Overrun effects in nuclear fusion within a single Coulomb exploding nanodroplet

We present a theoretical-computational study of intra-nanodroplet (INTRA) collisions, and of dd and dt nuclear fusion driven by nonuniform Coulomb explosion (CE) induced by overrun effects in (D₂)_n and (DT)_n nanodroplets. We explored two systems where distinct overrun effects induce INTRA nuclear reactions: (1) double-pulse ultraintense laser irradiation of homonuclear (D₂)_n nanodroplets, which attain a transient inhomogeneous density profile that serves as a target for the realization of nonuniform CE. Overrun effects between nuclei originating from different spatial regions of the exploding nanodroplet drive INTRA dd fusion; (2) single-pulse ultraintense laser irradiation of heteonuclear (DT)_n nanodroplets, which results in kinematic overrun effects driving INTRA dt fusion. We utilized scaled electron and ion dynamics simulations to explore the inner and outer ionization electron dynamics, the time dependent deuteron and triton density profiles, the velocities of nuclei and the INTRA fusion yields in the two systems. In system (1) we identify the formation of a localized "overrun shell" at the periphery of the exploding nanodroplet, which is characterized by a narrow spatial range of the fusion generation function, by maxima in the local density and in the spatially averaged local velocity, as well as in the bifurcation of the local velocities, which manifests overrun effects. In system (2) we identify a marked local density enhancement with dt fusion occurring within most of the entire volume of the exploding nanodroplet without shell formation. The four-orders-of-magnitude increase of the dt fusion yield in the one-pulse irradiated (DT)_n nanodroplet, as compared with the two-pulse irradiated (D₂)_n nanodroplet, originates from cumulative effects of density and cross section enhancement.