RESUMO
Using a free electron laser we have performed midinfrared transmission and reflection measurements in strongly scattering Ge powder. We have studied the wavelength dependence of the scattering properties and the optical absorption. Results indicate that our samples are close (kl(s) approximately 3) to the Anderson localization transition but still above it. This is in contrast to the recently reported strong localization of light (kl(s)<1) in a similar powder of lower refractive index particles (GaAs).
RESUMO
A gas of Rb atoms in a static electric field has been photoexcited to just above the classical ionization threshold by a phase-locked sequence of two far infrared pulses. A single laser pulse generates a series of ejected electron packets emerging at the saddle point of the potential; each of the ejected packets is characterized by a phase and a chirp. We calculate and measure these phases and chirps using the time dependent interference of the electronic wave function controlled by the delay between the two light pulses.
RESUMO
We present a quantum theory for the interaction of a quantum target with a time dependent matter beam. When several pulses in the incident beam arrive with a period tau, transitions between levels with an energy difference h/tau can be enhanced. Unlike all previous studies, we find that transitions in passive targets can distinguish between an incoherent beam and a beam with a coherent wave packet structure. As an example, we calculate the transition probability of Rb Rydberg atoms interacting with a pulsed electron beam.
RESUMO
We present a novel approach to the preparation of neutral (anti-)matter. The scheme is based on recombination of a free electron and an ion, and can be considered as the inverse of pulsed field ionization. We have obtained promising results on rubidium: at low densities already efficiencies of 0.3% were obtained. This is orders of magnitude more than has been achieved in previous recombination studies.
