Convert A.U. of Length (a.u.) to Picometer (pm) instantly.
About these units
A.U. of Length (a.u.)
The atomic unit of length, also known as the Bohr radius unit in atomic units, is approximately 5.29177 × 10⁻¹¹ meters. It is defined as the radius of the lowest-energy orbital of the hydrogen atom, providing a natural scale for describing atomic and quantum mechanical systems. Atomic units were devised to simplify equations in quantum chemistry and atomic physics by normalizing fundamental constants such as electron charge, Planck's constant, and electron mass to 1. In this system, many equations become dimensionless and far easier to manipulate mathematically. The atomic unit of length is essential in molecular orbital calculations, quantum simulations, and the study of electron behavior in atoms and molecules. Its use reflects an approach to physics in which units are chosen to match the natural scales of the systems being studied.
Picometer (pm)
At 10⁻¹² meters, the picometer occupies a scale close to the dimensions of atoms but slightly finer than typical atomic radii. Chemists use picometers to express covalent bond lengths, ionic radii, and atomic radii. For example, the radius of a hydrogen atom is about 53 pm. The unit also appears frequently in crystallography, where X-ray diffraction reveals lattice spacing on the order of a few hundred picometers. The picometer provides a numeric convenience: atomic structures are neither too large nor too small to measure accurately in this unit. In physics, picometer-scale distances become relevant when examining the interactions of electrons in tightly bound orbitals or in high-resolution measurements of electric dipole moments. It is a unit that bridges atomic size with the precision of modern measurement tools.