The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform

Cristina Femoni - One of the best experts on this subject based on the ideXlab platform.

  • Anisotropic charge transport in organic single crystals based on Dipolar Molecules
    Organic Electronics, 2008
    Co-Authors: Beatrice Fraboni, R. Dipietro, Antonio Castaldini, Anna Cavallini, Alessandro Fraleoni-morgera, Leonardo Setti, Ivan Mencarelli, Cristina Femoni
    Abstract:

    We studied the anisotropic charge transport properties of solution-grown organic single crystals based on a Dipolar Molecule (4-hydroxy-cyanobenzene) by field effect devices and by spectral photocurrent analyses. Optical excitation differently affects the flow of charge carriers along the two main planar crystal axes, altering the charge transport anisotropy induced by the molecular π-orbitals stacking. We attribute this behaviour to the presence of an intrinsic molecular dipole and to its different orientation within the crystal lattice and we advance a hypothesis on the nature of the observed band of deep trapping states.

  • Anisotropic Charge Transport in Organic Single Crystals Based on Dipolar Molecules
    MRS Proceedings, 2008
    Co-Authors: Beatrice Fraboni, Antonio Castaldini, Anna Cavallini, Leonardo Setti, Ivan Mencarelli, Riccardo Di Pietro, Alessandro Fraleoni, Cristina Femoni
    Abstract:

    We studied the anisotropic charge transport properties of solution-grown organic single crystals based on a Dipolar Molecule 4HCB (4-hydroxy-cyanobenzene) by electrical transport measurements, current-voltage and space charge limited current (SCLC), and by X-ray diffraction analyses. Optical excitation differently affects the flow of charge carriers along the two main planar crystal axis, altering the charge transport anisotropy induced by the molecular π-orbitals stacking. We attribute this behaviour to the presence of an intrinsic molecular dipole and to its different orientation within the crystal lattice. The anisotropy of transport along the three crystallographic directions has been assessed by electrical characterization and correlated to the crystal molecular packing as determined by X-ray analyses.

Tk Bose - One of the best experts on this subject based on the ideXlab platform.

  • ROTATIONAL RELAXATION OF RIGID Dipolar MoleculeS IN NONLINEAR DIELECTRIC SPECTRA
    Physical Review E, 1998
    Co-Authors: Kurt De Smet, Louis Hellemans, J. F. Rouleau, R. Courteau, Tk Bose
    Abstract:

    We present complete nonlinear dielectric spectra for a rigid Dipolar Molecule in dilute solution. The spectra are described theoretically by dispersions of the form as predicted by Coffey and Paranjape [Proc. R. Ir. Acad. 78, 17 (1978)] and by Alexiewicz and Kasprowicz-Kielich [Modern Nonlinear Optics, edited by M. Evans and S. Kielich (Wiley, New York, 1993), Vol. 85, pt. 1, p. 1] and are consistent with linear dielectric measurements.

Alex Brown - One of the best experts on this subject based on the ideXlab platform.

  • carrier envelope phase effects for a Dipolar Molecule interacting with two color pump probe laser pulses
    Physical Review A, 2004
    Co-Authors: Taiwang Cheng, Alex Brown
    Abstract:

    The interaction of a two-level Dipolar Molecule with two laser pulses, where one laser's frequency is tuned to the energy level separation (pump laser) while the second laser's frequency is extremely small (probe laser), is investigated. A Dipolar Molecule is one with a nonzero difference between the permanent dipole moments of the molecular states. As shown previously [A. Brown, Phys. Rev. A 66, 053404 (2002)], the final population transfer between the two levels exhibits a dependence on the carrier-envelope phase of the probe laser. Based on the rotating-wave approximation (RWA), an effective Hamiltonian is derived to account for the basic characteristics of the carrier-envelope phase dependence effect. By analysis of the effective Hamiltonian, scaling properties of the system are found with regard to field strengths, pulse durations, and frequencies. According to these scaling properties, the final-state population transfer can be controlled by varying the carrier-envelope phase of the probe laser field using lasers with weak field strengths (low intensities) and relatively long pulse durations. In order to examine the possible roles of background states, the investigation is extended to a three-level model. It is demonstrated that the carrier-envelope phase effect still persists in a well-defined manner even when neighboring energy levels are present. These results illustrate the potential of utilizing excitation in Dipolar Molecules as a means of measuring the carrier-envelope phase of a laser pulse or if one can manipulate the carrier envelope phase, as a method of controlling population transfer in Dipolar Molecules. The results also suggest that the carrier-envelope phases must be taken into account properly when performing calculations involving pump-probe excitation schemes with laser frequencies which differ widely in magnitude.

  • collision induced absorption in Dipolar Molecule homonuclear diatomic pairs
    SPECTRAL LINE SHAPES: Volume 11 15th ICSLS, 2003
    Co-Authors: Alex Brown, R H Tipping
    Abstract:

    Theoretical expressions for the collision-induced absorption spectra of a Dipolar and a homonuclear diatomic pair are presented. For the Dipolar species, the line strengths and transition frequencies are taken from the HITRAN database, whereas for the homonuclear Molecule, the polarizability matrix elements and spectroscopic parameters are obtained from the literature. As specific examples, we consider the double fundamental vibrational transition in CO2−N2, and the H2O−N2 transition in the region of the nitrogen fundamental. For the former pair, the theoretical results are in good agreement with experimental data. For the latter pair, we show that the collision-induced absorption for high humidity conditions is larger than that of N2−N2 pairs above 2500 cm−11, but for lower wavenumbers, it is much weaker than the measured foreign continuum resulting from the far wings of allowed transitions.

Beatrice Fraboni - One of the best experts on this subject based on the ideXlab platform.

  • Anisotropic charge transport in organic single crystals based on Dipolar Molecules
    Organic Electronics, 2008
    Co-Authors: Beatrice Fraboni, R. Dipietro, Antonio Castaldini, Anna Cavallini, Alessandro Fraleoni-morgera, Leonardo Setti, Ivan Mencarelli, Cristina Femoni
    Abstract:

    We studied the anisotropic charge transport properties of solution-grown organic single crystals based on a Dipolar Molecule (4-hydroxy-cyanobenzene) by field effect devices and by spectral photocurrent analyses. Optical excitation differently affects the flow of charge carriers along the two main planar crystal axes, altering the charge transport anisotropy induced by the molecular π-orbitals stacking. We attribute this behaviour to the presence of an intrinsic molecular dipole and to its different orientation within the crystal lattice and we advance a hypothesis on the nature of the observed band of deep trapping states.

  • Anisotropic Charge Transport in Organic Single Crystals Based on Dipolar Molecules
    MRS Proceedings, 2008
    Co-Authors: Beatrice Fraboni, Antonio Castaldini, Anna Cavallini, Leonardo Setti, Ivan Mencarelli, Riccardo Di Pietro, Alessandro Fraleoni, Cristina Femoni
    Abstract:

    We studied the anisotropic charge transport properties of solution-grown organic single crystals based on a Dipolar Molecule 4HCB (4-hydroxy-cyanobenzene) by electrical transport measurements, current-voltage and space charge limited current (SCLC), and by X-ray diffraction analyses. Optical excitation differently affects the flow of charge carriers along the two main planar crystal axis, altering the charge transport anisotropy induced by the molecular π-orbitals stacking. We attribute this behaviour to the presence of an intrinsic molecular dipole and to its different orientation within the crystal lattice. The anisotropy of transport along the three crystallographic directions has been assessed by electrical characterization and correlated to the crystal molecular packing as determined by X-ray analyses.

Kurt De Smet - One of the best experts on this subject based on the ideXlab platform.

  • ROTATIONAL RELAXATION OF RIGID Dipolar MoleculeS IN NONLINEAR DIELECTRIC SPECTRA
    Physical Review E, 1998
    Co-Authors: Kurt De Smet, Louis Hellemans, J. F. Rouleau, R. Courteau, Tk Bose
    Abstract:

    We present complete nonlinear dielectric spectra for a rigid Dipolar Molecule in dilute solution. The spectra are described theoretically by dispersions of the form as predicted by Coffey and Paranjape [Proc. R. Ir. Acad. 78, 17 (1978)] and by Alexiewicz and Kasprowicz-Kielich [Modern Nonlinear Optics, edited by M. Evans and S. Kielich (Wiley, New York, 1993), Vol. 85, pt. 1, p. 1] and are consistent with linear dielectric measurements.