Improved Parameterization for Combined Isotopomer Analysis of Diatomic Spectra and Its Application to HF and DF

A new way of representing vibration-rotation term values for multiple isotopomers of a given electronic state of a diatomic molecule is presented which resolves problems associated with the way the conventional combined isotopomer expansion represents the atomic mass-dependent JWKB and Born-Oppenheimer breakdown correction terms. Its application to infrared and microwave data for HF and DF yields new Dunham expansion coefficients and Born-Oppenheimer breakdown correction terms for this species. This procedure is implemented in a generally available computer program for fitting to various types of data involving one or several electronic states of multiple isotopomers of a diatomic molecule. Copyright 1999 Academic Press.     

A spectral study of tautomerism in 4-arylamino-1,2-naphthoquinones

The tautomerism of 4-arylamino-1,2-naphthoquinones in aqueous solutions has been investigated by UV-visible absorption spectroscopy. It has been demonstrated that in strongly acidic solutions (Ph 0·8), protonation of the 2-keto group leads to 2-hydroxy-1,4-naphthoquinone-4-arylimine as the more stable tautomer. However, weakly acidic or alkaline solutions (Ph 4–13) contain 4-arylamino-1,2-naphthoquinone as the more stable tautomer.     

Cu(II)-catalyzed direct and site-selective arylation of indoles under mild conditions

We have developed a new site-selective Cu(II)-catalyzed C-H bond functionalization process that can selectively arylate indoles at either the C3 or C2 position under mild conditions. The scope of the arylation process is broad and tolerates broad functionality on both the indole and aryl unit, which makes it amenable to further elaboration. The mechanism of the arylation reaction is proposed to proceed via a Cu(III)-aryl species that undergoes initial electrophilic addition at the C3 position of the indole motif. We speculate that site of indole arylation arises through a migration of the Cu(III)-aryl group from C3 to C2, and this can be controlled by the nature of the group on the nitrogen atom; free (NH)- and N-alkylindoles deliver the C3-arylated product, whereas N-acetylindoles afford the C2 isomer, both with excellent yield and selectivity.     

Tungsten L transition line shapes and energy shifts resulting from ionization in warm dense matter

Spectra of the W L transitions in the energy range 8–12 keV from warm dense plasmas generated by the Naval Research Laboratory's Gamble II pulsed power machine were recorded by a newly developed high-resolution transmission-crystal X-ray spectrometer with ±2 eV accuracy. The discharges have up to 2 MV voltage, 0.5 MA current, and produce up to 2.4 MJ/cm^?3 energy density. The plasma-filled rod pinch (PFRP) diode produces a plasma with N_e ≈ 10²² cm^?3 and T_e ≈ 50 eV during the time of maximum X-ray emission. By analyzing the line shapes, it was determined that the Lβ₂ inner-shell transition from the 4d_5/2 level was shifted to higher energy by up to 23 eV relative to nearby Lβ transitions from n = 3 levels. In addition, the Lβ₂ transition was significantly broader and asymmetric compared to the n = 3 transitions. The energy shift of the Lβ₂ transition results from the ionization of electrons outside the 4d shell that perturbs the transition energies in the ions to higher values. The increased line width and asymmetry result from unresolved transitions from a range of ionization states up to +28. The ionization distribution was determined by comparison of the measured energy shifts and widths to calculated transition energies in W ions, and the ionization was correlated with Gamble discharge parameters such as the anode type and the high voltage delay time. This work demonstrates a new hard X-ray spectroscopic diagnostic technique for the direct measurement of the ionization distribution in warm dense plasmas of the heavy elements W through U that is independent of the other plasma parameters and does not require interpretation by hydrodynamic, atomic kinetics, and radiative simulation codes.     

A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2H6/C2H4 Separation

Developing adsorptive separation processes based on C₂H₆-selective sorbents to replace energy-intensive cryogenic distillation is a promising alternative for C₂H₄ purification from C₂H₄/C₂H₆ mixtures, which however remains challenging. During our studies on two isostructural metal–organic frameworks ( Ni-MOF 1 and Ni-MOF 2 ), we found that Ni-MOF 2 exhibited significantly higher performance for C₂H₆/C₂H₄ separation than Ni-MOF-1 , as clearly established by gas sorption isotherms and breakthrough experiments. Density-Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni-MOF 2 induce more and stronger C−H⋅⋅⋅π with C₂H₆ over C₂H₄ while the suitable pore spaces enforce its high C₂H₆ uptake capacity, featuring Ni-MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg⁻¹ of polymer-grade C₂H₄ product from equimolar C₂H₆/C₂H₄ mixtures at ambient conditions.     

Recent developments in biokinetic models and the calculation of internal dose coefficients

In most cases the measurement of radioactivity in an environmental or biological sample will be followed by some estimation of dose and possibly risk, either to a population or an individual. This will normally involve the use of a dose coefficient (dose per unit intake value) taken from a compendium. In recent years the calculation of dose coefficients has seen many developments in both biokinetic modelling and computational capabilities. ICRP has recommended new models for the respiratory tract and for the systemic behavior of many of the more important elements. As well as this, a general age-dependent calculation method has been developed which involves an effectively continuous variation of both biokinetic and dosimetric parameters, facilitating more realistic estimation of doses to young people. These new developments were used in work for recent ICRP, IAEA and CEC compendia of dose coefficients for both members of the public (including children) and workers. This paper presents a general overview of the method of calculation of internal doses with particular reference to the actinides. Some of the implications for dose coefficients of the new models are discussed. For example it is shown that compared with data in ICRP Publications 30 and 54: the new respiratory tract model generally predicts lower deposition in systemic tissues per unit intake; the new biokinetic models for actinides allow for burial of material deposited on bone surfaces; age-dependent models generally feature faster turnover of material in young people. All of these factors can lead to substantially different estimates of dose and examples of the new dose coefficients are given to illustrate these differences. During the development of the new models for actinides, human bioassay data were used to validate the model. Thus, one would expect the new models to give reasonable predictions of bioassay quantities. Some examples of the bioassay applications, e.g., excretion data for the plutonium model, are discussed briefly.