Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session A26: Focus Session: Non-Adiabatic Dynamics: New Insights from Experiment and Theory I |
Hide Abstracts |
Sponsoring Units: DCP Chair: Richard Dawes, Missouri University of Science and Technology Room: 204A |
Monday, March 2, 2015 8:00AM - 8:36AM |
A26.00001: Representing Adiabatic Potential Energy Surfaces Coupled by Conical Intersections in their Full Dimensionality Using Coupled Quasi-Diabatic States Invited Speaker: David Yarkony The construction of fit single state potential energy surfaces (PESs), analytic representations of \textit{ab initio} electronic energies and energy gradients, is now well established. These single state PESs, which are essential for accurate quantum dynamics and have found wide application in more approximate quasi-classical treatments, have revolutionized adiabatic dynamics. The situation for nonadiabatic processes involving dissociative and large amplitude motion is less sanguine. In these cases, compared to single electronic state dynamics, both the electronic structure data and the representation are more challenging to determine. We describe the recent development and applications of algorithms that enable description of multiple adiabatic electronic potential energy surfaces coupled by conical intersections in their full dimensionality using coupled quasi-diabatic states. These representations are demonstrably quasi-diabatic, provide accurate representations of conical intersection seams and can smooth out the discontinuities in electronic structure energies due to changing active orbital spaces that routinely afflict global multistate representations. [Preview Abstract] |
Monday, March 2, 2015 8:36AM - 8:48AM |
A26.00002: Classical nuclear dynamics on a single time-dependent potential in electronic non-adiabatic processes Federica Agostini, Ali Abedi, Yasumitsu Suzuki, Seung Kyu Min, Neepa T. Maitra, E.K.U. Gross The Born-Oppenheimer (BO) approximation allows to visualize the coupled electron-nuclear dynamics in molecular systems as a set of nuclei moving on a single potential energy surface representing the effect of the electrons in a given eigenstate. Many interesting phenomena, however, such as vision or charge separation in organic photovoltaic materials, take place in conditions beyond its range of validity. Nevertheless, the basic construct of the adiabatic treatment, the BO potential energy surfaces, is employed to describe non-adiabatic processes and the full problem is represented in terms of adiabatic states and transitions among them in regions of strong non-adiabatic coupling. But the concept of single potential energy is lost. The alternative point of view [1] arising in the framework of the exact factorization of the electron-nuclear wave function [2] will be presented. A single, time-dependent, potential energy provides the force [3] driving the nuclear motion and is adopted as starting point for the development of quantum-classical [4] approximations to the full quantum mechanical problem. [1] Phys. Rev. Lett. 110 263001 (2013); [2] Phys. Rev. Lett. 105 123002 (2010); [3] Mol. Phys. 111 3625 (2013); [4] Europhys. Lett. 106 33001 (2014). [Preview Abstract] |
Monday, March 2, 2015 8:48AM - 9:24AM |
A26.00003: Non-adiabatic dynamics of reactions of O($^{1}$D) with Xe, CO, NO$_{2}$, and CO$_{2}$ from crossed atomic and molecular beam experiments Invited Speaker: Kristie Boering Reactions of the first excited state of atomic oxygen, O($^{1}$D), with small molecules such as CO, NO$_{2}$, and CO$_{2}$ continue to be of interest in aeronomy and atmospheric chemistry, thus providing additional motivation to understand the dynamics of these reactions and how well they are predicted by theory. In collaboration with Prof. Jim Lin of the Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan, we have studied the dynamics of quenching and non-quenching reactions between O($^{1}$D) and various small molecules using a universal crossed atomic and molecular beam apparatus. New experimental results for the dynamics of quenching of O($^{1}$D) by Xe and CO will be presented and compared with previous results for NO$_{2}$ (K.A. Mar, A.L. Van Wyngarden, C.-W. Liang, Y.T. Lee, J.J. Lin, K.A. Boering, J. Chem. Phys., 137, 044302, doi: 10.1063/1.4736567, 2012) and CO$_{2}$ (M.J. Perri, A.L. Van Wyngarden, K.A. Boering, J.J. Lin, and Y.T. Lee, J. Chem. Phys., 119(16), 8213-8216, 2003; M.J. Perri, A.L. Van Wyngarden, J.J. Lin, Y.T. Lee, and K.A. Boering, J. Phys. Chem. A, 108(39), 7995-8001, doi: 10.1021/jp0485845, 2004). Among the most intriguing of the new results are for quenching of O($^{1}$D) by Xe, for which marked oscillations in the differential cross sections were observed for the O($^{3}$P) and Xe products. The shape and relative phase of the oscillatory structure depended strongly on collision energy. This behavior is likely due to the quantum nature of the collision dynamics, caused by interferences among multiple curve crossing pathways accessible during electronic quenching, known as Stueckelberg oscillations. [Preview Abstract] |
Monday, March 2, 2015 9:24AM - 10:00AM |
A26.00004: Light, Molecules, Action: Broadband UV-visible transient absorption studies of excited state dynamics in photoactive molecules Invited Speaker: Roseanne Sension Broadband UV-visible transient absorption spectroscopy provides a powerful tool for the investigation of the dynamics of electronically excited molecules in the condensed phase. It is now possible to obtain transient spectra on a routine basis spanning the range from \textless 300 nm to \textgreater 800 nm with femtosecond time resolution. We have used this method to study the excited state dynamics and internal conversion of a range of molecular systems with potential application as optically powered molecular devices. The cyclohexadiene ring-opening reaction is the basis of a class of important optical switches and of the biological synthesis of previtamin D3. The ring-opening reaction is ultrafast, occurring on a picosecond to subpicosecond times scale depending on the substituents around the ring. These have a significant influence on the dynamics and electronic structure of the electronically excited molecule. The results of a series of transient absorption studies as a function of chromophore substitution and environment will be presented. The cis-trans isomerization of polyene molecules, especially substituted stilbenes, provides another important class of functional molecular transformations. Again the excited state dynamics can be ultrafast with photochemistry controlled by details of the curve crossings and conical intersections. Finally the photochemistry of the even more complex set of cobalamin chromophores with a photoalabile C-Co bond has been proposed as a tool for spatio-temporal control of molecule delivery including drug delivery. Broadband transient absorption spectroscopy has been used to investigate the ultrafast electronic dynamics of a range of cobalamin compounds with comparison to detailed theoretical calculations. The results of these studies will be presented. [Preview Abstract] |
Monday, March 2, 2015 10:00AM - 10:12AM |
A26.00005: Long-lived complexes in the F $+$ H$_{2}$O and F $+$ CH$_{3}$OH Hydrogen Abstraction Reactions Robert Continetti Extending our recent study of the benchmark four-atom F $\cdot$ H$_{2}$O system [1], we have now studied the dissociative photodetachment (DPD) of the seven-atom F$^-$ (CH$_{3}$OH) cluster as well. The energetics of this system dictate that DPD only occurs to the HF $+$ OCH$_{3} + $ e$^{-}$ product channel on the neutral potential energy surface resulting in diagonal banding in the photoelectron-photofragment coincidence spectrum consistent with resolved HF vibrational excitation in the products. Evidence for photodetachment to long-lived ($\mu$s) van der Waals complexes (FH---OCH$_{3})$ was also observed, as in the F-H$_{2}$O system. The metastable states involved in F-H$_{2}$O are best described as vibrational Feshbach resonances, and the energetics and dynamics of the metastable complexes in the two systems will be examined. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under award number DE-FG03-98ER14879. \\[4pt] [1] Otto, R.; Ma, J.; Ray, A. W.; Daluz, J. S.; Li, J.; Guo, H.; Continetti, R. E., Science \textbf{343} (2014) 396. [Preview Abstract] |
Monday, March 2, 2015 10:12AM - 10:24AM |
A26.00006: Non-adiabatic dynamics in the detachment continuum of radical anions Jan Verlet Using photoelectron (PE) spectroscopy at a range of photon energies above the detachment threshold of a radical anion, the dynamics of resonances can be identified by the appearance of various channels. These include: (i) direct and prompt autodetachment, which appears in the PE spectra at energies that increase linearly with photon energy; (ii) delayed autodetachment, which is shifted to lower kinetic energy and typically does not shift with photon energy; and (iii) thermionic emission from the radical anion ground state which appears as an exponential decay at low very low kinetic energy. Using time-resolved PE spectroscopy, the non-adiabatic dynamics leading to the formation of the ground state anion can be monitored in real time. In some cases, these dynamics occur on timescales that vastly out-compete autodetachment, even at energies of 3 eV above the neutral. The methodology has been applied to a number of quinone-related molecules and provides insights into how electron capture can lead to stable anions, which is of relevance in electron transfer reactions and astrophysics. [Preview Abstract] |
Monday, March 2, 2015 10:24AM - 10:36AM |
A26.00007: Photofragment vector correlations and rotational distributions from ozone dissociation at 266 and 248 nm Michelle Warter, Wei Wei, Simon North Ozone photolysis is very important in the atmosphere and has been studied by many people, but there are still mysteries involved in O3 dissociation. Velocity map ion imaging experiments on O$_{3}$ dissociation at 266 and 248 nm have been performed to reveal these mysteries. The even odd population alternations of the O$_{2}$ rotational distribution and the vector correlations have been studied to determine if there is a dynamical effect on the odd state depletion. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700