An energy level is an allowed energy eigenvalue of a Quantum Hamiltonian. Its corresponding energy eigenstates satisfy . Several independent energy eigenstates may share one energy level; their number is the energy-level degeneracy. A quantum superposition of different energy eigenstates need not have a definite energy, even though an ideal energy measurement yields one of the allowed outcomes.
Quantum confinement often produces discrete energy levels: the quantum harmonic oscillator has . An unconfined free particle instead has a continuous spectrum. In spectroscopy, a transition between two energy levels exchanges approximately with a photon; recoil and external fields can affect the measured frequency. Selection rules determine which energy differences produce observable spectral lines.
temperature can smear measured spectral or transport features through the spread of occupied energies and through temperature-dependent scattering. Fermi-edge occupation broadening and phonon-induced lifetime broadening are different mechanisms and should not be equated.
A nuclear energy level is an energy eigenvalue of an atomic nucleus. Differences between levels give nuclear excitation energies and the approximate gamma ray energies of transitions.
Excitation energy is an energy level's energy above a specified ground state. Emitted photon energies measure differences between levels, with a small recoil correction when the emitter has finite mass.
Articles by others on the same topic
Energy levels refer to the fixed energies an electron can have when it is in an atom or other quantum system. In quantum mechanics, electrons exist in discrete energy states, each corresponding to a different level of energy. Here’s a breakdown of the concept: 1. **Quantization**: In an atom, electrons cannot occupy just any energy level; instead, they can only exist in specific, quantized energy levels. This is a fundamental principle of quantum mechanics.