  Photoinduced IR absorption was measured in undoped (LaMn)_{1-\delta}O_{3} and
(NdMn)_{1-\delta}O_{3}. We observe broadening and a ~44% increase of the
midinfrared anti-Jahn-Teller polaron peak energy when La^{3+} is replaced with
smaller Nd^{3+}. The absence of any concurent large frequency shifts of the
observed PI phonon bleaching peaks and the Brillouin-zone-center internal
perovskite phonon modes measured by Raman and infrared spectroscopy indicate
that the polaron peak energy shift is mainly a consequence of an increase of
the electron phonon coupling constant with decreasing ionic radius <r_{A}> on
the perovskite A site. This indicates that the dynamical lattice effects
strongly contribute to the electronic band narrowing with decreasing <r_{A}> in
doped giant magnetoresistance manganites.
