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Pressure-induced transformations in molecular crystals

Description: A review is given on the unique features of the Moessbauer spectroscopy (MS) which by virtue of the quadrupole interaction and the lattice dynamics allows one to characterize some structural properties in the pressure-induced amorphous state of molecular crystals. Experiments were performed in GeI{sub 4}, SnI{sub 4} and SnBr{sub 4} by means of {sup 119}Sn and {sup 129}I MS with pressures to 35 GPa at cryogenic temperatures using diamond anvil cells.
Date: September 1, 1995
Creator: Taylor, R. D.; Hearne, G. R. & Pasternak, M. P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

{sup 31}P NMR analysis of coal moieties bearing -OH, -NH and -SH functions. Quarterly report, January 1, 1990--March 31, 1990

Description: Research continues on the structural analysis of coal. In attempting to derivatize solid coal for solid state NMR analysis, we observed {sup 31}P NMR shifts in an unexpected region; these interesting leads will be pursued on the chance that the reaction we have evoked holds potential for yielding new coal characterizational information. Two very gratifying results have emerged from our {sup 119}Sn chemical shift measurements of a limited set of model compounds in pyridine. Firstly, the chemical… more
Date: December 31, 1990
Creator: Verkade, J. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

{sup 31}P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions. Final technical report

Description: NMR reagents for the speciation and quantitation of labile-hydrogen functional groups and sulfur groups in coal ligands have been synthesized and evaluated. These reagents, which contain the NMR-active nuclei {sup 31}p, {sup 119}Sn or {sup 195}pt, were designed to possess improved chemical shift resolution over reagents reported in the literature. Our efforts were successful in the case of the new {sup 31}p and {sup 119}Sn reagents we developed, but the {sup 195}pt work on sulfur groups was onl… more
Date: August 31, 1991
Creator: Verkade, J. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

{sup 31}P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions. Quarterly report, June 1, 1991--August 31, 1991

Description: The purpose of this research is to develop a convenient, reliable and rapid NMR method for the determination of labile-hydrogen functional groups and organic sulfur compounds which are components of coal and coal-derived materials. For this purpose, the former functional groups, including water molecules, are derivatized with reagents containing NMR-active nuclei such as {sup 31}P or {sup 119}Sn, while sulfur groups are derivatized with {sup 195}Pt NMR tagging reagents. Knowledge of the heteroa… more
Date: December 31, 1991
Creator: Verkade, J. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

{sup 31}P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions. Quarterly report, October 1, 1990--December 31, 1990

Description: Research on coal structural analysis continues. Significant progress has been made in developing a new NMR approach to the reaction in which the phosphorus-containing product incorporates two {sup 31}P nuclei for every water molecule reacted. The latter circumstance allows more precise values of low water contents to be realized owing to better integration of the {sup 31}P NMR peak. We have measured a series of model pyridine/H{sub 2}O mixtures by our technique and the results are summarized he… more
Date: December 31, 1990
Creator: Verkade, J. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Predicted Changes of the Internal Conversion Rates IN119SN Due to Admixtures of Lower Multipole Order

Description: One conceivable basis for interlevel transfer from a long-lived isomer to a graser state might be to alter the multipolarity of the transfer step. As an example, in the case of /sup 119/Sn any mechanism that introduces angular momentum to admix M3 radiation into the normally M4 transition from the 89.6 keV, 11/2/sup -/ level to the 23.9 keV, 3/2/sup +/ state could greatly shorten its normal 293 day half-life. We have calculated the K-shell internal conversion rate for the 89.6 keV level in /sup… more
Date: January 1, 1985
Creator: Wender, S. A.; Baldwin, G. C.; Talbert, W. L. & Reiss, H. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Functional group analysis in coal by sup 31 P NMR spectroscopy

Description: The purpose of this research is to determine the labile-hydrogen functional group composition of coal and coal-derived materials by the nmr spectroscopy of their derivatives made with reagents containing the nmr-active nuclei {sup 31}P, {sup 119}Sn, or {sup 205}Tl. 7 refs.
Date: May 1, 1989
Creator: Verkade, J.G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Nuclear magnetic resonance with dc SQUID (Super-conducting QUantum Interference Device) preamplifiers

Description: Sensitive radio-frequency (rf) amplifiers based on dc Superconducting QUantum Interface Devices (SQUIDS) are available for frequencies up to 200 MHz. At 4.2 K, the gain and noise temperature of a typical tuned amplifier are 18.6 +- 0.5 dB and 1.7 +- 0.5 K at 93 MHz. These amplifiers are being applied to a series of novel experiments on nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR). The high sensitivity of these amplifiers was demonstrated in the observation of ''nuclea… more
Date: August 1, 1988
Creator: Fan, N.Q.; Heaney, M.B.; Clark, J.; Newitt, D.; Wald, L.; Hahn, E.L. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Very high pressure Moessbauer spectroscopy using diamond anvil cells

Description: The technique of generating very high pressure by means of Diamond Anvil Cells (DAC) for Mossbauer Effect applications is outlined. A comprehensive description is presented of the principles of DAC, modification for the use in M/umlt o/ssbauer Spectroscopy (MS), the Merrill--Bassett and Bassett cells, of pressure measurements, of gasketing and collimation, and of hydrostatic media. Examples of /sup 151/Eu, /sup 119/Sn and /sup 129/I are given showing the feasibility of DAC applications in MS. O… more
Date: January 1, 1988
Creator: Pasternak, M. P. & Taylor, R. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The Moessbauer effect of SnI/sub 4/ at high pressures

Description: Tetravalent tin iodide is a molecular crystal composed of SnI/sub 4/ tetrahedra loosely packed into a cubic configuration. Under pressure SnI/sub 4/ becomes metallic at about 15 GPa. We report a Moessbauer effect study of /sup 119/Sn and /sup 129/I in SnI/sub 4/ to pressures of 26 GPa. The spectra exhibit dramatic changes with pressure starting at about 10 GPa and show large pressure hysteresis effects upon reducing the pressure from 26 GPa. In the intermediate region tin exists in both Sn/sup … more
Date: January 1, 1987
Creator: Taylor, R. D.; Pasternak, M. & Farrell, J. N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Moessbauer study of metal cations in the chevrel phases

Description: Moessbauer effect studies at /sup 119/Sn and /sup 57/Fe sites have been made in Sn/sub 1/ /sub 0/Fe/sub 0/ /sub 1/Mo/sub 6/S/sub 8/ and Sn/sub 1/ /sub 0/Fe/sub 0/ /sub 4/Mo/sub 6/S/sub 8/ to examine the Sn- and Fe- motion and electronic states in the high T/sub c/, high H/sub c//sub 2/ superconductor SnMo/sub 6/S/sub 8/ with Fe additions. Above 50K the /sup 57/Fe spectra are asymmetric doublets with isomer shift and quadrupolar splitting similar to that of the intermediate temperature results i… more
Date: January 1, 1979
Creator: Stafford, B.; Barnet, C. D.; Kimball, C. W. & Fradin, F. Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

sup 31 P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions

Description: NMR reagents for the speciation and quantitation of labile-hydrogen functional groups and sulfur groups in coal ligands have been synthesized and evaluated. These reagents, which contain the NMR-active nuclei {sup 31}p, {sup 119}Sn or {sup 195}pt, were designed to possess improved chemical shift resolution over reagents reported in the literature. Our efforts were successful in the case of the new {sup 31}p and {sup 119}Sn reagents we developed, but the {sup 195}pt work on sulfur groups was onl… more
Date: August 31, 1991
Creator: Verkade, J. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

sup 31 P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions

Description: The purpose of this research is to develop a convenient, reliable and rapid NMR method for the determination of labile-hydrogen functional groups and organic sulfur compounds which are components of coal and coal-derived materials. For this purpose, the former functional groups, including water molecules, are derivatized with reagents containing NMR-active nuclei such as {sup 31}P or {sup 119}Sn, while sulfur groups are derivatized with {sup 195}Pt NMR tagging reagents. Knowledge of the heteroa… more
Date: January 1, 1991
Creator: Verkade, J. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

sup 31 P NMR analysis of coal moieties bearing -OH, -NH and -SH functions

Description: Research continues on the structural analysis of coal. In attempting to derivatize solid coal for solid state NMR analysis, we observed {sup 31}P NMR shifts in an unexpected region; these interesting leads will be pursued on the chance that the reaction we have evoked holds potential for yielding new coal characterizational information. Two very gratifying results have emerged from our {sup 119}Sn chemical shift measurements of a limited set of model compounds in pyridine. Firstly, the chemical… more
Date: January 1, 1990
Creator: Verkade, J. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Functional group analysis in coal and on coal surfaces by NMR spectroscopy

Description: An accurate knowledge of the oxygen-bearing labile hydrogen functional groups (e.g., carboxylic acids, phenols and alcohols) in coal is required for today's increasingly sophisticated coal cleaning and beneficiation processes. Phospholanes (compounds having the general structure -POCH{sub 2}CH{sub 2}O (1)) are being investigated as reagents for the tagging of liable hydrogen functional groups in coal materials with the NMR-active {sup 31}P nucleus. Of twelve such reagents investigated so far, 2… more
Date: January 1, 1990
Creator: Verkade, J.G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

sup 31 P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions

Description: Research on coal structural analysis continues. Significant progress has been made in developing a new NMR approach to the reaction in which the phosphorus-containing product incorporates two {sup 31}P nuclei for every water molecule reacted. The latter circumstance allows more precise values of low water contents to be realized owing to better integration of the {sup 31}P NMR peak. We have measured a series of model pyridine/H{sub 2}O mixtures by our technique and the results are summarized he… more
Date: January 1, 1990
Creator: Verkade, J. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Locating giant resonances with photoneutrons

Description: Recent studies of collective magnetic dipole resonances in heavy nuclei are reviewed with an emphasis on photoneutron experiments. In particular, the nuclear mass regions of 120, 140, and 208 are discussed in detail. New very-high-resolution photoneutron studies of /sup 208/Pb are presented. Applications of the photoneutron polarization method to the /sup 208/Pb(..gamma..,n/sub 0/)/sup 207/Pb and /sup 119/Sn(..gamma..,n/sub 0/)/sup 118/Sn reactions are reviewed. 12 figures, 2 tables)
Date: January 1, 1978
Creator: Holt, R.J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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