Cross sections for the electron-impact excitations (A)over-tilde1B1 and (B)over-tilde1A1 of H2O determined by high-energy electron scattering

Understanding the role of inelastic electron scattering in water is of fundamental importance in various fields ranging from atmospheric chemistry to radiation biology. The lack of accurate excitation cross sections for water results in a large uncertainty, for example, in the track structure simulation for modeling radiation damage to DNA. The large differences of the integral cross sections (ICSs) for the optical-allowed excitations (A) over tilde B-1(1) and (B) over tilde (1)A(1) of H2O among experiments and theories have been maintaining for decades. To resolve this issue, by combining the ab initio calculation with the electron correlation being taken into account accurately, we compare the ICSs determined by high-energy electron scattering with the existing experiments at low and intermediate energies and theories, where the present experiment eliminated the errors from the spectral deconvolution in low-energy measurements. Our work provides a recommendation for the ICSs of the two excitations from thresholds up to several keV, and suggests the existing selected ICSs for H2O be revised for accurate modeling radiation effects in biological matter and describing the transport properties of electrons in aqueous systems.