Measurement of the Microwave Lensing Shift in NIST-F1 and NIST-F2
Steven R. Jefferts, Stephan E. Barlow, Thomas P. Heavner, Neil Ashby
We present measurements of the microwave lensing frequency shift in the Primary Frequency Standards (PFS) NIST-F1 and NIST-F2. This frequency bias is reasonably controversial with differing theories giving quite different results. Our measurements are in good agreement with one of the two theories and significant disagreement (more than 2σ) with frequency shift as predicted by the other.