Properties of alkali atoms trapped in solid parahydrogen

Alkali atoms trapped in solid parahydrogen exhibit excellent spin coherence properties at high electron spin densities. We have studied potassium, rubidium, and cesium atoms trapped in parahydrogen. Different species exhibit order-of-magnitude differences in optical pumping and ensemble spin dephasing times. Using dynamical decoupling techniques, the spin coherence time can be extended by orders of magnitude. These properties and other measurements in parahydrogen will be presented. Future applications in quantum sensing and precision measurement will be discussed.