Chemical Activation of a Deuterium Molecule by Collision with a Quantum Electronic State-Selected Vanadium Cation

Abstract

By combining a newly developed spin–orbit electronic state-selected ion source for vanadium cations (V+) with a double quadrupole–double octopole mass spectrometer, we have investigated in detail the chemical reactivity or integral cross sections (σ’s) for the reactions of V+[a5D J (J = 0, 1), a5F J (J = 1, 2), and a3F J (J = 2, 3)] ion with a deuterium molecule (D2). The vanadium deuteride ion (VD+) is identified to be the only product ion formed in the center-of-mass collision energies of E cm = 0.1–10.0 V. No J dependence for the σ’s is discernible for individual electronic states, indicating that the spin–orbit coupling is weak and has little effect on the chemical reactivity of the titled reaction. The maximum σ value for the V+(a3F J ) state [σ­(a3F J )] is about 7 and 70 times larger than those for σ­(a5D J ) and σ­(a5F J ), respectively, showing that the triplet V+(a3F J ) state is dominantly more reactive than the quintet states. Although the V+(a5F J ) state is 0.3 eV higher than the V+(a5D J ) ground state, the chemical reactivity of the V+(a5F J ) state is significantly lower than that of the V+(a5D J ) state, clearly indicating that the differences in chemical activity observed are due to quantum electronic states rather than energy effects. The E cm thresholds determined for σ­(a5D J ), σ­(a5F J ), and σ­(a3F J ) are consistent with the respective energetics for the formation of VD+ from the V+(a5D J , a5F J , and a3F J ) + D2 reactions. The analysis of E cm threshold measurements yields a bond energy of D 0(V+–D) = 2.5 ± 0.2 eV, suggesting that the previously reported values are too low by up to 0.4 eV. The large differences for σ­(a5D J , a5F J , and a3F J ) observed here indicate that the activation of D2 by a V+ ion can be efficiently controlled by selecting the V+ electronic state as well as the E cm. The quantum state-selected σ values presented here can also serve as experimental benchmarks for first-principles theoretical reaction dynamics calculations.

Chemical Activation of Water Molecule by Collision with Spin–Orbit-State-Selected Vanadium Cation: Quantum-Electronic-State Control of Chemical Reactivity

“…According to the forbidden nature of the parity and electron spin selection rules, − these low-lying electronic states of TM cations are expected to be long-lived with radiative lifetimes significantly longer than the experimental cycles. This expectation has been confirmed in recent chemical reactivity studies of the V + (a 5 D J , a 5 F J , and a 3 F J ) + D 2 (CO 2 , CH 4 ) reactions. , The characteristics of low-lying in energy and long lifetimes make it mandatory to account for the chemical reactivity of individual electronic states for any realistic investigations of the bonding and catalytic properties of TM cations. Hence, the capability for performing quantitative chemical reactivity measurements as a function of low-lying electronic state represents a key experimental development, which is expected to provide valuable mechanistic understanding on the chemical reactivity of TM cations. − …”

“…Thus, we expect that by changing the quantum-electronic state is equivalent to altering the electron arrangement of reactant ion and thus can greatly alter its chemical reactivity. It has been speculated for a long while whether different forms of angular momentum states of TM ion can have different effects on chemical reactivity of ions. − The answer to this question requires spin–orbit electronic-state-selected σ measurements for ion–molecule reactions of TM ions, including those of the present study and the most recently reported experiments on the V + (a 5 D J , a 5 F J , and a 3 F J ) + D 2 (CO 2, , CH 4 ) reaction systems. , …”

“…However, due to the more complex electronic structures of TM cations, the state-of-the-art theoretical energetics and chemical dynamics calculations are known to have larger error limits for chemical reaction systems of TM species than those of main group elements. , To help with the further theoretical development and thus improve the accuracy of chemical reactivity predictions of ion–molecule reactions of TM cations, accurate experimental σ measurements are needed for the benchmarking efforts. The present spin–orbit electronic-state-selected σ measurements on the V + + H 2 O reaction, along with the most recently reported σ measurements for the V + + D 2 (CO 2 , CH 4 ) reactions, , have all been aimed to provide experimental benchmarking cross sections for the further development of more accurate theoretical procedures for reaction dynamics predictions of TM cations.…”

“…By combining this quantum-electonic-state-selected V + ion source with the double-quadruple-double-octopole (DQDO) mass spectrometer developed in our laboratory, we can obtain detailed σ measurements of ion–molecule reactions involving V + ions with neutral molecules as a function of the low-lying quantum-electronic state of V + ion as well as the E cm of the reaction. We have recently reported on detailed spin–orbit-electronic-state-selected σ measurements of the reaction systems of V + [a 5 D J ( J = 0, 2), a 5 F J ( J = 1, 2), and a 3 F J ( J = 2, 3),] + D 2 (CO 2 , CH 4 ). , As an ongoing research effort to investigate chemical reactivity between quantum-electronic-state-selected TM cations and neutral atmospheric molecules, we present in this work detailed σ measurements of the V + [a 5 D J ( J = 0, 2), a 5 F J ( J = 1, 2), and a 3 F J ( J = 2, 3)] + H 2 O reactions. We shows below that by electronic-state selection, these reactions can serve as an efficient source of H 2 .…”

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 .…”