Infrared Spectra and Quantum Chemical Calculations of the Uranium Carbide Molecules UC and CUC with Triple Bonds
2010-06-23T00:00:00Z (GMT) by
Laser evaporation of carbon-rich uranium/carbon alloys followed by atom reactions in a solid argon matrix and trapping at 8 K gives weak infrared absorptions for CUO at 852 and 804 cm−1. A new band at 827 cm−1 becomes a doublet with mixed carbon 12 and 13 isotopes and exhibits the 1.0381 isotopic frequency ratio, which is appropriate for the UC diatomic molecule, and another new band at 891 cm−1 gives a three-band mixed isotopic spectrum with the 1.0366 isotopic frequency ratio, which is characteristic of the linear CUC molecule. CASPT2 calculations with dynamical correlation find the CUC ground state as linear 3Σu+ with 1.840 Å bond length and molecular orbital occupancies for an effective bond order of 2.83. Similar calculations with spin-orbit coupling show that the UC diatomic molecule has a quintet (Λ = 5, Ω = 3) ground state, a similar 1.855 Å bond length, and a fully developed triple bond of 2.82 effective bond order.
CC BY-NC 4.0