There have been various comprehensive and stand-alone text books on the
introduction to Molecular Photochemistry available in market. A few fantastic books
to mention are: ‘Modern Molecular Photochemistry of Organic Molecules’ by N. J.
Turro et. al. and ‘Fundamentals of Photochemistry’ by K. K. Rohatgi- Mukherjee.
These books along with others give crystal clear idea on the common topics both in
pictorial and intuitive terms.
Absorption of light (W or visible) by the ground state of a molecule (So) generates
electronically excited states, either directly (the singlet states) or after intersystem crossing
from the singlet manifold (the triplet states). Alternatively, triplet states may be generated by
energy transfer from another excited state (a sensitiser). In both multiplicities, very fast
internal conversion leads to the lowest states (S1 and TI respectively). These states, although
still quite short lived (typical lifetime 610-8 s for S1 and ...