We discuss some recent developments in the implementation of the Schwinger multichannel method for electron-molecule collision calculations. The evaluation of matrix elements involving the operator VGp+'V, previously accomplished by insertion of a Gaussian basis on either side of Gz+', is now done by direct numerical quadrature. This approach avoids the necessity of very large Gaussian basis sets, allowing the size of the basis to reAect only the dynamical requirements of the scattering wave function. We 6nd that the reduction in the required basis size results in improved efBciency, in spite of the additional numerical efFort of performing the quadrature. Trial applications to electron-CH4 scattering in the static-exchange approximation and to electronic excitation of H2 illustrate the excellent convergence characteristics of the procedure.

We report an investigation on electron collisions with two nitrogen-containing compounds, namely ammonia (NH 3 ) and formamide (NH 2 CHO). For ammonia, both theoretical and experimental differential, integral, and momentum-transfer cross sections, as well as calculated grand-total and total absorption cross sections, are reported in the 50-500 eV incident energy range. Calculated results of various cross sections are also reported for energies below 50 eV. Experimentally, angular distributions of the scattered electrons were measured using a crossed electron beam-molecular beam geometry and then converted to absolute differential cross sections using the relative flow technique. Absolute integral and momentum-transfer cross sections for elastic e − -ammonia scattering were also derived from the measured differential cross sections. For formamide, only theoretical cross sections are presented in the 1-500 eV incident energy range. A single-center-expansion technique combined with the method of Padé was used in our calculations. For both targets, our calculated cross sections are compared with the present measured data and with the theoretical and experimental data available in the literature and show generally good agreement. Moreover, for formamide, two shape resonances located at 3.5 eV and 15 eV which correspond to the continuum 2 A and 2 A scattering symmetries, respectively, are identified. The former can be associated to the 2 B 1 shape resonance in formaldehyde located at around 2.5 eV, whereas the latter can be related to the 2 E resonance in ammonia at about 10 eV. Such correspondence is very interesting and so supports the investigation on electron interaction with small building blocks, instead of with larger biomolecules.

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 Padé'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.

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The distorted-wave approximation is applied for h e first time to study Ihe electronic excitation of a non-linear plyatomic target by electron impact Specifically, differential and inregal crass seaions for lhe X 'AI -t 'Ac(%I -t 3sa1) transition in HzO are reported in the energy range of 12-30 eV. The comparison with Ihe available experimental and theoretical msu11s is encouraging.

We present a joint theoretical-experimental study on electron scattering by propane (C 3 H 8) 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 2 to 500 eV. Also, experimental absolute elastic cross sections are reported in the 40-to 500-eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics. A theoretical method based on the single-center-expansion close-coupling framework and corrected by the Padé approximant 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 with our measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.

In this work, we present a joint theoretical and experimental study on electron-H 2 S collisions in the low-and intermediate-energy range. More specifically, we report measured elastic differential, integral, and momentumtransfer cross sections in the ͑100-500͒-eV energy range. In addition, calculated elastic cross sections in the ͑0.5-500͒-eV energy range are also reported. 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, an optical potential is used to represent the electron-molecule interaction. The Schwinger variational method combined with the distorted-wave approximation is used to solve the scattering equations. The comparison between our calculated and measured results as well as with other available experimental and theoretical data in the literature is encouraging.