Definition of Chemical Shift
Chemical shift is the frequency of resonance of a nucleus relative to the frequency of absorption of a standard in the presence of a magnetic field. The reference compound employed in this nuclear magnetic resonance spectroscopy is tetramethylsilane (TMS). The structure of the molecule in NMR spectroscopy is determined through location and the number of chemical shifts.
Moreover, in photoemission spectroscopy, these chemical shifts are used in determining the signals. The variations in the distribution of electrons change the NMR frequencies of the same nucleus. There are some factors that affect the chemical shift such as electronegativity of nearby atoms, electron density, and anisotropic induced magnetic field.