Manifestations of non-adiabatic multiphonon transitions in optical pro
perties of semiconductor quantum dots are theoretically analyzed accou
nting for the influence of the spherical confinement on the phonon ene
rgy spectrum. The role of phonon branches of different symmetry in the
spectra of Raman scattering is ascertained. The effects of non-adiaba
ticity of the exciton-phonon system are shown to significantly enhance
phonon-assisted transition probabilities and to lead to multiphonon o
ptical spectra which are considerably different from the Franck-Condon
progression. Calculated spectral progressions compare well with exper
imental data on photoluminescence and Raman scattering in CdSe and CdS
exS1-x quantum dots.