Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session W03: Ultrafast Dynamics in atoms and molecules |
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Chair: Luca Argenti, University of Central Florida Room: Wisconsin Center 101CD |
Friday, May 31, 2019 10:30AM - 11:00AM |
W03.00001: Is an efficient intermolecular energy transfer from vibrations to electronic motion possible ? Invited Speaker: Lorenz Cederbaum In this work we investigate the possibility of intermolecular vibrational energy transfer to electronic motion. Energy transfer of all kinds is of central importance for chemical reactivity and has been widely studied both experimentally and theoretically over many years including the transfer between the two kinds of energies, vibrational and electronic. The studies of the latter are, however, carried out in the framework of collisions where the collision complex formed and/or nonadiabatic coupling give rise to the transfer. Here, we concentrate on intermolecular vibrational energy transfer to electronic motion in weakly bound molecules, i.e., at internuclear distances at which they do not have a chemical bond and nonadiabatic coupling is negligible. We shall see that the transfer can be highly efficient [PRL 121, 223001 (2018)]. If time is left, intermolecular vibrational energy transfer between weakly bound molecules is also addressed. Here, most of the studies were done for describing \textit{resonant }vibrational energy transfer in the condensed phase. Very recently, it has been noticed that if the lifetime of the vibrationally excited molecule is much longer than that of its neighbor, efficient \textit{non-resonant} vibrational energy transfer can take place [doi.org/10.1080/00268976.2018.1473654]. [Preview Abstract] |
Friday, May 31, 2019 11:00AM - 11:30AM |
W03.00002: Ultrafast Dynamics of Single and Double Hydrogen Migration in Ethanol Invited Speaker: Nora Kling Hydrogen plays an important role in the chemistry of hydrocarbons, proteins and peptides, as well as most biomolecules. Intramolecular reactions where a hydrogen migrates from one bonding site to another has considerable impact on the chemical behavior of the molecule. Similarly, in molecules containing more than one hydrogen, multiple hydrogen migrations can occur, further altering the molecule's functionality or original identity. Using a pair of ultrashort (9 fs), intense (I\textasciitilde 10$^{\mathrm{14}}$ W/cm$^{\mathrm{2}})$ laser pulses in a pump-probe scheme, combined with 3D coincidence ion imaging (COLTRIMS), we explore the rich dynamics of the single and the double hydrogen migration reactions taking place in ethanol, CH$_{\mathrm{3}}$CH$_{\mathrm{2}}$OH. Four reaction channels are studied for this purpose, including three double coincidence channels: C$_{\mathrm{2}}$H$_{\mathrm{5}}^{\mathrm{+}} \quad +$ OH$^{\mathrm{+}}$, C$_{\mathrm{2}}$H$_{\mathrm{4}}^{\mathrm{+}} \quad +$ H$_{\mathrm{2}}$O$^{\mathrm{+}}$, C$_{\mathrm{2}}$H$_{\mathrm{3}}^{\mathrm{+}} \quad +$ H$_{\mathrm{3}}$O$^{\mathrm{+}}$, and one triple coincidence channel: H$^{\mathrm{+}} \quad +$ H$_{\mathrm{2}}$O$^{\mathrm{+}} \quad +$ C$_{\mathrm{2}}$H$_{\mathrm{3}}^{\mathrm{+}}$. The double coincidence channels are attributed to dynamics occurring in the ethanol cation. Simultaneously tracking the ion yields as a function of time between the pump and probe pulses for the three channels, we investigate the chemical kinetics for `no', single, and double hydrogen migration reactions. Furthermore, we investigate correlations between the different channels. The triple coincidence channel is attributed to dynamics occurring in the ethanol dication. Three precursor channels are identified through monitoring the kinetic energy release and momenta of the involved fragments. Newton and Dalitz plots help to decipher the relevant molecular motions at different pump-probe delays. Compared to some of the processes leading to single hydrogen migration, the probability of observing double hydrogen migration in the experiment is quite significant, suggesting that double hydrogen migration might play a more important role in the chemistry of charged organic compounds than generally assumed. The conclusions are supported by state-of-the-art molecular dynamics calculations. This work is funded by the NSF under grant No. 1700551. [Preview Abstract] |
Friday, May 31, 2019 11:30AM - 11:42AM |
W03.00003: Probing Ultrafast Electronic and Nuclear Dynamics during Ring-Opening Reactions Shashank Pathak, Jan Tross, Daniel Rolles, Mike Ashfold, Christopher Hansen, Rebecca Ingle, Rebecca Boll, Carlo Callegari, Michele Di Fraia, Oksana Plekan, Kevin Prince, Benjamin Erk, Raimund Feifel, Richard Squibb, Ruaridh Forbes, David Holland, Robert Mason, Arnaud Rouzee We report the results of a time-resolved photoelectron spectroscopy experiment performed using short-pulse and narrow-bandwidth extreme ultraviolet radiation provided by the seeded free-electron laser FERMI. We studied the UV-induced ring-opening and subsequent unimolecular dissociation of a heterocyclic ring molecule. Theoretical predictions suggest the existence of several ring-opened isomers with about 1-2 eV less binding energy as compared to the parent molecule. Our experiment probes the ultrafast electronic pathways leading to their creation. [Preview Abstract] |
Friday, May 31, 2019 11:42AM - 11:54AM |
W03.00004: Coincidence measurements of strong field molecular double ionization Chuan Cheng, Spiridoula Matsika, Thomas Weinacht We use few cycle intense ultrafast laser pulses and coincidence velocity map imaging to investigate strong field double ionization in molecules. We use a time stamping camera to make vector momentum measurements of electrons and ions, allowing us to distinguish between multiple double ionization channels. Different double ionization channels which result in different fragment ion pairs show different electron correlation patterns, indicating that the double ionization dynamics are influenced by the orbitals from which the electrons are removed. [Preview Abstract] |
Friday, May 31, 2019 11:54AM - 12:06PM |
W03.00005: Strong-field induced bond rearrangement in triatomic molecules S. Zhao, E. Wells, Bethany Jochim, Peyman Feizollah, Jyoti Rajput, F. Ziaee, Kanaka Raju P., B. Kaderiya, K. Borne, Y. Malakar, Ben Berry, J. Harrington, D. Rolles, A. Rudenko, K.D. Carnes, I. Ben-Itzhak, T. Severt A comparative study of strong-field induced bond rearrangement is carried out for three triatomic molecules: carbon dioxide (CO$_2$), carbonyl sulfide (OCS), and water (D$_2$O). Specifically, we use COLTRIMS to measure the branching ratio for the formation of AC$^+$ from ABC$^{2+}$ following double ionization by intense, short (23 fs, 790 nm) laser pulses. Our study shows that the branching ratio of D$_2$O$^{2+} \rightarrow$ D$_2^+$ + O$^+$ is higher than that of CO$_2^{2+} \rightarrow$ O$_2^+$ + C$^+$, which in turn is higher than that of OCS$^{2+} \rightarrow$ SO$^+$ + C$^+$, although all three values are within an order of magnitude of each other. Additionally, we examined the isotopic and linear-chirp dependencies of bond rearrangement in water. [Preview Abstract] |
Friday, May 31, 2019 12:06PM - 12:18PM |
W03.00006: Identifying the Role of Multielectron Excitations in Rydberg State Dissociation of Oxygen with Ultrafast Photoelectron Spectroscopy Alexander Plunkett, Arvinder Sandhu We investigated the fragmentation dynamics of highly excited states of molecular oxygen using femtosecond transient photoelectron spectroscopy. An XUV pump populates neutral Rydberg states converging to the $c\ ^4\Sigma_u^-$ state and a delayed IR probe serves to photoionize the Rydberg wavepacket, producing low energy electrons. We obtained transient photoelectron spectra by subtracting the XUV+IR and XUV alone photoionization data at various time delays and thereby studied the competing mechanisms of molecular autoionization and ultrafast dissociation. We observed the formation of 4p excited atomic oxygen fragment, which is not an expected dissociation product of the $(c\ ^4\Sigma_u^-)nl\sigma_g$ Rydberg series. We show that this fragment results from previously unexplored $(^4\Pi_g)4p$ repulsive state and, contrary to expectations, this multielectron excitation pathway presents a substantial cross section. Our study demonstrates that two-color time-resolved photoelectron spectroscopy is an excellent tool to study the fragmentation dynamics of such states, which are not easily probed by other means due to their repulsive nature. [Preview Abstract] |
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