The first electronic absorption band maximum of a polar and relatively rigid aromatic molecule appears at 310 nm but its fluorescence maximum in acetonitrile solution appears with a large Stokes shift at 450 nm . The most likely reason for the Stokes shift is
(a)Large change in molecular geometry in the excited state
(b)Increase in dipole moment of the molecule in the excited state
(c)Decrease in polarizability of the molecule in the excited state
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
For a rigid polar chromophore in a polar solvent a large Stokes shift arises from the increased excited-state dipole moment, which the solvent relaxes around before emission.