I understand that when d-orbitals split some electrons can occupy the higher orbitals by absorbing frequencies of light, but do these electrons then fall back to their original ground states? If so, why? Why don't they remain in a permanently excited state?

  • $\begingroup$ @KennyLau ΔE does not represent the difference between the excited state and the ground state, it represents the uncertainty in the energy of the excited state. Furthermore, it only gives a minimum bound on the lifetime, not a maximum. The energy-time uncertainty relationship is not incompatible with a persistent excited state. $\endgroup$
    – orthocresol
    May 28 '16 at 17:10
  • $\begingroup$ Oh, sorry for the misinformation. I've deleted them. $\endgroup$
    – Kenny Lau
    May 28 '16 at 17:16
  • $\begingroup$ Related: Color imparted to flame and color of coordination compounds $\endgroup$
    – Vishnu
    May 21 '20 at 2:08

I've heard someone mention that the electrons do indeed fall back to ground state but, you don't see that part of the emission spectra since the energy is dispersed everywhere and not just towards your eyes. This is why the colour comes from the absorbance spectra.

The reason is does not stay in the excited state is simply because it is unstable. It will gain energy and then release it as mentioned above, then repeat.


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