The ab initio calculation of very many triply ionized states of molecular systems

Formation and decay of core-orbital vacancies in the water molecule

“…By comparison with the photoelectron spectrum of water [40][41][42], where the valence bands (12.6, 14.7 and 18.4 eV) are centred at roughly 15 eV and the O2s-based inner valence band is at 32 eV, we can attribute the three bands crudely as 1: states with three outer valence vacancies; 2: states with two outer valence and one inner valence vacancy; and 3: states with one outer valence and two inner valence vacancies. This rough assignment is in agreement with the energies of states with leading configurations of these three types in our calculations and in the calculations of Handke et al [43] and also with the relative band intensities. Taking simple hole configurations only, allowing for doublets and quartets and assuming that Auger decay from outer valence (OV) and inner valence (IV) orbitals is equally probable, we count six OV-hole only configurations, six with one IV hole and two OV holes and three with two IV holes and one OV hole.…”

“…Triple ionisation energies of the water molecule were calculated several years ago within the ADC (algebraic diagrammatic construction) scheme [43] at the equilibrium geometry of the neutral molecule and have been recalculated by us using the CASSCF method. Both theoretical approaches give vertical triple ionisation energies of water near 83 eV which is above the apparent experimental onset seen in Fig.…”

Vertical triple ionization with diffusion quantum monte carlo

“…The trial wave function consists of a single Slater determinant of Hartree–Fock orbitals built as a linear combination of double‐zeta Slater functions, with exponents optimized in the equilibrium geometry of the water molecule 34. The orbitals of the neutral state were used to build the trial wave function for all the cations.…”

“…The orbitals of the neutral state were used to build the trial wave function for all the cations. The configurations of triply ionized states were obtained following the configuration for the ground state of the water, $1a_1^2 2a_1^2 1b_2^2 3a_1^2 1b_1^2$ , as described in Handke et al34…”

“…Table 1 shows the energies, E, obtained for the ground state (neutral state), the energies of the triply ionized states, TIPC, (triple ionization potential calculated with DQMC), and the values of triply ionized states, TIPR, obtained theoretically by Handke et al34…”