Combining relativistic quantum-chemistry theories and electron-momentum spectroscopy to study valence-electron structures of molecules

We report the combination of the Amsterdam density-functional relativistic quantum-chemistry program and electron-momentum spectroscopy to interpret electronic structures of molecules. We calculate momentum profiles of molecular orbital using the two-component relativistic theory. The momentum profiles of the complete valence shell orbitals of I2 and Au2 molecules are obtained in comparison between the nonrelativistic and relativistic calculations. The theoretical results show that relativistic effects have significant influences on the momentum distributions for valence orbitals of I2 and Au2. In order to verify the validity of the calculations, the high-resolution experimental momentum distributions of the 5P3/2 and 5P1/2 states of xenon are presented in comparison with relativistic quantum-chemistry theories.