Laser Cooling Trapping of Metastable Neon and Applications to Collision Measurements

Abstract

This thesis presents a new technique for measuring total absolute collision cross sections. Using this technique, the total absolute collision cross sections were determined for neon in the (3s)3P2 metastable state with ground state thermal atoms and molecules. A magneto-optical trap (MOT) is used in this technique which infers the cross sections via the measurement of population dynamics within the MOT to determine the collision cross section.

This technique is capable of providing benchmark measurements of total absolute collision cross sections. The measurements are unique for the low average collision energy which ranges between 11meV and 27meV for the dierent collision species and relatively low uncertainty of approximately 9.4%. The measurements were for neon in the (3s)3P2 metastable state with He, Ne, Ar, H2, O2, N2 and CO2. The measured cross sections were respectively 160±20Å2, 500±50Å2, 840±80Å2, 230±20Å2, 1000±100Å2, 1300.0±100Å2, 830±80Å2. The measurements made using this technique have small uncertainties, of the order of 10% of the measured cross section.

As Ne* does not have the energy to ionize He, the Ne*-He collision was entirely elastic and the validity of this technique was conrmed by comparing the experimental result for this collision with an approximation for the elastic collision cross section based on van der Waals forces. The calculation based on this approximation yielded an elastic cross-section of 168.88Å2 for the Ne*-He system. This theoretical value compared favourably and within the uncertainties of the experimental measurement for the Ne*-He collision of 160±20Å2.

To be able to perform these investigations a rebuild and partial redesign of the Griffith University metastable neon trapping apparatus was necessary and was included in this work.