New potential energy function for alkali halide molecules

A new repulsive term in the ionic interaction potential for computing the lattice energy, the rotational constant (α₀) and the vibrational constant (w₀x₀) of alkali halide molecules has been proposed as $\text{ψ(r) = Af}{}^{\mathrm{n}}\text{r}{}^{\mathrm{-n}}\text{e}{}^{\mathrm{<mtext>?r</mtext><mtext>\lambda </mtext>}}$, which apart from being generalised, dimensionally homogenous and physically sound yields better values for lattice energy, α₀ and w₀x₀ than the previously reported potentials models.     

Lattice dynamics of niobium carbide (NbC)

A consistent and comprehensive approach has been adopted to derive the framework of a deformation dipole model (DDM) which is capable of explaining successfully the lattice dynamics of ionic crystals. The application of this model to the case of the niobium carbide crystal has reproduced fairly well the phonon dispersion curves.     

Diode laser spectrum and analysis of the ν15 band of s-tetrazine

The analysis of the diode laser spectrum of the 1103-cm^?1 band of s-tetrazine has shown it to be A type, confirming its assignment to the ν₁₅(b_2u) mode. The results of the analysis of this band have been merged with the results of the earlier analysis of the ν₁₄ band and a set of parameters consistent with all available data has been obtained for the ground, ν₁₄, and ν₁₅ states of s-tetrazine.     

Sustainability of bioplastics: Opportunities and challenges

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Measurement of mercury isotopic ratio in stone meteorites by neutron activation analysis

¹⁹⁶Hg and²⁰²Hg isotopes have been measured by neutron activation analysis in samples of twelve stone meteorites. Hg is extracted from an irradiated sample by stepwise heating. The mercury concentrations vary from 0.07 to 33 ppm. While most of the samples give¹⁹⁶Hg/²⁰²Hg ratios similar to terrestrial value within error limits, in some cases large anomalies are observed. A number of control experiments have been devised, that show the absence of experimental artifacts, during sample preparation, neutron irradiation, chemical separation and counting stages. Several anomalous and normal Hg distillate have been re-irradiated as Hg-diethyl-dithio-carbamate complex to eliminate the influence of neutron self shielding and interfering reactions from matrix elements. The isotopic ratio patterns persist in the distillates too proving that any artifacts during meteorite irradiation and measurement are essentially absent. Both positive and negative anomalies are observed; however, the negative anomalies are much more frequent and abundant. In an extreme case of fine grained magnetic particles of Ambapur Nagla the¹⁹⁶Hg is apparently absent in the Hg released at 100 °C. A 2¹⁹⁶Hg/²⁰²Hg value is only 6% relative to the monitor. This experiment shows the robustness of neutron activation analysis and suggest some constrains on the formation history of stone meteorites.     

The near uv vapour absorption spectra of 1-hydroxynaphthalene and 2-hydroxynaphthalene

Vibrational analyses, of the electronic bands of 1-hydroxynaphthalene and 2-hydroxynaphthalene corresponding to the 312 nm electronic transition in naphthalene, have been carried out from the vapour phase absorption spectra recorded under high resolution. It is found that the prominent vibronic bands owe their large intensities to a different vibronic interaction than that in naphthalene. On leave from Pt. Jawaharlal Nehru College, Banda 210 001, India.