Two small particles composed of aluminium are brought near each other (but not touching). Describe what will happen to their plasmon absorption spectra for electric eld (a) parallel, (b) perpendicular, to the axis between the particles. For each case (a) and (b), briey state (i) how the wavelength of any observed absorption peaks relates to that of a single particle, (ii) how the dipoles are arranged, (iii) why some resonances are not observed