Excited state - wikipedia Excited state After absorbing energy, an electron may jump from the ground state to a higher energy excited state. Excitations of copper 3d orbitals on the CuO2 - plane of a high Tc superconductor ; The ground state ( blue ) is x2 - y2 orbitals ; the excited orbitals are in green ; the arrows illustrate inelastic x-ray spectroscopy In quantum mechanics, an excited state of a system ( such as an atom, molecule or nucleus ) is any quantum state of the system that has a higher energy than the ground state ( that is, more energy than the absolute minimum ). Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being raised to an excited state. The temperature of a group of particles is indicative of the level of excitation ( with the notable exception of systems that exhibit negative temperature ). The lifetime of a system in an excited state is usually short : spontaneous or induced emission of a quantum of energy ( such as a photon or a phonon ) usually occurs shortly after the system is promoted to the excited state, returning the system to a state with lower energy ( a less excited state or the ground state ). This return to a lower energy level is often loosely described as decay and is the inverse of excitation. Long - lived excited states are often called metastable. Long - lived nuclear isomers and singlet oxygen are two examples of this. Contents 1 Atomic excitation 2 Perturbed gas excitation 3 Calculation of excited states 4 Excited state absorption 5 Reaction 6 See also 7 References 8 External links Atomic excitation A simple example of this concept comes by considering the hydrogen atom. The ground state of the hydrogen atom corresponds to having the atom 's single electron in the lowest possible orbit ( that is, the spherically symmetric `` 1s '' wavefunction, which, so far, has demonstrated to have the lowest possible quantum numbers ). By giving the atom additional energy ( for example, by the absorption of a photon of an appropriate energy ), the electron is able to move into an excited state ( one with one or more quantum numbers greater than the minimum possible ). If the photon has too much energy, the electron will cease to be bound to the atom, and the atom will become ionized. After excitation the atom may return to the ground state or a lower excited state, by emitting a photon with a characteristic energy. Emission of photons from atoms in various excited states leads to an electromagnetic spectrum showing a series of characteristic emission lines ( including, in the case of the hydrogen atom, the Lyman, Balmer, Paschen and Brackett series. ) An atom in a high excited state is termed a Rydberg atom. A system of highly excited atoms can form a long - lived condensed excited state e.g. a condensed phase made completely of excited atoms : Rydberg matter. Hydrogen can also be excited by heat or electricity. Perturbed gas excitation A collection of molecules forming a gas can be considered in an excited state if one or more molecules are elevated to kinetic energy levels such that the resulting velocity distribution departs from the equilibrium Boltzmann distribution. This phenomenon has been studied in the case of a two - dimensional gas in some detail, analyzing the time taken to relax to equilibrium. Calculation of excited states Excited states are often calculated using coupled cluster, Møller -- Plesset perturbation theory, multi-configurational self - consistent field, configuration interaction, and time - dependent density functional theory. Excited state absorption The excitation of a system ( an atom or molecule ) from low - energy excited state to a high - energy excited state with the absorption of a photon is called excited state absorption ( ESA ). Excited state absorption is possible only when an electron has been already excited from the ground state to a lower excited state. The excited state absorption is usually an undesired effect, but it can be useful in upconversion pumping. The excited state absorption measurements are done using pump - probe techniques. However, it is not easy to measure them compared to ground - state absorption and in some cases complete bleaching of the ground state is required to measure excited state absorption. Reaction A further consequence is reaction of the atom in the excited state, as in photochemistry. Excited states give rise to chemical reaction. See also Rydberg formula Stationary state Repulsive state References Jump up ^ Hehre, Warren J. ( 2003 ). A Guide to Molecular Mechanics and Quantum Chemical Calculations ( PDF ). Irvine, California : Wavefunction, Inc. ISBN 1 - 890661 - 06 - 6. Jump up ^ Glaesemann, Kurt R. ; Govind, Niranjan ; Krishnamoorthy, Sriram ; Kowalski, Karol ( 2010 ). `` EOMCC, MRPT, and TDDFT Studies of Charge Transfer Processes in Mixed - Valence Compounds : Application to the Spiro Molecule ''. The Journal of Physical Chemistry A. 114 ( 33 ) : 8764 -- 8771. doi : 10.1021 / jp101761d. PMID 20540550. Jump up ^ Dreuw, Andreas ; Head - Gordon, Martin ( 2005 ). `` Single - Reference ab Initio Methods for the Calculation of Excited States of Large Molecules ''. Chemical Reviews. 105 ( 11 ) : 4009 -- 37. doi : 10.1021 / cr0505627. PMID 16277369. Jump up ^ Knowles, Peter J. ; Werner, Hans - Joachim ( 1992 ). `` Internally contracted multiconfiguration - reference configuration interaction calculations for excited states ''. Theoretica Chimica Acta. 84 : 95. doi : 10.1007 / BF01117405. Jump up ^ Foresman, James B. ; Head - Gordon, Martin ; Pople, John A. ; Frisch, Michael J. ( 1992 ). `` Toward a systematic molecular orbital theory for excited states ''. The Journal of Physical Chemistry. 96 : 135. doi : 10.1021 / j100180a030. Jump up ^ Glaesemann, Kurt R. ; Gordon, Mark S. ; Nakano, Haruyuki ( 1999 ). `` A study of FeCO+ with correlated wavefunctions ''. Physical Chemistry Chemical Physics. 1 ( 6 ) : 967 -- 975. Bibcode : 1999PCCP... 1... 967G. doi : 10.1039 / a808518h. Jump up ^ ( url = https://www.rp-photonics.com/excited_state_absorption.html ) Jump up ^ Dolan, Giora ; Goldschmidt, Chmouel R ( 1976 ). `` A new method for absolute absorption cross-section measurements : rhodamine - 6G excited singlet - singlet absorption spectrum ''. Chemical Physics Letters. 39 ( 2 ) : 320 -- 322. Bibcode : 1976CPL... 39... 320D. doi : 10.1016 / 0009 - 2614 ( 76 ) 80085 - 1. External links NASA background information on ground and excited states Quantum mechanics Background Introduction History timeline Classical mechanics Old quantum theory Glossary Fundamentals Bra -- ket notation Complementarity Density matrix Energy level ground state excited state degenerate levels zero - point energy Entanglement Hamiltonian Interference Decoherence Measurement Nonlocality Quantum state Superposition Tunnelling Scattering theory Symmetry in quantum mechanics Uncertainty Wave function collapse wave -- particle duality Formulations Formulations Heisenberg Interaction Matrix mechanics Schrödinger Path integral formulation Phase space Equations Dirac Klein -- Gordon Pauli Rydberg Schrödinger Interpretations Interpretations Bayesian Consistent histories Copenhagen de Broglie -- Bohm Ensemble Hidden variables Many - worlds Objective collapse Quantum logic Relational Stochastic Transactional Cosmological Experiments Afshar Bell 's inequality Cold Atom Laboratory Davisson -- Germer Delayed choice quantum eraser Double - slit Franck -- Hertz experiment Leggett -- Garg inequality Mach - Zehnder inter. Elitzur -- Vaidman Popper Quantum eraser Schrödinger 's cat Stern -- Gerlach Wheeler 's delayed choice Science Quantum Bayesianism Quantum biology Quantum calculus Quantum chemistry Quantum chaos Quantum cognition Quantum cosmology Quantum differential calculus Quantum dynamics Quantum evolution Quantum geometry Quantum group Quantum measurement problem Quantum mind Quantum probability Quantum stochastic calculus Quantum spacetime Technology Quantum algorithms Quantum amplifier Quantum bus Quantum cellular automata Quantum finite automata Quantum channel Quantum circuit Quantum complexity theory Quantum computing Timeline Quantum cryptography Quantum electronics Quantum error correction Quantum imaging Quantum image processing Quantum information Quantum key distribution Quantum logic Quantum logic gates Quantum machine Quantum machine learning Quantum metamaterial Quantum metrology Quantum network Quantum neural network Quantum optics Quantum programming Quantum sensing Quantum simulator Quantum teleportation Extensions Quantum statistical mechanics Relativistic quantum mechanics Quantum field theory history Quantum gravity Fractional quantum mechanics Portal : Physics Commons Retrieved from `` https://en.wikipedia.org/w/index.php?title=Excited_state&oldid=803935968 '' Categories : Quantum mechanics Hidden categories : All articles with unsourced statements Articles with unsourced statements from April 2016 Talk Contents Interaction About Wikipedia Asturianu Български Català Čeština Deutsch Eesti Español فارسی Français 한국어 Հայերեն Italiano עברית Lietuvių La. lojban. Nederlands 日本 語 Norsk Norsk nynorsk Polski Português Русский Slovenčina Slovenščina Српски / srpski Suomi Svenska தமிழ் Türkçe Українська Tiếng Việt 中文 Edit links This page was last edited on 5 October 2017, at 16 : 36. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: what is an atom in the excited state
Answer: any quantum state of the system that has a higher energy than the ground state (that is, more energy than the absolute minimum)