atomiyksiköissä

Atomiyksiköissä is a Finnish term that translates to "in atomic units". It refers to a system of natural units of measurement used in physics, particularly in atomic and molecular physics. In this system, fundamental physical constants are set to 1, simplifying many equations and calculations. The most common atomic unit system is the Hartree atomic unit system.

Key quantities set to one in the Hartree system include the elementary charge (e), the electron rest mass (m_e), and the reduced Planck constant (ħ). The Bohr radius (a_0) and the Hartree energy (E_h), which is twice the ionization energy of the hydrogen atom, are also defined as unity. This normalization eliminates the appearance of these fundamental constants in equations, making the relationships between different physical quantities more apparent.

The use of atomic units is prevalent in computational chemistry and theoretical physics. It streamlines calculations and allows for a more direct comparison of results across different theoretical models and experiments. While convenient for theoretical work, it's important to remember that these units are derived from fundamental physical constants and can be converted back to SI units when necessary for comparison with macroscopic measurements. The choice of which constants to set to one can vary, leading to slightly different atomic unit systems, but the Hartree system is by far the most widely adopted.