  The positron-electron annihilation gamma-ray spectra of linear alkanes
CnH2n+2 (n=1-12) have been studied systematically. A profile quality (PQ)
parameter, is introduced to assess the agreement between the obtained
theoretical profiles and the experimental measurements in the entire region of
energy shift of the spectra. Together with the Doppler shift of the gamma-ray
spectra, the two parameters,PQ and Doppler shift, are able to provide a more
comprehensive assessment of the calculated gamma-ray spectra with respect to
available experiment. Applying the recently developed docking model, the
present study determines the positrophilic electrons for individual alkanes
from which the gamma-ray spectral profiles are calculated. The results achieve
an excellent agreement with experiment, not only with respect to the Doppler
shift, but also with respect to the gamma-ray profiles in the photon energy
region up to 5 keV. The study further calculates the gamma-ray spectra of other
linear alkanes in the series without available experimental measurements, such
as heptane (C7H16), octane (C8H18), decane (C10H22) and undecane (C11H24). The
results obtained show a dominance of the positrophilic electrons in the lowest
occupied valence orbital (LOVO) in the positron-electron annihilation process,
in agreement with previous studies.
