Victor Kaufman

Interference at Great Retardations Obtained with a Calcium Atomic Beam Source

By employing a calcium atomic beam source in emission and by using a beam of high collimation very clear Fabry-Perot patterns of the resonance line of calcium, λ4226 A, were obtained with retardations of 60, 78, 94, 108, 120, and 130 cm. The corresponding order numbers are about 1.42, 1.85, 2.22, 2.56, 2.84, and 3.08 million and greatly surpass those obtainable with the best conventional cooled source available at present. The good definition of the fringes obtained with the retardation of 130 cm suggests that the limit of interference is considerably higher.

Calcium Atomic Beam Source and Interference beyond Two-Meter Retardation*

Fabry-Perot interference patterns of the resonance line of calcium, λ4226 A, have now been obtained at retardations of 153 and 204 cm by employing a highly collimated calcium atomic beam source in emission. The corresponding order numbers are 3.62 and 4.82 million. The appearance of these fringes suggests that the half-width of the line is less than 3×10−3 cm−1 which is one-fourth that of the proposed primary standard of length and one-tenth that of the present primary standard of wavelength. The use of an atomic beam source for the production of the length standard is discussed.