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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

Accurate C2H2 bond length extraction.The C–C (C–H) bond length estimates are presented as a function of the scattering electron energy and rescattering time in the top (bottom) quadrant. The expected equilibrium values of the acetylene cation are also shown (dashed black lines). The values of the best horizontal fits for each bond are displayed in the respective panels. See Supplementary Fig. 4 for details about the bond length estimate error bars.
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f4: Accurate C2H2 bond length extraction.The C–C (C–H) bond length estimates are presented as a function of the scattering electron energy and rescattering time in the top (bottom) quadrant. The expected equilibrium values of the acetylene cation are also shown (dashed black lines). The values of the best horizontal fits for each bond are displayed in the respective panels. See Supplementary Fig. 4 for details about the bond length estimate error bars.

Mentions: Next, we illustrate the possible attosecond temporal resolution30 of the technique in Fig. 4. We measure the doubly differential cross-section, which permits retrieving the C–C and C–H bond lengths as a function of the rescattering electron energy. On the basis of operating mid-infrared LIED in the quasi-static limit we can invoke the classical rescattering model to associate a specific time to the measured electron-rescattering energy. The top axis in Fig. 4 shows the corresponding return time for each electron energy and indicates that a temporal resolution below 100 as could be achieved by analysing at different rescattering energies. We further elaborate that the measured energy range can also be used to establish an unprecedented level of confidence and redundancy for the retrieved bond length. The extracted , , and values are consistent with the estimated ionic equilibrium values (dashed black lines)28 over the investigated energy range. As no significant structural rearrangements are expected after acetylene is ionized from a neutral to a cation28, fitting a horizontal line to the energy-dependent bond length estimates will yield an overall estimate of the C–C and C–H bond lengths. This fitting results in estimates of and for anti-aligned molecules while the same analysis with aligned molecules results in bond lengths of and . This method amounts to performing two-dimensional fitting over both electron energy and scattering angle, which is not possible with other techniques, and highlights the accuracy of the LIED method.


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)

Accurate C2H2 bond length extraction.The C–C (C–H) bond length estimates are presented as a function of the scattering electron energy and rescattering time in the top (bottom) quadrant. The expected equilibrium values of the acetylene cation are also shown (dashed black lines). The values of the best horizontal fits for each bond are displayed in the respective panels. See Supplementary Fig. 4 for details about the bond length estimate error bars.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Accurate C2H2 bond length extraction.The C–C (C–H) bond length estimates are presented as a function of the scattering electron energy and rescattering time in the top (bottom) quadrant. The expected equilibrium values of the acetylene cation are also shown (dashed black lines). The values of the best horizontal fits for each bond are displayed in the respective panels. See Supplementary Fig. 4 for details about the bond length estimate error bars.
Mentions: Next, we illustrate the possible attosecond temporal resolution30 of the technique in Fig. 4. We measure the doubly differential cross-section, which permits retrieving the C–C and C–H bond lengths as a function of the rescattering electron energy. On the basis of operating mid-infrared LIED in the quasi-static limit we can invoke the classical rescattering model to associate a specific time to the measured electron-rescattering energy. The top axis in Fig. 4 shows the corresponding return time for each electron energy and indicates that a temporal resolution below 100 as could be achieved by analysing at different rescattering energies. We further elaborate that the measured energy range can also be used to establish an unprecedented level of confidence and redundancy for the retrieved bond length. The extracted , , and values are consistent with the estimated ionic equilibrium values (dashed black lines)28 over the investigated energy range. As no significant structural rearrangements are expected after acetylene is ionized from a neutral to a cation28, fitting a horizontal line to the energy-dependent bond length estimates will yield an overall estimate of the C–C and C–H bond lengths. This fitting results in estimates of and for anti-aligned molecules while the same analysis with aligned molecules results in bond lengths of and . This method amounts to performing two-dimensional fitting over both electron energy and scattering angle, which is not possible with other techniques, and highlights the accuracy of the LIED method.

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