Publications by authors named "D Rolles"
We describe the design and performance of a magnetic bottle electron spectrometer (MBES) for high-energy electron spectroscopy. Our design features a 2 m long electron drift tube and electrostatic retardation lens, achieving sub-electronvolt (eV) electron kinetic energy resolution for high energy (several hundred eV) electrons with a close to 4π collection solid angle. A segmented anode electron detector enables the simultaneous collection of photoelectron spectra in high resolution and high collection efficiency modes.
View Article and Find Full Text PDFConjugated diene molecules are highly reactive upon photoexcitation and can relax through multiple reaction channels that depend on the position of the double bonds and the degree of molecular rigidity. Understanding the photoinduced dynamics of these molecules is crucial for establishing general rules governing the relaxation and product formation. Here, we investigate the femtosecond time-resolved photoinduced excited-state structural dynamics of ,-1,3-cyclooctadiene, a large-flexible cyclic conjugated diene molecule, upon excitation with 200 nm using mega-electron-volt ultrafast electron diffraction and trajectory surface hopping dynamics simulations.
View Article and Find Full Text PDFTime-resolved extreme ultraviolet spectroscopy was used to investigate photodissociation within the iodobenzene C-band. The carbon-iodine bond of iodobenzene was photolyzed at 200 nm, and the ensuing dynamics were probed at 10.3 nm (120 eV) over a 4 ps range.
View Article and Find Full Text PDFArticle Synopsis
- - The study investigates how bromoform (CHBr) behaves when exposed to near-infrared (NIR) light, focusing on its breakdown and isomerization in cationic states through advanced imaging techniques.
- - It is observed that the dissociation process, particularly when forming HBr and Br fragments, occurs with a delay compared to the faster breakdown of the C-Br bond.
- - Molecular dynamics simulations indicate that this delay results from temporary isomerization processes involving H- and Br-migrations before the final fragments are produced.
Article Synopsis
- Imaging hydrogen motion at ultrafast timescales is difficult due to the low mass and small scattering cross-section of hydrogen atoms and molecules.
- The study proposes a new method called time- and momentum-resolved photoelectron diffraction (TMR-PED) to address these challenges, demonstrated through the dissociation of a neutral hydrogen molecule from methanol dication.
- TMR-PED allows for direct imaging of hydrogen dynamics by analyzing molecular-frame photoelectron angular distributions, with supporting experiments showcasing the method's potential effectiveness at few-femtosecond resolution.