Hunter Kettering, Travis Driskell, James C. Camparo, The Aerospace Corporation

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It is well known that collision shifts (i.e., buffer-gas shifts) for microwave transitions in atomic clocks have a non-negligible temperature dependence. What is perhaps not so well known is that the same holds true for optical transitions. In particular, for collision shifts deriving from a C6 interatomic potential the buffergas collision shift scales like dn = dno (T/To ) k , where dno is the collision shift at the reference temperature To, and k is a parameter describing the collision shift’s temperature sensitivity. For the heavier noble gases and the alkali first-resonance lines, k is theoretically expected to equal 0.3; and this has recently been confirmed experimentally in our laboratory. Here, we describe progress in our experiments to measure k for the alkali first-resonance lines perturbed by the full family of noble-gases, where deviations from k = 0.3 are anticipated for the lighter noble-gases.