Comment on Sensitivity Coefficients to Variation of Fundamental Constants

Atoms and molecules can serve as sensitive probes of a possible variation of the fine structure constant a and electron-to-proton mass ratio mu. Two types of sensitivity coefficients are often used to quantify and compare the sensitivity of different species to the variation of fundamental constants. The dimensionless coefficients K are related to the fractional sensitivity, while dimensional factors q are related to the absolute sensitivity. Here, several common errors and misconceptions regarding these coefficients that frequently appear in the literature are discussed.