Analysis of Fluorescence Quenching of BPBD by Aniline in Toluene

Fluorescence quenching of 2-(4'-t-Butylphenyl)-5-(4"-biphenylyl)-1,3,4-oxadiazole (BPBD) by aniline in toluene has been carried out at room temperature by steady state and time resolved fluorescence spectroscopy. The Stern-Volmer plot by steady state method has been found to be non-linear showing a positive deviation, whereas by time-resolved method it is linear. In order to interpret these results we have used the ground state complex and sphere of action static quenching models. Using these models various rate parameters have been determined. Based on these models, with finite sink approximation model, we conclude that positive deviation Stern-Volmer plot is due to the simultaneous presence of dynamic and static quenching processes

Effective Atomic Number and Kerma for Photon Energy Absorption of Organic Scintillators

An attempt has been made to calculate the effective atomic number and Kerma for photon energy absorption of organic scintillators in the energy region 1 keV to 20 MeV. We have chosen seven organic scintillators viz., anthracene, stilbene, naphthalene, p -terphenyl, PPO, butyl PBD and PBD. The Z PEA, eff and Kerma values are calculated by using mass-energy absorption coefficient from Hubbell and Seltzer. We also calculated Z PI, eff for total photon interaction with coherent scattering by using WinXCom and compared with the Z PEA, eff

Studies on spectral variation of 2AAQ with solvent properties

Abstract: In order to understand the nature and extent of solute-solvent interactions, the spectral variations of 2-amino-9, 10-anthraquinone (2AAQ) molecule are analyzed by using the linear solvation energy relationship (LSER) concept formulated by Katritzky et al15. The independent contributions of general and specific solute-solvent interactions have been calculated using multiple linear regression analysis method. The strength of the dipolarity and polarizability interaction is more than the specific solute-solvent interactions. Further, the solvation studies in cyclohexane (CHX) - ethyl acetate (EA) and ethyl acetate (EA) - acetonitrile (AN) solvent mixtures indicate that this dye is preferentially solvated by CHX in CHX-EA solvent mixture and EA in EA-AN except in the case of EA20AN80 where solute molecule is preferentially solvated by AN rather than EA. The ground- and excited-state dipole moments of 2AAQ have been estimated by solvatochromic shift method. The change in dipole moment is calculated using the correlation of microscopic solvent polarity parameter with the Stoke’s shift. The ground state dipole moments are predicted theoretically in gas phase by Gaussian 03 software using B3LYP/6-31G* level of theory and by semi-empirical method (PM6 )

Studies on spectral variation of 2AAQ with solvent properties

18-26In order to understand the nature and extent of solute-solvent interactions, the spectral variations of 2-amino-9, 10-anthraquinone (2AAQ) molecule are analyzed by using the linear solvation energy relationship (LSER) concept formulated by Katritzky et al15. The independent contributions of general and specific solute-solvent interactions have been calculated using multiple linear regression analysis method. The strength of the dipolarity and polarizability interaction is more than the specific solute-solvent interactions. Further, the solvation studies in cyclohexane (CHX) - ethyl acetate (EA) and ethyl acetate (EA) - acetonitrile (AN) solvent mixtures indicate that this dye is preferentially solvated by CHX in CHX-EA solvent mixture and EA in EA-AN except in the case of EA20AN80 where solute molecule is preferentially solvated by AN rather than EA. The ground- and excited-state dipole moments of 2AAQ have been estimated by solvatochromic shift method. The change in dipole moment is calculated using the correlation of microscopic solvent polarity parameter with the Stoke’s shift. The ground state dipole moments are predicted theoretically in gas phase by Gaussian 03 software using B3LYP/6-31G* level of theory and by semi-empirical method (PM6 )

Energy dependence of effective atomic numbers for photon energy absorption of vitamins

Abstract: Mass -Energy absorption coefficient, Effective atomic numbers for photon energy absorption ) and photon interactions (Z PI,ef

On the Mechanism of Excitation Energy Transfer Involving Long and Short Range Interaction in Dilute Organic Liquid Scintillator Systems

The rate parameter K$\text{}_{3}$ of solvent-solute energy transfer and the rate parameter K$\text{}_{7b}$ for solvent-quencher energy transfer are determined experimentally under ultraviolet excitation for a system Ethyl 1 butyl-2-methyl-5 ethoxycarboxy methoxy indole-3-carboxylate (EBMEC) in a deoxygenated system comprising 1:9 mixture of toluene-cyclohexane as a function of temperature in the range of 20-70°C, using bromobenzene as a solvent quencher. The data is analysed in terms of compact equation formed by combining Voltz et al. and Birks and Conte models. The interaction distance for the energy transfer from the excited solvent to solute molecules and solvent to quencher molecules are determined using this equation. The magnitude of the interaction distance indicates that the excitation energy transfer takes place due to long-range interaction in the case of solvent-solute energy transfer and short-range interaction in the case of solvent quencher energy transfer in dilute systems