ANGSTREM
One Angstrem (1 Å) is a measure of length, which is equal to 10-10 meters. For example, it is known that interaction energy of two unit charges (that is, protonic or electronic charges) at the distance of 1 Å is near to 330 kcal/mole. The measure is used in optics, atomic physics, solid-state physics, molecular biology, etc.