Abstract
We report on an energy-sensitive imaging detector for studying the fragmentation of polyatomic molecules in the dissociative recombination of fast molecular ions with electrons. Technical details are described in the article.
The setup allows us to uniquely identify fragment masses and is thus capable of measuring branching ratios between different fragmentation channels, kinetic energy releases, and breakup geometries as a function of the relative ion-electron energy. The properties of the detection system, which has been installed at the Test Storage Ring (TSR) facility of the MPIK in Heidelberg, is illustrated by an investigation of the dissociative recombination of D2H+.
A huge isotope effect is observed when comparing the relative branching ratio between the D2 + H and the HD + D channel; the ratio 2B(D2 + H)/B(HD + D), which is measured to be 1.27 $\pm$ 0.05 at relative electron-ion energies around 0 eV, is found to increase to 3.7 $\pm$ 0.5 at $\sim$5 eV.