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Quenching of metastable states of antiprotonic helium atoms by collisions with H$_2$ molecules

Laser resonance transitions between normally metastable states of antiprotonic helium atoms were induced making use of state dependent quenching effects caused by trace admixtures of \mbox{H$_2$}\ to the target helium gas. With this method of ``\mbox{H$_2$}-assisted inverse resonances'' th...

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Detalles Bibliográficos
Autores principales: Ketzer, B, Hartmann, F J, Von Egidy, T, Maierl, C, Pohl, R, Eades, John, Widmann, E, Yamazaki, T, Kumakura, M, Morita, N, Hayano, R S, Hori, Masaki, Ishikawa, T, Torii, H A, Sugai, I, Horváth, D
Lenguaje:eng
Publicado: 1998
Materias:
Acceso en línea:http://cds.cern.ch/record/347040
Descripción
Sumario:Laser resonance transitions between normally metastable states of antiprotonic helium atoms were induced making use of state dependent quenching effects caused by trace admixtures of \mbox{H$_2$}\ to the target helium gas. With this method of ``\mbox{H$_2$}-assisted inverse resonances'' the decay rates of the states $(n,l)=(39,l),\ l=36,37,38$ and $(38,l),\ l=35,36,37$ of \mbox{$\overline{\mathrm{p}}$}\mbox{He$^{+}$}\ were determined as a function of the \mbox{H$_2$}\ admixture. The quenching cross sections at 30~K deduced therefrom for the states with $n=39$ were found to be of the order of the geometrical cross section for \mbox{$\overline{\mathrm{p}}$}\mbox{He$^{+}$}-\mbox{H$_2$}\ collisions ($2\cdot 10^{-15}$~cm$^2$), with a moderate decrease with increasing $l$. Within a given cascade with constant $v=n-l-1$, the quenching cross sections for states with $n=38$ are smaller by a factor of 4--6 than those for states with $n=39$.