H. A. Camp

Recoil ion momentum spectroscopy using magneto-optically trapped atoms

A novel apparatus has been developed in which atoms in a magneto-optical trap are used as targets in ion-atom collision experiments. The apparatus is an extension of earlier methodology in which the momentum of the recoiling target is measured and used to deduce the collision Q value and projectile scattering angle. In the present work, the low temperature of the target atoms yields increased momentum resolution, which in turn leads to improved Q value and scattering angle resolution. In addition, because the trapping process leaves some fraction of the atoms in an excited state, the new methodology is ideal for the study of collisions with excited targets. The prototypical system presented is low energy charge transfer between singly charged alkali ions and trapped rubidium atoms in the ground and first excited state.

MOTRIMS as a generalized probe of AMO processes

Magneto-optical trap recoil ion momentum spectroscopy (MOTRIMS) is one of the newest offshoots of the generalized TRIMS approach to ion–atom collisions. By using lasers instead of the more usual supersonic expansion to cool the target, MOTRIMS has demonstrated two distinct advantages over conventional TRIMS. The first is better resolution, now limited by detectors instead of target temperature. The second is its suitability for use in the study of laser-excited targets. In this presentation we will present a third advantage: The use of MOTRIMS as a general-purpose probe of AMO processes in cold atomic clouds of atoms and molecules. Specifically, the projectile ion beam can be used as a probe of processes as diverse as target dressing by femtosecond optical pulses, photo-association (laser-assisted cold collisions) photo-ionization, and electromagnetically-induced transparency. We will present data for the processes we have investigated, and speculations on what we expect to see for the processes we plan to investigate in the future.

Three-dimensional spatial imaging in multiphoton ionization rate measurements

An experiment is described in which an apparatus is used to demonstrate the feasibility of measuring multiphoton photoionization rates in the interaction of short pulsed lasers with atoms or molecules. With this methodology, the ionization rate is measured as a function of the spatial position in the beam-waist region of the laser through the direct three-dimensional spatial imaging of the ionization events. Thus, if the spatial dependence of the laser beam intensity were known, a series of experiments could yield the intensity dependence of multiphoton ionization without the assumptions or errors that are generally inherent in the integration over one or more dimensions in the laser focal volume.