AMOP Seminar
Dissociation Dynamics in Electron Attachment and Photoexcitation Reactions
3:30 pm –
5:00 pm
Jorgensen Hall Room: 145
Contact:
Physics Department, (402) 472-2770, paoffice@unl.edu
SPEAKER: Daniel Slaughter - Lawrence Berkeley National Lab
ABSTRACT:
Low energy electrons have importance in chemical processes initiated by ionizing radiation, because electrons are produced in high abundance with low energies in the range for electron-molecule resonances. These resonances drive molecular dissociation by inelastic scattering and dissociative electron attachment (DEA). In DEA, the energy of a free electron is efficiently converted into vibrational kinetic energy and dissociation into two or more atomic or molecular fragments. The process exhibits strong coupling between electronic and nuclear motion, resulting in rich nonadiabatic dynamics such as conical intersections or electron transfer between electronic states of the transient anion, that are very difficult, if not impossible to model without detailed experimental data1. New anion fragment momentum imaging experiments will be presented for DEA reactions involving formic acid, which is the simplest organic acid. A remarkable site-selectivity is found allowing, the electron attachment energy to control the relative yields C-H and O-H dissociation, producing neutral radicals HOCO or HCOO.
Recent ultrafast laser pump-probe experiments will also be reported2, where molecular dynamics of excited molecules are studied by time resolved photoelectron spectroscopy (TRPES). When correlated with mass-resolved ion yields measured in the same experiment, different dissociation channels can be assigned to specific electronic states and decay pathways involving conical intersections. Ongoing developments in TRPES and particle momentum imaging will soon enable ultrafast time resolved measurements of DEA dynamics.
References:
1. Slaughter D S, Belkacem A, McCurdy C W, Rescigno T N and Haxton D J 2016 Ion-momentum imaging of dissociative attachment of electrons to molecules, J. Phys. B: At. Mol. Opt. Phys. 2016 49 222001, https://doi.org/10.1088/0953-4075/49/22/222001
2. Champenois E G, Greenman L, Shivaram N, Cryan J P, Larsen K A, Rescigno T N, McCurdy C W, Belkacem A, Slaughter D S, Ultrafast Photodissociation Dynamics and Nonadiabatic Coupling between Excited Electronic States of Methanol Probed by Time-Resolved Photoelectron Spectroscopy, J. Chem. Phys. 2019, 150 (11), 114301, 10.1063/1.5079549
ABSTRACT:
Low energy electrons have importance in chemical processes initiated by ionizing radiation, because electrons are produced in high abundance with low energies in the range for electron-molecule resonances. These resonances drive molecular dissociation by inelastic scattering and dissociative electron attachment (DEA). In DEA, the energy of a free electron is efficiently converted into vibrational kinetic energy and dissociation into two or more atomic or molecular fragments. The process exhibits strong coupling between electronic and nuclear motion, resulting in rich nonadiabatic dynamics such as conical intersections or electron transfer between electronic states of the transient anion, that are very difficult, if not impossible to model without detailed experimental data1. New anion fragment momentum imaging experiments will be presented for DEA reactions involving formic acid, which is the simplest organic acid. A remarkable site-selectivity is found allowing, the electron attachment energy to control the relative yields C-H and O-H dissociation, producing neutral radicals HOCO or HCOO.
Recent ultrafast laser pump-probe experiments will also be reported2, where molecular dynamics of excited molecules are studied by time resolved photoelectron spectroscopy (TRPES). When correlated with mass-resolved ion yields measured in the same experiment, different dissociation channels can be assigned to specific electronic states and decay pathways involving conical intersections. Ongoing developments in TRPES and particle momentum imaging will soon enable ultrafast time resolved measurements of DEA dynamics.
References:
1. Slaughter D S, Belkacem A, McCurdy C W, Rescigno T N and Haxton D J 2016 Ion-momentum imaging of dissociative attachment of electrons to molecules, J. Phys. B: At. Mol. Opt. Phys. 2016 49 222001, https://doi.org/10.1088/0953-4075/49/22/222001
2. Champenois E G, Greenman L, Shivaram N, Cryan J P, Larsen K A, Rescigno T N, McCurdy C W, Belkacem A, Slaughter D S, Ultrafast Photodissociation Dynamics and Nonadiabatic Coupling between Excited Electronic States of Methanol Probed by Time-Resolved Photoelectron Spectroscopy, J. Chem. Phys. 2019, 150 (11), 114301, 10.1063/1.5079549