NOPR Collection:

INDO- EHP method for semiempirical calculation of molecular excited states: A case study with the low-lying states of ketene

Sat, 01 Dec 1990 00:00:00 GMT

Title: INDO- EHP method for semiempirical calculation of molecular excited states: A case study with the low-lying states of ketene Authors: Chandra, A K; Banerjee, M Abstract: Electron-hole potential (EHP) theory for singly excited states is developed within the Intermediate Neglect of Differential Overlap (INDO) approximation. The resulting model has been applied to investigate the molecular structure and transition energies for the excited states of ketene for which enough supporting data are available. A Walsh type analysis based on orbital energies and a population-based analysis of the different excitations have been performed with the help of EHP-improved orbitals. Page(s): 1143-1148

Electron energy loss spectra of alkali metal halides in the vapour phase

Sat, 01 Dec 1990 00:00:00 GMT

Title: Electron energy loss spectra of alkali metal halides in the vapour phase Authors: Pradeep, T Abstract: Electronic transitions of alkali metal halides in the vapour phase have been studied for the first time by low energy electron energy loss spectroscopy. All the observed transitions correspond to dissociation processes. The study has established similarities in the alkali metal halide spectra. Page(s): 1149-1152

Absorption and fluorescence characteristics of some 2-alkyl- and 2-aryl-benzoxazoles in different solvents and at various acid concentrations

Sat, 01 Dec 1990 00:00:00 GMT

Title: Absorption and fluorescence characteristics of some 2-alkyl- and 2-aryl-benzoxazoles in different solvents and at various acid concentrations Authors: Dey, Joy Krishna; Dogra, Sneh K Abstract: Absorption and fluorescence spectral characteristics of some 2-alkyl- and 2-aryl-benzoxazoles have been studied in different solvents and at various acid concentrations. Dual fluorescence observed in the monocations of 2-alkylbenzoxazoles is due to π*→π and charge transfer (CT) transitions, indicating the near degeneracy of excited singlet states. 2-Arylbenzoxazoles and the corresponding monocations exhibit only a single fluorescence band due to π*→π transition. pK_a values for the monocation-neutral equilibria in both S₀ and S₁ states of the molecules have been determined. Pariser-Parr-Pople method for all the molecules and CNDO/S method for 2-methyl-, and 2-phenylbenzoxazoles have been employed to calculate transition energies, transition polarization and charge densities at different atoms in the S₀ and S₁ states to substantiate experimental data and, hence, to verify the applicability of the methods for heterocycles containing two hetero atoms. Page(s): 1153-1164

Fluorescence spectral studies of the substituted azobenzenes in different solvents

Sat, 01 Dec 1990 00:00:00 GMT

Title: Fluorescence spectral studies of the substituted azobenzenes in different solvents Authors: Brahma, S K; Bandyopadhyay, C; Chakraburtty, A K Abstract: Absorption and emission spectra of 2-carboxy-2'-hydroxy-5'-methylazobenzene (MAB) and 2-carboxy-2'-hydroxy-5'-methoxyazobenzene (MeAB) have been studied in different solvents like dimethylsulphoxide, acetonitrile, dimethylformamide and 2-butanol. The dissociation constants of the two substituted azodyes in their ground and excited states have been also determined. Page(s): 1165-1168