What are the differences between radiative and non radiative transition?

Asked by  | 21st Mar, 2009, 11:15: AM

Expert Answer:

Radiative transitions involve the absorption, if the transition occurs to a higher energy level, or the emission, in the reverse case, of a photon. Nonradiative transitions arise through several different mechanisms, all differently labeled in the diagram. Relaxation of the excited state to its lowest vibrational level is labeled vr in the diagram. This process involves the dissipation of energy from the molecule to its surroundings, and thus it cannot occur for isolated molecules. A second type of nonradiative transition is internal conversion (ic), which occurs when a vibrational state of an electronically excited state can couple to a vibrational state of a lower electronic state. A third type is intersystem crossing (isc); this is a transition to a state with a different spin multiplicity. In molecules with large spin-orbit coupling, intersystem crossing is much more important than in molecules that exhibit only small spin-orbit coupling. This type of nonradiative transition can give rise to phosphorescence.

A Jablonski diagram representing fluorescence resonance energy transfer (FRET)

Answered by  | 31st Mar, 2009, 01:10: AM

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