Laser-induced Coulomb-explosion imaging of the CS2 dimer: The effect of non-Coulombic interactions

Carbon disulfide dimers ${({\mathrm{CS}}_{2})}_{2}$ are doubly ionized by an intense 40-fs laser pulse leading to fragmentation into a pair of ${{\mathrm{CS}}_{2}}^{+}$ cations. Unlike previous studies on atomic dimers, their kinetic energy, gained by mutual electrostatic repulsion, deviates strongly from the value determined by applying the Coulomb interaction approximation to the ${{({\mathrm{CS}}_{2})}_{2}}^{2+}$ ion. An ab initio calculation shows that inclusion of non-Coulombic interactions in ${{({\mathrm{CS}}_{2})}_{2}}^{2+}$ is crucial to account for the observed kinetic energy. These interactions result in 16 ${{({\mathrm{CS}}_{2})}_{2}}^{2+}$ electronic microstates, which obstructs accurate determination of intermolecular bond distances in ${({\mathrm{CS}}_{2})}_{2}$ from the fragments' kinetic energy. The situation will be similar for most other weakly bonded atomic and molecular complexes.