O. Benoist d'Azy

Université Paris-Sud 11, Orsay, Île-de-France, France

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Publications (8)13.76 Total impact

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    ABSTRACT: The fluorescence properties of two biaryl donor-acceptor compounds (4-dimethylamino-4′-cyanobiphenyl (DMACNB) and 4-dimethyl-anilino-1-cyanonaphthalene (DMACNN)) were compared in solvents of different polarity. Low temperature, steady state spectra were also studied in non-polar and polar media. The transient Stokes shifts measured with 30 ps excitation in 1-propanol and 1-hexanol at room temperature show that the charge transfer process is controlled by the dynamics of solvation. A large decrease in the radiative rate constant as a function of the solvent polarity and as a function of time in 1-hexanol solution was observed for DMACNN, whereas this effect was not significant in the case of DMACNB. These differences have been related to the larger steric hindrance to coplanarity in the phenylnaphthalene derivative with respect to that in the substituted biphenyl.
    Journal of Photochemistry and Photobiology A Chemistry 08/1995; 89(3):191-199. · 2.29 Impact Factor
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    ABSTRACT: Polycrystalline clean Mg has been bombarded by 5 keV Kr+ ions under few 10−6 Torr ultra pure oxygen partial pressure. The well resolved optical spectrum of molecular sputtered particles observed in the 480–501 nm region is attributed to the MgO B1Σ → X1ΣΔv = 0 transition. Computer simulations allow the determination of rotational and vibrational temperatures Trot = 1750 K and Tvib = 5000 K for the sputtered MgO molecules. The previous reported emission in the 480–520 nm region was observed only with contaminated oxygen.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/1993; · 1.19 Impact Factor
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    ABSTRACT: We have observed the time dependence of the motion of the atoms in a van der Waals complex (HgAr). This motion leads to direct dissociation or corresponds to vibrations in the potential well. The time evolution is similar to that observed in the femto-second domain for chemically bound molecules, i.e. it leads to appearance of transients and vibrational recurrences. In softening the potentials, the characteristic time for the movements of the atoms is slowed down to the picosecond. We have observed and analyzed the direct dissociation and the vibrational recurrences in the B potential well.
    Chemical Physics Letters 12/1992; · 1.99 Impact Factor
  • Source
    Laser Chemistry 01/1992;
  • Y. H. Meyer, O. Benoist D'Azy, M. M. Martin, E. Bréhéret
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    ABSTRACT: The spectral dependence of intensity transients is studied in a multimode pulsed dye laser. It is shown by numerical integration that damping of relaxation oscillations varies as a function of frequency. This new result is discussed in relation to the conceot of spectro-temporal evolution previously introduced and recently applied to short pulse generation.
    Optics Communications 10/1986; 60:64-68. · 1.54 Impact Factor
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    ABSTRACT: Resolved time spectra and decay curves of triptophan in polar solvents have been obtained and examined using the previous results for indol and NMI in the same solvents. Triptophan time resolved fluorescence ant its decay curves were different when the sample was fluid (room temperature) and when it was “glassy” (low temperature). Decay curves depending on frequency were obtained in fluid solutions, meanwhile for “glassy” samples did not appear such dependence. The similar results previously obtained for indole and NMI, were interpreted assuming the reorientation of the solvent dipole moments as a time-depending phenomenum during fluorescence.
    Journal of Molecular Structure 03/1986; 143:313–316. · 1.60 Impact Factor
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    ABSTRACT: The electronic states of the Hg–Ar complex have been studied in a supersonic free jet expansion using a laser double resonance technique. Detailed observations were made of the states correlating with the mercury 6 3P levels 3P0, 3P1, and 3P2. The states correlating with the 3P0 and 3P2 metastable states had not been studied previously since they are optically inaccessible from the ground state. A model was developed which accounts for the structures of the various states. The binding energies can be related simply to the average orientation of the 6p mercury orbital with respect to the internuclear axis. In addition, the Hg(7 3S1)–Ar Rydberg state was reinvestigated and shown conclusively to exhibit a double minimum potential, with a deep well similar to the Hg–Ar+ ion and a shallow van der Waals minimum at larger internuclear distances.
    The Journal of Chemical Physics 01/1986; 85:6324-6334. · 3.12 Impact Factor
  • O. Benoist^D'azy, F. Lahmani, C. Lardeux, D. Solgadi
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    ABSTRACT: The vibrational and rotational state distributions of the NO X 2Π fragment resulting from photodissociation of cis-CH3ONO excited in specific NO stretching vibrational levels of the neπ* state at 364, 350, 338, 328 and 318 nm have been determined. The NO X ν″ = 0, 1, 2, 3, 4 probed by two-photon laser-induced fluorescence exhibits a large amount of rotational excitation which is independent of the excitation wavelength. The NO X vibrational population varies with the vibrational level prepared in the parent excited molecule and the results show that the excess vibrational energy deposited in the N0 stretching mode of the CH3ONO nπ* state is retained in the vibration of the free NO fragment. The rotational excitation is interpreted in terms of interfragment ccupling due to the impulse applied to the recoiling fragments. The vibrational distribution is more likely to be explained by a simple model based on intrafragment coupling which takes into account the change in N0 bond length between the ground and dissociative state of the molecule.
    Chemical Physics 03/1985; 94:247-256. · 2.03 Impact Factor