Production and mean-lifetime measurement of metastableAr−ions

Lifetime measurements of the theoretically predicted metastable state ${}_{}{}^4{}_{}{}^{}\mathrm{S}$ of the ${\mathrm{Ar}}^{\mathrm{-}}$ ion favor the existence of only one state with a mean lifetime of 260±25 nsec. The ${\mathrm{Ar}}^{\mathrm{-}}$ was produced from a 600-keV ${\mathrm{Ar}}^0$ beam by a single electron capture from an Ar gas target. In similar collisions between ${\mathrm{Ne}}^0$ and Ar no (metastable) ${\mathrm{Ne}}^{\mathrm{-}}$ ions were detected.