The origin of beam disparity in emittance and betatron oscillation orbits, in and out of the polarization plane of the drive laser of laser-plasma accelerators, is explained in terms of betatron oscillations driven by the laser field. As trapped electrons accelerate, they move forward and interact with the laser pulse. For the bubble regime, a simple model is presented to describe this interaction in terms of a harmonic oscillator with a driving force from the laser and a restoring force from the plasma wake field. The resulting beam oscillations in the polarization plane, with period approximately the wavelength of the driving laser, increase emittance in that plane and cause microbunching of the beam. These effects are observed directly in 3D particle-in-cell simulations.

We model the absolute electron transfer (ET) rate and the vibrational quantum effects on ET rate previously observed experimentally for the ion pair complex Co(Cp) 2 + |V(CO) 6 -. We find that the absolute rate and vibrational rate effects cannot be predicted by the standard ET methods. In this work we analyze new resonance Raman, absorption, and infrared spectra and combine these results with density functional (DFT) quantum calculations of structure, vibrational modes, and solvent effects to predict absolute electron-transfer rates and vibrational quantum effects for ET. Related DFT calculations on Na + |V(CO) 6are used to support a spectroscopic identification of the ion pair geometry. The ET is from the radical pair state reached by chargetransfer absorption of the ion pair Co(Cp) 2 + |V(CO) 6 -. The weak coupling rate model based on the golden rule model of ET predicts absolute ET rates that are 135 times too large. From our DFT calculations on Co(Cp) 2 |V(CO) 6 we conclude that a small Jahn-Teller geometry change in both radicals can reduce the orbital overlap and electronic coupling in the radical pair state so that the effective coupling matrix element is much smaller than the 417 cm -1 inferred from the absorption spectrum. A new study of the electronic coupling versus geometry is required to test this suggestion versus the possibility that the weak coupling model is inappropriate for our molecule. The standard model, which emphasizes totally symmetric vibrations, also cannot explain prior experimental ET rates for quantum populations (V ) 0, 1, 2) in the nontotally symmetric CO stretching mode. These rate effects likely involve a fast IVR conversion from totally symmetric vibrations to IR active CO stretching motions followed by ET. The vibrational quantum effect on ET probably is caused by a breakdown in the Condon approximation, where an increase in the quantum number of vibration increases the electronic coupling matrix element. The models suggest a number of new experiments to probe the mechanism of ET in weak coupled molecules.

The triggering of wave-breaking in a three-dimensional laser plasma wake (bubble) is investigated. The Coulomb potential from a nanowire is used to disturb the wake field to initialize the wave-breaking. The electron acceleration becomes more stable and the laser power needed for self-trapping is lowered. Three-dimensional particle-in-cell simulations were performed. Electrons with a charge of about 100pC can be accelerated stably to energy about 170MeV with a laser energy of 460mJ. The first step towards tailoring the electron beam properties such as the energy, energy spread, and charge is discussed.

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