  The present study revealed quantum mechanically that the C1s binding energy
spectra of the small alkanes (upto six carbons) provide a clear picture of
isomeric chemical shift in linear alkanes and branched isomers, whereas the
valence binding energy spectra contain more sensitive information regarding the
length of the carbon chains. Total momentum cross sections of the alkanes
exhibit the information of the chain length as well as constitutional isomers
of the small alkanes. The C1s binding energies of small alkanes (including
isomers) are position specific and the terminal carbons have the lowest
energies. The length of an alkane chain does not apparently affect the C1s
energies so that the terminal carbons (289.11 eV) of pentane are almost the
same as those of hexane. The valence binding energy spectra of the alkanes are
characterized by inner valence and outer valence regions which are separated by
an energy gap at approximately 17 eV. The intensities of the total momentum
cross sections of the alkanes are proportional to the number of carbons in the
alkane chains whereas the shape of the cross sections in small momentum region
of p < 0.5 a.u. indicates their branched isomers.
