The dominant phonon wave vectors q∗ probed by the 2D Raman mode of pristine
and uniaxially strained graphene are determined via a combination of ab initio
calculations and a full two-dimensional integration of the transition matrix.
We show that q∗ are highly anisotropic and rotate about K with the polarizer
and analyzer condition relative to the lattice. The corresponding phonon-
mediated electronic transitions show a finite component along K-Γ that
sensitively determines q∗. We invalidate the notion of “inner” and “outer”
processes. The characteristic splitting of the 2D mode of graphene under
uniaxial tensile strain and given polarizer and analyzer setting is correctly
predicted only if the strain-induced distortion and red-shift of the in-plane
transverse optical (iTO) phonon dispersion as well as the changes in the
electronic band structure are taken into account.