[time-nuts] Is 5061A by itself a primary reference? Was: Modern Rb atomic reference vs classic Cs

[Hal Murray]

richard at karlquist.com said:
> At one time, only cesium standards were considered truly primary because of
> the definition of the second.  However, the quantum mechanical constants of
> other atoms such as Rb have been measured to much more accuracy than the 5071
> so that Rb standards can be considered traceable to Cs if they are otherwise
> of primary architecture.  The key idea is that all Rb atoms are absolutely
> identical.  Rb gas cells are of course never primary. 

Can the physics-nuts calculate the Rb frequency relative to Cs?

What's missing on a gas cell?  Is the problem theory or implementation?

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