Leigh Hargreaves

Excitation of the 4 lowest electronic transitions in methanol by low-energy electrons

We report differential and integral cross sections for electronic excitation of methanol by low-energy electron impact. Cross sections were measured for the four lowest-lying excited states at incident electron energies from 9 to 20 eV and at scattering angles from 5° through 130°. The measured cross sections were normalized against previously reported elastic scattering data determined using the relative flow method. Corresponding cross-section calculations were carried out using the complex Kohn variational method within a 7-channel close-coupling scheme and using the Schwinger multichannel method within an 11-channel close-coupling scheme.

Excitation of the six lowest electronic transitions in water by 9–20 eV electrons

We report differential and integral cross sections for excitation of the ^(3)B_1, ^(1)B_1, ^(3)A_2, ^(1)A_2, ^(3)A_1 and ^(1)A_1 states of H_(2)O by 9–20 eV electrons. The measurements are taken by conventional differential electron energy loss spectroscopy techniques, while the calculations employ the Schwinger multichannel method within a ten-channel approximation. The new data are compared with previous experimental and theoretical results. The present measurements and calculations agree reasonably well both with each other and with prior theoretical efforts but show discrepancies with prior measurements. Reasons for those discrepancies are considered and discussed.

Low-energy elastic electron scattering from chloromethane, CH3Cl

We report theoretical as well as (normalized) experimental differential and integral cross sections for vibrationally elastic scattering of low-energy electrons from chloromethane, CH_3Cl, also known as methyl chloride. The theoretical cross sections were computed using the Schwinger multichannel variational method in the single-channel approximation, with polarization effects included via virtual excitations. Cross section measurements were made at incident energies ranging from 0.5 to 100 eV and at scattering angles from 5° to 125°. We compare our data to earlier previous results for this molecule.

Low-energy elastic electron scattering form chloroethane, C2H5Cl

We report theoretical as well as (normalized) experimental differential and integral cross sections for vibrationally elastic scattering of low-energy electrons from chloroethane, C_2H_5Cl, also known as ethyl chloride. The theoretical cross sections were computed using the Schwinger multichannel variational method in the single-channel approximation, with polarization effects included via virtual excitations. Cross section measurements were made at incident energies ranging from 1 to 30 eV and at scattering angles from 10° to 125°. We compare our data to previous results for C_2H_5Cl and for the related molecule chloromethane.

Polarization correlations for electron-impact excitation of neon at 50 eV

We present measurements and calculations of linear and circular polarization correlations for angle-differential electron-impact excitation of the neon resonance transition at an impact energy of 50 eV, most importantly extended to large scattering angles up to 105°. The measured linear polarization parameters of the vacuum ultra-violet transition are in very good agreement with a number of theoretical predictions at all angles. At intermediate scattering angles, however, the circular polarization parameter measurements are only found to be in excellent agreement with theoretical results obtained with the B-spline R-matrix theory, but not with those from other models.

Modelling Ordinal Electoral Systems: The Uniqueness of South Australian Legislative Elections

Understanding the relationship between voting methods and electoral outcomes is one of the central challenges of electoral systems research. In the case of ordinal voting systems, theory and empirical models directly conflict as to whether particular ordinal voting methods significantly affect electoral outcomes. This conflict is partially due to the lack of a model that can simulate real legislative elections reliably enough to empirically test theoretical claims. In this research note, the authors argue that South Australian lower house elections constitute a unique legislative case where sufficient data are publicly available to generate such a model. They then describe the new model and critically examine its accuracy and limitations. They conclude that their model is sufficiently robust to form a basis for future research into the impact of ordinal voting systems on outcomes in legislative elections.

Electron-impact vibrational excitation of furan

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)].