Two fixed, spatially separated detectors are used to measure the decay in flight of a cooled, thermal beam of pulsed metastable helium atoms. The preliminary value obtained for the radiative lifetime of the metastable $2^{1}S_{0}$ state of helium is 20 \ifmmode\pm\else\textpm\fi{} 2 msec.Two fixed, spatially separated detectors are used to measure the decay in flight of a cooled, thermal beam of pulsed metastable helium atoms. The preliminary value obtained for the radiative lifetime of the metastable $2^{1}S_{0}$ state of helium is 20 \ifmmode\pm\else\textpm\fi{} 2 msec.

Physical Review LettersNov 16, 197038 citations

Long-Range Interaction between Metastable Helium and Ground State Helium

G. A. Victor, Kenneth M. Sando

The Journal of Chemical PhysicsDec 1, 197125 citations

Half-Life of Metastable Helium Atoms.

Jesse Truett Matthews

Jan 1, 19600 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

2^{1}S_{0}

state of helium is 20 \ifmmode\pm\else\textpm\fi{} 2 msec.

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.