American Institute of Physics, Chinese Journal of Chemical Physics, 6(26), p. 669-678
DOI: 10.1063/1674-0068/26/06/669-678
Full text: Download
We have conducted a two‐color visible‐ultraviolet (VIS‐UV) resonance‐enhanced laser photoionization and pulsed field ionization‐photoelectron (PFI‐PE) study of gaseous vanadium mononitride (VN) in the total energy range of 56900–59020 cm−1. The VN molecules were selectively excited to single rotational levels of the intermediate VN(D 3Π0, v′=0) state by using a VIS dye laser prior to photoionization by employing a UV laser. This two‐color scheme allows the measurements of rovibronically selected and resolved PFI‐PE spectra for the VN+(X 2Δ; v +=0, 1, and 2) ion vibrational bands. By simulating the rotationally resolved PFI‐PE spectra, J +=3/2 is determined to be the lowest rotational level of the ground electronic state, indicating that the symmetry of the ground VN+ electronic state is 2Δ3/2. The analysis of the PFI‐PE spectra for VN+ also yields accurate values for the adiabatic ionization energy for the formation of VN+(X 2Δ3/2), IE(VN)=56909.5±0.8 cm−1 (7.05588±0.00010 eV), the vibrational frequency ωe +=1068.0±0.8 cm−1, the anharmonicity constant ωe +χe +=5.8±0.8 cm−1, the rotational constants B e +=0.6563±0.0005 cm−1 and αe +=0.0069±0.0004 cm−1, and the equilibrium bond length, r e +=1.529 Å, for VN+(X 2Δ3/2); along with the rotational constants B e +=0.6578±0.0028 cm−1 and αe +=0.0085±0.0028 cm−1, and the equilibrium bond length r e +=1.527 Å for VN+(X 2Δ5/2), and the spin‐orbit coupling constant A=153.3±0.8 cm−1 for VN+(X 2Δ5/2,3/2). The highly precise energetic and spectroscopic data obtained in the present study are valuable for benchmarking the predictions based on state‐of‐the‐art ab initio quantum calculations.