Abstract

Doppler-free two-photon transitions to Rydberg states in alkali metals have been recommended as a potential source of reference lines or secondary standards for wavelength calibration, because they cover a wide range of the visible spectrum.¹ Observation of spectral lines for the two-photon transitions was made possible by use of a thermionic diode detector cell similar to that originally designed by Harvey.² The Pyrex cell enclosing the diode detector and containing natural Rb was placed in a two-chamber oven so that the temperature of the cell body and that of the sidearm Rb supply could be controlled independently.

© 1987 Optical Society of America