The equilibrium structure of trans-glyoxal from experimental rotational constants and calculated vibration-rotation interaction constants

In English A total of six high-resolution FT-IR spectra for trans-glyoxal-d(2), trans-glyoxal-d(1) and trans-glyoxal-C-13(2) were recorded with a resolution ranging from 0.003 to 0.004 cm(-1). By means of a simultaneous ground state combination difference analysis for each of these isotopologues using the Watson Hamiltonian in A-reduction and I-r-representation the ground state rotational constants are obtained. An empirical equilibrium structure is determined for trans-glyoxal using these experimental ground state rotational constants and vibration - rotation interaction constants calculated at the CCSD(T)/cc-pVTZ level of theory. The least-squares fit yields the following structural parameters for trans-glyoxal: r(e)(C-C) = 1.51453(38) Angstrom, r(e)(C-H) = 1.10071(26) Angstrom, re(C= O) = 1.20450(27) Angstrom, alpha(e)(CCH) = 115.251(24) degrees, and alpha(e)(HCO) = 123.472(19)degrees in excellent agreement with theoretical predictions at the CCSD(T)/cc-pVQZ level of theory.