• PRADEEP MALAN
• SHAILESH KUMAR SINGH

Abstract: - The present work embodies the observations of spectroscopic studies fluorescence spectroscopic, fluorescing abilities by recording fluorescence in liquid and solid matrices. A CNDO/S-CI calculation is used to know the electronic energy levels in laser dyes coumarin and its various substituted derivatives. Effect of solvents and substituents on the fluorescence spectra of dyes coumarin derivatives has also been studied. Upon excitation dipole moment of coumarin dyes changes which is estimated using sol vato-chromic theories and tried to explain in terms of resonance structures. The percentage polarization of fluorescence emission has also been measured in different organic solvents. Molecule on absorption of light get excited and subsequently emit photons is known as fluorescence. It take place due to the transition between excited and ground states of the same multiplicity in a time period of 10-1110-7 second after excitation. However, when emission occur from transition between states of different multiplicity, usually from a triplet excited state returning to a singlet ground state, is termed a phosphorescence. Besides these, there are other types of luminescence as well; for example, electroluminescence and chemiluminescence. The former take place when electrical energy excites molecules or atoms, whereas the latter is caused by a chemical reaction. Bioluminescence is a special example of chemiluminescence in which light is emitted by living organisms due to cellular oxidation of some substrate in the presence of an enzyme.

coumarin, CNDO/S-CI fluorescence emission, electroluminescence, fluorescing abilities, chemiluminescence, Bioluminescence.

"SPECIAL CHARACTERISATION OF HETEROCYCLIC COMPOUNDS ", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.6, Issue 6, page no.291-295, June-2019, Available :http://www.jetir.org/papers/JETIR1906B43.pdf

"SPECIAL CHARACTERISATION OF HETEROCYCLIC COMPOUNDS ", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.6, Issue 6, page no. pp291-295, June-2019, Available at : http://www.jetir.org/papers/JETIR1906B43.pdf