arXiv subjects

D. S. Slaughter

Publications and source records attributed to D. S. Slaughter.

5 recordsLinked to original sources

arXiv2025

The Polarization Projected Density Matrix: A Practical Way to Recover Molecular Frame Information from Isotropic Samples

We present a novel approach to model ultrafast time-dependent nonlinear optical polarization sensitive signals emitted from randomly-oriented molecules. By projecting the laboratory-frame analyzer polarization axis into the molecular frame and linking that axis with the density matrix through a tensor product, we demonstrate an approach to find a specific molecular orientation that yields a good approximation to simulated four-wave mixing signals produced by the same model but with averaging over molecular orientation.

physics.chem-ph↗

arXiv2023

Relativistic ultrafast electron diffraction at high repetition rates

The ability to resolve the dynamics of matter on its native temporal and spatial scales constitutes a key challenge and convergent theme across chemistry, biology, and materials science. The last couple of decades have witnessed ultrafast electron diffraction (UED) emerge as one of the forefront techniques with the sensitivity to resolve atomic motions. Increasingly sophisticated UED instruments are being developed that are aimed at increasing the beam brightness in order to observe structural signatures, but so far they have been limited to low average current beams. Here we present the technical design and capabilities of the HiRES (High Repetition Rate Electron Scattering) instrument, which blends relativistic electrons and high repetition rates to achieve orders of magnitude improvement in average beam current compared to the existing state-of-the-art UED instruments. The setup utilizes a novel electron source to deliver femtosecond duration electron pulses at up to MHz repetition rates for UED experiments. We provide example cases of diffraction measurements on solid-state and gas-phase samples, including both micro- and nanodiffraction modes, which showcase the potential of the instrument for novel UED experiments.

physics.ins-det↗

arXiv2021

Non-Equilibrium Dynamics in Two-Color, Few-Photon Dissociative Excitation and Ionization of D$_2$

D$_2$ molecules, excited by linearly cross-polarized femtosecond extreme ultraviolet (XUV) and near-infrared (NIR) light pulses, reveal highly structured D$^+$ ion fragment momenta and angular distributions that originate from two different 4-step dissociative ionization pathways after four photon absorption (1 XUV + 3 NIR). We show that, even for very low dissociation kinetic energy release $\le$~240~meV, specific electronic excitation pathways can be identified and isolated in the final ion momentum distributions. With the aid of {\it ab initio} electronic structure and time-dependent Schrödinger equation calculations, angular momentum, energy, and parity conservation are used to identify the excited neutral molecular states and molecular orientations relative to the polarization vectors in these different photoexcitation and dissociation sequences of the neutral D$_2$ molecule and its D$_2^+$ cation. In one sequential photodissociation pathway, molecules aligned along either of the two light polarization vectors are excluded, while another pathway selects molecules aligned parallel to the light propagation direction. The evolution of the nuclear wave packet on the intermediate \Bstate electronic state of the neutral D$_2$ molecule is also probed in real time.

physics.atom-ph↗

arXiv2020

Selective Bond-Breaking in Formic Acid by Dissociative Electron Attachment

We report the results of a joint experimental {and} theoretical study of dissociative electron attachment to formic acid (HCOOH) in the 6-9 eV region, where H$^-$ fragment ions are a dominant product. Breaking of the CH and OH bonds is distinguished experimentally by deuteration of either site. We show that in this region H$^-$ ions can be produced by formation of two {or possibly three} Feshbach resonance (doubly-excited anion) states, one of which leads to either C-H or O-H bond scission, while the other can only produce formyloxyl radicals by O-H bond scission. Comparison of experimental and theoretical angular distributions of the anion fragment allows the elucidation of state specific pathways to dissociation.

physics.chem-ph↗

arXiv2013

Dissociative electron attachment to carbon dioxide via the ^2Π_u shape resonance

Momentum imaging measurements from two experiments are presented and interpreted with the aid of new ab initio theoretical calculations to describe the dissociative electron attachment (DEA) dynamics. We address the problem of how the 4 eV ^2Π_u shape resonance in CO_2 proceeds to dissociate to CO(^1Σ^+) + O^-(^2P) by DEA.

physics.chem-ph↗