Mise en évidence de l'oxygène singulet 1Δg a 200 mbar dans une décharge contrôlée par faisceau d'électrons

The radiation from molecular oxygen metastables is observed at visible and infrared wavelengths. The results are quite different from those obtained with a corona discharge.Le rayonnement des métastables de l'oxygène moléculaire est observé dans le visible et l'infrarouge. Les résultats diffèrent nettement de ceux obtenus avec une décharge couronne

Kinetics of species produced by an electron-beam controlled discharge in oxygen at atmospheric pressure

Time evolution of charged species, metastable species and ozone is obtained from a computer code. Some results can be compared with previous experiments.L'évolution dans le temps des espèces chargées, des métastables et de l'ozone est obtenue à l'aide d'un programme de calcul. Certains résultats sont comparés à des expériences antérieures

Fluorescence quantum yield and lifetime of 'red' polydiacetylene chains isolated in their crystalline monomer matrix

The fluorescence yield, eta approximate to 0.30, and Lifetime, tau approximate to 52 ps, of recently discovered 'red' polydiacetylene isolated chains [R. Lecuiller, J. Berrehar, C. Lapersonne-Meyer, M. Schott, Phys. Rev. Lett. 80 (1998) 4068] have been measured at 15 K. These values show that the relaxation scheme of the 'red-chain' exciton is very different from that of the usual 'blue chains', and that excited states of A, symmetry are not present in the optical gap of red chains. Moreover, the radiative lifetime is very short at tau(rad) approximate to 170 ps. (C) 1999 Elsevier Science B.V. All rights reserved

Fluorescence yield and lifetime of isolated polydiacetylene chains: Evidence for a one-dimensional exciton band in a conjugated polymer

The fluorescence lifetime tau and quantum yield eta(f) of isolated red polydiacetylene chains dispersed in their monomer single crystal matrix were measured between 10 and 100 K. tau increases up to 120 ps at 40 K, then rapidly decreases at higher T. eta(f) is a continuously decreasing function of T. The radiative lifetime tau(r) is proportional to rootT in the whole T range studied. This is the expected behavior for a purely one-dimensional system without localization, a behavior which is not usually observed even in semiconductor quantum wires. An order of magnitude of the exciton effective mass m*approximate to0.3 is inferred. The nonradiative lifetime tau(nr) is constant up to 50 K, then decreases exponentially, indicating the opening of a thermally activated decay channel