Abstract

Magnetic-dipole transitions in the first triplet ³P⁽⁰⁾ of ⁴⁰Ca and ²⁴Mg are of partic- ular interest for the realization of frequency standards in the terahertz, domain. The incomplete LS coupling allows decay of the ${}^3{P}_j^{(0)}$ level with a lifetime of 0.5 ms for Ca and 2.4 ms for Mg, creating a natural population difference between the ³P, level and the ³P₀ or ³P₂ level that increases along an atomic beam.¹ We are interested in producing the highest population density in the ³P₀ or ³P₂ level of calcium in order to make feasible an atomic frequency standard with this element. Oscillators to induce the ³P₀-³P₁ or ³P₀-³P₁ transition at 1.6 and 3.2 THz, respectively, have a low-level signal, because to date no far-infrared lasers have operated sufficiently near these frequencies to permit tuning to resonance. Optical pumping has proved to be an efficient way for improving the signal-to-noise ratio in a Mg atomic frequency standard.^2,3

© 1994 Optical Society of America