Laser Absorption Spectroscopy on Pressure-Broadened Rubidium Dl Line

Citation

Goldberg, Emma Elizabeth (1999) Laser Absorption Spectroscopy on Pressure-Broadened Rubidium Dl Line. Senior thesis (Major), California Institute of Technology. doi:10.7907/nfk5-f961. http://resolver.caltech.edu/CaltechTHESIS:01102018-101102060

Abstract

A series of experiments run at the Stanford Linear Accelerator Center and in progress at the Thomas Jefferson National Accelerator Facility are investigating the spin structure of the neutron. In these experiments, a beam of polarized electrons is scattered by a target of polarized helium-3 gas. The ³He is polarized by spin-exchange collisions with optically pumped rubidium vapor, and the target polarization is measured with nuclear magnetic resonance (NMR) or electron resonance polarimetry (EPR). Because the signal size in each of these methods is proportional to the total number of polarized nuclei, to determine the percent target polarization it is essential to know the density of ³He in the target cell. The goal of my project is to develop a system to measure this density.

One way to measure the ³He density is to look at the broadening of the Dl spectral line of the Rb in the target cell. The main factor in the broadening of the line is collisions with other atoms- each collision spreads the energy levels a bit more, so the more ³He there is in the cell, the broader the spectral lines. To measure the linewidth, laser light of the appropriate wavelength (about 795 nm) is shone into the cell, and the transmitted intensity is recorded as the wavelength is scanned around the resonance.

In this paper, I will describe the experimental apparatus I used for this laser absorption spectroscopy, the spectra I obtained, and the analysis. I will also mention previous work done in this field and directions for future work.