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

paul swed paulswedb at gmail.com
Sat Oct 29 19:34:02 UTC 2011


Ammonia was the first clock wasn't it?
Potentially Na and K have reactive behaviors like catching on fire that
isn't attractive to a manufacturing process.

On Sat, Oct 29, 2011 at 3:12 PM, Poul-Henning Kamp <phk at phk.freebsd.dk>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.
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
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