Evolution of fragment-fragment correlations in reactions ofAu197andAg107,109withAr40from 7Ato 34AMeV

In-plane and out-of-plane angular correlations have been measured between fragments of Z>3, Li fragments, ${}_{}{}^{3,4}{}_{}{}^{}\mathrm{He}$, and ${}_{}{}^{1,2,3}{}_{}{}^{}\mathrm{H}$. The changing patterns for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ induced reactions of 7A, 17A, 27A, and 34A MeV give an overview of the decreasing importance of mass-symmetric fissionlike reactions at the expense of a broad range of more mass-asymmetric breakups. Evidence is given that these fragments come from a central collision group of reactions that have similar violence and from which many combinations of fragments and particles are ejected. Very similar azimuthal angular correlations are observed for particles with a Li fragment and for particles with a pair of heavier fragments (Z>3). This similarity suggests comparable strengths of association with the reaction plane for single Li fragments and for fragment pairs of Z>3. Azimuthal angular correlations for Li-Li pairs exhibit distinct asymmetries; their interpretation via trajectory-model calculations indicates mean delay times of ≊5×${10}^{\mathrm{-}22}$ s.