Microwave transition between "clock levels" of Cs beam

The microwave transition between two ground hyperfine sublevels of Cs atom has been observed by optical pumping and optical detecting. The maximum population difference between "0-0" sublevels in single laser pumping case is achieved. The "Ramsey pattern" of "0-0" clock level transition and "Rabi" transition structures are obtained, and their main characters agree with the theoretical results. A better Cs beam atomic clock performance would be expected when the inject microwave frequency is looked into the center of the "0-0" clock level transition" in this experimental setup.