Optical Metrology of Magnetically Trapped Hydrogen

摘要

A new technique for spectroscopy of atomic hydrogen has been developed, openingthe way to a thousand-fold increase in spectroscopic resolution of hydrogen-or any neutral atomic species, and perhaps making possible a new type of UV optical atomic clock. Two-photon Doppler-free spectroscopy of atoms confined in a magnetic trap has been carried out to observe the 1S to 2S two-photon (243nm) transition to a metastable state with an extremely long lifetime, 1/8 sec. The trap is highly nonperturbative, permitting observation times limited ultimately by the natural lifetime, yielding a natural linewidth of about 1 Hz. Initially a resolution of about three kHZ was achieved, higher than the best then achieved by other techniques and apparently limited only by laser jitter. Signal rates as high as 3000 counts per second were observed. The collection efficiency in the initial version of the apparatus is less than 10(exp -5), and the actual signal rate is greater than 10(exp 8) counts per second, almost astronomically high compared to previous methods. A direct measurement of the life time of the metastable 2S atoms was made and found to be close to the theoretical lifetime of 0.12 sec. This is the first time the 2S lifetime has been measured.