Inter-molecular relaxation energy

The results derived from Fig s. 5 and 6 are that the inter-molecular relaxation (polarization energy) shifts are essentially uniform for all the molecular cation states i.e., E 1.5 eV... 

Bock and coworkers104 have determined proton spin-lattice relaxation times for N,N-dideuterioaniline in perdeuteriobenzene and perdeuterioaniline solutions as a function of the concentration and temperature at 260-360 K. The activation energies of the intra- and inter-molecular relaxation rates were of similar magnitude, namely 4.5 and 4.4 kcalmol-1. At 293 K, the rotational correlation time of the aniline molecule in infinitely dilute perdeuteriobenzene solution was approximately half that of the partially deuteriated aniline molecule, namely 3.0 x 10-12 and 6.3 x ICC12 s 1, respectively. In infinitely dilute perdeuterioaniline the rotational correlation time of (V,iV-dideuterioaniline was 19 x ICC12 s. ... 

E (inter) = l-2eV (, 2, 5). Therefore the energies of molecular anions (cations) in condensed molecular media are about 2-4eV lower (higher) than the corresponding free-molecule orbitals. Detailed models of the various contributions to the relaxation energy are given elsewhere (, 5, 8). 

The photoinduced creation of an ion or exciton in condensed molecular media causes greater relaxation than in isolated molecules because the induced charge redistribution generates electronic and atomic relaxation in the other constitutents of the medium as well as in the excited molecule itself. The associated intermolecular contributions to the relaxation energy are comparable in magnitude to the intramolecular ones from the molecule itself, i.e., E (inter)=l-2eV, E (inter)=0.leV (4, 6, 10). 

At the same time the phenomenon of fracture reflects, in one way or another, the ultimate limit of deformation in a solid. It thus involves fundamental physical properties of the material such as its inter-atomic bonding, its surface energy and its crystal structure. It also involves crystallographic processes such as slip, stress induced phase transformations and twinning, whilst in molecular solids such as polymers other processes such as molecular relaxation behaviour may predominate. Fracture is clearly of great scientific interest and has attracted the attention of chemists and solid state physicists as well as engineers. 

For the selective enhancement of the wanted reaction channel by laser excitation of the reactands the time span At between photon absorption and completion of the reaction is of fundamental importance. The excitation energy n-hw (n = 1,2,...) pumped by photon absorption into a selected, excited molecular level may be redistributed into other levels by unwanted relaxation processes before the system ends in the wanted reaction channel. It can, for instance, be radiated by spontaneous emission, or it may be redistributed by intramolecular radiationless transitions, due to vibrational or spin-orbit couplings onto many other, nearly degenerated molecular levels which, however, may not lead to the wanted reaction channel. At higher pressures collision-induced intra- or inter-molecular energy transfer may... 

It might be anticipated that the intermolecular relaxation energies would be simply the static polarization energies of a molecular cation in the condepsed medium given, for example, by the Born model of solvation. That such cannot be the case is immediately evident upon noting that nonpolar polystyrene and condensed ethyl-benzene exhibit the same relaxation-energy shifts, E (inter)=1.5eV, polar poly(2-vinyl pyridine) and... 

To analyze these processes in more detail, one should take into account the photoexcitation of the molecule that results in electron, oscillatory, and rotational transitions, followed by different radiative and nonradiative, intramolecular and inter-molecular processes, like luminescence, internal conversion, and intermolecular energy or charge transfer. The oscillatory relaxation times are in the range 10 -10 s, lifetimes of the excited singlet states are lower than 10 s, and the intetmole-cular and intramolecular transitions occur in the time scale of nanoseconds and picoseconds therefore, to investigate these phenomena one needs tools, which allow the experiments to be performed in the time scale of the same order. This became... 

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