A probe of emission order and time delay for pairs of ejectiles in nuclear reactions

A new technique is described for studying the physics of nuclear reactions by measurement and analysis of ejectile pairs. Ejectile correlations at small relative angles are used to construct velocity difference spectra. Comparison of these spectra with three-body trajectory model calculations (e.g. for 2HLi pairs) suggests that their shapes can reflect the fraction of events with 2H emitted first, as well as the mean lifetime between 2H and Li emissions. An example is shown for the reaction 34 A MeV 40Ar + natAg; it confirms the notion that the so-called direct 2H emission (forward deuterons of high energy) occurs predominantly before Li fragment emission. This technique has many possibilities for the elucidation of ultrafast reaction pathways.