Spectroscopy of the 85Rb 4 state for hyperfine-structure determination

Abstract

We report a measurement of the hyperfine-structure constants of the 85Rb 4 state using two-photon optical spectroscopy of the 54 transition. The spectra are acquired by measuring the transmission of the low-power 795 nm lower-stage laser beam through a cold-atom sample as a function of laser frequency, with the frequency of the upper-stage, 1476 nm laser fixed. All 4 hyperfine components of the state are well-resolved in the experimental data. The dominant systematic is the light shift from the 1476 nm laser, which is addressed by extrapolating line positions measured for a set of 1476 nm laser powers to zero laser power. The analysis of our experimental data yields both the magnetic-dipole and electric-quadrupole constants for the 85Rb 4 level, without using earlier hyperfine measurements of other atomic levels. The respective results, 7.419(35) MHz and 4.19(19) MHz, are discussed in context with previous works. Our investigation may be useful for optical atomic clocks for precision metrology and emerging atom-based quantum technologies, all-infrared excitation of Rb Rydberg levels, and molecular physics.