This work focuses on a bundle of two van der Waals-coupled single wall carbon nanotubes. The non-resonant Raman spectra of inhomogeneous dimers of single walled of carbon nanotubes are calculated in the framework of spectral moments method, together with a bond-polarizability model. The evolution of the low frequency Raman-active modes as a function of the nanotube diameters is discussed. Effects of van der Waals coupling on charge transfer processes are also investigated. The obtained results are compared to experimental Raman data measured on dimer sample. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.