Electronic Excitations Preceding Shock Initiation in Explosives

Abstract

AbstractElectronic excitations which precede and can facilitate chemical reactivity of explosive molecules during shock passage will be discussed. The structurally similar family of explosives, TATB, DATB, Picramide and TNB were the focus of this work. It has been found that the energy of shake-up transitions observed in x-ray photoelectron spectra of these molecules shows a linear relation with the explosive sensitivity. To the contrary, optical absorption maxima, dependant upon dipole selection rules display a trend opposite that intuitively expected in relation to ease of initiation. The shake-up transitions are governed by monopole selection rules, so that the transitions between initial and final states of the same symmetry are allowed. The forbiddeness of the excited state may favor proton transfer, bond breakage and free radical formation relative to de-excitation by returning to the ground state. Electronic excitations of this type are believed to be important to multiphonon up pumping. The Is core hole resulting from photoionization creates a central coulomb force that shrinks the orbitals, simulating conditions similar to those of high pressure or shock passage. These factors may be at the heart of the correlation between the shake-up promotion energy and explosive sensitivity.