Dissociative charge transfer of singly- and doubly-charged rare gas ions with W(CO)₆

Charge exchange of the thermometer compound, W(CO)₆, with singly-charged rare gas ions yields internally excited W(CO)⁺₆ molecular ions. The internal energy distribution, P(ε), of the nascent ions is estimated by an approximate thermochemical method which is based on dissociation by successive CO losses. The average internal energy agrees well with expectation based on the known values of the rare gas recombination energies. The distribution of internal energies have half widths of 1–3 eV and maxima which correspond to the calculated heats of reaction. Energy deposition is only a weak function of collision energy, increasing by a few tenths of an electronvolt in the range 2.5–10 eV, and then remaining constant to 30 eV. Singly-charged argon and neon ions, but not the other singly-charged rare gas ions, show production of doubly-charged metal carbonyls due to contributions from Ar⁺ and Ne⁺ in long-lived excited states.

Charge exchange of W(CO)₆ with the doubly-charged rare gas ions shows three prominent processes: (i) single-electron transfer, which is accompanied by average internal energy depositions as high as 15 eV and gives products with wider and more asymmetric internal energy distributions than those which occur by charge exchange with the singly-charged rare gas ions; (ii) double-electron transfer to generate doubly- charged tungsten hexacarbonyl ions, W(CO)²⁺_n and WC(CO)²⁺_n; and (iii) the formation of unexcited W(CO)⁺₆ ions resulting from charge exchange between the nascent doubly-charged ion and neutral W(CO)₆. The maxima of the P(ε) curves for both single and doubel electron transfer agree with thermo-chemical predictions except that there is a small, systematic, difference in energy deposition for the single-electron transfer process which is ascribed to mutual coulombic repulsion of the products. Doubly-charged neon yields both ground state and excited state Ne⁺. The average internal energies for both single- and double-electron transfer are almost independent of the laboratory collision energy, indicating that long-range electron transfer is involved.