Improved all-order results for the one-loop QED correction to the   hyperfine structure in light H-like atoms
  A calculation of the one-loop self-energy and vacuum-polarization corrections to the hyperfine splitting of the 1s and 2s states in light H-like ions is carried out to all orders in the parameter Z \alpha. Using the known values for the Z \alpha-expansion coefficients, the numerical data obtained are extrapolated from Z=5 and higher to Z=0, 1, and 2, with the resulting accuracy being significantly better than in previous evaluations. Our calculation shifts the theoretical value of the normalized difference of the 1s and 2s hyperfine-structure intervals in ^3He^+ by 0.056 kHz and improves its accuracy. 
V. A. Yerokhin, A. N. Artemyev, V. M. Shabaev, and G. Plunien