Molecule fragmentation at the Dresden EBIS-A^a)

We report on molecule fragmentation measurements of propane in high dense electron beams of a room-temperature electron beam ion source, the so-called Dresden EBIS-A. After fragmentation of propane molecules in the electron beam the fragments were continuously extracted and $q∕A$ separated by a bifocal dipole magnet. Fragmentation spectra were measured at working gas pressures of $10−9mbar$ up to $10−8mbar$⁠, electron currents of $29mA$ up to $75mA$⁠, and electron energies of $11keV$ up to $15keV$⁠. Thereby all possible stoichiometric ratios of propane fragments were detected. At low electron beam currents the ion current output of the $CHx+$ $(x=0–3)$ and the $C2Hx+$ $(x=0–5)$ fragments is nearly identically. At higher electron currents the $CHx+$ $(x=0–3)$ peaks dominate the spectra and the ratio between the $C+$ peak and $CHx+$ $(x=0–3)$ peaks increases from 2:1 to 3:1. It was shown that the working gas pressure has no significant influence on the fragment distribution but on the total ion current.