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

Bob Camp lists at rtty.us
Sun Oct 30 15:50:15 EDT 2011


Hi

Oddly enough, reactivity / cell lifetime is indeed worse with both ammonia and mercury(!) than with Rb and Cs. At least that's the word from those who have tried them all….

Bob


On Oct 30, 2011, at 11:51 AM, Magnus Danielson wrote:

> 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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