| Autor: |
Burton MA; Department of Chemistry and Biochemistry, Department of Astronomy, Steward Observatory, University of Arizona, 1305 E. 4th Street, Tucson, Arizona 85719, USA., Cheng Q; Department of Chemistry, University of Memphis, Memphis, Tennessee 38152, USA., Halfen DT; Department of Chemistry and Biochemistry, Department of Astronomy, Steward Observatory, University of Arizona, 1305 E. 4th Street, Tucson, Arizona 85719, USA., Lane JH; Department of Chemistry and Biochemistry, Department of Astronomy, Steward Observatory, University of Arizona, 1305 E. 4th Street, Tucson, Arizona 85719, USA., DeYonker NJ; Department of Chemistry, University of Memphis, Memphis, Tennessee 38152, USA., Ziurys LM; Department of Chemistry and Biochemistry, Department of Astronomy, Steward Observatory, University of Arizona, 1305 E. 4th Street, Tucson, Arizona 85719, USA. |
| Abstrakt: |
Pure rotational spectra of Sc 13 C 2 (X̃ 2 A 1 ) and Sc 12 C 13 C (X̃ 2 A') have been measured using Fourier transform microwave/millimeter-wave methods. These molecules were synthesized in a DC discharge from the reaction of scandium vapor, produced via laser ablation, with 13 CH 4 or 13 CH 4 / 12 CH 4 , diluted in argon. The N Ka,Kc = 1 0,1 → 0 0,0, 2 0,2 → 1 0,1, 3 0,3 → 2 0,2 , and 4 0,4 → 3 0,3 transitions in the frequency range of 14 GHz-61 GHz were observed for both species, each exhibiting hyperfine splittings due to the nuclear spins of 13 C (I = 1/2) and/or Sc (I = 7/2). These data have been analyzed with an asymmetric top Hamiltonian, and rotational, spin-rotation, and hyperfine parameters have been determined for Sc 13 C 2 and Sc 12 C 13 C. In addition, a quartic force field was calculated for ScC 2 and its isotopologues using a highly accurate coupled cluster-based composite method, incorporating complete basis set extrapolation, scalar relativistic corrections, outer core and inner core electron correlation, and higher-order valence correlation effects. The agreement between experimental and computed rotational constants, including the effective constant (B + C), is ∼0.5% for all three isotopologues. This remarkable agreement suggests promise in predicting rotational spectra of new transition metal-carbon bearing molecules. In combination with previous work on Sc 12 C 2 , an accurate structure for ScC 2 has been established using combined experimental (B, C) and theoretical (A) rotational constants. The radical is cyclic (or T-shaped) with r (Sc-C) = 2.048(2) Å, r (C-C) = 1.272(2) Å, and ∠ (C-Sc-C) = 36.2(1)°. The experimental and theoretical results also suggest that ScC 2 contains a C 2 - moiety and is largely ionic. |
