Compare with Bohr radius and hartree .A system of non- SI units used in quantum chemistry to simplify calculations and mathematical expressions. The definitions of atomic units include physical constants (like the speed of light, the rest mass of the electron, and other quantities that never change), so that all constants drop out of expressions when atomic units are used.
ATOMIC UNIT
Meaning of ATOMIC UNIT in English
General chemistry English glossary. Английский глоссарий общей химии. 2012