Absolute hyperfine energy levels and isotope shift of Rb 5S–6S two-photon transition

Abstract

Using a Rb cell and a wavemeter, with a Doppler-free two-photon transition near 993 nm, we have measured the four hyperfine components (two isotopes, ΔF = 0) of the 5S–6S transition, finding the absolute energies of those transitions to a spectral resolution of 0.002 cm−1 = 60 MHz. We find the (87 minus 85) isotope shift of the 5S–6S transition to be +94(12) MHz. Using our single frequency cw laser with focused intensity up to 104 W cm−2 at the cell, we find no AC Stark or light shift of the lines at 6 MHz spectral resolution. We find no density shift of the lines at 6 MHz spectral resolution, for a range of Rb atom densities from 3 × 1011 to 5 × 1013 atoms/cm3.