Recent experiments on electron capture from elliptic Rydberg states by Ehrenreich et al. (1994) have shown that the total electron capture cross section depends strongly on the eccentricity, e, of the elliptic state and the orbit direction of the electron. By carrying out close-coupling calculations for protons colliding with elliptic H (n=3, 4, 5) atoms we show that the dependence of total capture cross section on e varies weakly with the principal quantum number n. We also present the dependence of the total capture cross section as function of the angle, phi , between the incoming ions and the classical plane of the elliptic orbital. Both the dependence on e and on phi are shown to be consistent with the criteria of velocity matching for the electron capture process.

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Encouraged by positive clinical results at the University of Illinois, mastery-style homework was integrated into a large semester-long preparatory physics course via an online homework system that used narrated animated video solutions as correctives. This paper discusses the impact and evolution of the homework in its first two years. The first iteration revealed that students were frustrated and did not engage with the system in an effective way. Intending to reduce that frustration and quell negative behavior, the mastery requirement was relaxed, transfer between versions was reduced, and the addition of a direct discussion with students about the homework were implemented in its second year. The results showed that details of implementation can substantially affect students' behavior; large and statistically significant effects were observed as a reduction in frustration (with self-identified "frustrated" students dropping from 60% in 2014 to 30% in 2015) and improvement in performance (average student mastery rate of 59% to 69%).

Electron capture cross sections from circular Rydberg states as a function of the angle p between the ion velocity and the angular momentum of the circular orbital have been reported recently by Hansen et al. [Phys. Rev. Lett. 71, 1522]. We show that the observed rp dependence can be explained in terms of the propensity rule that governs the dependence of electron capture cross sections on the magnetic quantum numbers of the initial excited states. We also carried out close-coupling calculations to show that electron capture from the circular H(3d, 4f, bg) states by protons at the same scaled velocity has nearly the same y dependence.PACS number(s): 34.60.+z, 34.70.+e

Cross sections for electron capture from Li(2s,2p) by proton impact have been calculated for energies in the range 10 eV-10 keV within the atomic orbital close-coupling (AO-CC) and the multicrossing Landau-Zener (MLZ) one-electron models. For the excited Li(2p) target the long-range mixing of the magnetic sublevels has been included in the MLZ calculations by means of a locking-radius model. The MLZ approximation to the AO-CC calculations is found to be appropriate at energies of about 10 eV. When diagonalizing the effective electronic Hamiltonian within the close-coupling basis a non-physical potential curve is disclosed. The cross section for capture from Li(2s) in particular is shown to be sensitive to this curve for energies below 50 eV. It is demonstrated how this problem is eliminated by including a pseudo-Li(1s) state in the AO-CC basis set.