Energiatasoon

Energiatasoon is a Finnish term used to describe the discrete energy states a quantum system can occupy. In physics and chemistry, these energy levels are the eigenvalues of the system's Hamiltonian and define the possible energies that parts of the system can have. The corresponding eigenstates are called energy eigenstates.

In atoms and ions, electrons occupy energy levels; optical transitions occur when electrons move between levels, emitting or absorbing photons with energy difference ΔE = hν. For hydrogen-like systems, the energy levels follow En ∝ -1/n^2, illustrating how levels get closer together as the principal quantum number increases.

In molecules, energy levels include vibrational and rotational levels; in solids, the concept extends to electronic energy bands, where closely spaced levels form allowed bands separated by gaps. The energy level structure determines chemical properties, spectra, and electrical behavior of materials.

Population of energy levels at finite temperature follows statistical rules: Boltzmann distribution for non-fermions, and Fermi-Dirac distribution for electrons; thermal broadening and interactions can smear discrete levels into resonances.

Energiatasoon is probed with spectroscopy and is central to fields such as quantum chemistry, solid-state physics, and laser technology, including LEDs and solar cells. Related concepts include energy gaps, energy spectra, and quantum states, which together describe how systems absorb, emit, and transport energy.