Femtosecond dynamics

Beil A, Luckhaus D, Quack M and Stohner J 1997 Intramolecular vibrational redistribution and unimolecular reactions concepts and new results on the femtosecond dynamics and statistics in CHBrCIF Ber. Bunsenges. Phys. Chem. 101 311-28... 

Kobayashi T 1994 Measurement of femtosecond dynamics of nonlinear optical responses Modern Noniinear Optics part 3, ed M Evans and S Kielich Adv. Chem. Rhys. 85 55-104... 

Zimdars D, Dadap J I, Eisenthal K B and Heinz T F 1999 Femtosecond dynamics of solvation at the air/water interface Chem. Phys. Lett. 301 112-20... 

Schoenlein R W, Peteanu L A, Wang Q, Mathles R A and Shank C V 1993 Femtosecond dynamics of cis-trans Isomerization In a visual pigment analog Isorhodopsin J. Phys. Chem. 97 12 087-92... 

In a recent experimental study of the femtosecond dynamics of a Diels-Alder reaction in the gas phase it has been suggested that both concerted and stepwise trajectories are present simultaneously It is interesting to read the heated debates between Houk and Dewar on the... 

T. Pauck, R. Hennig, M. Pcnter, U. Lemmer, U. Siegncr, R. F. Malm, U. Scherf, K. Mullen, H. Bassler, E.O. Gobel, Femtosecond dynamics of stimulated emission and photoinduced absorption in a PPP-typc ladder polymer Client. Phys. Lett. 1995, 244, 171. 

Wan C, Fiebig T, Kelley SO et al (1999) Femtosecond dynamics of DNA-mediated electron transfer. Proc Natl Acad Sci USA 96 6014... 

Cheng YM, Pu SC, Yu YC et al (2005) Spectroscopy and femtosecond dynamics of 7-N, N-diethylamino-3-hydroxyflavone. The correlation of dipole moments among various states to rationalize the excited-state proton transfer reaction. J Phys Chem A 109 11696-11706... 

Cheng YM, Pu SC, Hsu CJ et al (2006) Femtosecond dynamics on 2-(2 -hydroxy-4 -diethylaminophenyl)benzothiazole solvent polarity in the excited-state proton transfer. ChemPhysChem 7 1372-1381... 

Gregoire G, Dimicoli I, Mons M, Donder-Lardeux C, Jouvet C, Martrenchard S, Solgadi D (1998) Femtosecond dynamics of TICT state formation in small clusters the dimethyla-minobenzomethyl ester acetonitrile system. J Phys Chem A 102(41) 7896-7902... 

Pal SK, Peon J, Bagchi B, Zewail AH (2002) Biological water femtosecond dynamics of macromolecular hydration. J Phys Chem B 106(48) 12376-12395... 

Recently the two-step decomposition of azomethane was proved in the study of the femtosecond dynamics of this reaction [68]. The intermediate CH3N2 radical was detected and isolated in time. The reaction was found to occur via the occurrence of the first and the second C—N bond breakages. The lifetime of CH3N2 radical is very short, i.e., 70fsec. The quantum-chemical calculations of cis- and /nmv-azomcthanc dissociation was performed [69]. 

Pollard, W. T., and Mathies, R. A. (1992), Analysis of Femtosecond Dynamic Absorption Spectra of Nonstationary States, Ann. Rev. Phys. Chem. 43,497. 

Tamai and Masuhara [26] also worked on NOSH, but in 1-butanol. They could examine femtosecond dynamics for the C—O bond breaking and formation of a primary photo-product X, which formed within 1 psec and had a broad absorption with peaks at 450 and 700 nm. The spectrum of X then evolved, forming a broad merocyanine-type spectrum, which itself evolved with time to form the usual merocyanine spectrum in that solvent after less than 400 psec. The spectral broadening was said to be either due to the formation of a vibrationally hot ground state or to an equilibration between isomeric forms because the spectrum that formed at early times was similar to the spectrum usually obtained in cyclohexane. Tamai s spectra are shown in Fig. 3. 

Steiger et al. (205) suggested the Coni-02- structure based on femtosecond dynamics. Molecular orbital diagrams (24,25) and earlier LCAO-MO-SCF calculations (29) support this assignment. No ab initio or DFT results on the electronic structure of CoP-02 have been reported so far. 

The new generations of experiments are aimed at linking dynamical studies of these and other processes to the function. We have already begun research in this direction. In a recent publication [9] we reported studies of the femtosecond dynamics of an RNA-protein complex and then compared the results with those obtained for in vivo (E. Coli) transcription anti-termination activities. In two other studies we measured the activity of the protein Subtilisin Carlsberg, discussed above, to a substrate, and the role of hydration in interfacial binding and function of bovine pancreatic phospholipase at a substrate site. The goal in all these studies is to relate structures to the dynamics and hopefully to key features of the (complex ) function. 

Following another experimental approach, GWgoire et al [9] have tried to understand the influence of an increasing number of solvent molecules on the femtosecond dynamics of diatomic molecules, including the dimers Nal and Csl. Due to its relative simplicity, the isolated Nal molecule has been studied extensively with pump-probe techniques both experimentally [10], and theoretically [11,12], In this report, we investigate theoretically the femtosecond pump-probe ionization of Nal and Csl when aggregated with a molecule of acetonitrile CH3CN. 

Femtosecond dynamics of the solvated electron in water studied by time-resolved Raman spectroscopy... 

Femtosecond dynamics of excess electrons in a molten Na-NaBr system... 

Figure 9. Femtosecond dynamics of an elementary reaction (I2 — 21) in solvent (Ar) cages. The study was made in clusters for two types of excitation to the dissociative A state and to the predissociative B state. The potentials in the gas phase govern a much different time scale for bond breakage (femtosecond for A state and picosecond for B state). Based on the experimental transients, three snapshots of the dynamics are shown with the help of molecular dynamics simulations at the top. The bond breakage time, relative to solvent rearrangement, plays a crucial role in the subsequent recombination (caging) dynamics. Experimental transients for the A and B states and molecular dynamics simulations are shown.

Figure 13. Femtosecond dynamics of dissociation (Nal) reaction. Bottom Experimental observations of wavepacket motion, made by detection of the activated complexes [Nal] or the free Na atoms. Top Potential energy curves (left) and the exact quantum calculations (right) showing the wavepacket as it changes in time and space. The corresponding changes in bond character are also noted covalent (at 160 fs), covalent/ionic (at 500 fs), ionic (at 700 fs), and back to covalent (at 1.3 ps).

Figure 14. (a) Potential-energy surfaces, with a trajectory showing the coherent vibrational motion as the diatom separates from the I atom. Two snapshots of the wavepacket motion (quantum molecular dynamics calculations) are shown for the same reaction at / = 0 and t = 600 fs. (b) Femtosecond dynamics of barrier reactions, IHgl system. Experimental observations of the vibrational (femtosecond) and rotational (picosecond) motions for the barrier (saddle-point transition state) descent, [IHgl] - Hgl(vib, rot) + I, are shown. The vibrational coherence in the reaction trajectories (oscillations) is observed in both polarizations of FTS. The rotational orientation can be seen in the decay of FTS spectra (parallel) and buildup of FTS (perpendicular) as the Hgl rotates during bond breakage (bottom). 

For exchange reactions, the femtosecond dynamics of bond breaking and bond making were examined in the following system ... 

Figure 15. Femtosecond dynamics of the Br + I2 - Brf + I exchange reaction. Here, the collision complex is long lived, tc = 53 ps. As shown by the molecular dynamics, the [Brill complex is trapped in the transition-state region the reaction may also involve avoided crossings (see text).

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