Diatomic dications and dianions

Bond-Forming Chemistry in the Gas-Phase Reactions of Atomic and Molecular Dications and Trications

“…69 Such reactions had been shown by initial crossed-beam experiments to generate pairs of monocations as reaction products, for example, as in eqn. [4], making them ideally suited for investigation using a coincidence approach. 42 In the current implementation of these coincidence techniques to investigate the dynamics of the bimolecular reactivity of dications ( Figure 5), an approach that bears some similarity to the reaction microscope experiment, 73 a pulsed beam of energy-selected ions, containing the dication of interest, is generated from a specially designed ion source.…”

“…A particularly useful aspect of this coincidence approach is that for a three-body reaction (eqn. [4]), conservation of momentum in the CM frame allows the nascent momenta of the neutral third body (m n w n ) to be derived from the known masses (m 1 , m 2 ) and velocities (w 1 , w 2 ) of the detected pair of monocations for each reactive event: 24 0 ¼ m 1 w 1 + m 2 w 2 + m n w n [5] This analysis allows complete characterization of the kinematics of such three-body bimolecular reactions, which, as we will see later, provides a detailed and fascinating insight into their reaction mechanisms. For more experimental details of the coincidence experiments, and the subtleties of the data processing, the reader is referred to Refs.…”

“…In the years following the mass spectrometric observation of CO 2+ , a large number of diatomic molecular dications have been detected, 4 but for many years, small molecular dications were largely regarded as mass spectrometric curiosities. This situation started to change in the 1980s, when a series of new experimental techniques began to reveal the structure and properties of isolated molecular dications.…”

Molecular Dications in Planetary Atmospheric Escape

“…In the latter case, we have the so-called molecular dications. The reader can refer to some interesting recent review papers by Alagia et al [6] and by Sabzyan et al [13] in order to have an overview of the main characteristics and the importance of such doubly charged species. These ionic species can be produced by different techniques, such as mass spectrometry [14], ion-molecule reactions [15], and double photoionization processes [16][17][18][19].…”

“…In fact, molecular dications can be produced in very stable electronic states that allow them to survive several seconds, a lifetime compatible with collision events in such rarefied environments because the typical time between collisions at altitudes corresponding to the peak ionic density of planetary ionospheres is no longer than 1 s [28]. For such a reason, a stable doubly charged ion can be lost in such environments through one of the following reactions: (i) chemical reaction with a neutral partner; (ii) recombination with a thermal electron; or (iii) Coulomb explosion [6,13,28]. On the other hand, molecular dications can be formed in a metastable state having a lifetime shorter than 1 s, as discussed in the next section.…”