I. P. Sanches

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

We present a joint theoretical-experimental study on electron scattering by methanol (CH(3)OH) and ethanol (C(2)H(5)OH) 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 Padés 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.

Cross sections for elastic electron collisions on two hydrocarbon compounds: n-butane and benzene in the intermediate-energy range

In this work, we report an experimental-cross-section determination of elastic electron collisions with two hydrocarbon species, namely n-butane and benzene, in the intermediate-energy range. More specifically, absolute differential, integral and momentum-transfer cross sections are measured and reported in the (50–1000) 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. Integral and momentum-transfer cross sections are derived from the measured differential cross sections. Additionally, elastic cross sections are also calculated using the independent atom model at the static-exchange-polarization level of approximation. A comparison of our measured data with calculated and other experimental results available in the literature is made.

Role of adsorption effects on absolute electron-molecule cross-section calibration using the relative flow technique

In this work, we report an experimental investigation on relative flow-rate determination for vapors. The mechanism of adsorption-desorption of vapors on surfaces is considered. In contrast to previous investigations, our study shows that the adsorption of vapors on surfaces may significantly affect the flow-rate determination and consequently the measured cross sections. Particularly, for water, it can result in an overestimation of 35% in the cross sections.

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

We present a joint theoretical–experimental study on electron scattering by ethane (C2H6) 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.

An experimental study on elastic electron-trifluoromethane (CHF3) scattering in the low and intermediate energy ranges

In this work, we report an experimental study on elastic electron collisions with CHF3 in the low and intermediate energy range. More specifically, absolute differential, integral and momentum transfer cross sections are measured and reported in the 20–500 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. Integral and momentum transfer cross sections are derived from the measured differential cross sections. A comparison between our measured data with the theoretical and other experimental results available in the literature is made.

Experimental study on electron–hexafluoroethane (C2F6) collisions in the low- and intermediate-energy ranges

In this work, we report an experimental study on electron–hexafluoroethane (C2F6) collisions in the low- and intermediate-energy ranges. More specifically, absolute differential, integral and momentum-transfer cross sections for elastic e−–C2F6 are measured and reported in the 30–500 eV range. Also, electron-impact partial and total ionization cross sections for this target are reported at incident energies from threshold to 1000 eV. Both measurements were performed using a crossed electron beam–molecular beam geometry. The intensities of the scattered electrons and the signals of ionic fragments are converted to absolute cross sections using the relative flow technique. A comparison between our measured data and the theoretical and other experimental results available in the literature is made.