In the field of atomic and molecular physics, an "atomic unit of length" is a unit of measurement that is used to express distances at the atomic and molecular scale in a dimensionless way. It is part of a system of atomic units (a.u.) that simplifies calculations involving fundamental physical constants and properties of atoms and molecules.
The atomic unit of length (a.u. of length) is defined in terms of the Bohr radius (a₀), which is a fundamental constant in atomic physics. The Bohr radius is approximately 0.52917721067 angstroms (Å) or 5.2917721067 x 10^-11 meters (m).
In atomic units, the Bohr radius is set to exactly 1 a.u. of length. Therefore, when using atomic units, distances are expressed relative to the Bohr radius, and the value of 1 a.u. of length corresponds to the typical size scale of atomic and molecular structures.
The use of atomic units simplifies many quantum mechanical calculations and allows physicists and chemists to work with dimensionless quantities, making it easier to compare and analyze atomic and molecular properties.
A meter (m) is the base unit of length in the International System of Units (SI), which is the modern metric system used for scientific and everyday measurements in most countries around the world. The meter is defined as the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.
In more practical terms, a meter is approximately equal to:
Meters are commonly used for measuring various lengths and distances, including the dimensions of objects, the length of rooms or buildings, and distances between locations on Earth. It is a versatile unit of measurement that is widely used in science, engineering, construction, and everyday life.