What is the Bond Dissociation Energy of the Vanadium Hydride Cation?

Abstract

Recent electronic state-selected measurements of the reactions of atomic vanadium cations with D2 and CO2 are reanalyzed to properly account for the kinetic energy distribution of the reactant neutrals. The need for this is demonstrated in the present work by comparing the D2 data to that obtained previously in earlier experiments but unpublished. It is shown that the earlier data, which utilized a surface ionization source of V+, and the state-selected data for V+(a 5D2) are essentially identical in the threshold regions where they overlap. Differences in the electronic state energies and kinetic energy distributions of V+ in the two experiments are very small and much smaller than the kinetic energy distribution of the neutral reactant, which is identical in both experiments. It is shown that properly accounting for the latter distribution alters the conclusions regarding the threshold energy for the endothermic formation of VD+ such that recent conclusions regarding the bond energy of VD+ are substantially altered and found to reproduce the original bond energy determination. Accounting for all experiments, a revised best value for D0(VH+) is 2.07 ± 0.09 eV [or D0(VD+) = 2.10 ± 0.09 eV]. This conclusion is validated by high-level ab initio calculations. Differences in the new and older data sets for the V+ + D2 reaction at higher energies (above the onset for dissociation of the product ion) are also discussed. The same methodology is then applied to recent studies on the state-selected V+ + CO2 reaction.

Periodic trends in gas‐phase oxidation and hydrogenation reactions of lanthanides and 5d transition metal cations

“…One advantage of the SI source is that it can create a well‐defined distribution of electronic states because the ions are emitted from a hot filament (variable over a range of about 1800–2500 K and measured by optical pyrometry) and presumed to have a distribution characterized by this temperature. This assumption has been verified by observing cross section magnitudes varying as predicted with the filament temperature (Aristov & Armentrout, 1986; Aristov & Armentrout, 1987; Sunderlin & Armentrout, 1988), by comparison with ion mobility data for Co + (van Koppen et al, 1992), and more recently by comparison with results for spin‐orbit state‐selected vanadium cations (Armentrout et al, 2020; Ng et al, 2021). EI sources produce an unknown distribution of electronic states, but because the electron energy can be varied over a very wide range, this source can produce highly excited electronic states.…”

High-Level ab Initio Predictions for the Ionization Energies, Bond Dissociation Energies, and Heats of Formation of Vanadium Methylidene, Vanadium Methyl Species, and Their Cations (VCH2/VCH2+, VCH3/VCH3+)

“…Recently, the Ng group has combined a novel spin–orbit electronic state-selected ion source for vanadium cations with a double quadrupole–double octopole mass spectrometer to interrogate the reactivity V + [a 5 D J ( J = 0, 2), a 5 F J ( J = 1, 2), and a 3 F J ( J = 2, 3)] ion toward D 2 , CO 2 , O 2 , H 2 O, and CH 4 . − The apparatus has enabled unambiguous determination of integral cross sections (σ’s) in the center-of-mass collision energy range E cm = 0.1–10.0 eV for V + selected in a well-defined electronic state. The preparation of state-selected V + ions for the reaction was not achievable with the thermalized SI source employed in Armentrout’s work .…”