The thesis of Yuan Yu Jau entitled "New studies of optical pumping, spin resonances, and spin exchange in mixtures of inert gases and alkali-metal vapors" has been placed on deposit.

Any member of the University wishing to read the thesis may do so. Any objections should be submitted to me in writing. The principal advisor for this work was Will Happer. The abstract is below:

ABSTRACT

In this thesis, we present new studies of alkali-hyperfine resonances, new optical pumping for alkali-metal atoms, and the new results of spin exchange between alkali-metal atoms and xenon atoms.

We report a large light narrowing effect of the hyperfine end-resonance signals, which was predicted from our theory and observed in our experiments. By increasing the intensity of the circularly polarized pumping beam, alkali-metal atoms are optically pumped into a state of static polarization, and trapped into the hyperfine end-state. Spin exchange between alkali-metal atoms has minimal effect to the end-resonance from the highly spin-polarized atoms. The end-resonance shows narrower linewidth and larger signal amplitude at higher pumping power. The ground-state resonances of alkali-metal atoms are usually chosen for atomic clocks and atomic magnetometers. This result will possibly benefit the design of those two devices.

By studying the ground-state microwave resonances of alkali-metal atoms, we show that a study of the spin relaxations of atomic-clock resonances by people in the atomic-clock society is flawed. We employed a series of the "transient" measurements to determine two important spin-relaxation rates, S-damping rate and Carver rate, of rubidium and cesium in nitrogen buffer gas. Theoretical calculations were also carried out for helium buffer gas. Our results are consistent with the previous measurements, which were performed in our lab by other means.

Next, we present series studies of coherent population trapping (CPT), which is a promising technique of performing the same or better capability compared to the traditional microwave spectroscopy. For miniature atomic clocks, CPT method is thought to be the first choice. From our studies, we invented a new optical pumping method, push-pull optical pumping, which can pump atoms into nearly pure 0-0 superposition state. Push-pull optical pumping is a special CPT excitation, which only has one dark state. We believe this new invention will bring a big advantage to CPT frequency standards, the quantum state preparation for cold atoms or hot vapor, etc. We also investigated the pressure dependence of CPT excitation and the line shape of the CPT resonance theoretically and experimentally. These two properties are important for CPT applications. A theoretical study of "photon cost" of optical pumping is also presented.

Finally, we switch our attention to the problem of spin exchange between alkali-metal atoms and xenon gas. This mechanism is very important to the spin-exchange optical pumping. We report the first measurements of binary spin-exchange rate at high magnetic field (9.4 tesla). We present the first calculation of the magnetic decoupling curves of the binary spin-exchange rates by using two different methods, semi-classical approach (SCA) and distorted-wave Born approximation (DWBA).

Daniel Marlow
Chair, Dept. of Physics