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

Magnus Danielson magnus at rubidium.dyndns.org
Sun Oct 30 15:51:19 UTC 2011


On 10/29/2011 09:34 PM, paul swed wrote:
> 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.

A feature shared with H, Ru and Cs, which does not exclude them from 
being selected.

Cheers,
Magnus

> 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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