Two-Color Pulsed-Field Ionization-Photoelectron Spectroscopy: A Quest to Benchmark State-of-the-Art ab initio Quantum Electronic Structure Calculations of Spectroscopic and Energetic Properties for Transition Metal-Containing Species

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

“…As shown in the previous studies of the V + + D 2 (CO 2 , CH 4 ) reactions, , the endothermicity or positive E T values can be determined by E cm threshold or E T measurements of the σ curves, as depicted in Figure d, e, f, h, i. However, since reactions – are exothermic, and thus their σ curves do not exhibit distinct E cm thresholds, we have deduced the E T value of −0.9 eV for reaction by using known 0 K heats of formation (Δ f H 0 ’s) of the chemical species involved, along with the known D 0 value for VO + . ,− As pointed out previously, the a 5 F 1 and a 3 F 2 excited electronic states are known to be higher than the a 5 D 0 ground electronic state by 0.3 and 1.1 eV, respectively. After taking into account these electronic energies, we obtained the E T values as −1.2 eV for reaction and −2.0 eV for reaction .…”

“…On the right side of Figure , the possible product states are highlighted with the same color rule: i.e., black for quintet states and red for triplet states. Since the dominant product channel for the V + + H 2 O reaction system is VO + + H 2 , and the energetics for the VO + (X 3 Σ – , A 3 Δ, B 3 Φ, and C 3 Π) electronic states are known, , we have included the excited product states, VO + (A 3 Δ) + H 2 (X 1 Σ g + ), VO + (B 3 Φ) + H 2 (X 1 Σ + ), and VO + (C 3 Π) + H 2 (X 1 Σ g + ), in the energy level diagram, in addition to the VO + (X 3 Σ – ) + H 2 (X 1 Σ g + ) ground product state. All these product states are highlighted in red because they are all triplet 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+)

“…Our calculations at the MRCI+Q/aug-cc-pVTZ level not only have substantiated the quasi-degeneracy of the B 1 and B 2 states of VCH 2 0,+ established at CC levels, but also have predicted that the 3 A 1 state, which has been identified as ground state by Sicilia et al, is not in proximity to the 3 B 1 state. We assert that for all the MX/MX + systems we have studied thus far, there has never been any dispute between MRCI and CCSD­(T) in identification of ground electronic states.…”

“…Given the consistency of both schemes in previous computations on MX/MX + , we have taken the average of the two extrapolated values in the current protocol. , Since there is no marked improvement achieved by geometry optimization with the basis set beyond aug-cc-pwCVTZ-DK (see section ), all the subsequent single-point calculations have been simply performed with CCSD­(T)/aug-cc-pwCVTZ-DK structures.…”

“…The backbone of these procedures is made up of extrapolation to the complete basis set (CBS) limit at the CCSD­(T) level employing a sequence of correlation-consistent basis sets. Additional corrections accounting for various delicate electron correlation and scalar relativistic (SR) effects are subsequently applied. , Over the past decade, we have also been benchmarking the so-called CCSDTQ/CBS protocol (see next section for details) in predictions of ionization energy (IE), D 0 and Δ H f ° for MX/MX + (X = C, N, and O) based on the latest spectroscopic data measured by the two-color laser pulsed field ionization-photoelectron (PFI–PE) methods performed by the Ng group. − Specifically, our computed CCSDTQ/CBS IE values for MX molecules routinely display a deviation of ±20 meV from experimental values. However, the composite CC approaches have been benchmarked with a database mostly confined to diatomic M compounds.…”