Shallow electron centers in AgCl and AgBr have bean studied by pulsed
electron nuclear double resonance at 95 GHz. Information about the geo
metric structure and the ground-state wave function is obtained, which
confirms that these centers consist of an electron loosely bound to a
Coulombic trap. The microscopic models for these Coulombic traps, to
which we are led, differ from the ones suggested from previous optical
studies. It appears that the optical transition energies can be reaso
nably well accounted for by simple hydrogenlike and quantum-defect met
hods. Owing to the similarity between shallowly trapped and conduction
electrons, information about the lowest state of the conduction band
is derived, which reveals that this state is not mainly sliver s like.
as is frequently assumed, but also includes a substantial amount of c
hlorine s character.