Elastic electron scattering by fullerene, C60

We report cross sections for elastic scattering of low-energy electrons by fullerene, C60, calculated within the static-exchange approximation. The calculations are carried out via the Schwinger multichannel (SMC) method, equivalent in this case to the standard Schwinger variational principle. Combining the high parallel efficiency of the SMC method with a quadrature specially adapted to the high symmetry of C60 facilitates the most demanding step of the calculation and so permits the use of a large basis set. We analyze the structure of the cross section with reference to a simple spherical-shell model, and we compare our results to prior measurements and calculations

Electron scattering in ethene: Excitation of the ã 3B1u state, elastic scattering, and vibrational excitation

Experimental and calculated absolute differential cross sections for the scattering of low-energy electrons from ethene are presented. Emphasis is on the excitation of the ã 3B1u 3(pi,pi*) state, but selected elastic and vibrational excitation cross sections are also given. In contrast to earlier calculations, which were nearly a factor of 2 too large, the present calculation agrees very well with the experimental triplet excitation cross section in the threshold region. The improvement is due primarily to the inclusion of target polarization, which results in proper positioning of the pi* resonance, whose high-energy tail dominates the triplet state excitation near threshold. The present experimental elastic cross sections agree very well with recent calculations taking into account target polarization

Absolute angle-differential elastic cross sections for electron collisions with diacetylene

We report measured and calculated differential elastic cross sections for collisions of low-energy electrons with diacetylene (1,3-butadiyne). A generally satisfactory agreement between theory and experiment has been found. The calculated cross sections provide interesting insight into the underlying resonant structure

Low-energy electron scattering from C_4H_9OH isomers

We present differential, integral, and momentum-transfer cross sections for elastic scattering of low-energy electrons by three butanol isomers, isobutanol, t-butanol, and 2-butanol. Our results were calculated with the Schwinger multichannel method in the static-exchange plus polarization approximation for collision energies from 1 to 50 eV. The present results are compared with previous calculations and measurements for the remaining C_4H_9OH isomer, n-butanol [Khakoo et al., Phys. Rev. A 78, 062714 (2008)]. Distinctive behavior is observed in the differential cross sections at collision energies between 5 and 10 eV. In particular, whereas n-butanol exhibits an f-wave scattering pattern, the other isomers exhibit d-wave behavior. A similar pattern is found in the related alkanes when comparing straight-chain versus branched isomers. We discuss the possible connection of this behavior to shape resonances that influence the scattering

Low-energy electron scattering by silane (SiH_4)

We have applied the Schwinger multichannel formulation [K. Takatsuka and V. McKoy, Phys. Rev. A 24, 2473 (1981)] to the elastic scattering of low-energy (1–30-eV) electrons by silane. Our results, obtained within the fixed-nuclei, static-exchange approximation, are in generally good agreement with recent differential, integral, and momentum-transfer cross-section measurements between 5 and 30 eV. At lower energies, our results reflect the known limitations of the static-exchange approximation. Near the shape resonance, the calculated differential cross section shows significant enhancement at high angles, suggesting an explanation for differences between integral cross sections determined from integrated differential data and those obtained from transmission measurements

Low-energy electron collisions with tetrafluoroethene, C_2F_4

We report calculated cross sections for elastic and inelastic collisions of low-energy electrons with tetrafluoroethene, C_2F_4. The elastic cross section shows a number of resonance features, which we classify according to symmetry and analyze in relation to available experimental data. Electron-impact excitation cross sections are obtained for the 1^3B_(1u)(T) and 1^1B_(1u)(V) states arising from the π→π* transition, as well as for eight other low-lying excited states arising from excitations out of the highest occupied molecular orbital. As expected, the T and V states make the largest individual contributions to electron-impact excitation at low energies; however, the other states are shown to contribute significantly to the total excitation cross section at impact energies from 10 to 25 eV

Vibrational excitation of water by electron impact

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°–130° 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

Low-energy electron scattering by C_2HF_5

We report elastic and electronically inelastic cross sections for low-energy electron scattering by pentafluoroethane, C_2HF_5. Our calculations were performed using the Schwinger multichannel method. For elastic scattering, we calculated integral, differential, and momentum transfer cross sections for energies from 5 to 50 eV. In the inelastic case, we obtained integral and differential cross sections for electron-impact excitation of the 1 1,3A[prime] and 2 1,3A[prime] excited states at the three-channel level of approximation. At higher energies, the elastic differential cross sections are quite similar to existing theoretical results for C_2F_6. Limited electronic-structure calculations were carried out to explore the dissociation behavior of the excited states