Metastable state of CO2- with millisecond lifetime

The lifetimes of metastable CO2- ions, formed by charge exchange of CO2+ io ns in alkali-metal vapour or by sputtering, have been measured by a time-of -flight technique at the storage ring ASTRID. By the method of charge excha nge, two components with lifetimes in the time interval 3-8 ms can be accou nted for by the data. These lifetimes, presumably representing averages ove r several vibrational states,are much longer than the one previously assign ed to the lowest-lying electronic state of CO2-. The possible identity of t he electronic state associated with the millisecond lifetimes-is discussed.