Elastic and absorption cross sections for electron-nitrous oxide collisions

In this work, we present a joint theoretical-experimental study on electron-N2O collisions in the intermediate energy range. More specifically, calculated and measured elastic differential, integral, and momentum-transfer cross sections, as well as calculated total and absorption cross sections are reported. The measurements were performed using a crossed electron-beam-molecular-beam geometry. The angular distribution of the scattered electrons was converted to absolute cross sections using the relative-flow technique. Theoretically, a complex optical potential is used to represent the electron-molecule interaction dynamics in the present calculation. The Schwinger variational iterative method combined with the distorted-wave approximation is used to solve the scattering equations. The comparison of the present calculated results with the measured results as well as with the existing experimental and theoretical data shows good agreement.65

Electron scattering by methanol and ethanol: A joint theoretical-experimental investigation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)We present a joint theoretical-experimental study on electron scattering by methanol (CH3OH) and ethanol (C2H5OH) in a wide energy range. Experimental differential, integral and momentum-transfer cross sections for elastic electron scattering by ethanol are reported in the 100-1000 eV energy range. The experimental angular distributions of the energy-selected electrons are measured and converted to absolute cross sections using the relative flow technique. Moreover, elastic, total, and total absorption cross sections for both alcohols are calculated in the 1-500 eV energy range. A complex optical potential is used to represent the dynamics of the electron-alcohol interaction, whereas the scattering equations are solved iteratively using the Pade's approximant technique. Our calculated data agree well with those obtained using the Schwinger multichannel method at energies up to 20 eV. Discrepancies at high energies indicate the importance of absorption effects, included in our calculations. In general, the comparison between our theoretical and experimental results, as well as with other experimental data available in the literature, also show good agreement. Nevertheless, the discrepancy between the theoretical and experimental total cross sections at low incident energies suggests that the experimental cross sections measured using the transmission technique for polar targets should be reviewed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3695211]13611Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Elastic cross sections for e(-)-CH4 collisions at intermediate energies

A joint theoretical and experimental investigation on e(-)-CH4 elastic scattering in the intermediate energy range is reported. More specifically, calculated cross sections in the (1-500)-eV incident energy range, as well as measured absolute cross sections from 100 to 500 eV, are presented. A complex optical potential consisting of static, exchange, 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 experimental absolute elastic differential cross sections are determined using the relative flow technique. In general, our calculated results are in very good agreement with our experimental data and with other experimental and theoretical results available in the literature. Our study has shown the significant role played by the absorption effects on the calculated cross sections for incident energies of 50 eV and above. The importance of the nonspherical components of the e(-)-CH4 interaction potential has also been verified in our calculations.61

Elastic and absorption cross sections for electron scattering by ethylene in the intermediate energy range

In this work, we present a joint theoretical and experimental study on electron scattering by C2H4 in the intermediate energy range. Calculated elastic differential, integral, and momentum-transfer as well as total (elastic + inelastic) and absorption cross sections are reported at impact energies ranging from 10 to 500 eV. Also, experimental absolute elastic cross sections are reported in the 100-500 eV range. The measurements were performed using a crossed electron beam-molecular beam geometry. The angular distributions of the scattered electrons were converted to absolute cross sections using the relative flow technique. Theoretically, a complex optical potential was used to represent the electron-molecule interaction dynamics. The Schwinger variational iterative method combined with the distorted-wave approximation was used to solve the scattering equations. The comparison between our calculated and measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.37247148

Photostability of amino acids to Lyman alpha radiation: Glycine

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The amino acids already detected in Solar System bodies and researched in Interstellar Medium are of particular importance for the chemistry related to the origin of life since they are constituents of all living organisms. Several amino acids have been identified in meteorites carbonaceous with significant concentration, while the existence of glycine in regions of star formation has been claimed. To interpret the viability of amino acids in pre-biotic astrochemistry is important to investigate the stability of these compounds in extraterrestrial surroundings. This study investigates, in the laboratory, the stability of glycine to the action of ultraviolet radiation, in spectral region around the wavelength of the Lyman alpha line (1216 angstrom) produced by a hydrogen lamp. (252)Cf-PDMS of positive and negative desorbed ions was performed for glycine, before and during the irradiation, and the dependence of the ion desorption yields on the irradiation time is determined. As a result, the relative photostability curves of the molecular and dimer ions are observed to be a single exponential decay with a time constant 376 min for positive desorbed ions and 675 min for negative ones. The photodissociation cross section found for glycine molecule at room temperature, when positive secondary ions are considered, is 17 Mb: this value drops to 9 Mb when negative secondary ions are analyzed. This new methodology offers a complementary way of understanding the photonic interaction in amino acids, allowing discussion on polymerization and/or radiation induced phase transition effects. (C) 2011 Elsevier B.V. All rights reserved.30617781Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Electron interaction with dimethyl disulfide in the low- and intermediate-energy range

We report a joint theoretical-experimental investigation on elastic electron scattering by dimethyl disulfide in the low- and intermediate-energy regions. Experimental angular distributions of the elastically scattered electrons were measured in the 10-800 eV and 5°-130° ranges using a crossed electron beam-molecular beam geometry. The absolute values of the differential cross sections were obtained using the relative-flow technique. Also, integral and momentum-transfer cross sections were derived from the experimental differential cross sections via a numerical integration procedure. Theoretically, differential, integral, momentum-transfer, grand-total, and total absorption cross sections are reported in the 1-500 eV range. In our calculations, a complex optical potential was used to represent the collision dynamics and a single-center expansion method combined with the Padé approximation was used to solve the scattering equations. Our experimental data are in good agreement with the present calculated data. Comparisons with other theoretical results are also made

Low to intermediate energy elastic electron scattering from dichloromethane (CH 2 Cl 2 )

We report a theoretical-experimental investigation of electron scattering by dichloromethane (CH Cl ) in the low- and intermediate energy ranges. Experimental elastic differential cross sections (DCS), in the incident electron energy range of 0.5-800 eV and scattering angle range of 10°-130°, were measured using a crossed beam relative flow technique. Integral and momentum-transfer cross sections were determined from the experimental DCS. Theoretical elastic differential, integral, and momentum-transfer, as well as grand-total, and total absorption cross sections were also calculated for impact energies ranging from 0.5 to 500 eV. A complex optical Hartree-Fock potential represented the electron-target interaction and a single-center expansion method combined with a Padé approximation was used to solve the scattering equations. Three resonances: a A C-Cl kσ∗ resonance centered at about 3.5 eV, a B C-Cl kσ∗ resonance centered at about 5 eV and a broad A C-H kσ∗ resonance at about 10 eV were detected in our calculation. Further calculations of DCS were performed at an intermediate energy range of 50-800 eV, using the independent-atom model in which the atomic complex optical potential and partial-wave method were used to obtain atomic scattering amplitudes. Comparisons of our experimental and theoretical data with very recent experimental and theoretical results are made. 2 2 1 2 1 2 2

Cross sections for electron collisions with dimethyl ether

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)We report a joint theoretical-experimental investigation of electron collision with dimethyl ether (DME) in the low- and intermediate-energy ranges. Experimental absolute differential, integral, and momentum-transfer cross sections for elastic e(-)-DME scattering are reported in the 100-1000 eV energy range. Our measurements were performed using a crossed electron-beam-molecular-beam geometry. The angular distribution of the scattered electrons was converted to absolute cross section using the relative flow technique. Theoretically, elastic differential, integral, and momentum-transfer cross sections, as well as the grand-total and total absorption cross sections for electron collision with DME are calculated in the 1-1000 eV energy range. A single-center-expansion technique combined with the Pade approximant method is used in our calculations. A comparison between the present experimental and theoretical data shows very good agreement. Moreover, comparison with theoretical and experimental data for e(-)-ethanol (an isomer of DME) scattering shows interesting isomeric effects.882Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Cross sections for electron scattering by ethane in the low- and intermediate-energy ranges

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)We present a joint theoretical-experimental study on electron scattering by ethane (C(2)H(6)) in the low-and intermediate-energy ranges. Calculated elastic differential, integral and momentum transfer as well as total (elastic + inelastic) and total absorption cross sections are reported for impact energies ranging from 1 to 500 eV. Also, experimental absolute elastic cross sections are reported in the 40-500 eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics. A theoretical method based on the single-centre-expansion close-coupling framework and corrected by the Pade approximant technique is used to solve the scattering equations. The experimental angular distributions of the scattered electrons are converted to absolute cross sections using the relative flow technique. The comparison of our calculated results with our measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.4322Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP