Gas electron diffraction: Difference between revisions

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== Results ==

[[File:Examples P4 P3As.jpg|thumb|440x440px|Figure 5: Examples of molecular intensity curves (left) and their Fourier transforms, the radial distribution curves of P4 and P3As.]]

Figure 5 shows two typical examples of results. The molecular scattering intensity curves are used to refine a structural model by means of a [[Least-squares function approximation|least squares]] fitting [http://unexprog.org/ program]. This yieldyields precise structural information. The [[Fourier transformation]] of the molecular scattering intensity curves gives the radial distribution curves (RDC). These represent the probability to find a certain distance between two nuclei of a molecule. The curves below the RDC represent the diffrerencedifference between the experiment and the model, i.e. the quality of fit.

The very simple example in Figure 5 shows the results for evaporated white [[phosphorus]], P₄., Itwhich is a perfectly tetrahedral molecule and has thus only one P-P distance. This makes the molecular scattering intensity curve a very simple one; a sine curve which is damped due to molecular vibration. The radial distribution curve (RDC) shows a maximum at 2.1994 Å with a least-squares error of 0.0003 Å, represented as 2.1994(3) Å. The width of the peak represents the molecular vibration and is the result of [[Fourier transform]]ation of the damping part. This peak width means that the P-P distance varies by this vibration within a certain range given as a vibrational amplitude ''u'', in this example ''u''_T(P‒P) = 0.0560(5) Å.

The slightly more complicated molecule P₃As has two different distances P-P and P-As. Because their contributions overlap in the RDC, the peak is broader (also seen in a more rapid damping in the molecular scattering). The determination of these two independent parameters is more difficult and results in less precise parameter values than for P₄.

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* Determinations of the structures of gaseous elemental [[phosphorus]] P₄ and of the binary P₃As<ref>{{Cite journal|last1=Cossairt|first1=Brandi M.|last2=Cummins|first2=Christopher C.|last3=Head|first3=Ashley R.|last4=Lichtenberger|first4=Dennis L.|last5=Berger|first5=Raphael J. F.|last6=Hayes|first6=Stuart A.|last7=Mitzel|first7=Norbert W.|last8=Wu|first8=Gang|date=2010-06-23|title=On the Molecular and Electronic Structures of AsP3 and P4|journal=Journal of the American Chemical Society|volume=132|issue=24|pages=8459–8465|doi=10.1021/ja102580d|pmid=20515032|issn=0002-7863}}</ref>

* Determination of the structure of [[Buckminsterfullerene|C₆₀]]<ref>{{Cite journal|last1=Hedberg|first1=K.|last2=Hedberg|first2=L.|last3=Bethune|first3=D. S.|last4=Brown|first4=C. A.|last5=Dorn|first5=H. C.|last6=Johnson|first6=R. D.|last7=De Vries|first7=M.|date=1991-10-18|title=Bond Lengths in Free Molecules of Buckminsterfullerene, C60, from Gas-Phase Electron Diffraction|journal=Science|language=en|volume=254|issue=5030|pages=410–412|doi=10.1126/science.254.5030.410|pmid=17742230|bibcode=1991Sci...254..410H |s2cid=25860557|issn=0036-8075}}</ref> and C₇₀<ref>{{Cite journal|last1=Hedberg|first1=Kenneth|last2=Hedberg|first2=Lise|last3=Bühl|first3=Michael|last4=Bethune|first4=Donald S.|last5=Brown|first5=C. A.|last6=Johnson|first6=Robert D.|date=1997-06-01|title=Molecular Structure of Free Molecules of the Fullerene C70 from Gas-Phase Electron Diffraction|journal=Journal of the American Chemical Society|volume=119|issue=23|pages=5314–5320|doi=10.1021/ja970110e|issn=0002-7863}}</ref>

* Structure of [[tetranitromethane]]<ref>{{Cite journal|last1=Vishnevskiy|first1=Yury V.|last2=Tikhonov|first2=Denis S.|last3=Schwabedissen|first3=Jan|last4=Stammler|first4=Hans-Georg|last5=Moll|first5=Richard|last6=Krumm|first6=Burkhard|last7=Klapötke|first7=Thomas M.|last8=Mitzel|first8=Norbert W.|date=2017-08-01|title=Tetranitromethane: A Nightmare of Molecular Flexibility in the Gaseous and Solid States|journal=Angewandte Chemie International Edition|language=en|volume=56|issue=32|pages=9619–9623|doi=10.1002/anie.201704396|pmid=28557111|doi-access=free}}</ref>

* Absence of local C₃ symmetry in the simplest [[phosphonium ylide]] H₂C=PMe₃<ref>{{Cite journal|last1=Mitzel|first1=Norbert W.|last2=Brown|first2=Daniel H.|last3=Parsons|first3=Simon|last4=Brain|first4=Paul T.|last5=Pulham|first5=Colin R.|last6=Rankin|first6=David W. H.|date=1998|title=Differences Between Gas-Phase and Solid-State Molecular Structures of the Simplest Phosphonium Ylide, Me3P=CH2|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291521-3773%2819980703%2937%3A12%3C1670%3A%3AAID-ANIE1670%3E3.0.CO%3B2-S|journal=Angewandte Chemie International Edition|language=en|volume=37|issue=12|pages=1670–1672|doi=10.1002/(SICI)1521-3773(19980703)37:12<1670::AID-ANIE1670>3.0.CO;2-S|pmid=29711513|issn=1521-3773|url-access=subscription}}</ref> and in [[Aminophosphine|amino-phosphanes]] like P(NMe₂₎₃ and [[ylide]]s H₂C=P(NMe₂)₃<ref>{{Cite journal|last1=Mitzel|first1=Norbert W.|last2=Smart|first2=Bruce A.|last3=Dreihäupl|first3=Karl-Heinz|last4=Rankin|first4=David W. H.|last5=Schmidbaur|first5=Hubert|date=January 1996|title=Low Symmetry in P(NR 2 ) 3 Skeletons and Related Fragments: An Inherent Phenomenon|journal=Journal of the American Chemical Society|language=en|volume=118|issue=50|pages=12673–12682|doi=10.1021/ja9621861|issn=0002-7863}}</ref>

* Determination of intramolecular [[London dispersion force|London dispersion]] interaction effects on gas-phase and solid-state structures of diamondoid dimers<ref>{{Cite journal|last1=Fokin|first1=Andrey A.|last2=Zhuk|first2=Tatyana S.|last3=Blomeyer|first3=Sebastian|last4=Pérez|first4=Cristóbal|last5=Chernish|first5=Lesya V.|last6=Pashenko|first6=Alexander E.|last7=Antony|first7=Jens|last8=Vishnevskiy|first8=Yury V.|last9=Berger|first9=Raphael J. F.|last10=Grimme|first10=Stefan|last11=Logemann|first11=Christian|date=2017-11-22|title=Intramolecular London Dispersion Interaction Effects on Gas-Phase and Solid-State Structures of Diamondoid Dimers|journal=Journal of the American Chemical Society|volume=139|issue=46|pages=16696–16707|doi=10.1021/jacs.7b07884|pmid=29037036|issn=0002-7863}}</ref>

== Links ==

* http://molwiki.org/wiki/Main_Page—A{{Dead link|date=December 2022 |bot=InternetArchiveBot |fix-attempted=yes }} free encyclopaedia, mainly focused on molecular structure and dynamics.

* The story of gas-phase electron diffraction (GED) in [https://www.researchgate.net/publication/332484908_The_story_of_gas-phase_electron_diffraction_GED_in_Norway Norway] <ref>{{Cite journal|last=Kveseth|first=Kari|date=August 2019|title=The story of gas-phase electron diffraction (GED) in Norway|url=http://link.springer.com/10.1007/s11224-019-01309-w|journal=Structural Chemistry|language=en|volume=30|issue=4|pages=1505–1516|doi=10.1007/s11224-019-01309-w|s2cid=146084935 |issn=1040-0400|url-access=subscription}}</ref>

==References==