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Enhanced excitonic effects in the energy loss spectra of LiF and Ar at large momentum transfer
It is demonstrated that the bootstrap kernel [\onlinecite{sharma11}] for
finite values of crucially depends upon the matrix character of the
kernel and gives results of the same good quality as in the limit. The bootstrap kernel is further used to study the
electron loss as well as absorption spectra for Si, LiF and Ar for various
values of . The results show that the excitonic effects in LiF and Ar
are enhanced for values of away from the -point. The reason
for this enhancement is the interaction between the exciton and high energy
inter-band electron-hole transitions. This fact is validated by calculating the
absorption spectra under the influence of an external electric field. The
electron energy loss spectra is shown to change dramatically as a function of
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