The dependence of frequency upon microwave power of wall-coated and buffer-gas-filled gas cell Rb87 frequency standards

Abstract

Previous studies of a commerical passive gas cell Rb87 frequency standard showed a strong dependence of the output frequency νRb upon the microwave power Pμλ. A major conclusion of that work was that the dependence of νRb upon Pμλ was due to a line inhomogeneity effect. The line inhomogeneity interpretation suggested that substituting a wall coating for the usual buffer gas would reduce the dependence upon Pμλ. As a part of the present work, a wall coating (a form of paraffin) was used and a reduction of this dependence by a factor of 100 was obtained. The present work has led to a more convincing theoretical demonstration of the line inhomogeneity effect. The paper discusses some of the details of the analytical procedure. There are certain major requirements that a wall coating would have to satisfy if it is to be superior to the usual buffer gas, and these are discussed in the text. The advantages demonstrated by the present work indicate that further studies are warranted to determine if an improved standard could be built based on a wall coating.