Twisted triplet ethylene: anharmonic frequencies and spectroscopic parameters for C2H4, C2D4, and (13)C2H4.
Ethylene is an exceptional example of a stable closed-shell singlet molecule with a low-lying triplet state of very different symmetry. Triplet C2H4 (the ã (3)A1 state), which has a twisted D2d geometry, is studied herein with high-level theoretical methods, namely, CCSD(T) (coupled cluster theory with single, double, and perturbative triple excitations) and Dunning's correlation-consistent quadruple-ζ basis set (cc-pVQZ). Geometric parameters, including equilibrium (re) and vibrationally corrected (rg) values, are reported for C2H4, C2D4, and (13)C2H4. Harmonic and anharmonic vibrational frequencies are also predicted using second-order vibrational perturbation theory (VPT2). Challenges encountered for the wagging vibrational features are discussed.
Center for Computational Quantum Chemistry, University of Georgia , Athens, Georgia 30602, United States.
Xiao
X
Wang
Walter E
WE
Turner
Jay
J
Agarwal
Henry F
HF
Schaefer