[time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs

Attila Kinali attila at kinali.ch
Sun May 5 14:52:57 EDT 2013

On Sun, 05 May 2013 18:29:53 +0000
"Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:

> In message <51867DF4.4010006 at karlquist.com>, "Richard (Rick) Karlquist" writes:
> >BTW, it is important to understand that
> >the architecture is the key factor, not the flavor of atom.
> Well, somewhat.
> Some flavours of atoms don't work with some architectures, so for
> most of the stuff in reach for us, the atoms do indeed equate an
> architecture.

The alkali atoms are pretty much interchangable.
There have been masers from Rb as well as Cs, beam standards
from Rb and H, and Rb fountains. I have not read of any H fountain
yet, but i guess it's pretty difficult to build given that the
laser light needed for cooling is in the 120nm range (UV) and
lasers in that range are pretty difficult to build (there have
been laser spectroscopy experiments using 120nm lasers nevertheless)
and that H is very light, ie the fountain would get quite long.

I also have never seen a H gas cell standard, probably for the same reason
of needing UV light.

Other classes are charged ions, these are mostly positive charged atoms
where the outermost shell becomes an s orbital with a single electron.
Prime examples are alkaline earth metals (Be, Mg, Ca, Sr,..), but also
group 12 metals (Zn, Cd, Hg) and some lanthanide/actinide (e.g. Yb).
AFAIK these are mostly interchangable as well.

I do not know what the general property of laser cooled neutral atom
frequency standards is.

One property seldom explicitly mentioned is the nuclear spin. The alkali
metal standards seem to depend on the spin being half-integral, while
laser cooled ion standards seem to be possible with both integer (including 0)
and half integer spins.

			Attila Kinali

The people on 4chan are like brilliant psychologists
who also happen to be insane and gross.
		-- unknown

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