On 10/29/2011 08:19 PM, Attila Kinali wrote:
Moin,
Over the past years, i've read quite a bit on the different flavours
of atomic clocks and how they are build. I found explenations for
most questions i had, but for one thing: Why do all current designs
(with the exception of trapped ion optical clocks) use alkali metals
as reference? Is it because they can be aproximated as single electron
systems due to the one electron in the valence orbit?
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 did a search a few years ago and collected this list of frequencies:
http://rubidium.dyndns.org/~magnus/physics/hyperfine/
Actually, Thallium was a contender for the primary reference, as it is
known already back then to be less susceptible to magnetic pulling
effects than caesium. Thallium beams would mean about 3 times higher
frequency, so there was some question about the repeatability at the
time. The magnetic susceptibility is less of an issue now with servoed C
field.
You will also find that there is plenty more available. The above is not
a complete list, but as far as I got with the sources I had at the time.
I'm sure that I could get better data and more isotopes if I dug around
more.
Cheers,
Magnus
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