| We explore the effects of asymmetric laser pulses, those with a distinct, controllable difference in the up vs. down direction, on the combined electronic and nuclear dynamics of atomic and molecular processes such as nonsequential double ionization and multielectron dissociative ionization.;First, we use a two-color laser field to explore the directional fragment emission from multielectron dissociative ionization in N2, O 2, CO, and CO2. We find a robust, phase-dependent directional ejection of highly-charged fragments from asymmetric dissociation channels in all of these molecules. Moreover, after adopting an independent phase calibration, for all channels observed, the fragment with the highest ionization potential is preferentially emitted in the direction opposite to the laser field maximum. This is precisely opposite to predictions based on the standard model of enhanced ionization, although recent developments indicate that a sign error in the independent phase calibration may have been found.;In collaboration with a group of scientists lead by Dr. Matthias Kling at the Max Planck Institute for Quantum Optics (MPQ) in Garching, Germany, we develop a method to "tag" every < 5 fs laser pulse with the carrier-envelope phase, and demonstrate the effectiveness of this technique by studying the carrier-envelope phase dependence of nonsequential double ionization in argon. Using this method, we are able to extend data acquisition times to several days, greatly improving statistics, while requiring significantly less effort than traditional methods of phase stabilization.;With the use of two < 5 fs laser pulses in a pump-probe geometry, we, in collaboration with Dr. Kling's group at MPQ, study the dynamics of multielectron dissociative ionization in N2 and O2. We find evidence of electron localization into the N2(2,0) channel after ionization by the pump pulse followed by ionization of the neutral atom by the probe pulse in the delay-dependent production of the N2(2,1) channel. Similar electron localization and ionization of the neutral is observed in the production of the N2(1,1) channel. Using the phase tagging technique, we find no statistically significant directional fragment emission from N2 or O2 when induced by few-cycle laser pulses. |
