An application of the semi-empirical CNDO/2 and INDO methods to calculate the molecular dipole moment of iodine compounds has been made with all-valence electron scheme. Equilibrium geometries are obtained using experimental bond lengths and the various semi-empirical parameters required inscf-mo scheme are obtained from atomic Hartree-Fock calculations and by comparison withab initio calculations. Bothsp andspd valence basis sets are used.

Tris(glycine) calcium(II) dibromide single crystal has been irradiated with aγ-source to produce free radicals and the irradiated sample has been subjected toepr studies. The observed spectra reveal that an NH₄ radical is formed by rupturing glycine molecule due to irradiation. The unpaired electron is localized on the C-N bond. The proton hyperfine interaction on the unpaired spin shows orthorhombic symmetry and the spectroscopic splitting factor remains isotropic.

A theoretical study on the conformation of allyl halides from the calculation of nuclear spin-spin coupling constants by adopting the finite perturbation theory (FPT), is carried out in terms of the self-consistent, semi-empirical INDO (intermediate neglect of differential overlap) approximation of molecular orbital theory. Results of the calculations performed using ‘s’ and ‘p’ valence orbitals alone (‘sp’ basis) at INDO level approximation seem to replicate the experimental trend quite satisfactorily. Despite the overall agreement of the theoretical values with the experimental ones, the uncertainties in the INDO parametrization scheme lead to overestimation of certain coupling constants. The calculations also show that the orientation of the coupled protons with respect to the substituent halogen atom is an important factor to be considered.

The excess parameter studies in the microwave frequency region (X-band) on complex dielectric permittivity for the binary mixtures are reported. The methods employed are fixed cavity perturbation technique and adjustable plunger cavity technique. Also Gopalakrishna method is used to calculate the relaxation time of the polar solute in a non-polar solvent. The samples under study are acetonitrile, chlorobenzene, dimethyl formamide, carbon tetrachloride and benzene.

The cavity perturbation technique is employed for the characterisation of semiconductors at microwave frequency for its conductivity. Temperature variation of microwave conductivity studies provide the information regarding the band gap, scattering parameter and impurity ionization energy. Change in the real part of the dielectric permittivity with conductivity indicates the change in the momentum relaxation time.