  The most important bands for the evaluation of strain in graphene (the 2D and
2D prime modes) are investigated. It is shown that for Bernal-stacked bilayers,
the two-phonon Raman features have three different components that can be
assigned to processes originating solely from the top graphene layer, bottom
graphene layer, and from a combination of processes originating both from the
top and bottom layers. The individual components of the 2D and 2D prime modes
are disentangled. The reported results enable addressing the properties of
individual graphene layers in isotopically labelled turbostratic and
Bernalstacked graphene systems.
