Collision-Induced Dissociation of Multiply-Charged Anions

Electrospray ionization has proven to be a powerful method for the study of multiply-charged-anions (MCA) in the gas-phase. Stability of the MCA toward ionic fragmentation and electron detachment has attracted wide interest. The stability of dianions is due to the “repulsive Coulomb barrier” to the addition or removed of an excess electron to a negative ion. The repulsive Coulomb barrier (RCB) is primarily the result of a long-range Coulomb repulsion and the short-range polarizibility attraction between an electron and a negative ion. The RCB can render unbound MCAs metastable or add stability to bound MCAs. In this dissertation, a collision-induced dissociation (CID) technique has been applied to investigate the stability of dianions produced in the gas-phase.

In this work collision-induced dissociation of salt clusters is investigated in order to examine the role of the repulsive Coulomb barrier in the stability of these dianions against ionic fragmentation and electron detachment. In addition, the CID technique is performed to estimate the heights of inner and outer RCB for a group of dicarboxylate and disulfonic dianions with respect to electron detachment and ionic fragmentation. Furthermore, the decay pathways of these dianions are investigated experimentally and theoretically.

The importance of the collision-induced dissociation method in measuring the bond dissociation energies of singly-charged anions will also be emphasized. In this context, the bond dissociation energy of NaCl₂^- ion into NaCl and Cl^- ion is determined employing the CID technique. Experimental value of the bond dissociation energy is compared with theoretical values.