We present the results of time-resolved luminescence studies of poly[2-methoxy, 5-(2′-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV), as a pure film, in solution, in a gel formed by a network of ultrahigh molecular weight polyethylene (UHMW-PE), and in a blend with UHMW-PE. The luminescence has a characteristic lifetime of 200–300 ps at room temperature, increasing to 500–700 ps when the materials are cooled to 80 K; the decay time is approximately the same for all the physical forms of the material (solution, film, gel, blend). The relatively short lifetimes, compared to intrinsic values calculated from absorption and emission spectra, and the observed temperature dependence indicate that the luminescence decay is quenched by nonradiative processes. The time decay of the photoluminescence deviates from a single exponential for most forms of the MEH-PPV. Best fits to stretched exponential and double exponential expressions are presented. Steady state photoluminescence spectra and integrated luminescence vs pump intensity data are presented in order to establish which of the possible mechanisms are most important.

Degenerate ground-state conjugated polymers exhibit large third-order nonlinear optical susceptibilities, including substantial two-photon absorption. With the use of a machine architecture suited to these material properties, ultrafast optical processors are possible. A four-wave mixing optical correlator was built with an air-stable, processable, degenerate ground-state conjugated polymer, poly(1,6-heptadiester). The continuously updatable processor correlates two 5000-pixel images in less than 160 femtoseconds, achieving peak processing rates of 3 x 10(16) operations per second.

Articles you may be interested inInterpretations of XeI and XeBr bound-free emission spectra and reactive quenching of Xe(3 P 2) atoms by bromine and iodine containing molecules Absorption and emission spectra of matrixisolated XeF, KrF, XeCl, and XeBrThe strong ultraviolet emission bands ("Spectrum I") of XeBr, XeI, and KrF have been photographed following electron-beam excitation of appropriate noble gas/halide mixtures at moderate to high pressures. These diffuse spectra are analyzed through trial-and-error theoretical simulations. The upper-state vibrational frequencies are estimated to be 120± 10, 112±8, and 31O±20 cm-I for XeBr, XeI, and KrF, respectively. The analysis also yields approximate shapes for the lower-state potential curves in the Franck-Condon region. Lasing is observed in XeBr (2818 A) and KrF (2484,2491 A) but not in Xel.

B→X spontaneous and stimulated emission spectra of XeF have been photographed at medium resolution (2.0 Å/mm) and vibrationally analyzed. The assignments are made with the aid of trial-and-error Franck–Condon calculations and band profile simulations, which are described in detail. The strong laser emission near 3511 Å is primarily due to densely overlapped rotational lines in the 1–4 vibronic band, and that near 3532 Å probably includes numerous rotational transitions in the 0–2, 0–3, and 1–6 bands.

Using an axial electron-beam excitation scheme to excite mixture of argon, krypton, and fluorine, 108 J of laser energy, corresponding to a peak power of 1.9×109 W, was obtained from KrF at 2484 Å. In addition, ArF was observed to lase at 1933 Å with a maximum energy output of 92 J, corresponding to a power of 1.7×109 W. The maximum energy for KrF was obtained with total gas pressures of 1400 Torr using 4 Torr of fluorine and partial pressures of krypton greater than 100 Torr. When the partial pressure of krypton was less than 100 Torr both ArF and KrF were observed to laser simultaneously.

We have observed two new emission features in electron-beam-excited mixtures of molecular fluorine with either neon or helium. One feature is a continuum centered at 1080 Å which we attribute to NeF*. The other emission feature is a band system extending from 1500–1600 Å which we attribute to a transition of molecular fluorine. This transition lased near 1575 Å.

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