Search results for "Quantum"

Temporal coherence in mirrorless optical parametric oscillators

2012

International audience; One of the unique features of mirrorless optical parametric oscillators based on counterpropagating three-wave interactions is the narrow spectral width of the wave generated in the backward direction. In this work, we in- vestigate experimentally and numerically the influence that a strong phase modulation in the pump has on the spectral bandwidths of the parametric waves and on the efficiency of the nonlinear interaction. The effects of group-velocity mismatch and group-velocity dispersion are elucidated. In particular, it is shown that the substan- tial increase in temporal coherence of the backward-generated wave can be obtained even for pumping with a temporally…

Fano-resonances in High Index Dielectric Nanowires for Directional Scattering

2018

High refractive index dielectric nanostructures provide original optical properties thanks to the occurrence of size- and shape-dependent optical resonance modes. These modes commonly present a spectral overlap of broad, low-order modes (\textit{e.g}. dipolar modes) and much narrower, higher-order modes. The latter are usually characterized by a rapidly varying frequency-dependent phase, which - in superposition with the lower order mode of approximately constant phase - leads to typical spectral features known as Fano resonances. Interestingly, such Fano resonances occur in dielectric nanostructures of the simplest shapes. In spheroidal nanoparticles, interference between broad magnetic di…

Quantum dynamics of the oxygen isotopic exchange : lifetimes of metastable states of the ozone intermediate complex

2021

This thesis aims to describe the ozone dynamics during the isotopic exchange reactions of oxygen of type xO + yO zO (xO yO zO)* xO yO + zO, where x, y and z are the atomic masses of the stable oxygen isotopes (16, 17, 18). Firstly, we analyze several methods of accurate description of the atom interactions and numerical schemes to obtain the observables for the collision. Then, in a full-quantum hyperspherical formalism, we study the actual dynamics of the reactive process O + O2 -> O3* -> O2 + O. The metastable ozone created can then either decompose into oxygen by the inverse reaction, or relax into stable ozone by exchanging energy with the environment, typically N2 or O2 molecules. Thes…

Negatively Curved Nanographene with Heptagonal and [5]Helicene Units

2020

Negatively curved nanographene (NG) 4, having two heptagons and a [5]helicene, was unexpectedly obtained by aryl rearrangement and stepwise cyclodehydrogenations. X-ray crystallography confirmed the saddle-shaped structures of intermediate 3 and NG 4. The favorability of rearrangement over helicene formation following radical cation or arenium cation mechanisms is supported by theoretical calculations. NG 4 demonstrates a reversible mechanochromic color change and solid-state emission, presumably benefiting from its loose crystal packing. After resolution by chiral high-performance liquid chromatography, the circular dichroism spectra of enantiomers 4-(P) and 4-(M) were measured and showed …

Algebraic Study of XYn Molecules in Vibrationaly High Excited States

2008

Vibrational resonances in XYn non planar molecules: local versus normal modes formalism.

2007

L'influence de la nanosolvation sur la stabilité des peptides à l'étude du gaz

2013

ATOM-WALL COLLISIONS INFLUENCE ON DARKLINE ATOMIC RESONANCES IN SUBMICRON THIN VAPOUR CELLS.

2010

Recently it was demonstrated that miniaturization of alkali cells, i.e. the use of an extremely thin cell (ETC) for the applications using the electromagnetically induced transparency (EIT) effect, despite to intuitive expectation, does not cause a strong broadening of the dark-line (DL) linewidth. Here we present the conditions when a strong broadening of DL linewidth (more than by 10 times) can be easily observed due to atom-wall collisions influence and this could be a convenient and robust tool for atomwall (i.e. ETC's window material/temperature) collisions study. We present experimental and theoretical results on EIT realized in a Λ- system of 85Rb, D2 line, 5S-5P-5S for a Rb vapour c…

Landau‐Zener transition for association of an atomic Bose‐Einstein condensate with interparticle elastic interactions included.

2008

Qauntum control of molecular rotation and of processes in Nuclear Magnetic Resonance

2019

The goal of this thesis is to apply quantum control techniques to manipulate molecular rotation and to enhance the efficiency of processes in Nuclear Magnetic Resonance.These techniques have been used theoretically and experimentally to control the orientation of a symmetric top molecule by means of THz laser fields. This study has been extended to the case of a long interaction distance between the field and the sample. In this case, the molecule cannot be approximated as isolated. We have also shown the extend to which the time evolution of the degree of orientation can be shaped. Optimal control techniques were used to design the THz field which allows to reach the corresponding dynamics…