Rotationally resolved state-to-state photoionization and the photoelectron study of vanadium monocarbide and its cations (VC/VC⁺)

Abstract

Two-color VIS-UV laser pulsed filed ionization-photoelectron (PFI-PE) study and theoretical predictions for vanadium monocarbide (VC) neutral and its cation (VC+).

High-Level Ab Initio Predictions for the Ionization Energy, Bond Dissociation Energies, and Heats of Formation of Vanadium Methylidyne Radical and Its Cation (VCH/VCH+)

“…By the sum of all correlation contributions and corrections, we deduced an IE­(VCH) value of 6.785 eV at the CCSDTQ/CBS level at which the CV electronic correlations (up to CCSDT level), SR effect (up to CCSDTQ level), higher-order correction (up to CCSDTQ level), ZPVE corrections due to ZPVE, and SO interaction are all included. In light of the good agreement between CCSDTQ/CBS predictions and PFI-PE measurements, this suggests that the CC theory with quadruple electronic excitations is capable of predicting the IE of triatomic VCH achieving an accuracy of less than or equal to 20 meV, as demonstrated by our benchmarking works for diatomic MX molecules previously reported. ,,− …”

“…In comparison to our previous approach, in which the additional E CV and E SR at CCSDT and E SR at CCSDTQ are all respectively computed, the current methodology requires fewer single-point calculations. We will demonstrate that this simplified protocol of the CCSDTQ/CBS method yields very similar results using a previously studied VC/VC + system …”

“…The total CCSD­(T) energies are used to extrapolate the CBS limit ( E extrapolated CBS ) by two schemes: A three-point extrapolation scheme using the mixed exponential-Gaussian function of the form where X = 3, 4, and 5 representing the use of aug-cc-pwCVTZ-DK, aug-cc-pwCVQZ-DK, and aug-cc-pwCV5Z-DK basis sets, respectively. A two-point extrapolation scheme , using the simple power function involving the reciprocal of X . Here, X = 4 and 5 for aug-cc-pwCVQZ-DK and aug-cc-pwCV5Z-DK, respectively. The two schemes do not result in a significant difference in the extrapolated energetics as shown in previous calculations on MX/MX + ,,− and other main-group compounds; − the average of the extrapolated energies from the two schemes are used in the CCSDTQ/CBS procedure.…”

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+)

“…All the individual components for corrections (Δ E extrapolated CBS , Δ E ZPVE , Δ E SO , Δ E HOC‑T , and Δ E HOC‑Q ) accounted for CCSDTQ/CBS IE­(VCH 3 ) and IE­(VCH 2 ) are listed in Table . The theoretical , and experimental value of IE­(V), which is necessary for subsequent derivation of D 0 and Δ H ° values, is tabulated as well. The respective average of the Δ E extrapolated CBS utilizing the two variations of the extrapolation scheme for IE­(VCH 3 ) [IE­(VCH 2 )] is 6.752 [6.817] eV.…”

“…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.…”