Absolute scale determination for photoabsorption spectra and the calculation of molecular properties using dipole sum-rules

Absolute photoabsorption oscillator strengths (cross sections) for the valence and inner (P 2p, 2s) shells of phosphorus trifluoride (PF 3 ) have been measured using dipole ( e , e ) spectroscopy in the 5–300 eV equivalent photon energy region (1 eV FWHM). The discrete spectral structures in the valence region and in the vicinity of the phosphorus 2p inner shell have also been studied at higher resolution (0.05 and 0.1 eV FWHM, respectively). Using these data and the S(−2) sum rule, the electric-dipole polarizability for PF 3 has been determined for the first time. In addition, dipole ( e , e +ion) coincidence spectroscopy has been used to obtain the photoionization efficiencies, photoion branching ratios, and absolute partial oscillator strengths for the molecular and dissociative photoionization channels of PF 3 from the first ionization threshold up to and above the phosphorus L shell edges to 175 eV. A consideration of the photoabsorption and photoionization measurement together with thermochemical data and results from previously published photoelectron branching ratios and photoelectron-photoion coincidence (PEPICO) studies provides information on the dipole-induced breakdown pathways of PF 3 in the photon region below 100 eV.

Photoabsorption and photoionization of the valence and inner (P 2p, 2s) shells of PF3: Absolute oscillator strengths and dipole-induced breakdown pathways

Environmental context. The Clean Air Act amendments of 1990 identified mercury and associated compounds as hazardous air pollutants of particular concern to human health and the environment. Coal-fired power plants and municipal solid waste incinerators are significant sources of mercury-containing emissions. Adsorption represents a common technique used to alleviate mercury contamination. The present study uses molecular simulations to study the correlation between key surface characteristics of the adsorbent and its mercury capturing ability with a view to the selection and design of novel adsorbents. Abstract. In the present study, Monte Carlo simulations were used to model the physical adsorption of oxidised mercury (mercuric chloride) by zeolite NaX and activated carbon in the temperature range of 400–500 K. In particular, we considered zeolite NaX with spherical cavities and sodium cations, as well as activated carbon with slit carbon pores and hydroxyl, carboxyl and carbonyl sites, and layers of calcium hydroxide. The adsorption capacity and affinity of zeolite NaX were compared with those displayed by activated carbon with different acid sites and calcium hydroxide by assessing the impact on mercuric chloride adsorption within a practical range of magnitudes of the electrostatic interactions considered, namely charge-induced dipole and charge-quadrupole interactions, as well as dispersion interactions.

Molecular Simulation Studies on the Adsorption of Mercuric Chloride

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Molecular Simulation Studies on Adsorption of Mercuric Chloride

The bond and molecular polarizabilities are studied for the gas-phase metal halides using delta-function potential model of chemical binding on the basis of quantum mechanical approach. The applicability of the model is demonstrated. The contribution of the polarity corrections for the metal halides is thoroughly investigated and it has been found that it plays a significant role for fluorides. Our polarizability calculations resolve the discrepancy about the conformation of the barium dichloride and mercury dichloride and favour the nonlinear structure. Due to lack of experimental results for most of halides of transition metals, the decision whether to incorporate polarity corrections or not remains uncertain at this stage: we must await measurements of more experimental values before we reach any final conclusion. The ionic bond orders have been used for the first time to investigate polarizabilities of monomers and dimers of alkali halides. The results for dimers reveal that polarity contribution is essential for the lithium halides dimers and not for other dimers. The computed results will be asset for the interpretation of experimental measurements.

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A. N. Pandey

Papers

Quantum mechanical studies of bond and molecular polarizabilities of gas-phase metal halides