Electron momentum spectroscopy of formic acid

This study constitutes the first electron momentum study of the monomer of formic acid, without contributions from the dimer. Orbital energies and momentum distributions for the seven highest occupied orbitals are given. The experimental momentum distributions are compared with theoretical predictions of the wavefunction using density function theory with a B3LYP/TZVP basis set. It was found that the orbitals of s or hybrid character were well represented by the calculations, however the agreement between the experimental and theoretical data for the two p-type orbitals (2a″ and 1a″) was poor. This latter observation is consistent with previous results for π∗ orbitals studied with electron momentum spectroscopy.