Absolute Cross Sections and Angular Distributions for Charged Particles from Lithium-Lithium Nuclear Reactions

Abstract

Angular distributions in the barycentric coordinate system are presented for 24 charged-particle emissions from ${\mathrm{Li}}^7$ ${\mathrm{Li}}^7$, ${\mathrm{Li}}^7$ ${\mathrm{Li}}^6$, and ${\mathrm{Li}}^6$ ${\mathrm{Li}}^6$ interactions. These have been integrated, and the resulting total cross sections are tabulated. The total cross-section sums for a given projectile target combination are in reasonable agreement with theoretical estimates based on barrier penetration with nuclear radii given by $r_0{A}^{\frac{1}{3}}$ with $r_0=1.5\mathrm{}$ F. The largest total cross sections measured are approximately 40×${10}^{-28\mathrm{}}$ ${\mathrm{cm}}^2$. The angular distributions from ${\mathrm{Li}}^6$ ${\mathrm{Li}}^6$ and ${\mathrm{Li}}^7$ ${\mathrm{Li}}^7$ are symmetrical about 90° by necessity, those from ${\mathrm{Li}}^7$ ${\mathrm{Li}}^6$ are, in general, asymmetric and difficult to reconcile with a simple compound-nucleus interpretation of the reactions. Most of the intense particle emissions are cases in which the residual nucleus can be formed by ${\mathrm{Li}}^7$ capturing a deuteron or an alpha from ${\mathrm{Li}}^6$, or by ${\mathrm{Li}}^6$ capturing an alpha from ${\mathrm{Li}}^7$. To produce high cross sections these captures must be with $l=0\mathrm{}$ between the reacting clusters. The evidence supports the hypothesis that a prominent but not necessarily exclusive reaction mechanism is for one of the Li-Li reacting partners to be distorted into "reacting clusters," consisting of an $\alpha$ cluster from either of the lithiums, and a deuteron cluster from ${\mathrm{Li}}^6$ or a triton cluster from ${\mathrm{Li}}^7$.