Moleculelike metastable states of antiprotonic and mesic helium

Journal Article · Thu Oct 01 04:00:00 EDT 1992 · Physical Review A. General Physics; (United States)

DOI:https://doi.org/10.1103/PhysRevA.46.3776· OSTI ID:6947783

Shimamura, I ^[1]

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1. RIKEN (Institute of Physical and Chemical Research), Wako, Saitama 351-01 (Japan)

The exotic helium atom, consisting of a helium nucleus He{sup 2+}, an electron {ital e}{sup {minus}}, and a massive, negatively charged particle {ital X}{sup {minus}}, such as an antiproton ({ital {bar p}}) or a kaon ({ital K}{sup {minus}}), is studied theoretically. This exotic atom is more like a polar molecule with two nuclei He{sup 2+} and {ital X}{sup {minus}}, if {ital e}{sup {minus}} is in a low-lying orbital and {ital X}{sup {minus}} is in a highly excited orbital. Such states are generally formed in the capture of {ital X}{sup {minus}} by helium. The Born-Oppenheimer (BO) separation of the {ital e}{sup {minus}} motion and the He{sup 2+}-{ital X}{sup {minus}} motion is a good approximation for these states, and affords a transparent, unified perspective of exotic helium with different {ital X}{sup {minus}} and different isotopes of He{sup 2+}. A propensity rule that favors small transition energies (except for the smallest one) is found for radiative emission by low vibrational and high rotational levels. This rule resembles the selection rule for infrared emission by the usual diatomic polar molecules, and contradicts the conventional expectation that radiative transitions in exotic atoms favor larger transition energies. The radiative lifetimes {tau} of highly excited states formed immediately after the capture of {ital X}{sup {minus}} are of the order of {mu}sec for {sup 4}He{sup 2+}-{ital {bar p}}-{ital e}{sup {minus}} and {sup 3}He{sup 2+}-{ital {bar p}}-{ital e}{sup {minus}}, and those for {sup 4}He{sup 2+}-{ital K}{sup {minus}}-{ital e}{sup {minus}} are about half the values for the antiprotonic helium.

• OSTI ID: 6947783
• Journal Information: Physical Review A. General Physics; (United States), Journal Name: Physical Review A. General Physics; (United States) Vol. 46:7; ISSN 1050-2947; ISSN PLRAA
• Country of Publication: United States
• Language: English

Related Subjects

664500* -- Special Atoms & Molecules-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ANTIBARYONS
ANTIMATTER
ANTINUCLEI
ANTINUCLEONS
ANTIPARTICLES
ANTIPROTONS
ATOMS
AUGER EFFECT
BARYONS
BOUND STATE
CAPTURE
DECAY
ELECTRONIC STRUCTURE
ELEMENTARY PARTICLES
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FERMIONS
FLUIDS
GASES
HADRONIC ATOMS
HADRONS
HELIUM
MATTER
MESIC ATOMS
METASTABLE STATES
NONMETALS
NUCLEI
NUCLEONS
PARTICLE DECAY
RADIATIVE DECAY
RARE GASES
RYDBERG STATES