On Sun, 05 May 2013 18:29:53 +0000 "Poul-Henning Kamp" <p...@phk.freebsd.dk> wrote:
> In message <51867df4.4010...@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 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.