title: Rovibronically selected and resolved two-color laser photoionization and photoelectron study of cobalt carbide cation.
abstract: We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser photoionization efficiency and pulsed field ionization-photoelectron (PFI-PE) study of gaseous cobalt carbide (CoC) near its ionization onset in the total energy range of 61,200-64,510 cm(-1). The cold gaseous CoC sample was prepared by a laser ablation supersonically cooled beam source. By exciting CoC molecules thus generated to single N' rotational levels of the intermediate CoC∗((2)Σ(+); v') state using a VIS dye laser prior to UV laser photoionization, we have obtained N(+) rotationally resolved PFI-PE spectra for the CoC(+)(X(1)Σ(+); v(+) = 0 and 1) ion vibrational bands free from interference by impurity species except Co atoms produced in the ablation source. The rotationally selected and resolved PFI-PE spectra have made possible unambiguous rotational assignments, yielding accurate values for the adiabatic ionization energy of CoC(X(2)Σ(+)), IE(CoC) = 62,384.3 ± 0.6 cm(-1) (7.73467 ± 0.00007 eV), the vibrational frequency ωe (+) = 985.6 ± 0.6 cm(-1), the anharmonicity constant ωe (+)χe (+) = 6.3 ± 0.6 cm(-1), the rotational constants (Be (+) = 0.7196 ± 0.0005 cm(-1), αe (+) = 0.0056 ± 0.0008 cm(-1)), and the equilibrium bond length re (+) = 1.534 Å for CoC(+)(X(1)Σ(+)). The observation of the N(+) = 0 level in the PFI-PE measurement indicates that the CoC(+) ground state is of (1)Σ(+) symmetry. Large ΔN(+) = N(+) - N' changes up to 6 are observed for the photoionization transitions CoC(+)(X(1)Σ(+); v(+) = 0-2; N(+)) ← CoC∗((2)Σ(+); v'; N' = 6, 7, 8, and 9). The highly precise energetic and spectroscopic data obtained in the present study have served as a benchmark for testing theoretical predictions based on state-of-the-art ab initio quantum calculations at the CCSDTQ∕CBS level of theory as presented in the companion article.
authors.affiliation: Department of Chemistry, University of California, Davis, California 95616, USA.
authors.forename: Huang
authors.initials: H
authors.lastname: Huang
authors.forename: Yih Chung
authors.initials: YC
authors.lastname: Chang
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Luo
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Shi
authors.forename: Chow-Shing
authors.initials: CS
authors.lastname: Lam
authors.forename: Kai-Chung
authors.initials: KC
authors.lastname: Lau
authors.forename: C Y
authors.initials: CY
authors.lastname: Ng
mesh_terms: D017554:Carbon Compounds, Inorganic / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D003116:Color; D007834:Lasers; D055668:Photochemical Processes
chemical_list: D017554:Carbon Compounds, Inorganic; D002412:Cations; D003035:Cobalt