Reveal of small alkanes and isomers using calculated core and valence binding energy spectra and total momentum cross sections

TL;DR

This study uses quantum mechanical calculations of core and valence binding energy spectra and momentum cross sections to distinguish small alkane isomers and determine chain length, providing detailed spectral signatures for each.

Contribution

It introduces a computational approach combining core and valence spectra with momentum cross sections to identify isomeric and chain length differences in small alkanes.

Findings

C1s binding energies reveal isomeric chemical shifts and are position-specific.

Valence spectra are sensitive to chain length and contain inner and outer valence regions.

Momentum cross sections correlate with chain length and distinguish branched isomers.

Abstract

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.