Multichannel quantum defect theory of the hyperfine structure of high Rydberg states

The multichannel quantum defect theory (MQDT) of fine structure has been extended to hyperfine structure by dividing the configuration space into three parts: The α region, the i region, and the iF region, according to the competition among short-range interaction, spin-orbit interaction, and hyperfine interaction. Then an unperturbative theory of hyperfine structure in high Rydberg states is derived. The MQDT parameters of hyperfine structure have been categorized into two parts: one is contributed by short-range and spin-orbit interactions and has been given by an analogy with the MQDT parameters of fine structure; the other is contributed by spin-orbit and hyperfine interactions and has been given analytically. The hyperfine structure in high Rydberg states can then be calculated directly from the MQDT parameters of fine structure