Spectroscopy of NiCCH and Ossi, and the bond energies of VC, VS, and VN

Optical spectra of the supersonically cooled NiCCH radical have been recorded in the 530-650 nm region using the resonant two-photon ionization method, and five of the observed bands have been rotationally resolved. The rotationally resolved studies demonstrate that the ground state of NiCCH is of 𝑋̃ 2Î"5/2. Most of the observed bands are assigned to the 𝐴̃ 2Î"5/2 ← 𝑋̃ 2Î"5/2 electronic transition, which shows a progression in the Ni-C stretching mode, ν3. In addition, single excitations of the modes ν2 (C≡C stretch), ν4 (C≡C-H bend), and ν5 (Ni-C≡C bend) are observed, allowing these vibrational intervals to be determined for the 𝐴̃ 2Î"5/2 state. Hot bands also allow the determinationof ν5 in the ground 𝑋̃ 2Î"5/2 state. The optical spectrum of diatomic OsSi has been investigated for the first time. Two electronic band systems have been identified along with a number of unclassified bands. Nine bands have been investigated at rotational resolution, allowing the ground state to be identified as X 3Σâˆ'+ , arising from the 1σ21Ï€42σ23σ21δ2 configuration. The 0 ground X 3Σâˆ'+state is characterized by re = 2.1207(27) Ã… and Î"G1/2" = 516.315(4) cm-1 0 for the most abundant isotopologue, 192Os28Si (38.63%). The A1 excited electronic state is characterized by T0 = 15 727.7(7) cm-1, ωe = 397.0(7) cm-1, and re = 2.236(16) Ã… for 192Os28Si. The B1 excited electronic state is characterized by T0 = 18 468.71 cm-1, Î"G1/2 = 324.1 cm-1, and re = 2.1987(20) Ã… for 192Os28Si. The abrupt onset of predissociation in the congested electronic spectra of jet- cooled VC, VN, and VS has been observed using resonant two-photon ionization spectroscopy. Using this method, bond dissociation energies of D0(VC) = 4.1086(25) eV, D0(VN) = 4.9968(20) eV, and D0(VS) = 4.5353(25) eV are obtained. These values are compared to previous measurements and to computational results. The precision of these bond dissociation energies makes them good candidates for testing computational chemistry methods, particularly those that employ density functional theory.