期刊
JOURNAL OF CHEMICAL PHYSICS
卷 116, 期 9, 页码 3834-3840出版社
AMER INST PHYSICS
DOI: 10.1063/1.1447908
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We present a study on the ultrafast third-order nonlinearities of a novel series of iso-polydiacetylene oligomers (iso-PDAs). Unlike polydiacetylenes that contain a linearly-conjugated backbone, iso-PDAs have a backbone that is cross-conjugated. A new Kerr-gate technique, differential optical Kerr effect (DOKE) detection, is used to measure third-order nonlinear susceptibilities, chi((3)), and second hyperpolarizabilities, gamma, of monomer, dimer, trimer, pentamer, and heptamer samples in tetrahydrofuran (THF) solutions. A linear increase in gamma as a function of the number of repeat units is observed for all samples except the monomer, suggesting that the fixed-length linearly conjugated segments dominate the electronic polarizability. An added increase to the oligomer nonlinearities due to communication along the cross-conjugated path is not observed. The largest nonlinearity was observed in the heptamer sample, displaying a second hyperpolarizability relative to the THF solvent of gamma(heptamer)/gamma(THF)=181+/-9. In addition, an interesting feature arising out of the signal decay tail is present in the samples but absent in our THF solvent reference. (C) 2002 American Institute of Physics.
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