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

A total of six high-resolution FT-IR spectra for trans-glyoxal-d2, trans-glyoxal-d1and trans-glyoxal-13C2were 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 Ir-representation the ground state rotational constants are obtained. An empiricalequilibrium structure is determined for trans-glyoxal using these experimental ground state rotational constants and vibration–rotation interaction constants calculated at the CCSDTcc-pVTZ level of theory. The least-squares fit yields the following structural parameters for trans-glyoxal: reC–C  1.5145338 Å, reC–H  1.1007126 Å, reCO  1.2045027 Å, αeCCH  115.25124°, and αeHCO  123.47219° in excellent agreement with theoretical predictions at the CCSDTcc-pVQZ level of theory.