Question

explain the mechanism of how light is actually absorbed by atoms. thn explain the 4 possible fates of such absorbed energy. where does it go?

Answer 1

Energy is gained by the electrons by absorbing light.If the electrons have to jump from second energy level to the first energy level,they give off some of the energy by emitting light.

The atom that absorbs or emits light in discrete packets is called photons.

The absorption leaves the molecule in a higher energy state which is more reactive and less stable than the ground state.In the excited state they loose energy in the form of emission.The lifetime of this excited state is nanoseconds.

The process which has the emission of photon has radiative pathway and the others have non radiative pathway.

The most common process are shown in jablonski diagram where radiative pathway are represented by straight line and wavy line represent non radiative pathway.

Singlet states are represented by S ₀ ,S ₁ and triplet states by T ₁ ,T _2.

If S₀is populated then energy loss takes by fluroscence,vibrational relaxation and intersystem crossing.In triplet stage energy loss is by phosphorescence