arXiv:physics/0401095 · Physical Review A

Systematic study of the decay rates of antiprotonic helium states

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

Published Jul 8, 2004• 18 citations

arXiv HTML PDF

Abstract

A systematic study of the decay rates of antiprotonic helium (${\overline{p}}^{4}{\mathrm{He}}^{+}$ and ${\overline{p}}^{3}{\mathrm{He}}^{+}$) at CERN Antiproton Decelerator has been made by a laser spectroscopic method. The decay rates of some of its short-lived states, namely those for which the Auger rates ${\ensuremath{\gamma}}_{A}$ are much larger than their radiative decay rates $({\ensuremath{\gamma}}_{\mathrm{rad}}\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}{s}^{\ensuremath{-}1})$, were determined from the time distributions of the antiproton annihilation signals induced by laser beams, and the widths of the atomic resonance lines. The magnitude of the decay rates, especially their relation with the transition multipolarity, is discussed and compared with theoretical calculations.

DOI: 10.1103/physreva.70.012501

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Anomalies in the decay rates of antiprotonic helium-atom states

H. Yamaguchi, Takashi Ishikawa, Jun Sakaguchi +8 more

Physical Review AAug 15, 200234 citations

Auger transition rates for metastable states of antiprotonic helium He+p¯

V. I. Korobov, Isao Shimamura

Physical Review ADec 1, 199760 citations

Laser spectroscopic studies of state-dependent collisional quenching of the lifetimes of metastable antiprotonic helium atoms

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Observation of Cold, Long-Lived Antiprotonic Helium Ions

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First observation of laser-induced resonant annihilation in metastable antiprotonic helium atoms

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arXiv:physics/0401095 · Physical Review A

Systematic study of the decay rates of antiprotonic helium states

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

Published Jul 8, 2004• 18 citations

arXiv HTML PDF

Abstract

A systematic study of the decay rates of antiprotonic helium (

{\overline{p}}^{4}{\mathrm{He}}^{+}

and

{\overline{p}}^{3}{\mathrm{He}}^{+}

) at CERN Antiproton Decelerator has been made by a laser spectroscopic method. The decay rates of some of its short-lived states, namely those for which the Auger rates

{\ensuremath{\gamma}}_{A}

are much larger than their radiative decay rates

({\ensuremath{\gamma}}_{\mathrm{rad}}\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}{s}^{\ensuremath{-}1})

, were determined from the time distributions of the antiproton annihilation signals induced by laser beams, and the widths of the atomic resonance lines. The magnitude of the decay rates, especially their relation with the transition multipolarity, is discussed and compared with theoretical calculations.

DOI: 10.1103/physreva.70.012501

Related papers

Anomalies in the decay rates of antiprotonic helium-atom states

H. Yamaguchi, Takashi Ishikawa, Jun Sakaguchi +8 more

Six resonance transitions of the antiprotonic helium atom in helium gas at densities of $3\ifmmode\times\else\texttimes\fi{}{10}^{20}--3\ifmmode\times\else\texttimes\fi{}{10}^{21} {\mathrm{cm}}^{\ensuremath{-}3}$ were studied at the antiproton decelerator (AD) of CERN. The decay rates of the daughter states of these transitions were determined either from the time distributions of the resonance spikes or from the widths of the resonance lines. Whereas most of the observed decay rates agree with theoretical calculations of Auger rates, two states, $(n,l)=(37,33)$ and (32,31), were found to have decay rates two orders of magnitude larger than predicted by these calculations. The effect of coupling with near-lying electron-excited states is considered to be the reason for the anomaly of the (37, 33) state, as pointed out by Kartavtsev et al. [Phys. Rev. A $61,$ 062507 (2000)].Six resonance transitions of the antiprotonic helium atom in helium gas at densities of $3\ifmmode\times\else\texttimes\fi{}{10}^{20}--3\ifmmode\times\else\texttimes\fi{}{10}^{21} {\mathrm{cm}}^{\ensuremath{-}3}$ were studied at the antiproton decelerator (AD) of CERN. The decay rates of the daughter states of these transitions were determined either from the time distributions of the resonance spikes or from the widths of the resonance lines. Whereas most of the observed decay rates agree with theoretical calculations of Auger rates, two states, $(n,l)=(37,33)$ and (32,31), were found to have decay rates two orders of magnitude larger than predicted by these calculations. The effect of coupling with near-lying electron-excited states is considered to be the reason for the anomaly of the (37, 33) state, as pointed out by Kartavtsev et al. [Phys. Rev. A $61,$ 062507 (2000)].

Physical Review AAug 15, 200234 citations

Auger transition rates for metastable states of antiprotonic helium He+p¯

V. I. Korobov, Isao Shimamura

The rates of Auger transitions of antiprotonic helium ${}^{4}$ He ${}^{+}\overline{p}$ and ${}^{3}$ He ${}^{+}\overline{p}$ are calculated by using a variational scattering method with an elaborate three-body trial function. The shift of the energy levels of these systems due to the coupling with the Auger-decay channels is also obtained from this calculation. Thus an improvement is made over the previously calculated nonrelativistic energies. Together with the relativistic corrections calculated elsewhere, the theoretical transition wavelength between the states $(n,l)=(37,34)$ and $(38,33)$ of ${}^{4}$ He ${}^{+}\overline{p}$ , for example, is significantly improved to be 713.593 nm, which compares well with the experimental value 713.578$\ifmmode\pm\else\textpm\fi{} $0.006 nm. The calculated Auger lifetime of the level (38,33) is 3.2 ps, as compared with the value 4.1$ \ifmmode\pm\else\textpm\fi{}$0.2 ps deduced from the measured line broadening. Auger rates are calculated also using Fermi's golden-rule formula with a regular Coulomb function with no phase shift for the Auger electron. The results agree fairly well with the accurate variational results.The rates of Auger transitions of antiprotonic helium ${}^{4}$He${}^{+}\overline{p}$ and ${}^{3}$He${}^{+}\overline{p}$ are calculated by using a variational scattering method with an elaborate three-body trial function. The shift of the energy levels of these systems due to the coupling with the Auger-decay channels is also obtained from this calculation. Thus an improvement is made over the previously calculated nonrelativistic energies. Together with the relativistic corrections calculated elsewhere, the theoretical transition wavelength between the states $(n,l)=(37,34)$ and $(38,33)$ of ${}^{4}$He${}^{+}\overline{p}$, for example, is significantly improved to be 713.593 nm, which compares well with the experimental value 713.578$\ifmmode\pm\else\textpm\fi{}$0.006 nm. The calculated Auger lifetime of the level (38,33) is 3.2 ps, as compared with the value 4.1$\ifmmode\pm\else\textpm\fi{}$0.2 ps deduced from the measured line broadening. Auger rates are calculated also using Fermi's golden-rule formula with a regular Coulomb function with no phase shift for the Auger electron. The results agree fairly well with the accurate variational results.

Physical Review ADec 1, 199760 citations

Laser spectroscopic studies of state-dependent collisional quenching of the lifetimes of metastable antiprotonic helium atoms

M. Hori, H. A. Torii, R. Hayano +16 more

A laser spectroscopic method was developed to directly observe the lifetimes of individual states in metastable antiprotonic helium atoms $(\overline{p}{}^{4}{\mathrm{He}}^{+}).$ Collisional effects with surrounding helium atoms were studied in cryogenic gas targets at pressures between 0.1 and 9.0 bars and at temperatures between 5.5 and 7.0 K. The metastable state $(n,\mathcal{l})=(39,35)$ showed a lifetime of 1.5 $\ensuremath{\mu}\mathrm{s}$, regardless of density, whereas the lifetime of the energetically lower-lying state $(37,34)$ was found to shorten from 1.3 to 0.1 $\ensuremath{\mu}$s with increasing density. The lifetimes of the states $(38,34)$ and $(36,33)$ were determined to be 10 ns and 5 ns, respectively, showing the effects of the internal Auger process. When extrapolated to zero density, the measured lifetimes agreed with the results of calculations for the radiative and Auger widths. Using the fact that the state $(37,34)$ becomes short lived at high density, the resonance $(38,35)\ensuremath{\rightarrow}(37,34)$ at 529.62 nm was detected.A laser spectroscopic method was developed to directly observe the lifetimes of individual states in metastable antiprotonic helium atoms $(\overline{p}{}^{4}{\mathrm{He}}^{+}).$ Collisional effects with surrounding helium atoms were studied in cryogenic gas targets at pressures between 0.1 and 9.0 bars and at temperatures between 5.5 and 7.0 K. The metastable state $(n,\mathcal{l})=(39,35)$ showed a lifetime of 1.5 $\ensuremath{\mu}\mathrm{s}$, regardless of density, whereas the lifetime of the energetically lower-lying state $(37,34)$ was found to shorten from 1.3 to 0.1 $\ensuremath{\mu}$s with increasing density. The lifetimes of the states $(38,34)$ and $(36,33)$ were determined to be 10 ns and 5 ns, respectively, showing the effects of the internal Auger process. When extrapolated to zero density, the measured lifetimes agreed with the results of calculations for the radiative and Auger widths. Using the fact that the state $(37,34)$ becomes short lived at high density, the resonance $(38,35)\ensuremath{\rightarrow}(37,34)$ at 529.62 nm was detected.

Physical Review AMar 1, 199843 citations

Laser Studies of the Decay Chain of Metastable Antiprotonic Helium Atoms

R. Hayano, Frank E. Maas, H. A. Torii +14 more

Laser studies of metastable antiprotonic helium atoms, which we recently initiated by observing a sharp increase of the antiproton annihilation rate induced by laser-stimulated resonant transitions, have been extended. With a single laser tuned to the resonance already found at 597.26 nm, we have now established the time dependence of the upper state population. With two lasers ignited at variable time separation, we also studied the feeding of the upper state from higher atomic levels. The initial populations and level lifetimes of excited exotic atoms were determined.Laser studies of metastable antiprotonic helium atoms, which we recently initiated by observing a sharp increase of the antiproton annihilation rate induced by laser-stimulated resonant transitions, have been extended. With a single laser tuned to the resonance already found at 597.26 nm, we have now established the time dependence of the upper state population. With two lasers ignited at variable time separation, we also studied the feeding of the upper state from higher atomic levels. The initial populations and level lifetimes of excited exotic atoms were determined.

Physical Review LettersSep 12, 199463 citations

Observation of Cold, Long-Lived Antiprotonic Helium Ions

M. Hori, J. A. Eades, R. Hayano +8 more

Cold, two-body antiprotonic helium ions $\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}$ and $\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}$ with 100-ns-scale lifetimes, occupying circular states with the quantum numbers ${n}_{i}=28--32$ and ${\ensuremath{\ell}}_{i}={n}_{i}\ensuremath{-}1$ have been observed. They were produced by cooling three-body antiprotonic helium atoms in an ultra-low-density helium target at temperature $T\ensuremath{\sim}10\text{ }\text{ }\mathrm{K}$ by atomic collisions, and then removing their electrons by inducing a laser transition to an autoionizing state. The lifetimes of $\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}$ against annihilation induced by collisions were shorter than those of $\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}$ , and decreased for larger- ${n}_{i}$ states.Cold, two-body antiprotonic helium ions $\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}$ and $\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}$ with 100-ns-scale lifetimes, occupying circular states with the quantum numbers ${n}_{i}=28--32$ and ${\ensuremath{\ell}}_{i}={n}_{i}\ensuremath{-}1$ have been observed. They were produced by cooling three-body antiprotonic helium atoms in an ultra-low-density helium target at temperature $T\ensuremath{\sim}10\text{ }\text{ }\mathrm{K}$ by atomic collisions, and then removing their electrons by inducing a laser transition to an autoionizing state. The lifetimes of $\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}$ against annihilation induced by collisions were shorter than those of $\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}$, and decreased for larger-${n}_{i}$ states.

Physical Review LettersFeb 14, 200545 citations

First observation of laser-induced resonant annihilation in metastable antiprotonic helium atoms

N. Morita, M. Kumakura, Toshitsugu Yamazaki +14 more

We have observed the first laser-induced resonant transitions in antiprotonic helium atoms. These occur between metastable states and Auger dominated short lived states, and show that the anomalous longevity of antiprotons previously observed in helium media results from the formation of high-n high-l atomic states of p\ifmmode\bar\else\textasciimacron\fi{} ${\mathrm{He}}^{+}$ . The observed transition with vacuum wavelength 597.259\ifmmode\pm\else\textpm\fi{}0.002 nm is tentatively assigned to (n,l)=(39,35)\ensuremath{\rightarrow}(38,34).We have observed the first laser-induced resonant transitions in antiprotonic helium atoms. These occur between metastable states and Auger dominated short lived states, and show that the anomalous longevity of antiprotons previously observed in helium media results from the formation of high-n high-l atomic states of p\ifmmode\bar\else\textasciimacron\fi{}${\mathrm{He}}^{+}$. The observed transition with vacuum wavelength 597.259\ifmmode\pm\else\textpm\fi{}0.002 nm is tentatively assigned to (n,l)=(39,35)\ensuremath{\rightarrow}(38,34).

Physical Review LettersFeb 21, 1994140 citations

A systematic study of the decay rates of antiprotonic helium (

{\overline{p}}^{4}{\mathrm{He}}^{+}

and

{\overline{p}}^{3}{\mathrm{He}}^{+}

) at CERN Antiproton Decelerator has been made by a laser spectroscopic method. The decay rates of some of its short-lived states, namely those for which the Auger rates

{\ensuremath{\gamma}}_{A}

are much larger than their radiative decay rates

({\ensuremath{\gamma}}_{\mathrm{rad}}\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}{s}^{\ensuremath{-}1})

(n,l)=(37,33)

and (32,31), were found to have decay rates two orders of magnitude larger than predicted by these calculations. The effect of coupling with near-lying electron-excited states is considered to be the reason for the anomaly of the (37, 33) state, as pointed out by Kartavtsev et al. [Phys. Rev. A

61,

062507 (2000)].

The rates of Auger transitions of antiprotonic helium

{}^{4}

{}^{+}\overline{p}

and

{}^{3}

{}^{+}\overline{p}

are calculated by using a variational scattering method with an elaborate three-body trial function. The shift of the energy levels of these systems due to the coupling with the Auger-decay channels is also obtained from this calculation. Thus an improvement is made over the previously calculated nonrelativistic energies. Together with the relativistic corrections calculated elsewhere, the theoretical transition wavelength between the states

(n,l)=(37,34)

and

(38,33)

{}^{4}

{}^{+}\overline{p}

, for example, is significantly improved to be 713.593 nm, which compares well with the experimental value 713.578$\ifmmode\pm\else\textpm\fi{}

0.006 nm. The calculated Auger lifetime of the level (38,33) is 3.2 ps, as compared with the value 4.1

\ifmmode\pm\else\textpm\fi{}$0.2 ps deduced from the measured line broadening. Auger rates are calculated also using Fermi's golden-rule formula with a regular Coulomb function with no phase shift for the Auger electron. The results agree fairly well with the accurate variational results.

A laser spectroscopic method was developed to directly observe the lifetimes of individual states in metastable antiprotonic helium atoms

(\overline{p}{}^{4}{\mathrm{He}}^{+}).

Collisional effects with surrounding helium atoms were studied in cryogenic gas targets at pressures between 0.1 and 9.0 bars and at temperatures between 5.5 and 7.0 K. The metastable state

(n,\mathcal{l})=(39,35)

showed a lifetime of 1.5 $\ensuremath{\mu}\mathrm{s}$, regardless of density, whereas the lifetime of the energetically lower-lying state

(37,34)

was found to shorten from 1.3 to 0.1 $\ensuremath{\mu}$s with increasing density. The lifetimes of the states

(38,34)

and

(36,33)

were determined to be 10 ns and 5 ns, respectively, showing the effects of the internal Auger process. When extrapolated to zero density, the measured lifetimes agreed with the results of calculations for the radiative and Auger widths. Using the fact that the state

(37,34)

becomes short lived at high density, the resonance $(38,35)\ensuremath{\rightarrow}(37,34)$ at 529.62 nm was detected.

Cold, two-body antiprotonic helium ions

\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}

and

\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}

with 100-ns-scale lifetimes, occupying circular states with the quantum numbers

{n}_{i}=28--32

and ${\ensuremath{\ell}}_{i}={n}_{i}\ensuremath{-}1$ have been observed. They were produced by cooling three-body antiprotonic helium atoms in an ultra-low-density helium target at temperature $T\ensuremath{\sim}10\text{ }\text{ }\mathrm{K}$ by atomic collisions, and then removing their electrons by inducing a laser transition to an autoionizing state. The lifetimes of

\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}

against annihilation induced by collisions were shorter than those of

\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}

, and decreased for larger-

{n}_{i}

states.

{\mathrm{He}}^{+}

. The observed transition with vacuum wavelength 597.259\ifmmode\pm\else\textpm\fi{}0.002 nm is tentatively assigned to (n,l)=(39,35)\ensuremath{\rightarrow}(38,34).