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__when__a photon is absorbed in a transition corresponding to an energy difference of delta_E=E_final-E_initial? This uncertainty being roughly delta_t= planck's constant divided by delta_E?

So for example, if delta_E = 5 eV, delta_t = 4.14 fs/5 = 0.83 fs. (1fs = 1 femtosecond = 1e-15 seconds).