Imaging proton migration from X-rays and neutrons

Abstract

The short hydrogen bond in the urea–phosphoric acid system has been studied by multiple-temperature X-ray single crystal diffraction. The hydrogen atom is imaged using difference Fourier methods from these data and also from previous neutron diffraction data. The migration of the hydrogen atom is clearly observed using the X-ray difference Fourier maps. The hydrogen atom positions determined from these maps are more reliable than from X-ray refinements of this atom. A greater apparent shift of the proton is observed from X-ray than from neutron diffraction, as might be expected.