No abstract

A systematic study of the formation of CDn2+ and CHn2+ dications in fast charge-stripping collisions with Ar atoms was conducted. The experimental method was based on the detection of the D (or H) fragments of the molecular ion of interest, and thus reducing the effect of the fraction of molecular ions containing the 13C isotope and other beam impurities. We observed long-lived CD22+, CD42+, and CD52+ dications. In the same process neither long-lived CD2+ nor CD32+ were observed. The mean lifetime of CD22+ was determined to be 4.0±1.11.3 µs, and those of CD42+ and CD52+ were longer than 2.1 and 3.3 µs, respectively. The production cross sections of CDn2+ from different CDm+ beams were measured. Long-lived CD22+ was formed from all CDm+ beams (m2) and also directly from the rf ion source. In contrast, CD42+ and CD52+ were formed only from CD4+ and CD5+, respectively.

The existence of long-lived states of N − has been a topic investigated with conflicting experimental results. Highly excited spin-aligned states, however, were predicted to have long lifetimes and even be stable against autodetachment. We repeated the measurements of N − formation in 0.9 MeV N 2 + Ar charge-exchange collisions and found that the ions reported previously as N − [Heber et al., Phys. Rev. A 38, 4504 (1988)] are an O − fragment from a 0.9 MeV H 2 NO + impurity beam. This result adds to the comulating data indicating that N − is not going to affect carbon dating measurements using accelerator mass spectrometry.