Measurement of $\bf{Sr-N_{2}}$ elastic collision cross section in Magneto-Optical Trap

Todd A. Zimmerman

David E. Fagnan, J. Wang, Bruce G. Klappauf +2 more

Kristen Matherson, R. D. Glover, D. E. Laban +1 more

We present total absolute collision cross sections for neon in the $^{3}P_{2}$ metastable state with ground state, thermal atoms and molecules using a recently developed experimental technique. The technique utilizes a magneto-optical trap (MOT) and involves the measurement of MOT population dynamics to determine the cross section. Collision cross section measurements are presented for metastable neon in the $^{3}P_{2}$ state with He, Ne, Ar, ${\mathrm{H}}_{2}$, ${\mathrm{O}}_{2}$, and ${\mathrm{N}}_{2}$. The average thermal energy of the collision ranges from $11\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}27\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$. The measurements made using this technique have small errors, of the order of 10% of the measured cross section; the technique is capable of producing benchmark collision cross sections.

David E. Fagnan

This thesis discusses a new technique for measuring collision cross sections, using a magnetooptical trap (MOT) or magnetic trap as well as theoretical predictions for the resulting measurements based on scattering theory. The initial discussion focuses on a theoretical overview of the principles involved in laser cooling and trapping, magnetic trapping, and scattering theory. Following this, a detailed overview of the experimental instruments and methods describing the vacuum system, laser light, magnetic coils, imaging and control systems will be presented. In addition to an experimental overview, the methods and mechanical formulation involved in predicting cross sections and loss rates based on scattering theory are discussed. Finally, an overview of both experimental and theoretical results including cross sections and loss rates for the case of trapped 87Rb and background argon or helium gas will be given. The results gathered in this thesis show a strong dependence of elastic collision cross section on trap depth, which indicates that the majority of elastic collisions between ultra-cold rubidium and room temperature argon impart energy below 1K. These results suggest that the magnetic trap may be a better tool for measuring total elastic collision cross sections.

A. Fioretti, Jörg Helge Müller, Philippe Verkerk +3 more

J. A. MacAskill

Experiments involving a magneto-optical trap (MOT) as the target in electron impact cross section studies were carried out. The use of a MOT allows the kinematic properties of the target atoms, and their electronic states, to be controlled via operating parameters of the MOT's lasers. A MOT is capable of saturating the excited state of a gaseous target of atoms and provides a unique opportunity to measure exotic collision processes. Measurements use a trap-loss technique to relate the loss rate of atoms from the trap due to electron interactions to a collision cross section. Total scattering cross section measurements are given for the 62S 1/2 ground state and the 62P3/2 excited state of cesium. The excited state measurement is the first measurement of its kind. Total ionization cross sections are also presented for the both the 6 2S1/2 ground state and 62P3/2 excited state. The ionization cross sections are measured by adjusting the radiation force of the MOT lasers to damp the elastic scattering component of the total cross section. The ionization cross section for the excited state is the first experimental determination of its kind. Full details of the experimental apparatus and the analysis procedure are presented. The results of this experiment are combined with other experimental data and compared to the most recent calculations.Dept. of Physics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .M322. Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4996. Adviser: J. W. McConkey. Thesis (Ph.D.)--University of Windsor (Canada), 2003.