Fragmentation of the Excited Parent Ions, CH3Kr82+and CH3O18mdash;, Following the bgr;mdash;Decay of CH3Br82and the bgr;+Decay of CH3F18

摘要

The relative abundances of the fragment ions that result, respectively, from the bgr;mdash;decay of CH3Br82and bgr;+decay of CH3F18have been measured with a specially designed mass spectrometer. Following the bgr;mdash;decay of CH3Br82, only about 0.4 of the parent ion, CH3Kr+, remained intact, as was anticipated from the rather large recoil energy. The most abundant ion observed was CH3+, 89. A variety of other ions were also formed and their production is discussed in terms of excitation resulting from a sudden change in nuclear charge. The investigation of the fragment ions formed in the decay of CH3F18marks the first time a molecule undergoing positron decay has been so studied. The following negative ions were detected: CH3Omdash;, Omdash;, and Hmdash;. A large abundance of positive ions, however, was also observed. The origin of these positive ions is critically discussed; and calculations of the probabilities for electron shakeoff following both positron and negatron decay are given for several atomic systems.