Polyacetylene nonlinear

The importance of virtual solitons in the ground state to fran -polyacetylene nonlinear zero-point fluctuations, was subsequently developed in detail... 

Two lower states of the frans-(CH) are energetically degenerated as follows from symmetry conditions. Theory shows that electron excitation invariably includes the lattice distortion leading to polaron or soliton formations. If polarons have analogs in the three dimensional (3D) semiconductors, the solitons are nonlinear excited states inherent only to ID systems. This excitation may travel as a solitary wave without dissipation of the energy. So the 1-D lattice defines the electronic properties of the polyacetylene and polyconjugated polymers. 

Nearly thirty papers have been published on the possible polyacetylene applications as nonlinear elements including rectifying cells [105, 128-134] and heterojunctions [135-139]. 

Extensive ir-conjugation is also often associated with enhanced conductivity in organic systems (6). Polyacetylene and polythiophene which in the doped state exhibit very high electrical conductivity also exhibit relative large third-order nonlinear optical effects in... 

Large third order susceptibilities have recently been observed for trans-polyacetylene, heteroaromatic polymers, and poly[p-phenylene vinylene] (4-11). Such nonlinear phenomena in electroactive polymers due to intense laser irradiation has been linked to the photogeneration of charged solitons on time scales of the order 10 s, and values of (3w-w+w+w)—4x 10 esu for... 

Partially substituted derivatives of polyacetylene are synthesized via the ring-opening metathesis polymerization (ROMP) of cyclooctatetraene (COT) and its derivatives. Certain poly-COT derivatives afford soluble, highly conjugated poly acetylenes. These materials exhibit large third-order optical nonlinearities and low scattering losses. 

Kirtman, B., Dykstra C.E. and Champagne B., Major intermolecular effects on nonlinear electrical response in a hexatriene model of solid state polyacetylene. Chem.Phys.Lett (1999) 305 132-138. 

A soliton is a giant solitary wave produced in canals by a cancellation of nonlinear and dispersive effects. The connection between aqueous solitons and tsunamis ("harbor waves") is not definitively established. In "doped" conducting polyacetylene, a neutral soliton is a collective excitation of a polyacetylene oligomer that has amplitude for several adjacent sites [57],... 

In summary, semiconductor polymers such as polyacetylene and polythiophene have experimentally demonstrated nonlinear optical processes (photo-induced absorption, photo-induced bleaching and photo-luminescence) with characteristic time scales in the picosecond range or faster. These phenomena are intrinsic and originate from the instability of these conjugated polymers toward structural distortion. 

Another inherent property of polyacetylene chains, associated with the highly de-locahzed rc-system, is the polarizability in an electromagnetic field. The dipole moment induced by the oscillating electric field of electromagnetic radiation may be expressed as the sum of the hnear polarizabihty and nonlinear higher terms (hy-... 

As to the content of Volume 25, the Editors thank the authors for their contributions, which give an interesting picture of part of the current state of the art of the quantum theory of matter From nonlinear-optical calculations, over a study of ion motion in molecular channels, a treatment of molecular integrals over Gaussian basis functions, and an investigation of soliton dynamics in franr-polyacetylene, to applications of quantum molecular similarity measures. 

Nowadays, the relative importance of the vibrational response in linear and nonlinear processes is clear but does depend on the optical frequencies concerned. The results obtained for polyacetylene chains in the static limit are sketched in Fig. 36.24. 

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