Timeframes of Electron Excitation: Phosphorescence Excluded

[Charles123]

Excluding the process of Phosphorescence, an electron in an excited state will return directly or with a intermediate step to its grown state (like in a ruby LASER before the stimulated emission, where first absorbs a green photon, drops to an intermediary energy level and then emits a red photon by stimulation). But what determines the time it takes for this to happen?
Thank you
regards

 

[xAxis]

I think that time is indeterminate