S. J. Grunefeld, B. M. Roberts, J. S. M. Ginges, Phys. Rev. A **100**, 042506 (2019)

doi:10.1103/PhysRevA.100.042506

We have performed high-precision calculations of the hyperfine structure for n 2S_1/2 and n 2P_1/2 states of the alkali-metal atoms Rb, Cs, and Fr across principal quantum number n, and studied the trend in the size of the correlations. Our calculations were performed in the all-orders correlation potential method. We demonstrate that the relative correlation corrections fall off quickly with n and tend towards constant and non-zero values for highly-excited states. This trend is supported by experiment, and we utilize the smooth dependence on n to make high-accuracy predictions of the hyperfine constants, with uncertainties to within 0.1% for most states of Rb and Cs.

- S. J. Grunefeld, B. M. Roberts, J. S. M. Ginges, Phys. Rev. A
**100**, 042506 (2019)