28 research outputs found
Polarization sensitive spectroscopy of charged Quantum Dots
We present an experimental and theoretical study of the polarized
photoluminescence spectrum of single semiconductor quantum dots in various
charge states. We compare our high resolution polarization sensitive spectral
measurements with a new many-carrier theoretical model, which was developed for
this purpose. The model considers both the isotropic and anisotropic exchange
interactions between all participating electron-hole pairs. With this addition,
we calculate both the energies and polarizations of all optical transitions
between collective, quantum dot confined charge carrier states. We succeed in
identifying most of the measured spectral lines. In particular, the lines
resulting from singly-, doubly- and triply- negatively charged excitons and
biexcitons. We demonstrate that lines emanating from evenly charged states are
linearly polarized. Their polarization direction does not necessarily coincide
with the traditional crystallographic direction. It depends on the shells of
the single carriers, which participate in the recombination process.Comment: 11 pages, 9 figures. Revised versio
Dissociation of the benzene molecule by UV and soft X-rays in circumstellar environment
Benzene molecules, present in the proto-planetary nebula CRL 618, are ionized
and dissociated by UV and X-ray photons originated from the hot central star
and by its fast wind. Ionic species and free radicals produced by these
processes can lead to the formation of new organic molecules. The aim of this
work is to study the photoionization and photodissociation processes of the
benzene molecule, using synchrotron radiation and time of flight mass
spectrometry. Mass spectra were recorded at different energies corresponding to
the vacuum ultraviolet (21.21 eV) and soft X-ray (282-310 eV) spectral regions.
The production of ions from the benzene dissociative photoionization is here
quantified, indicating that C6H6 is more efficiently fragmented by soft X-ray
than UV radiation, where 50% of the ionized benzene molecules survive to UV
dissociation while only about 4% resist to X-rays. Partial ion yields of H+ and
small hydrocarbons such as C2H2+, C3H3+ and C4H2+ are determined as a function
of photon energy. Absolute photoionization and dissociative photoionization
cross sections have also been determined. From these values, half-life of
benzene molecule due to UV and X-ray photon fluxes in CRL 618 were obtained.Comment: The paper contains 8 pages, 9 figures and 4 tables. Accepted to be
published on MNRAS on 2008 November 2
Examples of Jahn-Teller Coupling Effects in Molecular Spectroscopy and Internal Conversion Dynamics*
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Determination of the range of slow electrons in solid polymethylmethacrylate by means of fluorescence measurements
The distance travelled by a photoelectron of low energy in an anthracene-doped polymer is very weakly dependent on its initial kinetic energy. 2 refs., 1 fig
Conical Diffraction Based Super-resolution System for Fluorescence Microscopy: System Description and Demonstration visualizing Biological Objects
Double photoionization processes in complex organic molecules : cases of Benzene
SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : RM 1619 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Single and double photoionization of aromatics : a comparative study of C(6)H(6) isomers between 25 and 70 eV
SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : RM 1094 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc