Polarisation potentials for positron-molecule collisions: positron-H, scattering
Model polarisation potentials for use in calculating positron-molecule cross sections are often based on approximations in which terms that depend on the sign of the charge of the projectile are neglected. Thus, these potentials do not fully distinguish between electron and positron scattering. The validity of using such potentials for positron- H2 collisions is investigated by performing scattering calculations using electron- and positron-H, model polarisation potentials. Results show that, because of differences in the way electrons and positrons distort the target charge cloud, sign-dependent terms in the adiabatic potential can significantly influence the total cross section. Low-energy cross sections are also shown to be rather sensitive to how non-adiabatic polarisation effects are taken into account. Using a cut-off fully adiabatic positron-H, polarisation potential, theoretical total cross sections in reasonably good agreement with recent measurements are obtained.
Electron-molecule interactions. III. A pseudo-potential method for e--N2 scattering
For Pt. II see Abstr. A43069 of 1970. The low energy scattering of electrons by molecular nitrogen is calculated using a pseudo-potential method. Expressions for the cross sections in terms of the calculated S matrix elements are developed and momentum transfer cross sections are obtained which are in good agreement with experiment. The theory is then extended to predict rotational excitation cross sections and differential cross sections. It is suggested that this approach may enable electron molecule collision cross sections involving complex molecules to be calculated.
Experimental observation of a strange nonchaotic attractor.
Evidence is presented for the existence of a strange nonchaotic attractor in a two-frequency quasi-periodically driven, buckled, magnetoelastic ribbon experiment. Scaling behavior in the Fourier amplitude spectrum is observed in agreement with predicted scaling behavior for strange nonchaotic attractors. Dimension measurements also support the existence of a strange nonchaotic attractor