Femtosecond time scale rearrangement

The closed cycle of interconversions occurs on an ultrafast time scale. Femtosecond studies (95CPL35) of the ESIPT rearrangement of 347 (R = Me) (commercial name Tinuvin-P) carried out over a wide spectral range... 

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.

Femtosecond photoionization mass spectrometry might be useful in the study of the three-dimensional structure of large biomolecules. When a selectively excitable and ionizable chromophore is located on the outer (surface) part of large molecule, one can be detached in the picosecond time scale. However, when the excitable chromophore is located in the inner part of the big molecule, its detachment will require a much longer time, which is needed for spatial rearrangement of the molecule. So, even the simple mass spectrometry of bioorganic molecules with femtosecond laser ionization can reveal some details of their spatial structure. 

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