Rydberg Constant Measurement Using cw Dye Laser and H* Atomic Beam
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.
KeywordsAtomic Beam Fundamental Constant Wavelength Measurement Collisional Effect Shot Noise Limit
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