1. Gas-phase Electron Diffraction
István Hargittai
Budapest University of Technology and Economics
and Hungarian Academy of Sciences
Gas-phase
Electron Diffraction
INTERNATIONAL SCHOOL OF CRYSTALLOGRAPHY
36thCourse: ELECTRON CRYSTALLOGRAPHY: NOVEL APPROACHES FOR
STRUCTURE DETERMINATION OF NANOSIZED MATERIALS
ERICE, SICILY: JUNE 9-20, 2004

2. Two-Volume Treatise on Gas-Phase Electron Diffraction

3. CO2 Curves from Gas-Phase Electron Diffraction

4. Brief History I 1912-15 X-ray crystallography, Laue, the Braggs, Debye
1924 de Broglie (wave nature of moving electrons)
1927 Davisson & Germer, G.P. Thomson solid-phase electron diffraction
1930 Mark and Wierl, first GED experiment
1932 James, molecular vibrations
1935 Pauling & Brockway, f(r)

5. Brief History II
Finbak, Debye, Karle and Karle rotating sector-microphotometer method
1950s modern experimental apparatus
1955 Bartell the physical meaning of geometrical parameters
Last decades combined and concerted application of various techniques
Fine effects (relativistic, Jahn-Teller, etc.)
Increasingly, quantum chemical calculations

6. Gas-phase electron diffraction experiment

7. Combined gas-phase electron diffraction/mass-spectrometric experiment

8. Total Intensity Distribution and “Background”

9. Molecular Intensities

10. Molecular Intensities

11. Probability Density Distributions

12. Scheme of Least-Squares Refinement

13. C6H3F3 and C6H3Cl3: Probability Density Distributions

14. Jahn-Teller Effect Edward Teller (1908-2003)
“A nonlinear, symmetric molecule with an orbitally degenerate electronic state is unstable and gets distorted, thereby removing the electronic degeneracy, until a nondegenerate ground state is achieved.”
Jahn, H.A.; Teller, E. Proc. R. Soc. London A 1937, 161, 220.

15. Jahn-Teller Effect MnF3
Jahn-Teller Effect MnF3
D3h
C2v C2v
Hargittai, M. et al. J. Am. Chem. Soc. 1997, 119, 9042.

16. MnF3 electron diffraction
Hargittai, M. et al. J. Am. Chem. Soc. 1997, 119, 9042.

17. HS-CH2-CH2-SH Conformational Analysis

18. Estimating Mole Ratios

19. REPRESENTATIONS OF AVERAGE STRUCTURESrg rα re
Perpendicular vibrations
yes no
Temperature
Isotope

20. Comparison with Other Techniques
Microwave spectroscopy
X-ray crystallography
Quantum chemical calculations
NMR spectroscopy
Vibrational spectroscopy
Mass spectrometry
Qualitative models