  The contribution of higher-order multipoles to radiative and non-radiative
decay of a single dipole emitter close to a spherical metallic nanoparticle is
re-examined. Taking a Ag spherical nanoparticle (AgNP) with the radius of 5 nm
as an example, a significant contribution (between 50% and 101% of the total
value) of higher-order multipoles to non-radiative rates is found even at the
emitter distance of 5 nm from the AgNP surface. On the other hand, the
higher-order multipole contribution to radiative rates is negligible.
Consequently, a dipole-dipole approximation can yield only an upper bound on
the apparent quantum yield. In contrast, the non-radiative rates calculated
with the quasistatic Gersten and Nitzan method are found to be in much better
agreement with exact electrodynamic results. Finally, the size corrected metal
dielectric function is shown to decrease the non-radiative rates near the
dipolar surface plasmon resonance.
