Observation of cold, long-lived antiprotonic helium ions.
Cold, two-body antiprotonic helium ions p 4He2+ and p 3He2+ with 100-ns-scale lifetimes, occupying circular states with the quantum numbers ni=28-32 and li=ni-1 have been observed. They were produced by cooling three-body antiprotonic helium atoms in an ultra-low-density helium target at temperature T approximately 10 K by atomic collisions, and then removing their electrons by inducing a laser transition to an autoionizing state. The lifetimes of p 3He2+ against annihilation induced by collisions were shorter than those of p 4He2+, and decreased for larger-ni states.
Hori
M
M
CERN, CH-1211 Geneva 23, Switzerland.
Eades
J
J
Hayano
R S
RS
Pirkl
W
W
Widmann
E
E
Yamaguchi
H
H
Torii
H A
HA
Juhász
B
B
Horváth
D
D
Suzuki
K
K
Yamazaki
T
T