A selected ion flow tube study of the reactions of gas-phase cations with PSCl3

Abstract

A selected ion flow tube was used to investigate the positive ion chemistry of thiophosphoryl chloride, PSCl3. Rate coefficients and ion product branching ratios have been determined at room temperature for reactions with 19 cations; H3O+, CF3+, CF+, NO+, NO2+, SF2+, SF+, CF2+, O2+, H2O+, N2O+, O+, CO2+, CO+, N+, N2+, Ar+, F+ and Ne+ (in order of increasing recombination energy). Complementary data described in the previous paper have been obtained for this molecule via the observation of threshold photoelectron photoion coincidences. For ions whose recombination energies are in the range 10–22 eV, comparisons are made between the product ion branching rations of PSCl3 from photoionisation and from ion–molecule reactions. In most instances, the data from the two experiments are well correlated, suggesting that long-range charge transfer is the dominant mechanism for these ion–molecule reactions; the agreement is particularly good for the atomic ions Ar+, F+ and Ne+. Some reactions (e.g. O2+ + PSCl3), however, exhibit significant differences; short-range charge transfer must then be occurring following the formation of an ion–molecule complex. For ions whose recombination energies are less than 10 eV (i.e. H3O+, CF3+, CF+ and NO+), reactions can only occur via a chemical process in which bonds are broken and formed, because the recombination energy of the cation is less than the ionisation energy of PSCl3.