Electron-impact dissociative excitation ofCDn+(n=2−5): Detection of light fragment ionsD+andD2+

Abstract

Absolute cross sections are reported for the electron-impact dissociative excitation of the deuterated hydrocarbon ions ${\mathrm{CD}}_{n}^{+}$ $(n=2\ensuremath{-}5)$ from threshold to 70 eV using a crossed beams technique. The method focuses on detecting and measuring light dissociation-product ions from a heavy target. The ion targets are typical of those formed in the discharge ion source, and some may be in excited electronic and/or vibrational states. A common feature of the studied targets was a dominant ${\mathrm{D}}^{+}$ formation cross section with almost the same absolute value of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ for all $n$ from 25 to 70 eV. The present measurements are compared with the available data, and for ${\mathrm{D}}^{+}$ from ${\mathrm{CD}}_{2}^{+}$ and ${\mathrm{CD}}_{5}^{+}$ the data agree well with recent results obtained with the storage-ring technique.