Physical Review Letters

Primary Populations of Metastable Antiprotonic H4e and H3e Atoms

M. Hori, J. A. Eades, R. Hayano, Takashi Ishikawa, Jun Sakaguchi, T. Tasaki, E. Widmann, H. Yamaguchi, H. A. Torii, Bertalan Juhász, D. Horváth, Toshitsugu Yamazaki

Published Aug 7, 2002• 53 citations

Publisher

Abstract

Initial distributions of metastable antiprotonic $^{\mathrm{4}}\mathrm{H}\mathrm{e}$ and $^{\mathrm{3}}\mathrm{H}\mathrm{e}$ atoms over principal ($n$) and angular momentum ($\ensuremath{\ell}$) quantum numbers have been deduced using laser spectroscopy experiments. The regions $n=37--40$ and $n=35--38$ in the two atoms account for almost all of the observed fractions [$(3.0\ifmmode\pm\else\textpm\fi{}0.1)%$ and $(2.4\ifmmode\pm\else\textpm\fi{}0.1)%$] of antiprotons captured into metastable states.

DOI: 10.1103/physrevlett.89.093401

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Physical Review Letters

Primary Populations of Metastable Antiprotonic H4e and H3e Atoms

M. Hori, J. A. Eades, R. Hayano, Takashi Ishikawa, Jun Sakaguchi, T. Tasaki, E. Widmann, H. Yamaguchi, H. A. Torii, Bertalan Juhász, D. Horváth, Toshitsugu Yamazaki

Published Aug 7, 2002• 53 citations

Publisher

Abstract

Initial distributions of metastable antiprotonic

^{\mathrm{4}}\mathrm{H}\mathrm{e}

and

^{\mathrm{3}}\mathrm{H}\mathrm{e}

atoms over principal (

n

) and angular momentum (

\ensuremath{\ell}

) quantum numbers have been deduced using laser spectroscopy experiments. The regions

n=37--40

and

n=35--38

in the two atoms account for almost all of the observed fractions [

(3.0\ifmmode\pm\else\textpm\fi{}0.1)%

and

(2.4\ifmmode\pm\else\textpm\fi{}0.1)%

] of antiprotons captured into metastable states.

DOI: 10.1103/physrevlett.89.093401

Related papers

Hydrogen-Assisted Laser-Induced Resonant Transitions between Metastable States of Antiprotonic Helium Atoms

B. Ketzer, F. J. Hartmann, Till von Egidy +13 more

Laser resonance transitions between normally metastable states of antiprotonic helium atoms were observed making use of state dependent quenching effects caused by small admixtures of ${\mathrm{H}}_{2}$ molecules. By selectively shortening the lifetimes of states with higher principal quantum number $n$ as compared to those of lower $n$ , this method for the first time provides access to all initially populated metastable states of $\overline{p}{\mathrm{He}}^{+}$ atoms. This was demonstrated by observing the transitions $(n,l)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(38,l)\ensuremath{\rightarrow}(39,l+1)$, $l\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}35,36,37$ and $(n,l)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(37,l)\ensuremath{\rightarrow}(38,l+1)$, $l\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}34,35,36$ .Laser resonance transitions between normally metastable states of antiprotonic helium atoms were observed making use of state dependent quenching effects caused by small admixtures of ${\mathrm{H}}_{2}$ molecules. By selectively shortening the lifetimes of states with higher principal quantum number $n$ as compared to those of lower $n$, this method for the first time provides access to all initially populated metastable states of $\overline{p}{\mathrm{He}}^{+}$ atoms. This was demonstrated by observing the transitions $(n,l)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(38,l)\ensuremath{\rightarrow}(39,l+1)$, $l\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}35,36,37$ and $(n,l)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(37,l)\ensuremath{\rightarrow}(38,l+1)$, $l\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}34,35,36$.

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Analysis of the lifetimes and fractions of antiprotons trapped in metastable states of antiprotonic helium

Isao Shimamura, Mineo Kimura

A recent paper by T. Yamazaki and K. Ohtsuki [Phys. Rev. A 45, 7782 (1992)] discusses properties of antiprotonic helium ( ${\mathrm{He}}^{2+}$ p\ifmmode\bar\else\textasciimacron\fi{}${\mathit{e}}^{\mathrm{\ensuremath{-}}}$) formed in collisions of antiprotons (p\ifmmode\bar\else\textasciimacron\fi{}) with helium. Here we point out problems with approximations and assumptions used in deriving the results of that paper.A recent paper by T. Yamazaki and K. Ohtsuki [Phys. Rev. A 45, 7782 (1992)] discusses properties of antiprotonic helium (${\mathrm{He}}^{2+}$p\ifmmode\bar\else\textasciimacron\fi{}${\mathit{e}}^{\mathrm{\ensuremath{-}}}$) formed in collisions of antiprotons (p\ifmmode\bar\else\textasciimacron\fi{}) with helium. Here we point out problems with approximations and assumptions used in deriving the results of that paper.

Physical Review ADec 1, 19942 citations

Initial distributions of metastable antiprotonic

^{\mathrm{4}}\mathrm{H}\mathrm{e}

and

^{\mathrm{3}}\mathrm{H}\mathrm{e}

atoms over principal (

n

) and angular momentum (

\ensuremath{\ell}

) quantum numbers have been deduced using laser spectroscopy experiments. The regions

n=37--40

and

n=35--38

in the two atoms account for almost all of the observed fractions [

(3.0\ifmmode\pm\else\textpm\fi{}0.1)%

and

(2.4\ifmmode\pm\else\textpm\fi{}0.1)%

] of antiprotons captured into metastable states.

Laser resonance transitions between normally metastable states of antiprotonic helium atoms were observed making use of state dependent quenching effects caused by small admixtures of

{\mathrm{H}}_{2}

molecules. By selectively shortening the lifetimes of states with higher principal quantum number

n

as compared to those of lower

n

, this method for the first time provides access to all initially populated metastable states of

\overline{p}{\mathrm{He}}^{+}

atoms. This was demonstrated by observing the transitions $(n,l)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(38,l)\ensuremath{\rightarrow}(39,l+1)$,

l\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}35,36,37

and $(n,l)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(37,l)\ensuremath{\rightarrow}(38,l+1)$,

l\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}34,35,36

Calculations of low-energy collisions of antiprotons

\overline{p}

with helium atoms in the ground

(1\phantom{\rule{4pt}{0ex}}^{1}\mathit{S})

and metastable

(2\phantom{\rule{4pt}{0ex}}^{3}\mathit{S}

and

2\phantom{\rule{4pt}{0ex}}^{1}\mathit{S})

states are carried out by using a semiclassical method and by further assuming that one of the two electrons is passive. Antiproton capture to form antiprotonic helium $(\ensuremath{\rightarrow}\overline{p}{\mathrm{He}}^{+}+e)$ and breakup ionization $(\ensuremath{\rightarrow}\overline{p}+{\mathrm{He}}^{+}+e)$ are investigated. The energy dependence of the capture and ionization cross sections and the distributions of the product states are presented and compared with previous theoretical calculations. For the metastable helium targets, most of the

\overline{p}{\mathrm{He}}^{+}

atoms produced in the capture have long lifetimes against subsequent Auger decays and can be observed experimentally. For the ground-state targets, however, the formation of such long-lived states is rather a rare event at low collision energies.

A recent paper by T. Yamazaki and K. Ohtsuki [Phys. Rev. A 45, 7782 (1992)] discusses properties of antiprotonic helium (

{\mathrm{He}}^{2+}

p\ifmmode\bar\else\textasciimacron\fi{}${\mathit{e}}^{\mathrm{\ensuremath{-}}}$) formed in collisions of antiprotons (p\ifmmode\bar\else\textasciimacron\fi{}) with helium. Here we point out problems with approximations and assumptions used in deriving the results of that paper.