Search results for "MTO"

Snapshot imaging of postpulse transient molecular alignment revivals

2008

Laser induced field-free alignment of linear molecules is investigated by using a single-shot spatial imaging technique. The measurements are achieved by femtosecond time-resolved optical polarigraphy (FTOP). Individual alignment revivals recorded at high resolution in ${\text{CO}}_{2}$, as well as simultaneous observation of several alignment revivals produced within the rotational period of the ${\text{O}}_{2}$ molecule are reported. The data are analyzed with a theoretical model describing the alignment experienced by each molecule standing within the interaction region observed by the detector. The temporal dynamics, intensity dependence, and degree of alignment are measured and compare…

Femtosecond Raman time-resolved molecular spectroscopy

2004

International audience; The applicability of several femtosecond time resolved non-linear coherent techniques such as Raman induced polarization spectroscopy (RIPS), degenerate four-wave mixing (DFWM) and coherent anti-Stokes Raman spectroscopy (CARS) for molecular spectroscopy is presented. All methods rely on the initial coherent excitation of molecular states producing wavepackets, whose time evolution is then measured. In the case of RIPS and DFWM only pure rotational transitions are involved, whereas in CARS vibrational states can be excited. First the methodology of concentration and temperature measurements using RIPS in gas mixtures involving N2, CO2, O2, and N2O is shown. In additi…

Experimental demonstration and numerical study of plasmon-soliton waves

2019

Merging the fields of plasmonics and nonlinear optics authorizes a variety of fascinating and original physical phenomena. In this work, we specifically study the combination of the strong light confinement ability of surface plasmon polaritons (SPP) with the beam self-trapping effect in a nonlinear optical Kerr medium. Although this idea of plasmon-soliton has been the subject of numerous theoretical papers since the eighties [1–4], up to now, no experimental evidence had been revealed yet. In the present study, a proper structure (Fig. 1a) has been designed and fabricated allowing the first experimental demonstration of these hybrid nonlinear waves merging spatial solitons and SPP. To be …

High speed cleaving of crystals with ultrafast Bessel beams

2017

International audience; We develop a novel concept for ultra-high speed cleaving of crystalline materials with femtosecond lasers. Using Bessel beams in single shot, fracture planes can be induced nearly all along the Bessel zone in sapphire. For the first time, we show that only for a pulse duration below 650 fs, a single fracture can be induced in sapphire, while above this duration, cracks appear in all crystallographic orientations. We determine the influential parameters which are polarization direction, crystallographic axes and scanning direction. This is applied to cleave sapphire with a spacing as high as 25 μm between laser impacts.

Charge-transfer driven by ultrafast spin-transition in a CoFe Prussian blue analogue

2020

Photoinduced charge-transfer is an important process in nature and technology and is responsible for the emergence of exotic functionalities, such as magnetic order for cyanide-bridged bimetallic coordination networks. Despite its broad interest and intensive developments in chemistry and material sciences, the atomic-scale description of the initial photoinduced process, which couples intermetallic charge-transfer and spin transition, has been debated for decades; it has been beyond reach due to its extreme speed. Here we study this process in a prototype cyanide-bridged CoFe system by femtosecond X-ray and optical absorption spectroscopies, enabling the disentanglement of ultrafast electr…

Thérapies ciblées et diabète

2017

Les étangs des Vosges comtoises

1989

Entre les vallées de l'Ognon et du Breuchin, le fort justement nommé Plateau des Mille Étangs constitue un milieu naturel et humain original à bien des égards. Compartiment du vieux socle primaire, affaissé ici en touches de piano, il offre une topographie, qui, de la ligne de faîte dominant la vallée de la Moselle au Nord, s'incline doucement vers le Sud, en direction de la dépression sous-vosgienne à laquelle il se raccorde insensiblement entre Lureet Luxeuil. Érodé au cours des temps géologiques par de longues phases de planation, dont les plus anciennes traces appartiennent à la surface post-hercynienne exhumée en maints endroits de sa couverture sédimentaire secondaire, il présente une…

Les migrations des étudiants francs-comtois vers les universités limitrophes

2001

La mobilité géographique des étudiants est un phénomène d'intérêt régional. Pourquoi va t-on étudier dans telle université, pour la qualité ou l' originalité de ses formations, pour la richesse culturelle de la ville qui l'héberge?

Collective Modes and Structural Modulation in Ni-Mn-Ga(Co) Martensite Thin Films Probed by Femtosecond Spectroscopy and Scanning Tunneling Microscopy.

2015

International audience; The origin of the martensitic transition in the magnetic shape memory alloy Ni-Mn-Ga has been widely discussed. While several studies suggest it is electronically driven, the adaptive martensite model reproduced the peculiar nonharmonic lattice modulation. We used femtosecond spectroscopy to probe the temperature and doping dependence of collective modes, and scanning tunneling microscopy revealed the corresponding static modulations. We show that the martensitic phase can be described by a complex charge-density wave tuned by magnetic ordering and strong electron-lattice coupling.

Les artistes comtois au temps de Hugues Sambin

2015

National audience