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Imaging an aligned polyatomic molecule with laser-induced electron diffraction.

Pullen MG, Wolter B, Le AT, Baudisch M, Hemmer M, Senftleben A, Schröter CD, Ullrich J, Moshammer R, Lin CD, Biegert J - Nat Commun (2015)

Bottom Line: Here we demonstrate the retrieval of multiple bond lengths from a polyatomic molecule by simultaneously measuring the C-C and C-H bond lengths in aligned acetylene.Our approach takes the method beyond the hitherto achieved imaging of simple diatomic molecules and is based on the combination of a 160 kHz mid-infrared few-cycle laser source with full three-dimensional electron-ion coincidence detection.Our technique provides an accessible and robust route towards imaging ultrafast processes in complex gas-phase molecules with atto- to femto-second temporal resolution.

View Article: PubMed Central - PubMed

Affiliation: ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain.

ABSTRACT
Laser-induced electron diffraction is an evolving tabletop method that aims to image ultrafast structural changes in gas-phase polyatomic molecules with sub-Ångström spatial and femtosecond temporal resolutions. Here we demonstrate the retrieval of multiple bond lengths from a polyatomic molecule by simultaneously measuring the C-C and C-H bond lengths in aligned acetylene. Our approach takes the method beyond the hitherto achieved imaging of simple diatomic molecules and is based on the combination of a 160 kHz mid-infrared few-cycle laser source with full three-dimensional electron-ion coincidence detection. Our technique provides an accessible and robust route towards imaging ultrafast processes in complex gas-phase molecules with atto- to femto-second temporal resolution.

No MeSH data available.


Related in: MedlinePlus

Simultaneous extraction of multiple bond lengths from polyatomic molecules.(a) The ratio of the H and C scattering cross-sections as a function of electron-scattering angle for typical energies used in LIED (50 and 100 eV) and CED/UED (25 keV). The ratios are much higher for the energies relevant to LIED and are also applicable over a much wider angular range (shaded regions). (b) Blue squares (red circles) show the experimental molecular contrast factor that results from the scattering of 60 eV electrons by aligned (anti-aligned) molecules. The best theoretical fits (dashed lines) allow the accurate extraction of the C–H and C–C bond lengths from both alignments. The s.d. error bars are derived from Poissonian statistics.
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f3: Simultaneous extraction of multiple bond lengths from polyatomic molecules.(a) The ratio of the H and C scattering cross-sections as a function of electron-scattering angle for typical energies used in LIED (50 and 100 eV) and CED/UED (25 keV). The ratios are much higher for the energies relevant to LIED and are also applicable over a much wider angular range (shaded regions). (b) Blue squares (red circles) show the experimental molecular contrast factor that results from the scattering of 60 eV electrons by aligned (anti-aligned) molecules. The best theoretical fits (dashed lines) allow the accurate extraction of the C–H and C–C bond lengths from both alignments. The s.d. error bars are derived from Poissonian statistics.

Mentions: To visualize complex molecules, LIED needs to be able to retrieve multiple bond lengths between different atomic species. We demonstrate that our implementation of LIED fulfills this promise and is even able to image the (typically) elusive hydrogen atom by exploiting the fact that we measure the full doubly differential cross-section. At the tens of keV electron energies used in UED, a hydrogen atom has a scattering cross-section (σH) that is typically much less than that of a C atom (σC). Figure 3a presents the σH/σC ratio29 for a 25 keV electron as a function of the scattering angle (green curve). The ratio is maximal for scattering angles between 0 and 5° that are typical in UED (shaded region) but even in this range σH/σC<0.05. The electron energies used in LIED result in much higher values of the σH/σC ratio, as is also presented in Fig. 3a for 50 eV (red curve) and 100 eV (blue curve) electrons, because of a minimum in the C atom differential cross-section. Both of the presented energies have wide angular regions where σH/σC>0.10 and a peak of σH/σC>0.50 is observed near 80° for 50 eV electrons. The shaded regions represent the much wider scattering angles for which the LIED technique is valid.


Imaging an aligned polyatomic molecule with laser-induced electron diffraction.

Pullen MG, Wolter B, Le AT, Baudisch M, Hemmer M, Senftleben A, Schröter CD, Ullrich J, Moshammer R, Lin CD, Biegert J - Nat Commun (2015)

Simultaneous extraction of multiple bond lengths from polyatomic molecules.(a) The ratio of the H and C scattering cross-sections as a function of electron-scattering angle for typical energies used in LIED (50 and 100 eV) and CED/UED (25 keV). The ratios are much higher for the energies relevant to LIED and are also applicable over a much wider angular range (shaded regions). (b) Blue squares (red circles) show the experimental molecular contrast factor that results from the scattering of 60 eV electrons by aligned (anti-aligned) molecules. The best theoretical fits (dashed lines) allow the accurate extraction of the C–H and C–C bond lengths from both alignments. The s.d. error bars are derived from Poissonian statistics.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491169&req=5

f3: Simultaneous extraction of multiple bond lengths from polyatomic molecules.(a) The ratio of the H and C scattering cross-sections as a function of electron-scattering angle for typical energies used in LIED (50 and 100 eV) and CED/UED (25 keV). The ratios are much higher for the energies relevant to LIED and are also applicable over a much wider angular range (shaded regions). (b) Blue squares (red circles) show the experimental molecular contrast factor that results from the scattering of 60 eV electrons by aligned (anti-aligned) molecules. The best theoretical fits (dashed lines) allow the accurate extraction of the C–H and C–C bond lengths from both alignments. The s.d. error bars are derived from Poissonian statistics.
Mentions: To visualize complex molecules, LIED needs to be able to retrieve multiple bond lengths between different atomic species. We demonstrate that our implementation of LIED fulfills this promise and is even able to image the (typically) elusive hydrogen atom by exploiting the fact that we measure the full doubly differential cross-section. At the tens of keV electron energies used in UED, a hydrogen atom has a scattering cross-section (σH) that is typically much less than that of a C atom (σC). Figure 3a presents the σH/σC ratio29 for a 25 keV electron as a function of the scattering angle (green curve). The ratio is maximal for scattering angles between 0 and 5° that are typical in UED (shaded region) but even in this range σH/σC<0.05. The electron energies used in LIED result in much higher values of the σH/σC ratio, as is also presented in Fig. 3a for 50 eV (red curve) and 100 eV (blue curve) electrons, because of a minimum in the C atom differential cross-section. Both of the presented energies have wide angular regions where σH/σC>0.10 and a peak of σH/σC>0.50 is observed near 80° for 50 eV electrons. The shaded regions represent the much wider scattering angles for which the LIED technique is valid.

Bottom Line: Here we demonstrate the retrieval of multiple bond lengths from a polyatomic molecule by simultaneously measuring the C-C and C-H bond lengths in aligned acetylene.Our approach takes the method beyond the hitherto achieved imaging of simple diatomic molecules and is based on the combination of a 160 kHz mid-infrared few-cycle laser source with full three-dimensional electron-ion coincidence detection.Our technique provides an accessible and robust route towards imaging ultrafast processes in complex gas-phase molecules with atto- to femto-second temporal resolution.

View Article: PubMed Central - PubMed

Affiliation: ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain.

ABSTRACT
Laser-induced electron diffraction is an evolving tabletop method that aims to image ultrafast structural changes in gas-phase polyatomic molecules with sub-Ångström spatial and femtosecond temporal resolutions. Here we demonstrate the retrieval of multiple bond lengths from a polyatomic molecule by simultaneously measuring the C-C and C-H bond lengths in aligned acetylene. Our approach takes the method beyond the hitherto achieved imaging of simple diatomic molecules and is based on the combination of a 160 kHz mid-infrared few-cycle laser source with full three-dimensional electron-ion coincidence detection. Our technique provides an accessible and robust route towards imaging ultrafast processes in complex gas-phase molecules with atto- to femto-second temporal resolution.

No MeSH data available.


Related in: MedlinePlus