Ionisation of PF₃: absolute partial electron ionisation cross sections and the formation and reactivity of dication states

Abstract

Single and multiple electron ionization of PF3 is characterized and quantified by a joint computational and experimental investigation. Absolute cross sections are presented and the properties of two low-lying dication states revealed.

Calculated electron impact ionisation fragmentation patterns

“…Such branching ratios are measured, usually at a single electron collision energy, by mass spectroscopy experiments or in specialist experiments designed specifically to study fragmentation patterns [14][15][16][17][18][19][20]. These experiments often provide only relative cross sections but they can then be made absolute using BEB or similar procedures [21]. However, there are many cases where measured branching ratios do not exist as a function of electron collision energy; for these it would be desirable to have a reliable theoretical procedure for predicting them.…”

Bimolecular reactions of CH2CN2+ with Ar, N2 and CO: reactivity and dynamics

“…The above methodology has been successfully used in previous work to determine the geometries and energetics of dications. 88,99 Readers are referred to the SI for the full geometrical data for each dication structure.…”

Electron ionisation of cyanoacetylene: ionisation cross sections and dication formation

“…The number of 'triples' detected is significantly lower than the number of 'pairs' in the electron energy regime we investigate, and the number of real quadruple arrivals is negligible. Therefore, as in our previous investigations with this instrument [23,24,32,33], we do not collect or process any quadruple arrival events and neglect the very minor contribution of quadruple ionisation to our data set.…”

“…Relative uncertainties are relatively high, unsurprisingly, at PICS values close to our experimental detection limit, that is for the low abundance ions such as N 2+ and C 2 NH 2+ at electron energies of 50 eV and 75 eV. To generate absolute values from the relative cross sections, we normalise to a BEB calculation of the total ionisation cross section over the energy range of interest, as described in our recent publication [23].…”

“…Relative PICS and PS-PICS are first determined from an ion-ion coincidence experiment [22]. The binary encounter Bethe (BEB) model is then employed to calculate the total ionisation cross section at each electron energy investigated, and these total ionisation cross sections are used to place the relative experimental values on an absolute scale, as described in detail in previous work [23]. A complementary computational study of the dication states reveals a rich geometric landscape allowing a rationalization of the unimolecular dissociation of HC 3 N 2+ we observe in our experiments.…”