The bond length and electronic structure of V2

Abstract

We report of the first gas-phase electronic spectrum of V2. The dimer was generated in an expansion cooled molecular beam by laser vaporization of vanadium metal. Using the technique of resonant two photon ionization spectroscopy a strong band system with origin near 7000 Å was observed. Rotationally resolved spectra of this band system conclusively demonstrate that the transition is of the type 3Πu(a)←3Σ−g(a), and we assign the 3Σ−g state as the ground electronic state of V2. The short ground state bond length re″=1.77 Å and high vibrational frequency ωe″=535 cm−1 are indicative of extensive 3d-orbital participation in the bonding of this molecule. The unusual case (a) coupling and large second-order spin-orbit splitting observed in the 3Σ−g state implies that the ground state electronic configuration contains a half-filled π(3d) or δ (3d) orbital. The most plausible valence configuration consistent with the data is σg(3d)2πu(3d)+σg(4s)2δg(3d)2. In the excited state there is strong evidence of predissociation occuring for levels higher than 14 872 cm−1 above the ground state, thus providing an upper bound of 1.85 eV for the dissociation energy of V2.

The electronic structure and spectroscopy of V2

“…A previously unassigned transition observed near 15 000 cm Ϫ1 has been assigned as B 3 ⌺ u Ϫ ←X 3 ⌺ g Ϫ . Both that and the observed AЈ 3 ⌺ u Ϫ ←X 3 ⌺ g Ϫ transition are assigned as u ← g promotions, which disagrees with the assignment of the symmetry of the AЈ 3 ⌺ u Ϫ ←X 3 ⌺ g Ϫ of Langridge-Smith et al 7 The new assignment is supported by evidence from both experimental and theoretical studies, and an analysis of the similar u ← g transition in Cr 2 . Finally, the 1 ⌺ u ϩ state isoconfigurational with AЈ 3 ⌺ u Ϫ is suggested as a possibility for one of the unassigned states observed in the range 11 250-12 500 cm Ϫ1 .…”

“…As an example, consider the excited AЈ 3 ⌺ u Ϫ state of the vanadium dimer that has been observed experimentally. The transition to this state was tentatively assigned as a ␦ u ←␦ g promotion, 7 and the results of DFT calculations, the SCF orbitals reported in Table I, and experimental results on the V 2 ϩ cation indicate that the excited configuration may arise from u ← g promotion. In either case, the ground and excited states are correlated in a balanced way since both promotions are within the and ␦ orbital manifold, and that manifold has been correlated with a full CI treatment.…”

“…Of the three possibilities Spain et al assigned the transition as d␦ u ←d␦ g based on intuitive molecular orbital concepts ͑that d␦ u ←d␦ g should be at lower energy than d g ←d u or d u ←d g ͒, the fact that the bond distance changes only slightly, indicating that the electron is not promoted from a strongly-bonding orbital, and the results of X␣ calculations. 17 The symmetry of the orbitals involved in the A 3 ⌸ u ←X 3 ⌺ g Ϫ transition reported by Langridge-Smith et al 7 was also reconsidered by Spain et al 13 in light of the X␣ calculations, 17 which indicated that the transition could involve the 4p u orbitals. Three possibilities were identified, including 4p u ←4s g , 4p u ←d␦ g , and d␦ g ←d u , but no way was found to distinguish between them.…”

Structures and magnetism of multinuclear vanadium-pentacene sandwich clusters and their 1D molecular wires

“…As shown in the supplementary material, 51 our calculated results are in good agreement with earlier reported values. 12,13,17,19,[52][53][54][55][56][57] Therefore, the functional and basis sets used in current work should be appropriate for the studied sandwich clusters.…”

Electronic and geometric structures of Co2Cn− and V2Cn−: Initial growth mechanisms of late and early 3d transition-metal carbide clusters

“…In Co 2 C n Ϫ , the spin state oscillates between sextet (Sϭ 5 2 ) and quartet (Sϭ 3 2 ), while that of Co 2 is reported to be quintet (Sϭ2) by theoretical calculations; 41,42 in V 2 C n Ϫ , on the other hand, the spin state changes between doublet (Sϭ 1 2 ) and quartet (Sϭ 3 2 ) alternately, while V 2 is known to be in spin triplet (Sϭ1). 43 As discussed above, there is one marked contrast between early and late 3d-metal carbide clusters in the structure and the growth process. As proposed in our recent paper, 26 the structure of VC 2…”