Observation of quadrupole and dipole diamagnetic shifts in atomic ground-state hyperfine structure

A high-precision laser optical-pumping experiment on the S122 ground state of atomic rubidium in magnetic fields of up to 8 T has led to the first observation of a magnetically induced quadrupole hyperfine interaction, in both Rb85 and Rb87. The quadrupole coupling constant was measured to be 7.0(6) × 10-4 Hz T-2 in Rb85. The diamagnetic shift in dipole hyperfine structure was also measured in both Rb85 and Rb87. The fractional dipole shift was found to be independent of isotope with a value a=5.2(2)×10-10 T-2, confirming and extending previous results for Rb85 only.