Pure hyperfine spectra of KRb in its vibronic ground state: Towards the determination of nuclear spin–spin interaction

The Zeeman-hyperfine-rotational spectra of ⁴⁰K⁸⁷Rb within its vibronic ground state at a magnetic field of 545.9 G are investigated by adopting the latest molecular constants available, and the results are in good agreement with the experimental observation made by Ospelkaus et al. Phys. Rev. Lett.104 030402 (2010). However, the calculated spectra generally shift by −3.6 kHz from the experimental ones, which implies the inaccuracy of the effective rotational constant. Therefore, we refit the spectra and obtain a new B_eff = 1113952(1) kHz, which reduces the overall root-mean-square deviation from 10.8 kHz to 7.9 kHz. Furthermore, the pure hyperfine spectra within the J = 0 and 1 rotational states are simulated. We find that the scalar nuclear spin–spin interaction dominates the hyperfine splitting of J = 0 despite it being slightly indirectly affected by the nuclear electric quadruple interaction due to the rotational perturbation, while the nuclear electric quadrupole interactions dominate the splitting, and the scalar and tensor nuclear spin–spin interactions also affect the splitting of J = 1. The detailed hyperfine-rotational perturbations are studied. Therefore, the scalar and tensor nuclear spin–spin interaction constants can be precisely determined by simultaneously measuring the pure hyperfine radio-frequency spectra of the J = 0 and 1 states in the vibronic ground state.