Double radio optical resonances in thermal 87Rb vapor

In this paper we compare two different excitation schemes of rubidium gas-cell frequency standard. The first scheme is based on the one laser optical pumping and the second scheme is based on the “two-lasers” optical pumping firstly proposed by J. Deng for light shift compensation. We present stability estimations for both schemes supposing that the gas cell has 15 mb of N₂ and the laser line width is about 100 MHz. Our calculations do not show the expected significant improvement of the stability in the case of “two-lasers” scheme. This result is connected to the broadening of the absorption line. To avoid this broadening one needs to use a buffer gas pressure around 1 mb and a laser line width of 10 MHz or less.