Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session P26: Focus Session: Quantum Control III |
Hide Abstracts |
Sponsoring Units: DCP Chair: Vlasta Bonacic-Koutecky, Humboldt-Universität zu Berlin Room: Morial Convention Center 218 |
Wednesday, March 12, 2008 8:00AM - 8:36AM |
P26.00001: Use of Ultrafast Molecular Dynamics and Optimal Control for Identifying Biomolecules Invited Speaker: With F.COURVOISIER,L.GUYON,V.BOUTOU, and M.ROTH,J. ROSLUND, H. RABITZ, Princeton University. The identification and discrimination of molecules that exhibit almost identical structures and spectra using fluorescence spectroscopy is considered quite difficult. In order to evaluate the capability of optimal control for discriminating between the optical emissions of nearly identical molecules, we developed a new approach called ``optimal dynamic discrimination (ODD). A proof of principle ODD experiment has been performed using Riboflavin (RBF) and Flavin Mononucleotide (FMN) as model system. We used a complex multipulse control field made of a pair of pulses (UV and IR). The UV part (400 nm) is optimally shaped using a control learning loop while the IR component (800 nm) is FT-limited (100 fs) and set at a definite time delay with respect to the UV pulse. Clear discrimination was observed for optimally shaped pulses, although the linear spectra from both molecules are virtually identical. A further experiment showed that, by using the optimal pulse shapes that maximize the fluorescence depletion in FMN and RBF in a differential manner, the concentration of both molecules could be retrieved while they were mixed in the same solution. The ODD demonstration sets out a promising path for future applications, as for example fluorescence microscopy where endogenous fluorescence spectra of many biomolecules overlap. [Preview Abstract] |
Wednesday, March 12, 2008 8:36AM - 9:12AM |
P26.00002: Spinning Tops in External Fields. From High Harmonic Generation to Control of Transport in the Nanoscale Invited Speaker: Nonadiabatic alignment is a coherent approach to control over the spatial properties of molecules, wherein a short, moderately- intense laser pulse is applied to populate a broad rotational wavepacket with fascinating properties. In the limit of small isolated molecules, nonadiabatic alignment has evolved in recent years into an active field of theoretical and experimental research with a rich variety of applications. Following a brief review of the essential physics underlying nonadiabatic alignment, we discuss one of these applications, namely the use of high harmonics generated from aligned molecules as a probe of the underlying electronic dynamics and rotational coherences. Next, we extend the alignment concept to dissipative media, including dense gases, solutions, and interfaces. We illustrate the application of rotational wavepackets as a probe of the dissipative properties of dense media and propose a means of disentangling population relaxation from decoherence effects via strong laser alignment. We extend alignment to control the torsional motions of polyatomic molecules, and apply torsional control in solutions to manipulate charge transfer events, suggesting a potential route to light controlled molecular switches. Turning to interfaces, we introduce a route to guided molecular assembly, wherein laser alignment is extended to induce long-range orientational order in molecular layers. Finally, we combine the nonadiabatic alignment concept with recent research on nanoplasmonics and on conductance via molecular junctions to develop an approach to optical control of transport in the nanoscale. [Preview Abstract] |
Wednesday, March 12, 2008 9:12AM - 9:48AM |
P26.00003: Enhancing vibrational selectivity and 2D IR spectroscopies with mid-IR pulse shaping Invited Speaker: We report on the capabilities of a new pulse shaper that operates directly in the mid-infrared. This shaper can adjust the phase and amplitudes of 500 frequency elements to generate complex time-domain pulses. In this talk, experiments will be reported using this shaper to coherently control the vibrational excitations of condensed phase molecules with adaptive learning feedback control. We will also report how this shaper can be used to collect two-dimensional infrared (2D IR) spectra by programming the pulse sequences. 2D IR spectroscopy via pulse shaping is extremely rapid, highly accurate, and more flexible than traditional means for collecting spectra. Taken together, mid-IR pulse shaping allows for new experiments in ground state coherent control and probing vibrations with unprecedented accuracy using new multidimensional spectroscopies. [Preview Abstract] |
Wednesday, March 12, 2008 9:48AM - 10:00AM |
P26.00004: Combined Dimensionality Reduction in Search and Detection Spaces via Diffusion Mapping Dmitri Romanov, Stanley Smith, John Brady, Ronald Coifman, Robert Levis Strong-field control settings involve highly nonlinear processes. Typically, both search and detection spaces are high-dimensional (with dimension $\sim $100 each). This poses considerable problems to analysis and interpretation of the process-related data. Here, we use the recently developed nonlinear statistical method of diffusion mapping to effectively reduce the combined dimensionality of the search and detection space and to sample essential patterns in the lower-dimensional representation. The diffusion maps are constructed and analyzed for the case study of maximizing integrated intensity in a second harmonic generation experiment. The use of a sampling set of 1000 random pulses in the diffusion mapping is sufficient for effective dimensionality reduction and for revealing the inherent structure of the process-related data. Extrapolation of the low-dimensional diffusion-space pattern helps indicate the area in the search space that is most amenable to effective optimization. The diffusion-mapping algorithm is sufficiently fast and robust that may make it a valuable preprocessing tool for optimal pulse searching. [Preview Abstract] |
Wednesday, March 12, 2008 10:00AM - 10:12AM |
P26.00005: Selective Rotational Manipulations of Close Molecular Species -- isotopes and isomers Yehiam Prior, Sharly Fleischer, Ilya Sh. Averbukh We experimentally demonstrate a new approach to selective excitation of close molecular species in mixtures. We apply two time delayed, ultrashort laser pulses where the first pulse rotationally excites both components in a binary mixture, and the second pulse de-excites one, while enhancing the excitation degree of the other. In our work we implemented this approach to molecular nitrogen, and study the cases of molecular isotopes and molecular spin isomers. The case of molecular isotopes is based on the mass difference between the molecular components which results in a slightly different revival period of the repetitive alignment that follows excitation by an ultrashort pulse. Following the revival process, one can distinguish between the isotopic components and selectively affect them. The case of spin isomers is more complicated since there are no differences in their mechanical or electrical properties. Here we utilize the symmetry and statistics of the specific molecular wavefunction and demonstrate highly selective ($\sim $18:1) excitation of Ortho/Para nitrogen. Numerical simulations agree very well with the observed results. Since this process is nonresonant and does not require any special conditions like temperature etc. this approach is general and can be applied to most symmetric molecules. [Preview Abstract] |
Wednesday, March 12, 2008 10:12AM - 10:24AM |
P26.00006: Anti-Correlated Pigment Fluctuations of Allophycocyanin for Highly Efficient Photosynthetic Light Harvesting in Cyanobacteria Andrew Moran, Rene Nome, Norbert Scherer The phycobiliprotein, allophycocyanin (APC), is an excellent model system for the study of light harvesting pigment interactions with a protein bath. This work investigates the relaxation of electronic excitations in APC with electric field-resolved transient grating and photon echo spectroscopies. Transient grating experiments observe a 35 fs internal conversion process between single exciton levels. Most importantly, our analysis shows that anti-correlated phycocyanobilin pigment energy level fluctuations cause the anti-diagonal orientation of the node in the measured dispersive photon echo spectrum. We believe this novel observation to reflect concerted protein bath fluctuations over the 2 nm length scale that separates the pigments. Consideration of the Forster energy transfer rate theory suggests that APC has evolved with this property to enhance its photosynthetic light harvesting efficiency. [Preview Abstract] |
Wednesday, March 12, 2008 10:24AM - 10:36AM |
P26.00007: ABSTRACT WITHDRAWN |
Wednesday, March 12, 2008 10:36AM - 10:48AM |
P26.00008: Understanding the relaxation of excited-state cis-1,3,5-hexatriene in order to augment the preferred pathway for control Michael Orozco, Kuo-Chun Tang, Roseanne Sension A study of the ground and excited-state relaxation of cis-1,3,5-hexatriene in various solvents and temperatures has been performed. The role solvent plays in the relaxation dynamics and relaxation pathways has been assessed and modeled to achieve a better understanding of the energy landscape. This information will be used to determine the preferred relaxation pathways and inform efforts to use sculpted UV pulses to influence the excited state dynamics through pump-dump interactions. Finally, further experiments are proposed wherein UV pulse-shaping will used to study and control other reactive systems. [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