What is Excited: Definition and 171 Discussions

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.

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  1. MTd2

    N-pole excited states of the proton?

    Does the proton have n-pole excited states? Or n-pole excited states exist only for A>1?
  2. B

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  3. Z

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  4. Z

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  5. N

    Why are nuclear excited states always eigenstates of parity?

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  6. L

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  7. S

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  8. X

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  9. P

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  10. A

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  11. G

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  12. M

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  13. dlgoff

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  14. P

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  15. Z

    How long does it take for a valence electron being excited to conduction band?

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  16. F

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  17. E

    Lifetime of an Excited State

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  18. K

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  19. B

    Variational Principle on First Excited State

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  20. M

    When the electrons in silicon are excited by visible light and jump

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  21. G

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  22. V

    Probability of being in ground & 1st excited state of widened infinite well

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  23. D

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  24. D

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  25. E

    Mutual Inductance: Coil 1 Excited, Coil 2 Open Circuited

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  26. J

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  28. B

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  29. L

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  30. D

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  31. L

    Rotational energy of nuclear excited states

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  32. E

    Ground or excited states.Please check.

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  33. S

    Binding energy of an electron in an excited state?

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  34. A

    Do shielding materials get excited and start reactions?

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  35. O

    Calculating Probability of Particle in First Excited State

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  36. M

    Nuclear Shell Model - Spin-parity of excited states

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  37. D

    Excited vs. Ground state masses of atom

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  38. W

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  39. B

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  40. N

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  41. M

    Chemistry Photosystems in Plant Cells: Transferring Excited Electron Energy

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  42. T

    Why do electrons in excited states decay to the ground state?

    Hello, Non-relativistic quantum mechanics doesn't explain why the electron in the hydrogen atom (for example) "decays" from excited states to the ground state. Which theory does explain this phenomenon (from basic principles) ? Thanks.
  43. F

    Calculating Remaining Kinetic Energy After Excited State

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  44. B

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  45. P

    Calculating the Excited State Lifetime of 223Ra Nucleus

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  46. T

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  47. E

    What Is the Likely Spin Parity of an Excited 60Co Nucleus?

    Homework Statement I am asked to determine the most likely I\pi state for an excited 60Co nucleus (a 59Co nucleus that has just been hit by a neutron). I have determined already from the previous part of the problem that the excited state has energy of ~7 MeV compared to the ground state. Not...
  48. B. Elliott

    How long have fans been waiting for the Tron 2 preview?

    After 26 long years... finally!:cool: This is a bootleg of the preview that was shown at Comic-Con just two days ago. So far it sounds like it's coming out in 2011. Edit: removed clip
  49. X

    Energy levels of electrons excited by photons

    I've been researching the change of energy levels of electrons when excited by photons. The equations I have found are... E_n = (-2pi^2 * m * e^4 * Z^2)/(n^2 * h^2) Which gives us the energy of the electron at a particular energy level. m = mass of electron e = electric charge of...
  50. Ahmed Abdullah

    How Long Can an Atom Stay in an Excited State?

    How long an atom remains excited? How can we prolong the excited state of an atom? Whether its possible. Thx
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