Millimeter-wave spectroscopy and multichannel quantum-defect-theory analysis of high Rydberg states of xenon: The hyperfine structure of 129Xe+ and 131Xe+

Millimeter-wave transitions between high-n Rydberg states of several isotopes of xenon have been recorded at sub-megahertz resolution. The fine and, for 129Xe and 131Xe, hyperfine structures of s, p, d, and f Rydberg states with principal quantum number in the range 52≤n≤64 have been determined from combination differences and analyzed using multichannel quantum defect theory. Improved eigenquantum defects and channel interaction parameters for the odd- and even-parity Rydberg states of xenon and the hyperfine structure of the 2P3/2 ground state of 129Xe+ and 131Xe+ have been obtained. Nearly degenerate p and d fine or hyperfine levels are very easily mixed by even weak stray electric fields.