Molecular alignment in gaseous flow-detected by molecular fragmentation following electron impact double ionization

A new technique for the analysis of molecular targets with respect to the alignment of the axes of the molecules is described. The ionic fragments from the decay of doubly charged ions created by electron impact are detected in coincidence. From the spatial distribution of the coincidence rate the alignment of the molecular axes can be determined. A rather high degree of alignment has been found in molecular beams from multichannel arrays. A simple model for the explanation of this surprising finding is discussed.