🚀 go-pugleaf

>I was vague because I was in a hurry.  Looking at the reference more
>carefully (H. Poth, "Antiprotonic, Hyperonic, and Antihydrogen Atoms,"
>*Proceedings of the First Workshop on Antimatter Physics at Low
>Energy*, Fermilab, 1986-- it may not be the definitive source of
>information, but had the advantage of being on the shelf in my
>office), I see that Poth says the delay between capture of a p-bar
>into an atomic orbit and its annihilation is less than 1E-10 seconds
>in most solids and liquids. (B. Higgins, 11 Jan 93 16:08:55 GMT)

It seems that antiprotons can live inside matter far longer than was
initially thought. In 1947, Fermi and Teller calculated a 10^-13 seconde
value ( 0.1 picosecond). But from bubble chambers experiments with
negative pions and kaons, it was inferred that the real time could be
100 picoseconds (which is the value quoted by Bill Higgins). Now, first
at the KEK Japanese laboratory, and then at CERN, it has been shown
that, inside liquid helium at 6 atm. pressure, 4% of the antiprotons
live several microseconds. If the helium is "contaminated" with a
small amount of hydrogen (0.04 %) this time is divided by about 10.
Such an effect had been predicted in 1964 by G.T.Condo (Oak Ridge).
According to him, the quantum numbers of some of the exotic helium
atoms built in this way could prevent the immediat release of the
second electron. In this case, according to Pauli's exclusion
principle, deep collisions of the exotic atom with its neighboring
ordinary atoms would be prevented, and the anti-proton would "fall"
slowly towards the nucleus via successive electromagnetic transitions.
However, it is not clear that this explanation is the good one.
Many questions remain, in particular is this a specific property of
helium.

J. Pharabod

Reference:"Antiprotons refractaires a l'annihilation", Courrier CERN,
June 1992.