In Spectroscopy Department Charge transfer contribution to SERS, crystalline state reactions, vibrational relaxation and molecular geometry have been investigated using Laser Raman Spectroscopy. Absorption, steady state and time resolved luminescence spectroscopy have been used to study energy transfer in restricted geometries, photo induced electron transfer in donor acceptor systems, second order spin orbit coupling and photorotamerism in certain heterocyclic molecules, photoenolization in excited state, orientation and aggregation of molecules in Langmuir - Blodgett films. Dynamical behaviour of Goldstone and soft mode in the vicinity of phase transition temperature has been studied and a theoretical approach to the variation of phase transition temperature from non chiral to chiral smectic C* phase has been adopted. Nonlinear electrical conduction, dark and photoconduction have been investigated in some organometallic compounds and conducting polymers organised in LB films. A fish-freshness biosensor has been developed. Monte-Carlo simulaltechnique has been utilised for multipolar and exchange mediated energy transfer and trapping in a temary solid. Time dependent linear response theory has been applied to study collective excitation modes of many particle systems. The effect of Debye plasma on the excitation spectrum of atomic systems was investigated. Hyperspherical coordinate approach has been applied for studying correlation effects in low Z atomic systems. A highly correlated wavefunction involving interparticle coordinates is being used for studying double excitation effects in two particle systems. Theoretical investigation of multiphoton ionisation of small molecules under intense laser field and study of the vibrational branching ratio and photoelectron angular distribution has been performed. Lasing without population inversion in H₂ from autoionising states has been investigated.