Delayed annihilation time spectra (DATS) of antiprotons in room-temperature helium gas have been studied as a function of the concentration of admixed noble gases (Ne, Ar, Kr, Xe) as well as molecular gases ([Formula Presented],[Formula Presented],[Formula Presented]) at the low-energy antiproton ring at CERN. The DATS were a superposition of two exponential components, one with a lifetime of several 100 ns and the other with a lifetime 1–3 μs. They showed a shorter average lifetime ([Formula Presented]) than DATS of pure helium. Ne, Ar, and Kr were found to affect [Formula Presented] only slightly even in concentrations up to 20%, while Xe showed a much stronger influence. In the case of molecular gases, the presence of [Formula Presented] influenced the DATS much less than [Formula Presented] and [Formula Presented], which destroyed the metastability almost completely in concentrations of 100 ppm and less. The decay rate of the slow component of DATS was found to exhibit a linear relation to the number density of the admixture. From this a collisional destruction (“quenching”) cross section [Formula Presented] was extracted. No evidence for a delayed annihilation of antiprotons in pure Ne, Kr, and Xe was observed.
|Number of pages||11|
|Journal||Physical Review A - Atomic, Molecular, and Optical Physics|
|Publication status||Published - 1996|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics