accuracy of the single-event (SE) and condensed-history (CH) models of electron transport in MCNP6.1 when simulating characteristic Kα, total K (=Kα + Kβ) and Lα X-ray emission from thick targets bombarded by electrons with energies from 5 keV to 30 keV. It is shown that the MCNP6.1 implementation of the CH model for the K-shell impact ionization leads to underestimation of the K yield by 40% or more for the elements with atomic numbers Z < 15 and overestimation of the Kα yield by more than 40% for the elements with Z > 25. The Lα yields are underestimated by more than an order of magnitude in CH mode, because MCNP6.1 neglects X-ray emission caused by electron-impact ionization of L, M and higher shells in CH mode (the Lα yields calculated in CH mode reflect only X-ray fluorescence, which is mainly caused by photoelectric absorption of bremsstrahlung photons). The X-ray yields calculated by MCNP6.1 in SE mode (using ENDF/B-VII.1 library data) are more accurate: the differences of the calculated and experimental K yields are within the experimental uncertainties for the elements C, Al and Si, and the calculated Kα yields are typically underestimated by (20-30)% for the elements with Z > 25, whereas the Lα yields are underestimated by (60-70)% for the elements with Z > 49. It is also shown that agreement of the experimental X-ray yields with those calculated in SE mode is additionally improved by replacing the ENDF/B inner-shell electron-impact ionization cross sections with the set of cross sections obtained from the distorted-wave Born approximation (DWBA), which are also used in the PENELOPE code system. The latter replacement causes a decrease of the average relative difference of the experimental X-ray yields and the simulation results obtained in SE mode to approximately 10%, which is similar to accuracy achieved with PENELOPE. This confirms that the DWBA inner-shell impact ionization cross sections are significantly more accurate than the corresponding ENDF/B cross sections when energy of incident electrons is of the order of the binding energy.

Method of making a silicon nanowire device

DOEpatents

None, None

2017-05-23

There is provided an electronic device and a method for its manufacture. The device comprises an elongate silicon nanowire less than 0.5 .mu.m in cross-sectional dimensions and having a hexagonal cross-sectional shape due to annealing-induced energy relaxation. The method, in examples, includes thinning the nanowire through iterative oxidation and etching of the oxidized portion.

Compton Scattering Cross Sections in Strong Magnetic Fields: Advances for Neutron Star Applications

NASA Astrophysics Data System (ADS)

Eiles, Matthew; Gonthier, P. L.; Baring, M. G.; Wadiasingh, Z.

2013-04-01

Various telescopes including RXTE, INTEGRAL and Suzaku have detected non-thermal X-ray emission in the 10 - 200 keV band from strongly magnetic neutron stars. Inverse Compton scattering, a quantum-electrodynamical process, is believed to be a leading candidate for the production of this intense X-ray radiation. Magnetospheric conditions are such that electrons may well possess ultra-relativistic energies, which lead to attractive simplifications of the cross section. We have recently addressed such a case by developing compact analytic expressions using correct spin-dependent widths and Sokolov & Ternov (ST) basis states, focusing specifically on ground state-to-ground state scattering. However, inverse Compton scattering can cool electrons down to mildly-relativistic energies, necessitating the development of a more general case where the incoming photons acquire nonzero incident angles relative to the field in the rest frame of the electron, and the intermediate state can be excited to arbitrary Landau levels. In this paper, we develop results pertaining to this general case using ST formalism, and treating the plethora of harmonic resonances associated with various cyclotron transitions between Landau states. Four possible scattering modes (parallel-parallel, perpendicular-perpendicular, parallel-perpendicular, and perpendicular-parallel) encapsulate the polarization dependence of the cross section. We present preliminary analytic and numerical investigations of the magnitude of the extra Landau state contributions to obtain the full cross section, and compare these new analytic developments with the spin-averaged cross sections, which we develop in parallel. Results will find application to various neutron star problems, including computation of Eddington luminosities in the magnetospheres of magnetars. We express our gratitude for the generous support of the Michigan Space Grant Consortium, of the National Science Foundation (REU and RUI), and the NASA Astrophysics Theory and Fundamental Program.

Measurement of the production cross-section of pair of top quarks in a final state with di-electrons in the data collected by D0 experiment in Run-IIa (in French)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin Dit Latour, Bertrand

2008-09-29

The top quark has been discovered in 1995 by CDF and D0 collaborations in proton-antiproton collisions at the Tevatron. The amount of data recorded by both experiments makes it possible to accurately measure the properties of this very massive quark. This thesis is devoted to the measurement of the top pair production cross-section via the strong interaction, in a final state composed of two electrons, two particle jets and missing transverse energy. It is based on a 1 fb -1 data set collected by the D0 experiment between 2002 and 2006. The reconstruction and identification of electrons and jets ismore » of major importance in this analysis, and have been studied in events where a Z boson is produced together with one or more jets. The Z+jets process is indeed the dominant physics background to top pair production in the dielectron final state. The primary goal of this cross-section measurement is to verify Standard Model predictions. In this document, this result is also interpreted to indirectly extract the top quark mass. Moreover, the cross-section measurement is sensitive to new physics such as the existence of a charged Higgs boson. The selection established for the cross-section analysis has been used to search for a H + boson lighter than the top quark, where the latter can decay into a W + or H + boson and a b quark. The model that has been studied makes the assumption that the H + boson can only decay into a tau lepton and a neutrino.« less

Transmission effects in unfolding electronic-vibrational electron-molecule energy-loss spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Shiyang; Khakoo, Murtadha A.; Johnson, Paul V.

2006-03-15

The results of an investigation concerning the sensitivity of conventional unfolding methods applied to electronic-vibrational electron-energy-loss spectra to the transmission efficiency of electron spectrometers are presented. This investigation was made in an effort to understand differences in the differential cross sections for excitation of low-lying electronic states determined experimentally by various groups using electronic-vibrational energy-loss spectra of N{sub 2}. In these experiments, very similar spectral unfolding methods were used, which relied on similar Franck-Condon factors. However, the overall analyses of the electron scattering spectra (by the individual groups) resulted in large differences among the differential cross sections determined from thesemore » energy-loss spectra. The transmission response of the experimental apparatus to different-energy scattered electrons has often been discussed as a key factor that caused these disagreements. The present investigation shows in contrast that the effect of transmission is smaller than that required to independently explain such differences, implying that other systematic effects are responsible for the existing differences between measurements.« less

Effect of the Mott cross section on the determination of the charge of ultraheavy cosmic rays from emulsion tracks

NASA Technical Reports Server (NTRS)

Eby, P. B.; Morgan, S. H.; Parnell, T. A.

1978-01-01

Energy deposition due to secondary electrons is calculated as a function of distance from the axis of the track of a heavy ion. The calculation incorporates the empirical formulas of Kobetich and Katz (1968) for delta-ray energy dissipation. Both the Mott and Born-approximation expressions for the delta-ray energy distributions are used, and the results are compared. The energy deposition projected along a line perpendicular to the track is also calculated. These results are used to estimate the effect that the use of the Mott cross section would have in the interpretation of photometric measurements on emulsion tracks of trans-iron cosmic-ray particles. It is shown that the use of 50 keV as a characteristic track-formation electron energy to estimate the effect of the Mott cross section systematically overestimates charge as derived from emulsions for Z greater than 20.

Theoretical studies of photoexcitation and ionization in H2O

NASA Technical Reports Server (NTRS)

Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; Mckoy, B. V.; Langhoff, S. R.; Langhoff, P. W.

1982-01-01

Theoretical studies using Franck-Condon and static-exchange approximations are reported for the complete dipole excitation and ionization spectrum in H2O, where (1) large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground state equilibrium geometry, and (2) previously devised moment-theory techniques are employed in constructing the continuum oscillator-strength densities from the calculated spectra. Comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact-excitation cross sections, and dipole and synchrotron-radiation studies of partial-channel photoionization cross sections. The calculated partial-channel cross sections are found to be atomic-like, and dominated by 2p-kd components. It is suggested that the latter transition couples with the underlying 1b(1)-kb(1) channel, accounting for a prominent feature in recent synchrotron-radiation measurements.

Measurement of beauty photoproduction near threshold using di-electron events with the H1 detector at HERA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aaron, F. D.; Alexa, C.; Andreev, V.

The cross section formore » $$ep \\to e b\\bar{b} X$$ in photoproduction is measured with the H1 detector at the $ep$-collider HERA. The decay channel $$b\\bar{b} \\to ee X^\\prime$$ is selected by identifying the semi-electronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality $$Q^2 \\le 1 GeV^2$$, the inelasticity $$0.05 \\le y \\le 0.65$$ and the pseudorapidity of the $b$-quarks $$|\\eta(b)|$$,$$|\\eta(\\bar{b})| \\le 2$$. The differential production cross section is measured as a function of the average transverse momentum of the beauty quarks <$$P_T$$(b)> down to the threshold. The results are compared to next-to-leading-order QCD predictions.« less

Prediction of e± elastic scattering cross-section ratio based on phenomenological two-photon exchange corrections

NASA Astrophysics Data System (ADS)

Qattan, I. A.

2017-06-01

I present a prediction of the e± elastic scattering cross-section ratio, Re+e-, as determined using a new parametrization of the two-photon exchange (TPE) corrections to electron-proton elastic scattering cross section σR. The extracted ratio is compared to several previous phenomenological extractions, TPE hadronic calculations, and direct measurements from the comparison of electron and positron scattering. The TPE corrections and the ratio Re+e- show a clear change of sign at low Q2, which is necessary to explain the high-Q2 form factors discrepancy while being consistent with the known Q2→0 limit. While my predictions are in generally good agreement with previous extractions, TPE hadronic calculations, and existing world data including the recent two measurements from the CLAS and VEPP-3 Novosibirsk experiments, they are larger than the new OLYMPUS measurements at larger Q2 values.

Electron Impact Ionization of Heavier Ions including relativistic effects

NASA Astrophysics Data System (ADS)

Saha, B. C.; Haque, A. K. F.; Uddin, M. A.; Basak, A. K.

2006-11-01

The demands of the electron impact ionization cross sections in diverse fields are enormous. And this is hard to fulfill either by experimental or ab initio calculations. So various analytical and semi-classical models are applied for a rapid generation of ionization cross sections accurately. We have applied a modified version [1] of the Bell et. al. equations [2] including both the ionic and relativistic corrections. In this report we show how to generalize the MBELL parameters for treating the orbital quantum numbers nl dependency; the accuracy of the procedure is tested by evaluating cross sections for various species and energies. Detail results will be presented at the meeting. [1] A. K. F. Haque, M. A. Uddin, A. K. Basak, K. R. Karim and B. C. Saha, Phys. Rev. A73, 052703 (2006). [2] K. L. Bell, H. B. Gilbody, J. G. Hughes, A. E. Kingston, and F. J. Smith, J. Phys. Chem. Ref. Data 12, 891 (1983).

Effects of model approximations for electron, hole, and photon transport in swift heavy ion tracks

NASA Astrophysics Data System (ADS)

Rymzhanov, R. A.; Medvedev, N. A.; Volkov, A. E.

2016-12-01

The event-by-event Monte Carlo code, TREKIS, was recently developed to describe excitation of the electron subsystems of solids in the nanometric vicinity of a trajectory of a nonrelativistic swift heavy ion (SHI) decelerated in the electronic stopping regime. The complex dielectric function (CDF) formalism was applied in the used cross sections to account for collective response of a matter to excitation. Using this model we investigate effects of the basic assumptions on the modeled kinetics of the electronic subsystem which ultimately determine parameters of an excited material in an SHI track. In particular, (a) effects of different momentum dependencies of the CDF on scattering of projectiles on the electron subsystem are investigated. The 'effective one-band' approximation for target electrons produces good coincidence of the calculated electron mean free paths with those obtained in experiments in metals. (b) Effects of collective response of a lattice appeared to dominate in randomization of electron motion. We study how sensitive these effects are to the target temperature. We also compare results of applications of different model forms of (quasi-) elastic cross sections in simulations of the ion track kinetics, e.g. those calculated taking into account optical phonons in the CDF form vs. Mott's atomic cross sections. (c) It is demonstrated that the kinetics of valence holes significantly affects redistribution of the excess electronic energy in the vicinity of an SHI trajectory as well as its conversion into lattice excitation in dielectrics and semiconductors. (d) It is also shown that induced transport of photons originated from radiative decay of core holes brings the excess energy faster and farther away from the track core, however, the amount of this energy is relatively small.

Electronic excitation of carbonyl sulphide (COS) by high-resolution vacuum ultraviolet photoabsorption and electron-impact spectroscopy in the energy region from 4 to 11 eV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Limão-Vieira, P., E-mail: plimaovieira@fct.unl.pt; Department of Physics, Sophia University, Tokyo 102-8554; Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA

2015-02-14

The electronic state spectroscopy of carbonyl sulphide, COS, has been investigated using high resolution vacuum ultraviolet photoabsorption spectroscopy and electron energy loss spectroscopy in the energy range of 4.0–10.8 eV. The spectrum reveals several new features not previously reported in the literature. Vibronic structure has been observed, notably in the low energy absorption dipole forbidden band assigned to the (4π←3π) ({sup 1}Δ←{sup 1}Σ{sup +}) transition, with a new weak transition assigned to ({sup 1}Σ{sup −}←{sup 1}Σ{sup +}) reported here for the first time. The absolute optical oscillator strengths are determined for ground state to {sup 1}Σ{sup +} and {sup 1}Πmore » transitions. Based on our recent measurements of differential cross sections for the optically allowed ({sup 1}Σ{sup +} and {sup 1}Π) transitions of COS by electron impact, the optical oscillator strength f{sub 0} value and integral cross sections (ICSs) are derived by applying a generalized oscillator strength analysis. Subsequently, ICSs predicted by the scaling are confirmed down to 60 eV in the intermediate energy region. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of carbonyl sulphide in the upper stratosphere (20–50 km)« less

Free-Free Transitions of e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident Electron Energies

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Sinha, C.

2012-01-01

The free-free transition is studied for an electron-hydrogen in the ground state at low incident energies in the presence of an external homogenous, monochromatic, and linearly polarized laser-field inside a hot dense plasma.The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit, assuming that the plasma frequency is much higher than the laser frequency. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption /emission and no photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

Observation of enhanced zero-degree binary encounter electron production with decreasing charge-state q in 30 MeV O{sup q+} + O{sub 2} collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zouros, T.J.M.; Wong, K.L.; Hidmi, H.I.

We have measured binary encounter electron production in collisions of 30 MeV O{sup q+} projectiles (q=4-8) and O{sub 2} targets. Measured double differential BEe cross-sections are found to increase with decreasing charge-state q, in agreement with similar previously reported zero-degree investigations for H{sub 2} and He targets. However, measurements for the same system but at 25{degrees} shows the opposite trend, that BEe cross sections decrease slightly with decreasing charge state.

Electron-Impact Excitation Cross Sections for Modeling Non-Equilibrium Gas

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Liu, Yen; Panesi, Marco; Munafo, Alessandro; Wray, Alan; Carbon, Duane F.

2015-01-01

In order to provide a database for modeling hypersonic entry in a partially ionized gas under non-equilibrium, the electron-impact excitation cross sections of atoms have been calculated using perturbation theory. The energy levels covered in the calculation are retrieved from the level list in the HyperRad code. The downstream flow-field is determined by solving a set of continuity equations for each component. The individual structure of each energy level is included. These equations are then complemented by the Euler system of equations. Finally, the radiation field is modeled by solving the radiative transfer equation.

Low-energy electron scattering from atomic hydrogen. I. Ionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Childers, J.G.; James, K.E. Jr.; Bray, Igor

2004-02-01

Absolute doubly differential cross sections for the ionization of atomic hydrogen by electron impact have been measured at energies ranging from near threshold to intermediate values. The measurements are normalized to the accurate differential cross section for the electron-impact excitation of the H 1 {sup 2}S{yields}2 {sup 2}S+2 {sup 2}P transition. These measurements were made possible through the use of a moveable target source which enables the collection of hydrogen energy loss spectra free of all backgrounds. The measurements cover the incident electron energy range of 14.6-40 eV and scattering angles from 12 deg. to 127 deg., and are inmore » very good agreement with the results of the latest theoretical models--the convergent close-coupling model and the exterior complex scaling model.« less

Measurement of electron neutrino quasielastic and quasielasticlike scattering on hydrocarbon at $$\\langle E_{\

DOE PAGES

Wolcott, J.

2016-02-25

The first direct measurement of electron neutrino quasielastic and quasielasticlike scattering on hydrocarbon in the few-GeV region of incident neutrino energy has been carried out using the MINERvA detector in the NuMI beam at Fermilab. The flux-integrated differential cross sections in the electron production angle, electron energy, and Q 2 are presented. The ratio of the quasielastic, flux-integrated differential cross section in Q 2 for ν e with that of similarly selected ν μ-induced events from the same exposure is used to probe assumptions that underpin conventional treatments of charged-current νe interactions used by long-baseline neutrino oscillation experiments. Furthermore, themore » data are found to be consistent with lepton universality and are well described by the predictions of the neutrino event generator GENIE.« less

A review of electron-nucleus bremsstrahlung cross sections between 1 and 10 MeV

NASA Astrophysics Data System (ADS)

Mangiarotti, A.; Martins, M. N.

2017-12-01

More than 80 years have passed since the first calculations of electron-nucleus bremsstrahlung cross sections were published by Sommerfeld, for non-relativistic electrons, and, independently, by Sauter, Bethe and Heitler, and Racah, for relativistic electrons. The Bethe-Heitler expression, that is based on the first Born approximation and includes the screening of the Coulomb field of the nucleus by the atomic electrons, has proven to work well at moderately high energies where the Landau-Pomeranchuk-Migdal effect is negligible. We review the current theoretical and experimental status with a highlight on electrons with kinetic energies between 1 and 10 MeV. The choice is motivated by the peculiar difficulties present in this energy region, where it is necessary to treat simultaneously the interaction with the Coulomb field beyond the first Born approximation and the effect of screening. A fully numerical approach within the S-matrix formalism has proven to be extremely difficult above a few MeV, because the number of partial waves needed for an accurate evaluation is prohibitively large. Here we focus on analytic results, including the more complex ones employing the Furry-Sommerfeld-Maue wave functions and taking into account the next-to-leading order, and discuss the advantages and limitations in light of the best available data. The influence of multiple scattering in the target is investigated under the actual experimental conditions. A comparison with the widely used cross section tabulations by Seltzer and Berger is also presented.

Elastic and transport cross sections for inert gases in a hydrogen plasma

NASA Astrophysics Data System (ADS)

Krstic, Predrag

2005-05-01

Accurate elastic differential and integral scattering and transport cross sections have been computed using a fully quantum-mechanical approach for hydrogen ions (H^+, D^+ and T^+) colliding with Neon, Krypton and Xenon, in the center of mass energy range 0.1 to 200 eV. The momentum transfer and viscosity cross sections have been extended to higher keV collision energies using a classical, three-body scattering method. The results were compared with previously calculated values for Argon and Helium, as well as with simple analytical models. The cross sections, tabulated and available through the world wide web (www-cfadc.phy.ornl.gov) are of significance in fusion plasma modeling, gaseous electronics and other plasma applications.

Quantum tachyons

NASA Astrophysics Data System (ADS)

Tomaschitz, R.

2005-02-01

The interaction of superluminal radiation with matter in atomic bound-bound and bound-free transitions is investigated. We study transitions in the relativistic hydrogen atom effected by superluminal quanta. The superluminal radiation field is coupled by minimal substitution to the Dirac equation in a Coulomb potential. We quantize the interaction to obtain the transition matrix for induced and spontaneous superluminal radiation in hydrogen-like ions. The tachyonic photoelectric effect is scrutinized, the cross-sections for ground state ionization by transversal and longitudinal tachyons are derived. We examine the relativistic regime, high electronic ejection energies, as well as the first order correction to the non-relativistic cross-sections. In the ultra-relativistic limit, both the longitudinal and transversal cross-sections are peaked at small but noticeably different scattering angles. In the non-relativistic limit, the longitudinal cross-section has two maxima, and its minimum is located at the transversal maximum. Ionization cross-sections can thus be used to discriminate longitudinal radiation from transversal tachyons and photons.

Measurements of top quark pair relative differential cross-sections with ATLAS in pp collisions at $$\\sqrt{s} = 7\\ \\mbox{TeV}$$

DOE PAGES

Aad, G.; Abajyan, T.; Abbott, B.; ...

2013-01-15

Measurements are presented of differential cross sections for top quark pair production in pp collisions at √s = 7 TeV relative to the total inclusive top quark pair production cross-section. A data sample of 2.05 fb -1 recorded by the ATLAS detector at the Large Hadron Collider is used. Relative differential cross-sections are derived as a function of the invariant mass, the transverse momentum and the rapidity of the top quark pair system. Events are selected in the lepton (electron or muon) + jets channel. The backgroundsubtracted differential distributions are corrected for detector effects, normalized to the total inclusive topmore » quark pair production cross-section and compared to theoretical predictions. The measurement uncertainties range typically between 10 % and 20 % and are generally dominated by systematic effects. No significant deviations from the Standard Model expectations are observed.« less

Theoretical study of ArH+ dissociative recombination and electron-impact vibrational excitation

NASA Astrophysics Data System (ADS)

Abdoulanziz, A.; Colboc, F.; Little, D. A.; Moulane, Y.; Mezei, J. Zs; Roueff, E.; Tennyson, J.; Schneider, I. F.; Laporta, V.

2018-06-01

Cross sections are presented for dissociative recombination and electron-impact vibrational excitation of the ArH+ molecular ion at electron energies appropriate for the interstellar environment. The R-matrix method is employed to determine the molecular structure data, i.e. the position and width of the resonance states. The cross sections and the corresponding Maxwellian rate coefficients are computed using a method based on the Multichannel Quantum Defect Theory. The main result of the paper is the very low dissociative recombination rate found at temperatures below 1000K. This is in agreement with the previous upper limit measurement in merged beams and offers a realistic explanation to the presence of ArH+ in exotic interstellar conditions.

Cross-sectional aspect ratio modulated electronic properties in Si/Ge core/shell nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Nuo; Lu, Ning; Yao, Yong-Xin

2013-02-28

Electronic structures of (4, n) and (m, 4) (the NW has m layers parallel to the {1 1 1} facet and n layers parallel to {1 1 0}) Si/Ge core/shell nanowires (NWs) along the [1 1 2] direction with cross-sectional aspect ratio (m/n) from 0.36 to 2.25 are studied by first-principles calculations. An indirect to direct band gap transition is observed as m/n decreases, and the critical values of m/n and diameter for the transition are also estimated. The size of the band gap also depends on the aspect ratio. These results suggest that m/n plays an important role inmore » modulating the electronic properties of the NWs.« less

MORPH-I (Ver 1.0) a software package for the analysis of scanning electron micrograph (binary formatted) images for the assessment of the fractal dimension of enclosed pore surfaces

USGS Publications Warehouse

Mossotti, Victor G.; Eldeeb, A. Raouf; Oscarson, Robert

1998-01-01

MORPH-I is a set of C-language computer programs for the IBM PC and compatible minicomputers. The programs in MORPH-I are used for the fractal analysis of scanning electron microscope and electron microprobe images of pore profiles exposed in cross-section. The program isolates and traces the cross-sectional profiles of exposed pores and computes the Richardson fractal dimension for each pore. Other programs in the set provide for image calibration, display, and statistical analysis of the computed dimensions for highly complex porous materials. Requirements: IBM PC or compatible; minimum 640 K RAM; mathcoprocessor; SVGA graphics board providing mode 103 display.

Electron impact ionization dynamics of para-benzoquinone

NASA Astrophysics Data System (ADS)

Jones, D. B.; Ali, E.; Ning, C. G.; Colgan, J.; Ingólfsson, O.; Madison, D. H.; Brunger, M. J.

2016-10-01

Triple differential cross sections (TDCSs) for the electron impact ionization of the unresolved combination of the 4 highest occupied molecular orbitals (4b3g, 5b2u, 1b1g, and 2b3u) of para-benzoquinone are reported. These were obtained in an asymmetric coplanar geometry with the scattered electron being observed at the angles -7.5°, -10.0°, -12.5° and -15.0°. The experimental cross sections are compared to theoretical calculations performed at the molecular 3-body distorted wave level, with a marginal level of agreement between them being found. The character of the ionized orbitals, through calculated momentum profiles, provides some qualitative interpretation for the measured angular distributions of the TDCS.

Electron- and positron-impact ionization of inert gases

NASA Astrophysics Data System (ADS)

Campeanu, R. I.; Walters, H. R. J.; Whelan, Colm T.

2018-06-01

Triple-differential cross sections (TDCS) are presented for the electron and positron impact ionization of inert gas atoms in a range of geometries where a number of significant few body effects compete to define the shape of the TDCS. Using both positrons and electrons as projectiles has opened up the possibility of performing complementary studies which could effectively isolate competing interactions which cannot be separately detected in an experiment with a single projectile. A comparison is presented between theory and the recent experiments of [Gavin, deLucio, and DuBois, Phys. Rev. A 95, 062703 (2017), 10.1103/PhysRevA.95.062703] for e± and contrasted with the results from earlier electron experiments. For the special case of xenon(5 p ), cross sections are presented for both electron- and positron-impact ionization in kinematics where the electron case appears well understood. The kinematics are then varied in order to focus on the possible role of distortion, exchange, and target wave-function effects.

Comptonization of thermal photons by relativistic electron beams

NASA Technical Reports Server (NTRS)

Daugherty, Joseph K.; Harding, Alice K.

1989-01-01

This paper presents a numerical calculation of gamma-ray emission produced by Compton scattering of relativistic electron beams on background thermal radiation, which includes spatial dependence of electron energy losses and cyclotron resonance scattering in a strong magnetic field. In the first version, the scattering is described by the fully relativistic Klein-Nishina cross section, but the magnetic field is neglected. In the second version, the scattering is described by the magnetic resonant cross section in the Thomson limit. It is found that when the magnetic field is not included, electron energy losses are important only at higher neutron star surface temperatures (T about 3,000,000 K). In the presence of a strong magnetic field, (10 to the 12th G), resonant scattering greatly increases electron energy losses, making scattering very efficient even at lower surface temperatures. Resulting photon and electron spectra for both cases ae discussed in relation to models for pulsar X-ray and gamma-ray emission.

Comparison of the effect of soft-core potentials and Coulombic potentials on bremsstrahlung during laser matter interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi R.; Becker, Valerie R.; Barrington, Kasey; Thurston, Jeremy; Ramunno, Lora; Ackad, Edward

2018-04-01

An intense, short laser pulse incident on rare-gas clusters can produce nano-plasmas containing energetic electrons. As these electrons undergo scattering, from both phonons and ions, they emit bremsstrahlung radiation. Here, we compare a theory of bremsstrahlung emission appropriate for the interaction of intense lasers with matter using soft-core potentials and Coulombic potentials. A new scaling for the radiation cross-section and the radiated power via bremsstrahlung is derived for a soft-core potential (which depends on the potential depth) and compared with the Coulomb potential. Calculations using the new scaling are performed for electrons in vacuum ultraviolet, infrared and mid-infrared laser pulses. The radiation cross-section and the radiation power via bremsstrahlung are found to increase rapidly with increases in the potential depth of up to around 200 eV and then become mostly saturated for larger depths while remaining constant for the Coulomb potential. In both cases, the radiation cross-section and the radiation power of bremsstrahlung decrease with increases in the laser wavelength. The ratio of the scattering amplitude for the soft-core potential and that for the Coulombic potential decreases exponentially with an increase in momentum transfer. The bremsstrahlung emission by electrons in plasmas may provide a broadband light source for diagnostics.

Photoionization of Ne Atoms and Ne + Ions Near the K Edge: PrecisionSpectroscopy and Absolute Cross-sections

DOE PAGES

Müller, Alfred; Bernhardt, Dietrich; Borovik, Alexander; ...

2017-02-17

Single, double, and triple photoionization of Ne + ions by single photons have been investigated at the synchrotron radiation source PETRA III in Hamburg, Germany. Absolute cross-sections were measured by employing the photon-ion merged-beams technique. Photon energies were between about 840 and 930 eV, covering the range from the lowest-energy resonances associated with the excitation of one single K-shell electron up to double excitations involving one K- and one L-shell electron, well beyond the K-shell ionization threshold. Also, photoionization of neutral Ne was investigated just below the K edge. The chosen photon energy bandwidths were between 32 and 500 meV,more » facilitating the determination of natural line widths. The uncertainty of the energy scale is estimated to be 0.2 eV. For comparison with existing theoretical calculations, astrophysically relevant photoabsorption cross-sections were inferred by summing the measured partial ionization channels. Discussion of the observed resonances in the different final ionization channels reveals the presence of complex Auger-decay mechanisms. The ejection of three electrons from the lowest K-shell-excited Ne + (1s2s 2p 6 2S 1/2) level, for example, requires cooperative interaction of at least four electrons.« less

Electron impact elastic and excitation cross-sections of the isomers of C4F6 molecule for plasma modeling

NASA Astrophysics Data System (ADS)

Gupta, Dhanoj; Song, Mi-Young; Baluja, K. L.; Choi, Heechol; Yoon, Jung-Sik

2018-06-01

We report the calculations of elastic (along with its symmetry components) and electronic excitation cross sections by electron impact of the three isomers of C4F6, namely, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluoro-2-butyne (2-C4F6), and hexafluorocyclobutene (c-C4F6) belonging to the point groups C2, D3d, and C2v, respectively, using the R-matrix approach. The electron energy range is from 0.01 eV to 12 eV. We have employed the cc-pVTZ basis set for C and F atoms to generate self-consistent field molecular orbitals to construct the target states for all the isomers included in our calculations. All the target states are constructed by including correlation effects in a configuration interaction (CI) approach. The target properties such as vertical excitation energies and dipole moment of all the isomers are in reasonable agreement with the literature values. Differences in the cross sections of these isomers are strongly influenced by the effect of correlation and polarization effects and their geometrical extent. We have included the ground state and many excited states of each isomer in the trial wave function of the entire scattering system. The resulting elastic cross sections are compared with the available experimental results. The agreement is reasonably good for energies above 5 eV. The shape resonances detected at 2.57, 2.95, and 3.20 eV for c-C4F6, 1,3-C4F6, and 2-C4F6 isomers are associated with the negative anion formation of C3F3- as observed in the mass spectrometry experiments. We have also performed 1-state CI calculation for all the isomers that include only the correlated ground state. The position of resonances shifts to lower energies as the number of target states is increased compared to 1-state calculation for all the isomers. The elastic cross section for 2-C4F6 isomer is larger than the other isomers because of its larger spatial extent. The present cross section data are important for plasma simulation and modeling, especially related to fluorocarbon plasma.

Dissociative attachment of electrons to N2O

NASA Technical Reports Server (NTRS)

Krishnakumar, E.; Srivastava, S. K.

1990-01-01

Cross sections for the production of O(-) from N2O by the process of dissociative electron attachment have been measured for electron-impact energies ranging from 0 to 50 eV. Three new O(-) peaks are observed. The present data above 5-eV electron-impact energy differ considerably from the previous measurements.

Determination of photoionization cross-sections of different organic molecules using gas chromatography coupled to single-photon ionization (SPI) time-of-flight mass spectrometry (TOF-MS) with an electron-beam-pumped rare gas excimer light source (EBEL): influence of molecular structure and analytical implications.

PubMed

Eschner, Markus S; Zimmermann, Ralf

2011-07-01

This work describes a fast and reliable method for determination of photoionization cross-sections (PICS) by means of gas chromatography (GC) coupled to single-photon ionization mass spectrometry (SPI-MS). Photoionization efficiency (PIE) data for 69 substances was obtained at a photon energy of 9.8 ± 0.4 eV using an innovative electron-beam-pumped rare gas excimer light source (EBEL) filled with argon. The investigated analytes comprise 12 alkylbenzenes as well as 11 other substituted benzenes, 23 n-alkanes, ten polyaromatic hydrocarbons, seven aromatic heterocycles, and six polyaromatic heterocycles. Absolute PICS for each substance at 9.8 eV are calculated from the relative photoionization efficiencies of the compounds with respect to benzene, whose photoionization cross-section data is well known. Furthermore, a direct correlation between the type of benzene substituents and their absolute PICS is presented and discussed in depth. Finally, comparison of previously measured photoionization cross-sections for 20 substances shows good agreement with the data of the present work.

Cross Sections for Electron-Impact Dissociation of Alternative Etching Gas, C3HF7O

NASA Astrophysics Data System (ADS)

Tanaka, Hideyuki; Toyoda, Hirotaka; Sugai, Hideo

1998-09-01

The search for alternative for perfluorocarbon gases from the environmental point of view has resulted in a new etching gas, C3HF7O (1,2,2,2-tetrafluoroethyl-trifluoromethyl ether, abbreviated as HFE-227). In this paper, the first measurement of the absolute cross sections for the dissociation of HFE-227, is reported.The neutral dissociation is measured from the threshold to 250 eV by appearance mass spectrometry in a dual electron beam device.The threshold energies for the neutral dissociation into CF, CF2 and CF3 are 14.7, 12.5 and 11.2 eV, respectively.The cross sections for the dissociation from HFE-227 into CF3 and CF are larger than those from c-C4F8 (octafluorocyclobutane), but not for the dissociation into CF2.Besides the neutral dissociation, the cross sections for the dissociative ionization of HFE-227 are extensively measured for the formation of twelve ionic species, i.e., CO+, CHO+, CF+, CHF+, CFO+, CF2+, CHF2+, CF3+, CHF3+, C2HF2O+, C2HF4+ and C2HF4O+.

Is localized infrared spectroscopy now possible in the electron microscope?

PubMed

Rez, Peter

2014-06-01

The recently developed in-column monochromators make it possible to record energy-c spectra with resolutions better than 30 meV from nanometer-sized regions. It should therefore in principle be possible to detect localized vibrational excitations. The scattering geometry in the electron microscope means that bond stretching in the specimen plane or longitudinal optic phonons dominate the scattering. Most promising for initial studies are vibrations with energies between 300 and 400 meV from hydrogen bonded to other atoms. Estimates of the scattering cross-sections on the basis of a simple model show that they are about the same as inner shell scattering cross-sections. Cross-sections also increase with charge transfer between the atoms, and theory incorporating realistic charge distributions shows that signal/noise is the only limitation to high-resolution imaging. Given the magnitude of the scattering cross-sections, minimizing the tail of the zero-loss peak is just as important as achieving a small-width at half-maximum. Improvements in both resolution and controlling the zero-loss tail will be necessary before it is practical to detect optic phonons in solids between 40 and 60 meV.

Measurement of Neutrino and Antineutrino Charged-Current Inclusive Cross Sections with the MINERvA Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devan, Joshua D.

2015-01-01

Neutrinos are a nearly massless, neutral particle in the Standard Model that only interact via the weak interaction. Experimental confirmation of neutrino oscillations, in which a neutrino created as a particular type (electron, muon or tau) can be observed as a different type after propagating some distance, earned the 2015 Nobel Prize in Physics. Neutrino oscillation experiments rely on accurate measurements of neutrino interactions with matter, such as that presented here. Neutrinos also provide a unique probe of the nucleus, complementary to electron scattering experiments. This thesis presents a measurement of the charged-current inclusive cross section for muon neutrinos and antineutrinos in the energy range 2 to 50 GeV with the MINERvA detector. MINERvA is a neutrino scattering experiment in the NuMI neutrino beam at Fermilab, near Chicago. A cross section measures the probability of an interaction occurring, measured here as a function of neutrino energy. To extract a cross section from data, the observed rate of interactions is corrected for detector efficiency and divided by the number of scattering nucleons in the target and the flux of neutrinos in the beam. The neutrino flux is determined with the low-more » $$\

Electron-impact dissociative excitation and ionization of N{sub 2}D{sup +}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fogle, M.; Bahati, E. M.; Bannister, M. E.

Absolute cross sections for electron-impact dissociation of N{sub 2}D{sup +} producing N{sub 2}{sup +}, ND{sup +}, and N{sup +} ion fragments were measured in the 5- to 100-eV range using a crossed electron-ion beams technique. In the 5- to 20-eV region, in which dissociative excitation (DE) is the principal contributing mechanism, N{sub 2}{sup +} production dominates. The N{sub 2}{sup +} + D dissociation channel shows a large resonant-like structure in the DE cross section, as observed previously in electron impact dissociation of triatomic dihydride species [M. Fogle, E. M. Bahati, M. E. Bannister, S. H. M. Deng, C. R. Vane,more » R. D. Thomas, and V. Zhaunerchyk, Phys. Rev. A 82, 042720 (2010)]. In the dissociative ionization (DI) region, 20- to 100-eV, N{sub 2}{sup +}, ND{sup +}, and N{sup +} ion fragment production are comparable. The observance of the ND{sup +} and N{sup +} ion fragments indicate breaking of the N - N bond along certain dissociation channels.« less

Cross-sectional characterization of the dewetting of a Au/Ni bilayer film.

PubMed

Cen, Xi; Thron, Andrew M; Zhang, Xinming; van Benthem, Klaus

2017-07-01

The solid state dewetting of Au/Ni bilayer films was investigated by cross-sectional transmission electron microscopy techniques, including energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy and precession electron diffraction. After annealing under high vacuum conditions the early stage of film agglomeration revealed significant changes in film morphology and chemical distribution. Both Au and Ni showed texturing. Despite the initial deposition sequence of the as-deposited Au/Ni/SiO 2 /Si interface structure, the majority of the metal/SiO 2 interface was Au/SiO 2 after annealing at 675°C for 1h. Void nucleation was predominantly observed at Au/Ni/SiO 2 triple junctions, rather than grain boundary grooving at free surface of the metal film. Detailed cross-sectional characterization reveals that the Au/Ni interface in addition to small amounts of metal alloying strongly affects film break-up and agglomeration kinetics. The formation of Au/SiO 2 interface sections is found to be energetically preferred over Ni/SiO 2 due to compressive stress in the as-deposited Ni layer. Void nucleation is observed at the film/substrate interface, while the formation of voids at Ni/Au phase boundaries inside the metal film is caused by the Kirkendall effect. Copyright © 2016 Elsevier B.V. All rights reserved.

Total photoproduction cross section measurement at HERA energies

NASA Astrophysics Data System (ADS)

Ahmed, T.; Andreev, V.; Andrieu, B.; Arpagaus, M.; Babaev, A.; Bärwolff, H.; Bán, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Beck, G. A.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bergstein, H.; Bernardi, G.; Bernet, R.; Berthon, U.; Bertrand-Coremans, G.; Besançon, M.; Biddulph, P.; Binder, E.; Bizot, J. C.; Blobel, V.; Borras, K.; Bosetti, P. C.; Boudry, V.; Bourdarios, C.; Brasse, F.; Braun, U.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Clarke, D.; Clegg, A. B.; Colombo, M.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cvach, J.; Dainton, J. B.; Danilov, M.; Dann, A. W. E.; Dau, W. D.; David, M.; Deffur, E.; Delcourt, B.; del Buono, L.; Devel, M.; de Roeck, A.; Dingus, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Drescher, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Eberle, M.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellis, N. N.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Feng, Y.; Fensome, I. F.; Ferencei, J.; Ferrarotto, F.; Flauger, W.; Fleischer, M.; Flower, P. S.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Fuhrmann, P.; Gabathuler, E.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gellrich, A.; Gennis, M.; Gensch, U.; Genzel, H.; Gerhards, R.; Gillespie, D.; Godfrey, L.; Goerlach, U.; Goerlich, L.; Goldberg, M.; Goodall, A. M.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Greif, H.; Grindhammer, G.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Handschuh, D.; Hanlon, E. M.; Hapke, M.; Harjes, J.; Hartz, P.; Haydar, R.; Haynes, W. J.; Heatherington, J.; Hedberg, V.; Hedgecock, R.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herma, R.; Herynek, I.; Hildesheim, W.; Hill, P.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Huet, Ph.; Hufnagel, H.; Huot, N.; Ibbotson, M.; Jabiol, M. A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Jönsson, L.; Johannsen, K.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kasarian, S.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Kaufmann, H. H.; Kenyon, I. R.; Kermiche, S.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhler, T.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurça, T.; Kurzhöfer, J.; Kuznik, B.; Lander, R.; Landon, M. P. J.; Langkau, R.; Lanius, P.; Laporte, J. F.; Lebedev, A.; Leuschner, A.; Leverenz, C.; Levin, D.; Levonian, S.; Ley, Ch.; Lindner, A.; Lindström, G.; Loch, P.; Lohmander, H.; Lopez, G. C.; Lüers, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, A.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Mikocki, S.; Milone, V.; Monnier, E.; Moreau, F.; Moreels, J.; Morris, J. V.; Morton, J. M.; Müller, K.; Murín, P.; Murray, S. A.; Nagovizin, V.; Naroska, B.; Naumann, Th.; Newton, D.; Nguyen, H. K.; Niebergall, F.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg, M.; Oberlack, H.; Obrock, H.; Olsson, J. E.; Orenstein, S.; Ould-Saada, F.; Pascaud, C.; Patel, G. D.; Peppel, E.; Peters, S.; Phillips, H. T.; Phillips, J. P.; Pichler, Ch.; Pilgram, W.; Pitzl, D.; Prosi, R.; Raupach, F.; Rauschnabel, K.; Reimer, P.; Ribarics, P.; Riech, V.; Riedlberger, J.; Rietz, M.; Robertson, S. M.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Royon, C.; Rudowicz, M.; Ruffer, M.; Rusakov, S.; Rybicki, K.; Ryseck, E.; Sacton, J.; Sahlmann, N.; Sanchez, E.; Sankey, D. P. C.; Savitsky, M.; Schacht, P.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmitz, W.; Schröder, V.; Schulz, M.; Schwind, A.; Scobel, W.; Seehausen, U.; Sell, R.; Seman, M.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Smolik, L.; Soloviev, Y.; Spitzer, H.; Staroba, P.; Steenbock, M.; Steffen, P.; Steinberg, R.; Steiner, H.; Stella, B.; Stephens, K.; Stier, J.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Taylor, R. E.; Thompson, G.; Thompson, R. J.; Tichomirov, I.; Trenkel, C.; Truöl, P.; Tchernyshov, V.; Turnau, J.; Tutas, J.; Urban, L.; Usik, A.; Valkar, S.; Valkarova, A.; Vallee, C.; van Esch, P.; Vartapetian, A.; Vazdik, Y.; Vecko, M.; Verrecchia, P.; Vick, R.; Villet, G.; Vogel, E.; Wacker, K.; Walker, I. W.; Walther, A.; Weber, G.; Wegener, D.; Wegner, A.; Wellisch, H. P.; Willard, S.; Winde, M.; Winter, G.-G.; Wolff, Th.; Womersley, L. A.; Wright, A. E.; Wulff, N.; Yiou, T. P.; Áçek, J.; Závada, P.; Zeitnitz, C.; Ziaeepour, H.; Zimmer, M.; Zimmermann, W.; Zomer, F.

1993-01-01

We present first results on the total photoproduction cross section measurement with the H1 detector at HERA. The data were extracted from low Q2 collisions of 26.7 GeV electrons with 820 GeV protons. The γp total cross section has been measured by two independent methods in the γp center of mass energy range from 90 to 290 GeV. For an average center of mass energy of 195 GeV a value of σtot (γp) = 159 +/- 7 (stat.) +/- 20 (syst.) μb was obtained. Supported by the Swedish Natural Science Research Council.

Time-dependent density functional theory description of total photoabsorption cross sections

NASA Astrophysics Data System (ADS)

Tenorio, Bruno Nunes Cabral; Nascimento, Marco Antonio Chaer; Rocha, Alexandre Braga

2018-02-01

The time-dependent version of the density functional theory (TDDFT) has been used to calculate the total photoabsorption cross section of a number of molecules, namely, benzene, pyridine, furan, pyrrole, thiophene, phenol, naphthalene, and anthracene. The discrete electronic pseudo-spectra, obtained in a L2 basis set calculation were used in an analytic continuation procedure to obtain the photoabsorption cross sections. The ammonia molecule was chosen as a model system to compare the results obtained with TDDFT to those obtained with the linear response coupled cluster approach in order to make a link with our previous work and establish benchmarks.

Subtraction method of computing QCD jet cross sections at NNLO accuracy

NASA Astrophysics Data System (ADS)

Trócsányi, Zoltán; Somogyi, Gábor

2008-10-01

We present a general subtraction method for computing radiative corrections to QCD jet cross sections at next-to-next-to-leading order accuracy. The steps needed to set up this subtraction scheme are the same as those used in next-to-leading order computations. However, all steps need non-trivial modifications, which we implement such that that those can be defined at any order in perturbation theory. We give a status report of the implementation of the method to computing jet cross sections in electron-positron annihilation at the next-to-next-to-leading order accuracy.

Reciprocity in the electronic stopping of slow ions in matter

NASA Astrophysics Data System (ADS)

Sigmund, P.

2008-04-01

The principle of reciprocity, i.e., the invariance of the inelastic excitation in ion-atom collisions against interchange of projectile and target, has been applied to the electronic stopping cross section of low-velocity ions and tested empirically on ion-target combinations supported by a more or less adequate amount of experimental data. Reciprocity is well obeyed (within ~10%) for many systems studied, and deviations exceeding ~20% are exceptional. Systematic deviations such as gas-solid or metal-insulator differences have been looked for but not identified on the present basis. A direct consequence of reciprocity is the equivalence of Z1 with Z2 structure for random slowing down. This feature is reasonably well supported empirically for ion-target combinations involving carbon, nitrogen, aluminium and argon. Reciprocity may be utilized as a criterion to reject questionable experimental data. In cases where a certain stopping cross section has not been or cannot be measured, the stopping cross section for the inverted system may be available and serve as a first estimate. It is suggested to build in reciprocity as a fundamental requirement into empirical interpolation schemes directed at the stopping of low-velocity ions. Examination of the SRIM and MSTAR codes reveals cases where reciprocity is obeyed accurately, but deviations of up to a factor of two are common. In case of heavy ions such as gold, electronic stopping cross sections predicted by SRIM are asserted to be almost an order of magnitude too high.

Neutrino-induced reactions on nuclei

NASA Astrophysics Data System (ADS)

Gallmeister, K.; Mosel, U.; Weil, J.

2016-09-01

Background: Long-baseline experiments such as the planned deep underground neutrino experiment (DUNE) require theoretical descriptions of the complete event in a neutrino-nucleus reaction. Since nuclear targets are used this requires a good understanding of neutrino-nucleus interactions. Purpose: Develop a consistent theory and code framework for the description of lepton-nucleus interactions that can be used to describe not only inclusive cross sections, but also the complete final state of the reaction. Methods: The Giessen-Boltzmann-Uehling-Uhlenbeck (GiBUU) implementation of quantum-kinetic transport theory is used, with improvements in its treatment of the nuclear ground state and of 2p2h interactions. For the latter an empirical structure function from electron scattering data is used as a basis. Results: Results for electron-induced inclusive cross sections are given as a necessary check for the overall quality of this approach. The calculated neutrino-induced inclusive double-differential cross sections show good agreement data from neutrino and antineutrino reactions for different neutrino flavors at MiniBooNE and T2K. Inclusive double-differential cross sections for MicroBooNE, NOvA, MINERvA, and LBNF/DUNE are given. Conclusions: Based on the GiBUU model of lepton-nucleus interactions a good theoretical description of inclusive electron-, neutrino-, and antineutrino-nucleus data over a wide range of energies, different neutrino flavors, and different experiments is now possible. Since no tuning is involved this theory and code should be reliable also for new energy regimes and target masses.

Evidence for Neutrals-Foreshock Electrons Impact at Mars

NASA Astrophysics Data System (ADS)

Mazelle, C. X.; Meziane, K.; Mitchell, D. L.; Garnier, P.; Espley, J. R.; Hamza, A. M.; Halekas, J.; Jakosky, B. M.

2018-05-01

Backstreaming electrons emanating from the bow shock of Mars reported from the Mars Atmosphere and Volatile EvolutioN/Solar Wind Electron Analyzer observations show a flux fall off with the distance from the shock. This feature is not observed at the terrestrial foreshock. The flux decay is observed only for electron energy E ≥ 29 eV. A reported recent study indicates that Mars foreshock electrons are produced at the shock in a mirror reflection of a portion of the solar wind electrons. In this context, and given that the electrons are sufficiently energetic to not be affected by the interplanetary magnetic field fluctuations, the observed flux decrease appears problematic. We investigate the possibility that the flux fall off with distance results from the impact of backstreaming electrons with Mars exospheric neutral hydrogen. We demonstrate that the flux fall off is consistent with the electron-atomic hydrogen impact cross section for a large range of energy. A better agreement is obtained for energy where the impact cross section is the highest. One important consequence is that foreshock electrons can play an important role in the production of pickup ions at Mars far exosphere.

Nonequilibrium calculations of the role of electron impact in the production of NO and its emissions

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.

2009-04-01

We review our recent work on nonequilibrium modelling of the density of nitric oxide and its infrared emissions in the Earth's upper atmosphere. The aim of these studies was to investigate the contribution of electron impact excitation to the NO density and the sensitivity of this process to the electron impact cross sections. The results are compared with satellite measurements of NO densities in equatorial and auroral high-latitude conditions and with rocket measurements of infrared emissions in auroral conditions. Particular findings are that electron impact excitation of N2 makes a significant contribution to the NO density at altitudes around 105 km and to auroral infrared emissions for the (1 → 0) ground-state emission from NO. The sensitivity of the NO fundamental emissions to various measured and theoretical integral cross sections is investigated and found to be significant.

Elucidating the charge carrier separation and working mechanism of CH3NH3PbI(3-x)Cl(x) perovskite solar cells.

PubMed

Edri, Eran; Kirmayer, Saar; Mukhopadhyay, Sabyasachi; Gartsman, Konstantin; Hodes, Gary; Cahen, David

2014-03-11

Developments in organic-inorganic lead halide-based perovskite solar cells have been meteoric over the last 2 years, with small-area efficiencies surpassing 15%. We address the fundamental issue of how these cells work by applying a scanning electron microscopy-based technique to cell cross-sections. By mapping the variation in efficiency of charge separation and collection in the cross-sections, we show the presence of two prime high efficiency locations, one at/near the absorber/hole-blocking-layer, and the second at/near the absorber/electron-blocking-layer interfaces, with the former more pronounced. This 'twin-peaks' profile is characteristic of a p-i-n solar cell, with a layer of low-doped, high electronic quality semiconductor, between a p- and an n-layer. If the electron blocker is replaced by a gold contact, only a heterojunction at the absorber/hole-blocking interface remains.

Plasma-screening effects on the electron-impact excitation of hydrogenic ions in dense plasmas

NASA Technical Reports Server (NTRS)

Jung, Young-Dae

1993-01-01

Plasma-screening effects are investigated on electron-impact excitation of hydrogenic ions in dense plasmas. Scaled cross sections Z(exp 4) sigma for 1s yields 2s and 1s yields 2p are obtained for a Debye-Hueckel model of the screened Coulomb interaction. Ground and excited bound wave functions are modified in the screened Coulomb potential (Debye-Hueckel model) using the Ritz variation method. The resulting atomic wave functions and their eigenenergies agree well with the numerical and high-order perturbation theory calculations for the interesting domain of the Debye length not less than 10. The Born approximation is used to describe the continuum states of the projectile electron. Plasma screening effects on the atomic electrons cannot be neglected in the high-density cases. Including these effects, the cross sections are appreciably increased for 1s yields 2s transitions and decreased for 1s yields 2p transitions.

Electron- and proton-induced ionization of pyrimidine

NASA Astrophysics Data System (ADS)

Champion, Christophe; Quinto, Michele A.; Weck, Philippe F.

2015-05-01

The present work describes a quantum-mechanically based model of the electron- and proton-induced ionization of isolated pyrimidine molecules. The impact energies range from the target ionization threshold up to ~1 keV for electrons and from 10 keV up to 10 MeV for protons. The cross-section calculations are performed within the 1st Born approximation in which the ejected electron is described by a Coulomb wave whereas the incident and the scattered projectiles are both described by plane waves. The pyrimidine target is described using the Gaussian 09 software package. The theoretical predictions obtained are in good agreement with experimental absolute total cross sections, while large discrepancies are observed between existing semi-empirical models and the present calculations. Contribution to the Topical Issue "COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy", edited by Andrey Solov'yov, Nigel Mason, Gustavo García, Eugene Surdutovich.

Coherence Measurements for Excited to Excited State Transitions in Barium

NASA Technical Reports Server (NTRS)

Trajmar, S.; Kanik, I.; Karaganov, V.; Zetner, P. W.; Csanak, G.

2000-01-01

Experimental studies concerning elastic and inelastic electron scattering by coherently ensembles of Ba (...6s6p (sub 1)P(sub 1)) atoms with various degrees of alignment will be described. An in-plane, linearly-polarized laser beam was utilized to prepare these target ensembles and the electron scattering signal as a function of polarization angle was measured for several laser geometries at fixed impact energies and scattering angles. From these measurements, we derived cross sections and electron-impact coherence parameters associated with the electron scattering process which is time reverse of the actual experimentally studied process. This interpretation of the experiment is based on the theory of Macek and Herte. The experimental results were also interpreted in terms of cross sections and collision parameters associated with the actual experimental processes. Results obtained so far will be presented and plans for further studies will be discussed.

Triple Differential Cross Sections for Ionization of Laser-Aligned Mg Atoms by electron impact

NASA Astrophysics Data System (ADS)

Amami, Sadek; Madison, Don; Nixon, Kate; Murray, Andrew

2013-09-01

3DW (3-body distorted wave) triple differential cross sections have been calculated for electron impact ionization of magnesium atoms aligned by lasers. Calculations have been performed for the kinematics of the experiment performed by Kate Nixon and Andrew Murray at Manchester, England [K. L. Nixon and A. J. Murray 2011 Phys. Rev. Lett. 106, 123201]. An incident projectile was produced with energy of 41.91eV, scattered and ejected electrons were detected with equal energies (E1 =E2 =20eV), the scattered projectile was detected at a fixed angle of 30deg, and the ejected electrons were detected at angles ranging between 0circ; - 180circ; . The theoretical 3DW results will be compared with the experimental data. This work is supported by the US National Science Foundation under Grant.No.PHY-1068237.

Electron and positron interaction with pyrimidine: A theoretical investigation

NASA Astrophysics Data System (ADS)

Sinha, Nidhi; Antony, Bobby

2018-03-01

Pyrimidine (C4H4N2) is considered as the building block of nucleobases, viz., cytosine, thymine and uracil. They provide a blueprint for probing the scattering of radiation by DNA and RNA bases. In this article, we report the elastic and total scattering cross-sections for electron and positron scattering from the pyrimidine molecule, employing a spherical complex optical potential (SCOP) formalism for an extensive energy range of 10 eV to 5 keV. In the case of positron scattering, the original SCOP formalism is modified to adequately solve the positron-target dynamics. Moreover, a reasonable agreement is observed between the present results and other available datasets, for both electron and positron scattering. The cross-sections for electron and positron impact scattering by pyrimidine are necessary input data for codes that seek to simulate radiation damage, and hence are useful to model biomolecular systems.

Dissociation of CH4 by electron impact: Production of metastable hydrogen and carbon fragments

NASA Technical Reports Server (NTRS)

Finn, T. G.; Carnahan, B. L.; Zipf, E. C.

1974-01-01

Metastable fragments produced by electron impact excitation of CH4 have been investigated for incident electron energies from threshold to 300 eV. Only metastable hydrogen and carbon atoms were observed. Onset energies for the production of metastable hydrogen atoms were observed at electron impact energies of 22.0 + or - .5 eV, 25.5 + or - .6 eV, 36.7 + or - .6 eV and 66 + or - 3 eV, and at 26.6 + or - .6 eV for the production of metastable carbon atoms. Most of the fragments appear to have been formed in high-lying Rydberg states. The total metastable hydrogen cross section reaches a maximum value of approximately 1 X 10 to the minus 18th power sq cm at 100 eV. At the same energy, the metastable carbon cross section is 2 x 10 to the minus 19th power sq cm.

Theoretical and Experimental Triple Differential Cross Sections for Electron Impact Ionization of SF6

NASA Astrophysics Data System (ADS)

Chaluvadi, Hari; Nixon, Kate; Murray, Andrew; Ning, Chuangang; Colgan, James; Madison, Don

2014-10-01

Experimental and theoretical Triply Differential Cross Sections (TDCS) will be presented for electron-impact ionization of sulfur hexafluoride (SF6) for the molecular orbital 1t1g. M3DW (molecular 3-body distorted wave) results will be compared with experiment for coplanar geometry and for perpendicular plane geometry (a plane which is perpendicular to the incident beam direction). In both cases, the final state electron energies and observation angles are symmetric and the final state electron energies range from 5 eV to 40 eV. It will be shown that there is a large difference between using the OAMO (orientation averaged molecular orbital) approximation and the proper average over all orientations and also that the proper averaged results are in much better agreement with experiment. Work supported by NSF under Grant Number PHY-1068237. Computational work was performed with Institutional resources made available through Los Alamos National Laboratory.

Radiative recombination data for tungsten ions: III.  W{sup 14+}–W{sup 23+}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trzhaskovskaya, M.B., E-mail: Trzhask@MT5605.spb.edu; Nikulin, V.K.

2014-09-15

This paper completes the cycle of our calculations of the radiative recombination and photoionization data for tungsten ions. Presented here are the photoionization and radiative recombination cross sections, radiative recombination rate coefficients, and radiated power loss rate coefficients for ten tungsten impurity ions from W{sup 14+} to W{sup 23+}. These data are required in diagnostics and modeling fusion plasmas studied in such devices as ITER, ASDEX Upgrade, and EBIT. Partial photoionization cross sections have been fitted by an analytical expression with five fit parameters tabulated here. Total radiative recombination cross sections are presented in the electron energy range from 1 eVmore » to ∼80 keV. Radiative recombination rates and radiated power loss rates are given in the temperature range from 10{sup 4}  K to 10{sup 9}  K. Calculations have been performed on the basis of the fully relativistic treatment of photoionization and radiative recombination taking into account all significant multipoles of the radiative field. Electron wave functions have been obtained by the Dirac–Fock method with the proper consideration of the electron exchange. The relativistic Maxwell–Jüttner distribution of continuum electrons has been used in calculations of radiative recombination rates and radiated power loss rates. This decreases values of the rates noticeably at a high temperature as compared to the usual non-relativistic Maxwell–Boltzmann distribution. -- Highlights: •Radiative recombination data for ten tungsten ions W{sup 14+}–W{sup 23+} are presented. •Photoionization cross sections are also given. •Calculations are fully relativistic including all multipoles of the radiative field. •We use the Dirac–Fock method to obtain the electron wave functions. •The data are required for diagnostics and modeling fusion plasmas studied in ITER.« less

Nuclear-Recoil Differential Cross Sections for the Two Photon Double Ionization of Helium

NASA Astrophysics Data System (ADS)

Abdel Naby, Shahin; Ciappina, M. F.; Lee, T. G.; Pindzola, M. S.; Colgan, J.

2013-05-01

In support of the reaction microscope measurements at the free-electron laser facility at Hamburg (FLASH), we use the time-dependent close-coupling method (TDCC) to calculate fully differential nuclear-recoil cross sections for the two-photon double ionization of He at photon energy of 44 eV. The total cross section for the double ionization is in good agreement with previous calculations. The nuclear-recoil distribution is in good agreement with the experimental measurements. In contrast to the single-photon double ionization, maximum nuclear recoil triple differential cross section is obtained at small nuclear momenta. This work was supported in part by grants from NSF and US DoE. Computational work was carried out at NERSC in Oakland, California and the National Institute for Computational Sciences in Knoxville, Tennessee.

Quantum-confinement effects on conduction band structure of rectangular cross-sectional GaAs nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, H., E-mail: tanaka@semicon.kuee.kyoto-u.ac.jp; Morioka, N.; Mori, S.

2014-02-07

The conduction band structure and electron effective mass of GaAs nanowires with various cross-sectional shapes and orientations were calculated by two methods, a tight-binding method and an effective mass equation taking the bulk full-band structure into account. The effective mass of nanowires increases as the cross-sectional size decreases, and this increase in effective mass depends on the orientations and substrate faces of nanowires. Among [001], [110], and [111]-oriented rectangular cross-sectional GaAs nanowires, [110]-oriented nanowires with wider width along the [001] direction showed the lightest effective mass. This dependence originates from the anisotropy of the Γ valley of bulk GaAs. Themore » relationship between effective mass and bulk band structure is discussed.« less

SU-E-T-489: Quantum versus Classical Trajectory Monte Carlo Simulations of Low Energy Electron Transport.

PubMed

Thomson, R; Kawrakow, I

2012-06-01

Widely-used classical trajectory Monte Carlo simulations of low energy electron transport neglect the quantum nature of electrons; however, at sub-1 keV energies quantum effects have the potential to become significant. This work compares quantum and classical simulations within a simplified model of electron transport in water. Electron transport is modeled in water droplets using quantum mechanical (QM) and classical trajectory Monte Carlo (MC) methods. Water droplets are modeled as collections of point scatterers representing water molecules from which electrons may be isotropically scattered. The role of inelastic scattering is investigated by introducing absorption. QM calculations involve numerically solving a system of coupled equations for the electron wavefield incident on each scatterer. A minimum distance between scatterers is introduced to approximate structured water. The average QM water droplet incoherent cross section is compared with the MC cross section; a relative error (RE) on the MC results is computed. RE varies with electron energy, average and minimum distances between scatterers, and scattering amplitude. The mean free path is generally the relevant length scale for estimating RE. The introduction of a minimum distance between scatterers increases RE substantially (factors of 5 to 10), suggesting that the structure of water must be modeled for accurate simulations. Inelastic scattering does not improve agreement between QM and MC simulations: for the same magnitude of elastic scattering, the introduction of inelastic scattering increases RE. Droplet cross sections are sensitive to droplet size and shape; considerable variations in RE are observed with changing droplet size and shape. At sub-1 keV energies, quantum effects may become non-negligible for electron transport in condensed media. Electron transport is strongly affected by the structure of the medium. Inelastic scatter does not improve agreement between QM and MC simulations of low energy electron transport in condensed media. © 2012 American Association of Physicists in Medicine.

Crossing the Internet Threshold: An Instructional Handbook. 2nd Edition.

ERIC Educational Resources Information Center

Tennant, Roy; Ober, John; Lipow, Anne G.

This how-to manual for the beginning Internet user contains sections on: the authors; an overview of computer networking; Internet basics, including a glossary, information on getting connected and keeping current, and a bibliography; electronic mail, including electronic discussions and electronic journals: Internet Remote Login (Telnet); File…

Electron Impact Ionization and Dissociative Ionization of C2H2

NASA Technical Reports Server (NTRS)

Srivastava, S. K.

1995-01-01

By utilizing a crossed electron beam collision geometry, a combination of time-of-flight (TOF) and quadrupole mass spectrometers, and the relative flow technique1 normalized values of cross sections and appearance energies (AP) were obtained for the formation of singly and multiply ionized species resulting from the ionization and dissociation of C2H2. Details ont he apparatus and technique have been published previously.2,3.

Dissociative Excitation of Acetylene Induced by Electron Impact: Excitation-emission Cross-sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Országh, Juraj; Danko, Marián; Čechvala, Peter

The optical emission spectrum of acetylene excited by monoenergetic electrons was studied in the range of 190–660 nm. The dissociative excitation and dissociative ionization associated with excitation of the ions initiated by electron impact were dominant processes contributing to the spectrum. The spectrum was dominated by the atomic lines (hydrogen Balmer series, carbon) and molecular bands (CH(A–X), CH(B–X), CH{sup +}(B–A), and C{sub 2}). Besides the discrete transitions, we have detected the continuum emission radiation of ethynyl radical C{sub 2}H(A–X). For most important lines and bands of the spectrum we have measured absolute excitation-emission cross sections and determined the energy thresholdsmore » of the particular dissociative channels.« less

Investigating the origin of efficiency droop by profiling the voltage across the multi-quantum well of an operating light-emitting diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Taewoong; Seong, Tae-Yeon; School of Materials Science and Engineering, Korea University, Seoul 136-713

Efficiency droop is a phenomenon in which the efficiency of a light-emitting diode (LED) decreases with the increase in current density. To analyze efficiency droop, direct experimental observations on the energy conversion occurring inside the LED is required. Here, we present the measured voltage profiles on the cross section of an operating LED and analyze them with the cross-sectional temperature profiles obtained in a previous study under the same operation conditions. The measured voltage profiles suggest that with increases in the injection current density, electron depletion shifts from the multi-quantum well through an electron blocking layer to the p-GaN region.more » This is because electron leakage increases with increases in current density.« less

Calculation of the total electron excitation cross section in the Born approximation using Slater wave functions for the Li (2s yields 2p), Li (2s yields 3p), Na (3s yields 4p), Mg (3p yields 4s), Ca (4s yields 4p) and K (4s yields 4p) excitations. M.S. Thesis

NASA Technical Reports Server (NTRS)

Simsic, P. L.

1974-01-01

Excitation of neutral atoms by inelastic scattering of incident electrons in gaseous nebulae were investigated using Slater Wave functions to describe the initial and final states of the atom. Total cross sections using the Born Approximation are calculated for: Li(2s yields 2p), Na(3s yields 4p), k(4s yields 4p). The intensity of emitted radiation from gaseous nebulae is also calculated, and Maxwell distribution is employed to average the kinetic energy of electrons.

Differential cross sections for excitation of H 2 by low-energy electron impact

DOE PAGES

Hargreaves, Leigh R.; Bhari, S.; Adjari, B.; ...

2017-10-31

Experimental and theoretical differential cross sections (DCS) for the electron-impact excitation of molecular hydrogen to themore » $$B{}^{1}{{\\rm{\\Sigma }}}_{u}^{+}$$, $$c{}^{3}{{\\rm{\\Pi }}}_{u}$$, $$a{}^{3}{{\\rm{\\Sigma }}}_{g}^{+}$$, $$C{}^{1}{{\\rm{\\Pi }}}_{u}$$, and the $$E(F){}^{1}{{\\rm{\\Sigma }}}_{g}^{+}$$ states are presented at incident energies near to threshold. The experimental DCSs were taken at incident energies of 14, 15, 16 and 17.5 eV and for scattering angles from 10° to 130°. In conclusion, the theoretical DCSs are from the convergent close-coupling method which has recently successfully modeled differential electron scattering from H 2 when compared with available experiment at energies of 17.5 eV and above.« less

Differential cross sections for excitation of H 2 by low-energy electron impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hargreaves, Leigh R.; Bhari, S.; Adjari, B.

Experimental and theoretical differential cross sections (DCS) for the electron-impact excitation of molecular hydrogen to themore » $$B{}^{1}{{\\rm{\\Sigma }}}_{u}^{+}$$, $$c{}^{3}{{\\rm{\\Pi }}}_{u}$$, $$a{}^{3}{{\\rm{\\Sigma }}}_{g}^{+}$$, $$C{}^{1}{{\\rm{\\Pi }}}_{u}$$, and the $$E(F){}^{1}{{\\rm{\\Sigma }}}_{g}^{+}$$ states are presented at incident energies near to threshold. The experimental DCSs were taken at incident energies of 14, 15, 16 and 17.5 eV and for scattering angles from 10° to 130°. In conclusion, the theoretical DCSs are from the convergent close-coupling method which has recently successfully modeled differential electron scattering from H 2 when compared with available experiment at energies of 17.5 eV and above.« less

Double photoionization of the Be isoelectronic sequence

NASA Astrophysics Data System (ADS)

Barmaki, S.; Albert, M. A.; Belliveau, J.; Laulan, S.

2018-05-01

We investigate the double photoionization (DPI) process along the Be isoelectronic sequence (Be‑Ne6+) by solving the time-dependent Schrödinger equation with a spectral method of configuration interaction type. The results that we obtain of the DPI cross sections are in a good agreement with other reported data. We also present the first results of double-to-single photoionization cross sections ratios for Be-like ions in support of possible photofragmentation experiments with x-ray free electron lasers. Finally, we probe the mutual interaction of the valence electrons at different photon energies and examine the subsequent redistribution of the excess photon energy among them.

Nonharmonic oscillations of nanosized cantilevers due to quantum-size effects

NASA Astrophysics Data System (ADS)

Olsen, Martin; Gradin, Per; Lindefelt, Ulf; Olin, Håkan

2010-02-01

Using a one-dimensional jellium model and standard beam theory we calculate the spring constant of a vibrating nanowire cantilever. By using the asymptotic energy eigenvalues of the standing electron waves over the nanometer-sized cross-section area, the change in the grand canonical potential is calculated and hence the force and the spring constant. As the wire is bent more electron states fits in its cross section. This has an impact on the spring “constant” which oscillates slightly with the bending of the wire. In this way we obtain an amplitude-dependent resonance frequency of the oscillations that should be detectable.

A measurement of hadron production cross sections for the simulation of accelerator neutrino beams and a search for muon-neutrino to electron-neutrino oscillations in the Δm 2 about equals 1-eV 2 region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmitz, David W.

2008-01-01

A measurement of hadron production cross-sections for the simulation of accelerator neutrino beams and a search for muon neutrino to electron neutrino oscillations in the Δm 2 ~ 1 eV 2} region. This dissertation presents measurements from two different high energy physics experiments with a very strong connection: the Hadron Production (HARP) experiment located at CERN in Geneva, Switzerland, and the Mini Booster Neutrino Experiment (Mini-BooNE) located at Fermilab in Batavia, Illinois.

Charge equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

NASA Technical Reports Server (NTRS)

Rule, D. W.; Omidvar, K.

1979-01-01

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, are considered. Electron loss of the beam has been taken into account by means of the first Born approximation, allowing for the target atom to remain unexcited or to be excited to all possible states. Electron-capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms and capture into all excited states of the projectile. The capture and loss cross sections are found to be within 20%-30% of the existing experimental values for most of the cases considered. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation, and collisional inner-shell ionization, taking into account the fluorescence yield of the ions, has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated, and error estimates made for the results.

A formula for calculating theoretical photoelectron fluxes resulting from the He/+/ 304 A solar spectral line

NASA Technical Reports Server (NTRS)

Richards, P. G.; Torr, D. G.

1981-01-01

A simplified method for the evaluation of theoretical photoelectron fluxes in the upper atmosphere resulting from the solar radiation at 304 A is presented. The calculation is based on considerations of primary and cascade (secondary) photoelectron production in the two-stream model, where photoelectron transport is described by two electron streams, one moving up and one moving down, and of loss rates due to collisions with neutral gases and thermal electrons. The calculation is illustrated for the case of photoelectrons at an energy of 24.5 eV, and it is noted that the 24.5-eV photoelectron flux may be used to monitor variations in the solar 304 A flux. Theoretical calculations based on various ionization and excitation cross sections of Banks et al. (1974) are shown to be in generally good agreement with AE-E measurements taken between 200 and 235 km, however the use of more recent, larger cross sections leads to photoelectron values a factor of two smaller than observations but in agreement with previous calculations. It is concluded that a final resolution of the photoelectron problem may depend on a reevaluation of the inelastic electron collision cross sections.

Electron-impact ionization of silicon tetrachloride (SiCl4).

PubMed

Basner, R; Gutkin, M; Mahoney, J; Tarnovsky, V; Deutsch, H; Becker, K

2005-08-01

We measured absolute partial cross sections for the formation of various singly charged and doubly charged positive ions produced by electron impact on silicon tetrachloride (SiCl4) using two different experimental techniques, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam apparatus. The energy range covered was from the threshold to 900 eV in the TOF-MS and to 200 eV in the fast-neutral-beam apparatus. The results obtained by the two different experimental techniques were found to agree very well (better than their combined margins of error). The SiCl3(+) fragment ion has the largest partial ionization cross section with a maximum value of slightly above 6x10(-20) m2 at about 100 eV. The cross sections for the formation of SiCl4(+), SiCl+, and Cl+ have maximum values around 4x10(-20) m2. Some of the cross-section curves exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30 eV followed by a broad second maximum at around 100 eV. This is similar to what has been observed by us earlier for another Cl-containing molecule, TiCl4 [R. Basner, M. Schmidt, V. Tamovsky, H. Deutsch, and K. Becker, Thin Solid Films 374 291 (2000)]. The maximum cross-section values for the formation of the doubly charged ions, with the exception of SiCl3(++), are 0.05x10(-20) m2 or less. The experimentally determined total single ionization cross section of SiCl4 is compared with the results of semiempirical calculations.

Charge-changing cross-section measurements of C-1612 at around 45 A MeV and development of a Glauber model for incident energies 10 A -2100 A MeV

NASA Astrophysics Data System (ADS)

Tran, D. T.; Ong, H. J.; Nguyen, T. T.; Tanihata, I.; Aoi, N.; Ayyad, Y.; Chan, P. Y.; Fukuda, M.; Hashimoto, T.; Hoang, T. H.; Ideguchi, E.; Inoue, A.; Kawabata, T.; Khiem, L. H.; Lin, W. P.; Matsuta, K.; Mihara, M.; Momota, S.; Nagae, D.; Nguyen, N. D.; Nishimura, D.; Ozawa, A.; Ren, P. P.; Sakaguchi, H.; Tanaka, J.; Takechi, M.; Terashima, S.; Wada, R.; Yamamoto, T.; RCNP-E372 Collaboration

2016-12-01

We have measured for the first time the charge-changing cross sections (σCC) of C-1612 on a 12C target at energies below 100 A MeV. To analyze these low-energy data, we have developed a finite-range Glauber model with a global parameter set within the optical-limit approximation which is applicable to reaction cross section (σR) and σCC measurements at incident energies from 10 A to 2100 A MeV. Adopting the proton-density distribution of 12C known from the electron-scattering data, as well as the bare total nucleon-nucleon cross sections and the real-to-imaginary-part ratios of the forward proton-proton elastic scattering amplitude available in the literatures, we determine the energy-dependent slope parameter βp n of the proton-neutron elastic differential cross section so as to reproduce the existing σR and interaction cross-section data for 12C+12C over a wide range of incident energies. The Glauber model thus formulated is applied to calculate the σR's of 12C on a 9Be and 27Al targets at various incident energies. Our calculations show excellent agreement with the experimental data. Applying our model to the σR and σCC for the so-called neutron-skin 16C nucleus, we reconfirm the importance of measurements at incident energies below 100 A MeV. The proton root-mean-square radii of C-1612 are extracted using the measured σCC's and the existing σR data. The results for C-1412 are consistent with the values from the electron scatterings, demonstrating the feasibility, usefulness of the σCC measurement, and the present Glauber model.