Cryogenic H maser in a strong B field

Abstract

We study the spin-exchange frequency shift of the cryogenic hydrogen maser for B≠0. A general expression is derived in terms of populations of ground-state hyperfine levels. The coefficients in this expression are calculated in the degenerate-internal-states approximation, as well as to first order in the hyperfine plus Zeeman splitting. Numerical results are compared with rigorous coupled-channel calculations. Some implications are pointed out for the frequency stability of the H maser in a magnetic field.