I know when light strikes an object it excites electrons into higher energy states. I know thermal energy is basically just a lot of atomic and molecular kinetic energy. Does the excitation of the electron when struck by light cause a molecule to vibrate or make atoms move faster?

  • 3
    $\begingroup$ Atoms do not vibrate. Atomic bonds or molecules do. Electron excitation is part of thermal energy and redistributes toward translation, vibration and rotation energy, respecting quantisation discrimination. $\endgroup$
    – Poutnik
    Sep 26, 2022 at 5:32
  • $\begingroup$ Quantum excited states, rotational, vibrational, electronic, are heat content only when in thermal equilibrium. Absorption of radiation does not raise the temperature until the excited states deactivate by collisions, emission etc. transferring the quantized energy into random velocity of molecules and thermally equilibrated quantized states. $\endgroup$
    – jimchmst
    Oct 1, 2022 at 22:04

1 Answer 1


When light hits an object, different things can happen. The light can be reflected or absorbed. When visible light is absorbed, it will usually excite electronic states.

This excitation typically does not last long. As Poutnik mentioned in the comments, the excitation energy can dissipate in the form of vibration, rotation or translation. It can also be emitted or partially emitted, either quickly (fluorescence) or slowly (phosphorescence). The energy can be transferred to another electron (exciton transfer) or result in breaking a bond (photochemistry).

When the energy ends up as thermal energy, the mechanism of dissipation is described as coupling (e.g. vibrionic coupling) or non-radiative decay. I am not aware of a simple conceptual explanation of how this happens other than a coupled oscillator.


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