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

[Attila Kinali]

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.

			Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson