The SPR absorption spectrum of a nano-rod is seen to have two peaks with the longer wavelength peak corresponding to the absorption by the longitudinal plasmons and the other to the transverse plasmons. When the intensities are compared.. longitudinal plasmon peaks are almost always more intense than transverse ones. Why?
The intensity of a plasmon resonance is related to the magnitude of the transition dipole moment. Longitudinal resonances have a larger transition dipole moment compared to transverse resonances, and so have more intense absorption peaks. You can rationalize this by imagining the change in dipole moment from a longitudinal versus transverse electron density oscillation.