Formation of long-lived CD_n²⁺and CH_n²⁺dications

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.

Reexamining if long-livedN−anions are produced in fast dissociative electron-capture collisions

“…To distinguish between atomic and molecular ions following the same trajectory (i.e., having the same E / q) we used the "foil-mesh" method described in detail elsewhere [20][21][22]. Briefly, a thin foil is placed on the trajectory of the ion of interest a few centimeters in front of the detector and the detector is covered with a low transmission mesh (about 30%).…”

“…If this is the case, then, dissociative charge exchange will become the first possible mechanism for forming such exotic atomic states. In the measurements reported in this paper, we took advantage of the improved energy resolution of particle detectors and used a few recently reported experimental methods that can help one distinguish between an atomic and molecular ion [20][21][22].…”