Collision and Motional Averaging Effects in Cryogenic Atomic Hydrogen Masers

摘要

Substantial progress has been made toward optimizing the performance of the neonsurface cryogenic hydrogen maser, preparatory to measuring the hyperfine induced frequency shifts (HIFS) in collisions between hydrogen atoms at low temperatures. Self-excited maser oscillation has been achieved at temperatures from 8.5 to 11.5 K. There is little surface relaxation at the higher temperatures. There is substantial collision broadening at the highest achievable atom densities, which is useful for spin exchange cavity tuning and which indicates the presence of measurable HIFS. We have also made significant progress in understanding the Doppler effect in motional averaging systems such as the cryogenic maser.