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Jun25-10, 12:45 PM
P: 560
Quote Quote by alxm View Post
Well I was thinking if you specifically generate triplet helium and then ..
That was my other main concern: By what method would you "specifically generate triplet helium"??(not BEC)

This is a 'forbidden' transition; It can only occur (in an isolated atom) due to two-photon processes, which one can think of as a decay to a 'virtual' level in-between the two states. For Helium it's not symmetric; one of the photons carries more energy than the other, so you end up with two peaks, one at ~70 nm and one at ~2400. (See e.g. this paper, if you want some details)
Thanks for the G W Drake link. I'm not too sure I understand it all....Of course, Selection rules prohibit single photon transitiion .... so it goes two photon route...OK, but this rate is extremely low, right?
I have read elsewhere that the most probable decay is thru 'collisional' process, I am not sure what that refers to ...any info there?

GW Drake has a later article in which it appears as if he is saying that there is a MORE probable Magnetic dipole transition to ground state I reading that right?
See here: