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

Magnus Danielson magnus at rubidium.dyndns.org
Sun Oct 30 11:50:09 EDT 2011


On 10/29/2011 09:12 PM, Poul-Henning Kamp wrote:
> 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.

Sodium lamps is common, so it's not a big issue. Buth large cavities to 
support sub 1 GHz frequencies is unpractical, but possible.

The high temperature is however an issue for stability once you look 
close enough.

Cheers,
Magnus




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