  Theoretical description of oscillations of electron liquid in large metallic
nanospheres (with radius of few tens nm) is formulated within
random-phase-approximation semiclassical scheme. Spectrum of plasmons is
determined including both surface and volume type excitations. It is
demonstrated that only surface plasmons of dipole type can be excited by
homogeneous dynamical electric field. The Lorentz friction due to irradiation
of electro-magnetic wave by plasmon oscillations is analyzed with respect to
the sphere dimension. The resulting shift of resonance frequency turns out to
be strongly sensitive to the sphere radius. The form of e-m response of the
system of metallic nanospheres embedded in the dielectric medium is found. The
theoretical predictions are verified by a measurement of extinction of light
due to plasmon excitations in nanosphere colloidal water solutions, for Au and
Ag metallic components with radius from 10 to 75 nm. Theoretical predictions
and experiments clearly agree in the positions of surface plasmon resonances
and in an emergence of the first volume plasmon resonance in the e-m response
of the system for limiting big nanosphere radii, when dipole approximation is
not exact.
