Publikace ÚTF

The potential energy surface of the ground state of the water anion H2O− is carefully mapped
using multireference CI calculations for a large range of molecular geometries. Particular attention is paid
to a consistent description of both the O
−
+H2 and OH
−
+H asymptotes and to a relative position of
the anion energy to the ground state energy of the neutral molecule. The autodetachment region, where
the anion state crosses to the electronic continuum is identified. The local minimum in the direction of
the O− + H2 channel previously reported by Werner et al. [J. Chem. Phys. 87, 2913 (1987)] is found
to be slighly off the linear geometry and is separated by a saddle from the autodetachment region. The
autodetachment region is directly accessible from the OH
−
+H asymptote. For the molecular geometries in
the autodetachment region and in its vicinity we also performed fixed-nuclei electron-molecule scattering
calculations using the R-matrix method. Tuning of consistency of a description of the correlation energy in
both the multireference CI and R-matrix calculations is discussed. Two models of the correlation energy
within the R-matrix method that are consistent with the quantum chemistry calculations are found. Both
models yield scattering quantities in a close agreement. The results of this work will allow a consistent
formulation of the nonlocal resonance model of the water anion in a future publication.