An experimental and theoretical study of the HOMO of W(CO)6: Vibrational effects on the electron momentum density distribution

► Our high resolution (e, 2e) experiment can be conducted at various impact energies, which is an important feature because several recent works have observed strong distorted wave effects in some molecular orbitals. ► It is first time to calculate molecular orbital momentum distributions using the relativistic quantum chemistry theory with our new developed method. Before this, all relativistic calculations of momentum distribution (MD) are limited to atomic orbitals. ► As indicated in present work, the low frequency vibrational mode will cause a large amplitude nuclear motion for a floppy molecule at room temperature, which will change the orbital momentum distributions. Before this, most of EMS works focused on the multi-conformers coexistence to explain the experimental results.