Inelastic x-ray scattering study of the state-resolved differential cross section of Compton excitations in helium atoms

Abstract

The state-resolved differential cross sections for both the $1{s}^{2}$ ${}^{1}{S}_{0}\ensuremath{\rightarrow}1s2s$ ${}^{1}{S}_{0}$ monopolar transition and the $1{s}^{2}$ ${}^{1}{S}_{0}\ensuremath{\rightarrow}1s2p$ ${}^{1}{P}_{1}$ dipolar transition of atomic helium had been measured over a large momentum transfer region by high-resolution inelastic x-ray scattering (IXS). The almost-perfect match of the present measurement with the theoretical calculations gives a stringent test of the theoretical method and the calculated wave functions. Our results demonstrate that high-resolution IXS is a powerful tool for studying the excitations in atoms and molecules.