Diffusion Monte Carlo study of positron binding to glyoxal

In this letter, we present computational results on positron binding to glyoxal ( C 2 H 2 O 2 ). Results are reported using Hartree–Fock, configuration interaction, and diffusion Monte Carlo methods, the latter employing both single- and multi-configurational trial wavefunctions. We find that a positron binds to the cis isomer but not to the trans isomer. Our best estimate of the positron affinity for the cis isomer is 131 ± 22 meV. This is approximately seven times larger than the binding of an excess electron in the dipole field of cis-glyoxal.