lines are partially blended. Thus, it appears that Chiu's equations give very reasonable predictions for the intensities of this mixed magnetic-dipole-e1ectric-quadrupole transition.Wilkinson and Mulliken,2 using relatively poor uncalibrated photographic data on the a lIIgf-X ll;g+ system and employing line-strength formulas developed only for a ll;g+f-ll;g+ transition 9 (admittedly very tentatively), estimated Q/D=0.15, which is of the order of magnitude of the value obtained here. This presumably more precise value of 0.33 leads to a value of X in Eq. (1) of 9 a.u. instead of 4.5 a.u. given previously.The above determined ratio is certainly not in disagreement with the crude theoretical prediction of Q/ D"-'0.1 mentioned earlier. Nevertheless, Condon 7 has studied such transitions for p2, p3, and p4 configura-9 H. M. James and A. S. Coolidge, Astrophys. J. 85, 438 (1938).THE JOURNAL OF CHEMICAL PHYSICS 2683 tions in atoms, and has found quite variable values for this ratio. It does appear that a careful theoretical study of the vibronic matrix elements for this particular transition would be most helpful.It is perhaps worth mentioning that the line-intensity study reported here is one of the few experimental tests on intensities in forbidden transitions in diatomic molecules and only the fourth in the vacuum ultraviolet. lO ACKNOWLEDGMENTSThe authors wish to express their appreciation to Mr.The structures of ethylene and deuteroethylene were investigated by electron diffraction to resolve apparent discrepancies between earlier diffraction and spectroscopic studies. Satisfactory agreement with the previous diffraction study was found for five of the six molecular parameters determined but a difference of five standard deviations was encountered for the C-H bond length. Mean bond lengths and standard errors for C2H, obtained in the present investigation were rg (CH)=1.1030±0'()()l s A and r g (CC)=1.3369± 0.0016 A. Corresponding lengths for C2D, were r g (CD)=1.099±0.003 A and r g (CC)=1.338±0.003 A.Bond angles, corrected for shrinkage effects, were L CCH= 121.4±0.6° and L CCD= 121.4±0.8°. The new diffraction results are compared with mean bond lengths and angles calculated from spectroscopic rotational constants taking rotation-vibration interactions into account. Excellent agreement is found. Significant differences exist, however, between the conventional bond-length parameters derived by spectroscopy and diffraction. Root-mean-square amplitudes of vibration were also determined by diffraction, and these agreed satisfactorily with amplitudes calculated from vibrational frequencies.

Rare earth elements (REE) are of strategic importance because they find numerous applications in various sectors of the global economy.The concern about the REE supply challenge has led to increasing interest and research in the recovery of REE from end-of-life products and secondary sources such as coal and coal by-products. The work reported here was focused on examining the technical feasibility of physical separation techniques for the enrichment of REE from coal and coal by-products. Particle size, magnetic and density separations were performed on coal, coal ash, clay and shale samples. It was found that the samples responded to particle size separation differently. For all ash samples, higher REE concentrations were found in the finer fractions. For the clay and shalesamples, however, the REE concentrations decrease as the particle size reduces possibly because RE minerals were not effectively released by grinding. Magnetic separation showed that REE are enriched in non-magnetic fractions for all ash samples. All samples responded similarly to density separation. Among the three methods, density separation showed the highest enrichment of REE. A combination of these methods is recommended. Finally, correlations between elements were demonstrated, which leads to the classification of three groups containing mainly Al/Si, Fe and Ca, respectively. REE are strongly associated with the Al/Si group.

No abstract

A solid sorbent for carbon dioxide capture was developed on the basis of montmorillonite nanoclay, which is a low-cost and easily available bulk material. This high specific surface area, platelet-like nanoclay with hydroxyl groups on edges was treated with aminopropyltrimethoxysilane and polyethylenimine to provide sites for CO2 capture. CO2 sorption tests showed fast kinetics and capture capacities as high as 7.5 wt % at atmospheric pressure and about 17 wt % at 2.07 MPa pressure in the temperature range of 75–85 °C. The regeneration of these nanoclays can be achieved using nitrogen at 100 °C or CO2 (dry or humid) at 155 °C as the sweep gases. Furthermore, pressure swing operation, employing vacuum at 85 °C, is also effective in regenerating the sorbent. This work shows that amine-modified montmorillonite nanoclay has the potential to provide a high-performing solid sorbent for CO2 capture.

International audienceA series of cross-linked polyether-based 1,2,3-triazolium ion conducting membranes are prepared via the combination of thermally promoted Huisgen 1,3-dipolar cycloaddition of a dialkyne and a diazide poly(trimethylene ether glycol) monomers with in-situ N-alkylation of the resulting poly(1,2,3-triazole)s with varying contents of 1,10-diiododecane as cross-linking agent. The resulting free-standing membranes have T(g)s below -60 degrees C, T(d)s up to 230 degrees C, and Young's modulus up to 4.2 MPa. The overall combined reaction kinetics were studied by DSC yielding an activation energy of 76 kJ/mol by the Kissinger method. These ion conducting membranes have conductivities up to 10(-6) S/cm at 30 degrees C under anhydrous conditions. They have potential to be used in CO2 separation applications as they exhibit CO2 permeability of 59-110 Barrer and CO2/N-2 selectivity of 25-48