We have investigated the transmission
of the 5 keV proton beam
through a graphene sheet containing monovacancy, adatom, and Stone–Wales
defects. The proton–graphene interaction potential was constructed
using the Doyle–Turner's proton–carbon interaction
potential.
The closed form of the scattering law was obtained using the momentum
approximation. Angular distributions of the transmitted protons were
analyzed using the morphological method based on the inspection of
the rainbow patterns in the impact parameter and scattering angle
planes generated by the rainbow scattering. We have demonstrated that
rainbows in the impact parameter plane are attracted and repelled
by the nearest saddles and maxima of the reduced proton–graphene
interaction potential. This explains why the rainbow pattern is so
sensitive to the redistribution of the potential extrema caused by
defects. Each defect type produces its distinctive rainbow pattern
that dominantly determines the shape of the angular distribution.
The ridge maxima of the angular distributions were investigated and
related to the spectrum of the Jacobian matrix of the map generated
by the scattering law. In the end, it has been shown how observed
rainbow patterns could be used to determine the unknown defect densities
of the complicated sample containing a combination of the different
defect types.