  Investigations of low-energy electron-scattering of the lanthanide atoms Eu,
Nd, Tb, Tm demonstrate that electron-correlation effects and core polarization
are the dominant fundamental many-body effects responsible for the formation of
metastable states of negative ions. Ramsauer Townsend minima, shape resonances
and binding energies of the resultant anions are identified and extracted from
the elastic total cross sections calculated using the complex angular momentum
method. The large discrepancy between the recently measured electron affinity
of 0.116 and the previously measured value of 1.053 eV for Eu is resolved.
Also, the previously measured electron affinities for Nd, Tb and Tm are
reconciled and new values are extracted from the calculated total cross
sections. The large electron affinities found here for these atoms, should be
useful in negative ion nanocatalysis, including methane conversion to methanol
without CO2 emission, with significant environmental impact.. The powerful
complex angular momentum method which requires only a few poles, yields
reliable binding energies for the metastable states of negative ions with no a
priori knowledge of experimental or other theoretical data and should be
applicable to other complex systems for the fundamental understanding of their
interactions.
