Chemistry as a function of the fine-structure constant and the electron-proton mass ratio

Abstract

In standard computations in theoretical quantum chemistry the accepted values of the fundamental physical constants are assumed. Alternatively, the tools of computational quantum chemistry can be used to investigate hypothetical chemistry that would result from different values of these constants, given the same physical laws. In this work, the dependence of a variety of basic chemical quantities on the values of the fine-structure constant and the electron-proton mass ratio is explored. In chemistry, the accepted values of both constants may be considered small, in the sense that their increase must be substantial to seriously impact bond energies. It is found that if the fine-structure constant were larger, covalent bonds between light atoms would be weaker, and the dipole moment and hydrogen-bonding ability of water would be reduced. Conversely, an increase in the value of the electron-proton mass ratio increases dissociation energies in molecules such as ${\mathrm{H}}_{2}$, ${\mathrm{O}}_{2}$, and CO${}_{2}$. Specifically, a sevenfold increase in the fine-structure constant decreases the strength of the O--H bond in the water molecule by 7 kcal mol${}^{\ensuremath{-}1}$ while reducing its dipole moment by at least $10%$, whereas a 100-fold increase in the electron-proton mass ratio increases the same bond energy by 11 kcal mol${}^{\ensuremath{-}1}$.