scholarly journals Combined Gas Electron Diffraction and Mass Spectrometric Experimental Setup at Bielefeld University

2020 ◽  
Author(s):  
Yury Vishnevskiy ◽  
Sebastian Blomeyer ◽  
Christian G. Reuter ◽  
Oleg A. Pimenov ◽  
Sergey A. Shlykov
Keyword(s):  
Acetic Acid ◽  
Electron Diffraction ◽  
Mass Spectra ◽  
Data Interpretation ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Experimental Setup ◽  
Experimental Conditions ◽  
Diffraction Patterns

We have designed and constructed a combined experimental setup for synchronous measurements of electron diffraction patterns and mass-spectra of gas samples. Test measurements have been performed for acetic acid at two temperatures, 296 and 457 K, respectively. Electron diffraction data have been analysed taking into account mass spectra measured in the same experiments. From the diffraction intensities molecular structures and mole fractions of the acetic acid monomer and dimer have been refined. The obtained results demonstrate the importance of measuring mass spectra in gas electron diffraction experiments. In particular, it is possible to detect the sample decomposition, which can be used for the optimization of experimental conditions and for the data interpretation. The determined in this work length of the hydrogen bond in the acetic acid dimer, re(O<sup>...</sup>H) = 1.657(9) Å, is in good agreement with modern theoretical predictions. We recommend to measure diffraction patterns of acetic acid for the calibration of the sample pressure in the diffraction point.<br>

scholarly journals Combined Gas Electron Diffraction and Mass Spectrometric Experimental Setup at Bielefeld University

2020 ◽  
Author(s):  
Yury Vishnevskiy ◽  
Sebastian Blomeyer ◽  
Christian G. Reuter ◽  
Oleg A. Pimenov ◽  
Sergey A. Shlykov
Keyword(s):  
Acetic Acid ◽  
Electron Diffraction ◽  
Mass Spectra ◽  
Data Interpretation ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Experimental Setup ◽  
Experimental Conditions ◽  
Diffraction Patterns

We have designed and constructed a combined experimental setup for synchronous measurements of electron diffraction patterns and mass-spectra of gas samples. Test measurements have been performed for acetic acid at two temperatures, 296 and 457 K, respectively. Electron diffraction data have been analysed taking into account mass spectra measured in the same experiments. From the diffraction intensities molecular structures and mole fractions of the acetic acid monomer and dimer have been refined. The obtained results demonstrate the importance of measuring mass spectra in gas electron diffraction experiments. In particular, it is possible to detect the sample decomposition, which can be used for the optimization of experimental conditions and for the data interpretation. The determined in this work length of the hydrogen bond in the acetic acid dimer, re(O<sup>...</sup>H) = 1.657(9) Å, is in good agreement with modern theoretical predictions. We recommend to measure diffraction patterns of acetic acid for the calibration of the sample pressure in the diffraction point.<br>

scholarly journals Low Pressure Gas Electron Diffraction: an Experimental Setup and Case Studies

2020 ◽  
Author(s):  
Yury Vishnevskiy ◽  
Sebastian Blomeyer ◽  
Christian G. Reuter
Keyword(s):  
Electron Diffraction ◽  
Benzoic Acid ◽  
Low Pressure ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Experimental Setup ◽  
Critical Comparison ◽  
Diffraction Patterns ◽  
Predicted Values ◽  
Semi Empirical

<div>Principles of low pressure gas electron diffraction(LPGED) are introduced. An experimental setup has</div><div>been constructed for measuring electron diffraction patterns of gaseous samples at pressures below 10−3</div><div>mbar. Test measurements have been performed for benzoic acid at T = 287 K corresponding to a vapor </div><div>pressure of the substance P = 2 × 10−4 mbar, for iodoform CHI3 at T = 288 K (P = 4 × 10−4 mbar) and for carbon tetraiodide CI4 at T = 290K (P = 1 × 10−4 mbar). Due to the low experimental temperature thermal decomposition of CI4 has been prevented, which was unavoidable in previous classical measurements at higher temperatures.</div><div>From the obtained data the molecular structures have been successfully refined. The most important</div><div>semi-empirical equilibrium molecular parameters are re(Car–Car)av = 1.387(5) Å in benzoic acid, re(C–I)</div><div>= 2.123(3) Å in iodoform and re(C–I) = 2.133(7) Å in carbon tetraiodide. The determined parameters</div><div>showed consistency with theoretically predicted values. A critical comparison with results of the earlier</div><div>investigations has also been done.</div>

scholarly journals Low Pressure Gas Electron Diffraction: an Experimental Setup and Case Studies

2020 ◽  
Author(s):  
Yury Vishnevskiy ◽  
Sebastian Blomeyer ◽  
Christian G. Reuter
Keyword(s):  
Electron Diffraction ◽  
Benzoic Acid ◽  
Low Pressure ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Experimental Setup ◽  
Critical Comparison ◽  
Diffraction Patterns ◽  
Predicted Values ◽  
Semi Empirical

<div>Principles of low pressure gas electron diffraction(LPGED) are introduced. An experimental setup has</div><div>been constructed for measuring electron diffraction patterns of gaseous samples at pressures below 10−3</div><div>mbar. Test measurements have been performed for benzoic acid at T = 287 K corresponding to a vapor </div><div>pressure of the substance P = 2 × 10−4 mbar, for iodoform CHI3 at T = 288 K (P = 4 × 10−4 mbar) and for carbon tetraiodide CI4 at T = 290K (P = 1 × 10−4 mbar). Due to the low experimental temperature thermal decomposition of CI4 has been prevented, which was unavoidable in previous classical measurements at higher temperatures.</div><div>From the obtained data the molecular structures have been successfully refined. The most important</div><div>semi-empirical equilibrium molecular parameters are re(Car–Car)av = 1.387(5) Å in benzoic acid, re(C–I)</div><div>= 2.123(3) Å in iodoform and re(C–I) = 2.133(7) Å in carbon tetraiodide. The determined parameters</div><div>showed consistency with theoretically predicted values. A critical comparison with results of the earlier</div><div>investigations has also been done.</div>

scholarly journals Molecular Structure of Pyrazinamide: a Critical Assessment of Modern Gas Electron Diffraction Data from Three Laboratories

2020 ◽  
Author(s):  
Arseniy A. Otlyotov ◽  
Georgiy V. Girichev ◽  
Anatolii N. Rykov ◽  
Timo Glodde ◽  
Yury Vishnevskiy
Keyword(s):  
Molecular Structure ◽  
Electron Diffraction ◽  
Structure Refinement ◽  
Diffraction Method ◽  
Detailed Examination ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Data Sets ◽  
Background Elimination ◽  
Diffraction Patterns

<div><div>Accuracy and precision of molecular parameters determined by modern gas electron diffraction method</div><div>have been investigated. Diffraction patterns of gaseous pyrazinamide have been measured independently in three laboratories, in Bielefeld (Germany), Ivanovo (Russia) and Moscow (Russia). All data sets have been analysed in equal manner using highly controlled background elimination procedure and flexible restraints in molecular structure refinement. In detailed examination and comparison of the obtained results we have determined the average experimental precision of 0.004 Å for bond lengths and 0.2 degrees for angles. The corresponding average deviations of the refined parameters from the ae-CCSD(T)/ccpwCVTZ theoretical values were 0.003 Å and 0.2 degrees. The average precision for refined amplitudes of interatomic vibrations was determined to be 0.005 Å. It is recommended to take into account these values in calculations of total errors for refined parameters of other molecules with comparable complexity.</div></div><div><br></div>

scholarly journals Molecular Structure of Pyrazinamide: a Critical Assessment of Modern Gas Electron Diffraction Data from Three Laboratories

2020 ◽  
Author(s):  
Arseniy A. Otlyotov ◽  
Georgiy V. Girichev ◽  
Anatolii N. Rykov ◽  
Timo Glodde ◽  
Yury Vishnevskiy
Keyword(s):  
Molecular Structure ◽  
Electron Diffraction ◽  
Structure Refinement ◽  
Diffraction Method ◽  
Detailed Examination ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Data Sets ◽  
Background Elimination ◽  
Diffraction Patterns

<div><div>Accuracy and precision of molecular parameters determined by modern gas electron diffraction method</div><div>have been investigated. Diffraction patterns of gaseous pyrazinamide have been measured independently in three laboratories, in Bielefeld (Germany), Ivanovo (Russia) and Moscow (Russia). All data sets have been analysed in equal manner using highly controlled background elimination procedure and flexible restraints in molecular structure refinement. In detailed examination and comparison of the obtained results we have determined the average experimental precision of 0.004 Å for bond lengths and 0.2 degrees for angles. The corresponding average deviations of the refined parameters from the ae-CCSD(T)/ccpwCVTZ theoretical values were 0.003 Å and 0.2 degrees. The average precision for refined amplitudes of interatomic vibrations was determined to be 0.005 Å. It is recommended to take into account these values in calculations of total errors for refined parameters of other molecules with comparable complexity.</div></div><div><br></div>

The Molecular Structures of Hexamethyldistannane, (CH3)6Sn2, and Dimethylditellurane, (CH3)2Te2, by Gas Electron Diffraction

1990 ◽  
Vol 45 (8) ◽  
pp. 1143-1146 ◽  
Author(s):  
Arne Haaland ◽  
Andreas Hammel ◽  
Hanne Thomassen ◽  
Hans V. Volden ◽  
Harkesh B. Singh ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Molecular Models

Gas electron diffraction data of (CH3)6Sn2 and (CH3)2Te2 are consistent with molecular models of D3 and C2 symmetry and bond distances Sn–Sn = 277.6(3) pm and Te–Te = 268.6(3) pm, respectively.

The Molecular Structures and Conformational Preferences of Simple Molecules Containing Bonds Between a Trivalent Group 15 and a Divalent Group 16 Element: The Molecular Structures of Dimethyl(methylthio)stibane and Dimethyl(methylseleno)stibane, (CH3)2SbECH3 E = S or Se, by Gas Electron Diffraction

1993 ◽  
Vol 48 (8) ◽  
pp. 1065-1068 ◽  
Author(s):  
Arne Haaland ◽  
Hans Peter Verne ◽  
Hans Vidar Volden ◽  
Hans Joachim Breunig ◽  
Sabahittin Gülec
Keyword(s):  
Electron Diffraction ◽  
Dihedral Angle ◽  
Diffraction Data ◽  
Lone Pair ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Conformational Preferences ◽  
Group 15 ◽  
Simple Molecules

Gas electron diffraction data of (CH3)2SbECH3 E = S or Se, show that the predominant conformer is one where the dihedral angle defined by the E–C bond, the Sb–E bond and the presumed direction of the lone pair at the Sb atom falls in the range –45 to +45°. The Sb–S and Sb–Se bond distances are 241.4(8) and 255.5(3) pm, respectively.

The Molecular Structures and Conformational Preferences of Bis(dimethylstibyl)- Oxane, -Sulfane and -Selane, E(SbMe2)2, E = O, S or Se, Me = CH3, by Density Functional Theory Calculations and Gas Electron Diffraction

1997 ◽  
Vol 52 (2) ◽  
pp. 296-300 ◽  
Author(s):  
Arne Haaland ◽  
Vasili Ivanovitch Sokolov ◽  
Hans Vidar Volden ◽  
Hans Joachim Breunig ◽  
Michael Denker ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electron Diffraction ◽  
Density Functional ◽  
Lone Pair ◽  
Density Functional Theory Calculations ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Functional Theory ◽  
Anti Conformer

Abstract Density Functional Theory calculations on E(SbMe2)2, E = O, S or Se, Me = CH3, indicate that the equilibrium structures are syn-syn or near syn-syn conformers with over-all C2 symmetry. The barriers restricting rotation about E-Sb bonds are very low, the equilibrium values for the dihedral angles ϕ(Sb-E-Sb-lp) where lp denotes the direction of the electron lone pair on one of the Sb atoms are probably less than 45°. The calculations further indicate the existence of syn-anti conformers some 4 kJ mol-1 above the more stable syn-syn. Gas electron diffraction data show that both conformers are present in gaseous O(SbMe2)2, while the presence of the syn-anti conformer in gaseous Se(SbMe2)2 is uncertain; least-squares refinements yielded the mole fraction χ = 0.27(18). The Sb-O and Sb-Se bond distances are 197.6(14) and 255.1(5) pm respectively, the valence angles of the syn-syn conformers are <SbOSb = 122.3(16)° and <SbSeSb = 96.3(11)°. It is suggested that the wide <SbOSb angle is due to across-angle repulsion between the Sb atoms.

Dynamical Scattering in Electron Diffraction of wet Protein Crystals

1980 ◽  
Vol 38 ◽  
pp. 42-43
Author(s):  
B. B. Chang ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Scattering Theory ◽  
Protein Crystals ◽  
Electron Diffraction Data ◽  
Specimen Thickness ◽  
Major Question ◽  
X Ray ◽  
Scattering Effects ◽  
Diffraction Patterns ◽  
Acceleration Voltage

The significance of dynamical scattering effects remains the major question in the structural analysis by electron diffraction of protein crystals preserved in the hydrated state. In the few cases (single layers of purple membrane and 400-600 Å thick catalase crystals examined at 100 kV acceleration voltage) where electron-diffraction patterns were used quantitatively, dynamical scattering effects were considered unimportant on the basis of a comparison with x-ray intensities. The kinematical treatment is usually justified by the thinness of the crystal. A theoretical investigation by Ho et al. using Cowley-Moodie multislice formulation of dynamical scattering theory and cytochrome b5as the test object2 suggests that kinematical analysis of electron diffraction data with 100-keV electrons would not likely be valid for specimen thickness of 300 Å or more. We have chosen to work with electron diffraction patterns obtained from actual wet protein crystals (rat hemoglobin crystals of thickness range 1000 to 2500 Å) at 200 and 1000 kV and to analyze these for dynamical effects.

Sign in / Sign up

Export Citation Format

Share Document