研究领域

Bioinorganic Chemistry/Biophysical Chemistry/Chemical Biology/Energy Science/Optics and Imaging/Physical Chemistry/Sustainable Chemistry/Ultrafast Dynamics/Ultrafast Laser Spectroscopy and Chemical Reaction Dynamics

The majority of interesting reactions from a biological, environmental, or engineering perspective occur in fluid condensed phase environments. In such an environment a chemical reaction is controlled by intermolecular interactions with the surrounding solvent bath as well as by the intramolecular Hamiltonian. Interaction with the solvent often results in a situation where reactions are controlled by the competition between intramolecular and intermolecular energy relaxation on time scales ranging from femtoseconds to picoseconds. In the laboratory, state-of-the-art ultrafast lasers and spectroscopic techniques are employed in the observation and control of photoinitiated reactions. These investigations are made possible by the continuing development of tunable femtosecond light sources from the far UV to the near IR, and the development of techniques to precisely control the phase and amplitude of coherent light pulses The principle objectives of the research program in our group are: (1) To develop a detailed understanding of the fundamental processes which govern chemical reaction dynamics in fluid environments. Studies of small molecules permit connections between theoretical calculations and experimental measurements. We are using ultrafast spectroscopy and theoretical modeling to investigate isomerization dynamics in small polyene molecules. (2) To use "designer" light pulses to control chemical reactions in condensed phases. Bond-selective control of chemical reactions has been a long standing goal of modern chemical physics. Early attempts using selective laser excitation were thwarted by fast intramolecular energy redistribution. Now ultrafast laser pulses, optical pulse shaping, and feedback algorithms have been successfully combined to control bond dissociation reactions in simple isolated molecules. We are using coherent sculpted light pulses to control unimolecular bond dissociation, and isomerization reactions in solution. (3) To use short pulses to establish synchronization and study enzyme mechanism in complicated biological systems. Our current investigations are concentrating on the bond-cleavage mechanism in B12 dependent enzymes. this critical system.

近期论文

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Anderson, C. P., Spears, K. G., Wilson, K. R. and Sension R. J., 2013 "Solvent Dependent Branching Between C-I and C-Br Bond Cleavage Following 266 nm Excitation of CH2BrI." Journal of Chemical Physics, v139, 194307. Rury, A. S. and Sension, R. J. 2013 "Broadband Ultrafast Transient Absorption of Iron(III) Tetraphenylporphyrin Chloride in the Condensed Phase." Chemical Physics, v422, 220-228. Arruda, B. C., Peng, J., Smith, B., Spears, K. G., and Sension, R. J. 2013 "Photochemical Ring-Opening and Ground State Relaxation in a-Terpinene with Comparison to Provitamin D3" Journal of Physical Chemistry B, v117(16), 4696-4704. Arruda, B. C., Smith, B., Spears, K. G., and Sension, R. J. 2013 "Ultrafast Ring-Opening Reactions: A Comparison of a-Terpinene, a-Phellandrene, and 7-Dehydrocholesterol with 1,3-Cyclohexadiene." Faraday Discussion v163, 159-171. Rury, A. S., Goodrich, L. E., Galinato, M. G. I., Lehnert, N. and Sension, R. J. 2012 "Ligand Recruitment and Spin Transitions in the Solid-State Photochemistry of Fe(III)TPPCl." Journal of Physical Chemistry A, v116(32) 8321-8333. Petrovic, V. S., Siano, M., White, J. L., Berrah, N., Bostedt, C., Bozek, J. D., Broege, D., Chalfin, M., Coffee, R. N., Cryan, J., Fang, L., Farrell, J. P., Frasinski, L. J., Glownia, J. M., Guehr, M., Hoener, M., Holland, D., Kim, J., Marangos, J. P., Martinez, T., McFarland, B. K., Minns, R. S., Miyabe, S., Schorb, S., Sension, R. J., Spector, L. S., Squibb, R., Tao, H., Underwood, J. G., Bucksbaum, P. H., 2012 "Transient x-ray fragmentation: Probing a prototypical photoinduced ring opening" Physical Review Letters, v108, 253006. White, J. L., Carroll, E. C., Spears, K. G., and Sension, R. J. 2012 "Extracting information from adaptive control experiments." Israel Journal of Chemistry, v52, 397-406. Tang, K.-C. and Sension, R. J. 2011 "The influence of the optical pulse shape on excited state dynamics in provitamin D3." Faraday Discussion, v153, 117-129. Tang, K.-C., Rury, A. S., Orozco, M. B., Egendorf, J., Spears, K. G., and Sension, R. J. 2011 "Ultrafast electrocyclic ring-opening of 7-dehydrocholesterol in solution: The influence of solvent on excited state dynamics." Journal of Chemical Physics, v134(10), 104503. Tang, K.-C., Rury, A., Peng, J., Spears, K. G., and Sension, R. J. 2011 "Excited State Dynamics in Provitamin D3: A New Twist for the Cyclohexadiene Chromophore." Ultrafast Phenomena XVII, eds. M. Chergui, D. M. Jonas, E. Riedle, R. Schoenlein, A. J. Taylor, Oxford: Oxford University Press, p. 421-423. Peng, J. And Sension, R. J. 2011 , "Ultrafast Excited-State Dynamics and Photochemistry of Base-off Alkylcobalamins." Ultrafast Phenomena XVII, eds. M. Chergui, D. M. Jonas, E. Riedle, R. Schoenlein, A. J. Taylor, Oxford: Oxford University Press, p. 499-501. Peng, J., Tang, K.-C., McLoughlin, K., Yang, Y., Forgach, D., and Sension, R.J. 2010 "Ultrafast excited-state dynamics and photolysis in base-off B12 coenzymes and analogs: Absence of the trans-nitrogenous ligand opens a channel for rapid nonradiative decay." Journal of Physical Chemistry B, v114(38) 12398-12405. Tang, K.-C., Peng, J., Spears, K. G., and Sension, R. J., 2010 "Photoinitiated bond dissociation in bromoiodomethane: Comparison of one-photon and two-photon excitation and the formation of iso-CH2Br-I and iso-CH2I-Br in solution." Journal of Chemical Physics v132(14) 141101. Stickrath, A., Carroll, E. C., Dai, X., Harris, D. A., Rury, A., Smith, B., Tang, K.-C., Wert, J. and Sension, R. J., 2009 "Solvent dependent cage dynamics of small nonpolar radicals: Lessons from the photodissociation and geminate recombination of alkylcobalamins." Journal of Physical Chemistry A v113 (30) 8513-8522. Florean, A. C., Cardoza, D., White, J. L., Lanyi, J. K., Sension, R. J. and Bucksbaum, P. H., 2009 "Control of retinal isomerization in bacteriorhodopsin in the high intensity regime." Proceedings of the National Academy of Science, USA, v106 (27) 10896-10900. Florean, A. C., Cardoza, D., White, J. L., Sension, R. J., and Bucksbaum, P. H. 2009 "Coherent Control of Retinal Isomerization in Bacteriorhodopsin in the High Intensity Regime" Ultrafast Phenomena XVI , eds. P. Corkum, S. De Silvestri, K. Nelson, E. Riedle, R. Schoenlein, Berlin: Springer-Verlag p. 430-432. Carroll, E. C., White, J. L., Florean, A. C., Bucksbaum, P. H., and Sension, R. J. 2008, "Multiphoton Control of the 1,3-Cyclohexadiene Ring-Opening Reaction in the Presence of Competing Solvent Reactions" Journal of Physical Chemistry A, v112 (30) 6811-6822 (Feature Article). Carroll, E. C., Florean, A. C., Bucksbaum, P. H., Spears, K. G., and Sension, R. J. 2008, "Phase control and the competition between electronic transitions in a solvated laser dye" Chemical Physics, v350, 75-86. Harris, D. A., Stickrath, A. B., Carroll, E. C., and Sension, R. J., 2007, "The influence of environment on the electronic structure of cob(III)alamins: Time-resolved absorption studies of the S1 state spectrum and dynamics." Journal of the American Chemical Society, v129 (24) 7578-7585. Sension, R. J., 2007, "Quantum path to photosynthesis" News and Views, Nature, v. 446, 740-741.