original question: What is the unit of length in [Atomic units]?
answer: bohr radius
answer type: Unit of Length.
auxiliary information: Atomic units form a system of natural units which is especially convenient for atomic physics calculations. There are two different kinds of atomic units, Hartree atomic units and Rydberg atomic units, which differ in the choice of the unit of mass and charge. This article deals with Hartree atomic units, where the numerical values of the following four fundamental physical constants are all unity by definition: Electron mass ; Elementary charge ; Reduced Planck's constant ; Coulomb's constant . In Hartree units, the speed of light is approximately . Atomic units are often abbreviated "a.u." or "au", not to be confused with the same abbreviation used also for astronomical units, arbitrary units, and absorbance units in different contexts.
What is the name for the [Atomic units] of length?