Abstract: A stabilized atomic clock system uses a stabilized 780.2 nm pump laser for exciting rubidium-85 atoms fluorescing to optically pump rubidium-87 atoms both contained in a gas cell enclosed in a resonant microwave cavity for broadcasting a 6834.7 MHz microwave signal matched to Rb87 hyperfine ground states which are insensitive to pump laser wavelength fluctuations of the pump laser providing the fluorescence optical pumping of the Rb87 atoms to create a population imbalance sensed by a stabilized 794.7 nm probe laser transmitting a probe beam through the cell to a probe laser photodetector generating a probe laser signal used to stabilize the microwave signal to the atomic system and used to generate a constant frequency tick rate signal that is consequently insensitive to pump laser frequency drift due to reduced light shift coefficient.