This RUI program will measure frequency shifts due to the effects of hyperfine structure during low energy electron spin exchange collisions between ground state hydrogen atoms in a cryogenic hydrogen maser operating near 11K with solid neon storage surfaces. Monte Carlo techniques will be used to model all other potential perturbations of the oscillation frequency of the hydrogen maser and the cryogenic hydrogen maser being used at the Harvard Center for Astrophysics to measure the hyperfine induced collision shifts near 0.5. The results will probe the breakdown of the Born-Oppenheimer approximation in low energy atomic collisions and the degree to which collisions between hydrogen atoms may limit the potential stability of cryogenic hydrogen maser frequency standards.
