[time-nuts] Atomic clocks - Why alkali metals?

Poul-Henning Kamp phk at phk.freebsd.dk
Sat Oct 29 15:12:39 EDT 2011


In message <20111029201927.b7a1130c.attila at kinali.ch>, Attila Kinali writes:

>Is it because they can be aproximated as single electron
>systems due to the one electron in the valence orbit?

Yes.  Basically that electron is in a "figure of eight" orbital
which means that it passes straight through, or possibly just
very close by, the proton, allowing their spin moments to interact.

>Related to this is the question why only H, Rb and Cs are used.
>Although, from my point of view there isnt anything that speaks
>against using Li, K or Na, these are not used at all. At least i
>couldnt find any papers or other documents describing frequency
>standards build on these elements.

I belive K has been tried.

I belive the preference for H, Rb & Cs is that getting them as
single atoms doesn't require high temperatures.

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