Rydberg Constant Measurement Using cw Dye Laser and H* Atomic Beam

Abstract

We would like to describe a new experiment which we have in progress for obtaining a greatly improved value for the Rydberg. The accuracy of measureryents using classical techniques¹ have been limited to about 2 × 10⁷ by Doppler broadening and discharg effects. A recent improvement of accuracy to about 1 × 10⁻⁸ was obtained² by using a pulsed dye laser to obtain laser saturated-absorption of the Balmer α line in a hydrogen discharge, thereby eliminating Doppler broadenir. We hope to achieve an accuracy between 1 × 10⁻⁹ and 1 × 10⁻¹⁰ though use of a recently developed extremely stable cw dye laser³ to produce saturated absorption of the Balmer α line in an atomic eam of 2 s hydrogen atoms. Simultaneous excitation with RF⁴ should yield a double-resonance linewidth of about 1 MHz. Use of an atomic beam should eliminate systematic errors due to collisional effects and extraneous electromagnetic fields such as are encountered in discharges. For measuring the Balmer α wavelength to obtain the Rydberg, we shall use the frequency-controlled Fabry-Perot interferometer whig was used for the wavelength measurement of the 3.39 μ CH₄ line⁵. This 3.39 μ CH₄ line will be used as the length standard for the measurement. We expect the accI5acy of our wavelength measurement to be limited to a few × 10⁻¹⁰ by already investigated systematic errors inherant in our interferometer, mainly diffraction effects.