https://doi.org/10.1007/s100530170246
Collisional quenching of metastable states of antiprotonic helium by hydrogen and deuterium molecules
1
Physik-Department, Technische Universität München,
85747 Garching, Germany
2
CERN, European Organization for Nuclear
Research, 1211 Genève 23, Switzerland
3
Institute for Molecular Science,
Myodaiji, Okazaki 444, Japan
4
Department of Physics, University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan
5
Institute of Particle and Nuclear Studies,
3-2-1 Midori-cho, Tanashi, Tokyo 188-8501, Japan
6
Central Research Institute for Physics, Research Institute
for Particle and Nuclear Physics, 1525 Budapest, Hungary
Corresponding author: a bernhard.ketzer@cern.ch
Received:
2
October
2000
Published online: 15 March 2001
The quenching of metastable states of antiprotonic helium by collisions with
hydrogen and deuterium molecules was studied. A systematic investigation of the
delayed annihilation time spectra at various 
and 
admixture
ratios at the ppm level revealed characteristic changes of their shape, which
indicated a
strong
principal and orbital quantum number dependent
quenching of levels in both cases. Applying a laser
spectroscopy technique to measure the lifetimes of individual states and
cascades we deduced and quenching cross-sections for the states
(n,l)=(39,35) and (37,34). These
cross-sections
establish for molecules
the strong
increase of the quenching efficiency with increasing principal quantum number
n of the state under investigation
previously reported
for the case of
admixtures.
Our experiments indicate that
the low-n state (37,34)
is somewhat less affected by than by , while the high-n state
(39,35) is equally quenched by both isotopes.
PACS: 36.10.-k – Exotic atoms and molecules (containing mesons, muons, and other unusual particles) / 42.62.Fi – Laser spectroscopy / 34.20.Gj – Intermolecular and atom-molecule potentials and forces
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001
