scholarly journals A deep UV trigger for ground-state ring-opening dynamics of 1,3-cyclohexadiene

2019 ◽  
Vol 5 (9) ◽  
pp. eaax6625 ◽  
Author(s):  
Jennifer M. Ruddock ◽  
Haiwang Yong ◽  
Brian Stankus ◽  
Wenpeng Du ◽  
Nathan Goff ◽  
...  
Keyword(s):  
Electronic State ◽  
Ground State ◽  
Ground Electronic State ◽  
Source Analysis ◽  
Time Resolved ◽  
X Ray Scattering ◽  
Linac Coherent Light Source ◽  
Scattering Anisotropy ◽  
Kinetics Of ◽  
Single Bonds

We explore the photo-induced kinetics of 1,3-cyclohexadiene upon excitation at 200 nm to the 3p state by ultrafast time-resolved, gas-phase x-ray scattering using the Linac Coherent Light Source. Analysis of the scattering anisotropy reveals that the excitation leads to the 3px and 3py Rydberg electronic states, which relax to the ground state with a time constant of 208 ± 11 fs. In contrast to the well-studied 266 nm excitation, at 200 nm the majority of the molecules (76 ± 3%) relax to vibrationally hot cyclohexadiene in the ground electronic state. A subsequent reaction on the ground electronic state surface leads from the hot cyclohexadiene to 1,3,5-hexatriene, with rates for the forward and backward reactions of 174 ± 13 and 355 ± 45 ps, respectively. The scattering pattern of the final hexatriene product reveals a thermal distribution of rotamers about the carbon-carbon single bonds.

In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

2019 ◽  
Author(s):  
Hao Wu ◽  
Jeffrey Ting ◽  
Siqi Meng ◽  
Matthew Tirrell
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Polyelectrolyte Complex ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

Quantum dynamics of the photostability of pyrazine

2015 ◽  
Vol 17 (44) ◽  
pp. 29518-29530 ◽  
Author(s):  
Matthieu Sala ◽  
Stéphane Guérin ◽  
Fabien Gatti
Keyword(s):  
Electronic State ◽  
Ground State ◽  
Quantum Dynamics ◽  
Ground Electronic State ◽  
Conical Intersection ◽  
Radiationless Decay

We propose a new mechanism for the radiationless decay of photoexcited pyrazine to its ground electronic state involving a conical intersection between the dark Au(nπ) state and the ground state.

scholarly journals In situ structural kinetics of picosecond laser-induced heating and fragmentation of colloidal gold spheres

2020 ◽  
Vol 22 (9) ◽  
pp. 4993-5001 ◽  
Author(s):  
Anna Rosa Ziefuss ◽  
Stefan Reich ◽  
Sven Reichenberger ◽  
Matteo Levantino ◽  
Anton Plech
Keyword(s):  
Colloidal Gold ◽  
Picosecond Laser ◽  
Time Resolved ◽  
Gold Colloids ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

The structural and energetic pathway of picosecond laser fragmentation of gold colloids has been clarified by time-resolved X-ray scattering.

Time-Resolved Small-Angle X-ray Scattering Study of the Kinetics of Disorder−Order Transition in a Triblock Copolymer in a Selective Solvent for the Middle Block

2003 ◽  
Vol 36 (21) ◽  
pp. 8097-8106 ◽  
Author(s):  
Huifen Nie ◽  
Rama Bansil ◽  
Karl Ludwig ◽  
Milos Steinhart ◽  
Čestmír Koňák ◽  
...  
Keyword(s):  
Small Angle ◽  
Triblock Copolymer ◽  
Order Transition ◽  
Selective Solvent ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Kinetics Of ◽  
Ray Scattering

Kinetics of lysozyme refolding: structural characterization of a non-specifically collapsed state using time-resolved X-ray scattering

1998 ◽  
Vol 276 (1) ◽  
pp. 225-237 ◽  
Author(s):  
Lingling Chen ◽  
Gudrun Wildegger ◽  
Thomas Kiefhaber ◽  
Keith O Hodgson ◽  
Sebastian Doniach
Keyword(s):  
Structural Characterization ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Lysozyme Refolding ◽  
Kinetics Of ◽  
Ray Scattering

scholarly journals Photodissociation of Iso-Propoxy (I-C3H7O) Radical at 248 Nm

2020 ◽  
Author(s):  
Erin Sullivan ◽  
Steven Saric ◽  
Daniel Neumark
Keyword(s):  
Electronic State ◽  
Ground State ◽  
Branching Ratio ◽  
Ground Electronic State ◽  
Angular Distributions ◽  
Translational Energy ◽  
Energy And Angular Distributions ◽  
Three Body ◽  
State Dissociation

<p>Photodissociation of the <i>i</i>-C<sub>3</sub>H<sub>7</sub>O radical is investigated using fast beam photofragment translational spectroscopy. Neutral <i>i</i>-C<sub>3</sub>H<sub>7</sub>O radicals are produced through the photodetachment of a fast beam of <i>i</i>-C<sub>3</sub>H<sub>7</sub>O<sup>-</sup> anions and are subsequently dissociated using 248 nm (5.0 eV). The dominant product channels are CH<sub>3</sub> + CH<sub>3</sub>CHO and OH + C<sub>3</sub>H<sub>6</sub> with some contribution from H + C<sub>3</sub>H<sub>6</sub>O. CH<sub>3</sub> and H loss are attributed to dissociation on the ground electronic state of <i>i</i>-C<sub>3</sub>H<sub>7</sub>O, but in a nonstatistical manner because RRKM dissociation rates exceed the rate of energy randomization. Translational energy and angular distributions for OH loss are consistent with ground state dissociation, but the branching ratio for this channel is considerably higher than predicted from RRKM rate calculations. These results corroborate what has been observed previously in C<sub>2</sub>H<sub>5</sub>O dissociation at 5.2 eV that yields CH<sub>3</sub>, H, and OH loss. Additionally, <i>i</i>-C<sub>3</sub>H<sub>7</sub>O undergoes three-body fragmentation to CH<sub>3</sub> + CH<sub>3</sub> + HCO and CH<sub>3</sub> + CH<sub>4</sub> + CO. These three-body channels are attributed to dissociation of <i>i</i>-C<sub>3</sub>H<sub>7</sub>O to CH<sub>3</sub> + CH<sub>3</sub>CHO, followed by secondary dissociation of CH<sub>3</sub>CHO on its ground electronic state.</p>

scholarly journals Photodissociation of Iso-Propoxy (I-C3H7O) Radical at 248 Nm

2020 ◽  
Author(s):  
Erin Sullivan ◽  
Steven Saric ◽  
Daniel Neumark
Keyword(s):  
Electronic State ◽  
Ground State ◽  
Branching Ratio ◽  
Ground Electronic State ◽  
Angular Distributions ◽  
Translational Energy ◽  
Energy And Angular Distributions ◽  
Three Body ◽  
State Dissociation

<p>Photodissociation of the <i>i</i>-C<sub>3</sub>H<sub>7</sub>O radical is investigated using fast beam photofragment translational spectroscopy. Neutral <i>i</i>-C<sub>3</sub>H<sub>7</sub>O radicals are produced through the photodetachment of a fast beam of <i>i</i>-C<sub>3</sub>H<sub>7</sub>O<sup>-</sup> anions and are subsequently dissociated using 248 nm (5.0 eV). The dominant product channels are CH<sub>3</sub> + CH<sub>3</sub>CHO and OH + C<sub>3</sub>H<sub>6</sub> with some contribution from H + C<sub>3</sub>H<sub>6</sub>O. CH<sub>3</sub> and H loss are attributed to dissociation on the ground electronic state of <i>i</i>-C<sub>3</sub>H<sub>7</sub>O, but in a nonstatistical manner because RRKM dissociation rates exceed the rate of energy randomization. Translational energy and angular distributions for OH loss are consistent with ground state dissociation, but the branching ratio for this channel is considerably higher than predicted from RRKM rate calculations. These results corroborate what has been observed previously in C<sub>2</sub>H<sub>5</sub>O dissociation at 5.2 eV that yields CH<sub>3</sub>, H, and OH loss. Additionally, <i>i</i>-C<sub>3</sub>H<sub>7</sub>O undergoes three-body fragmentation to CH<sub>3</sub> + CH<sub>3</sub> + HCO and CH<sub>3</sub> + CH<sub>4</sub> + CO. These three-body channels are attributed to dissociation of <i>i</i>-C<sub>3</sub>H<sub>7</sub>O to CH<sub>3</sub> + CH<sub>3</sub>CHO, followed by secondary dissociation of CH<sub>3</sub>CHO on its ground electronic state.</p>

scholarly journals A multi-step nucleation process determines the kinetics of prion-like domain phase separation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Erik W. Martin ◽  
Tyler S. Harmon ◽  
Jesse B. Hopkins ◽  
Srinivas Chakravarthy ◽  
J. Jeremías Incicco ◽  
...  
Keyword(s):  
Phase Separation ◽  
Size Distribution ◽  
Mixing Time ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Assembly Kinetics ◽  
Domain Phase ◽  
Kinetics Of ◽  
Liquid Liquid Phase Separation

AbstractCompartmentalization by liquid-liquid phase separation (LLPS) has emerged as a ubiquitous mechanism underlying the organization of biomolecules in space and time. Here, we combine rapid-mixing time-resolved small-angle X-ray scattering (SAXS) approaches to characterize the assembly kinetics of a prototypical prion-like domain with equilibrium techniques that characterize its phase boundaries and the size distribution of clusters prior to phase separation. We find two kinetic regimes on the micro- to millisecond timescale that are distinguished by the size distribution of clusters. At the nanoscale, small complexes are formed with low affinity. After initial unfavorable complex assembly, additional monomers are added with higher affinity. At the mesoscale, assembly resembles classical homogeneous nucleation. Careful multi-pronged characterization is required for the understanding of condensate assembly mechanisms and will promote understanding of how the kinetics of biological phase separation is encoded in biomolecules.

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