Search results for "EXCITATION"
showing 10 items of 1290 documents
"Safe" Coulomb excitation of 30Mg.
2004
We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient $\gamma$ -spectrometer MINIBALL. Using $^{30}$Mg ions accelerated to an energy of 2.25MeV/u together with a thin $^{nat}$Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative de-excitation $\gamma$ -ray yields the B(E2; 0$^{+}_{gs} \rightarrow 2^{+}_{1}$) value of $^{30}$Mg was determined to be 241(31)$e^{2}$fm$^{4}$. Our result is lower than values obtained at projectile fragmenttion facilities using the intermediate-ene…
Local detection of the optical magnetic field in the near zone of dielectric samples
2000
International audience; We present a study of the influence of the probe composition on the formation of constant-height photon scanning tunneling microscope images when observing a dielectric sample. Dramatic effects due to the metallization of the tip are presented and discussed in detail. We show how the recorded images can look quite different when the probe is dielectric or coated with gold. Comparison with numerical calculations indicate that the experimental signals are of electric or magnetic nature depending on the composition of the tip. For well-defined conditions, gold-coated tips provide images of the distribution of the magnetic field intensity associated with the optical near…
Dielectric-loaded surface plasmon-polariton waveguides at telecommunication wavelengths: Excitation and characterization
2008
International audience; The excitation and propagation of strongly confined surface plasmon-polariton (SPP) waveguide modes, supported by 500-nm-wide and 550-nm-high dielectric ridges fabricated on smooth gold films, are investigated at telecommunication wavelengths using a scanning near-field optical microscope. Different tapering structures for coupling of SPPs, excited at bare gold surfaces, into dielectric-loaded SPP waveguide (DLSPPW) modes are considered. The DLSPPW mode confinement and propagation loss are characterized. The DLSPPW mode propagation along an S bend having the smallest curvature radius of 2.48 mu m is shown, demonstrating the potential of DLSPPW technology for the real…
Modèles quantiques à deux états avec croisements de niveaux décrits par les fonctions de Heun
2019
The thesis is devoted to the fundamental problem of excitation and manipulation of quantum systems, having discrete energy spectrum, via external laser fields. We examine the semiclassical time- dependent quantum two-state problem, when the external electromagnetic field is resonant or quasi-resonant for some two of many levels of the system. The focus of the thesis is on the analytic description of the non- adiabatic evolution of quantum systems subject to excitation by level-crossing field configurations. In the present thesis we classify the complete set of the semiclassical time-dependent quantum two-state models solvable in terms of the five function of the Heun class.Main results of t…
Revised Analysis of the Structure of the v1 Band of Methane
1983
Abstract The CARS spectrum of the v 1 band of 12 CH 4 at a pressure of 14 mbar was recorded using cw excitation in the cavity of a ring argon ion laser. The analysis of the intensity profile of the obarred spectrum led to the detection of inconsistencies with the hitherto proposed calculated positions of transitions with J = 7 to J = 10 and to a relocation of the corresponding lines.
Discontinuity induced angular distribution of photon plasmon coupling
2011
Metal-dielectric transitions are important structures that can display a host of optical characteristics including excitation of plasmons. Metal-dielectric discontinuities can furthermore support plasmon excitation without a severe condition on the incident angle of the exciting photons. Using a semi-infinite thin gold film, we study surface plasmon (SP) excitation and the associated electromagnetic near-field distribution by recording the resulting plasmon interference patterns. In particular, we measure interference periods involving SPs at the scanable metal/air interface and the buried metal/glass one. Supported by optical near-field simulations and experiments, we demonstrate that the …
Specificity and Sensitivity Characterization of a Gallium Arsenide Resonant Bio-Sensor
2018
International audience; The characterization of the performances of a Gallium Arsenide (GaAs) based biosensor, in terms of sensitivity and specificity, is reported. The design of the sensor consists in a resonant membrane fabricated in GaAs crystal that operates at shear modes of bulk acoustic waves generated by lateral field excitation. The transducer element was fabricated by using typical clean room microfabrication techniques. The backside of the membrane is functionalized by a self-assembled monolayer (SAM) of alkanethiols to immobilize bio-receptors, which will allow the specific capture of the analyte of interest. The theoretical sensitivity of the sensor had been determined by model…
On the measurement and prediction of the sound absorption coefficient of air-cavity backed perforated plates considering the holes interaction effect…
2012
International audience; This paper deals with the measurement and prediction of air cavity backed perforated plates considering the holes interaction effect under relatively low sound excitation. A revised expression for the radiation contribution is proposed to properly account for the holes interaction effect. This expression is integrated in the characteristic impedance expression following Atalla and Sgard [J. Sound Vib. 303, 195-208 (2007)] model. Perforated plate specimens with different centre-to-centre holes distances (pitches) are built and tested using an impedance tube. The particular cases of holes interaction effect with constant low porosity and of holes interaction effect wit…
Sound absorption coefficient of a porous material covered with a low open area perforated plate under high sound excitation
2012
International audience; The sound absorption coefficient of porous materials covered with low open area perforated plate is studied under high sound intensities in the absence of mean flow. The theoretical considerations are based on the equivalent fluid following the Johnson-Champoux-Allard approach and the use of the transfer matrix method. To take into account the high sound levels effects, the air flow resistivity of each layer is modified following the Forchheimer law. Two specimens of perforated plate are built and tested when backed by a polymeric foam and a fibrous material. A specific impedance tube setup is developed for the measurement of the surface acoustic impedance for sound …
Penning-trap-assisted study of excitations in $^{88}$Br populated in β decay of $^{88}$Se
2017
Excited levels of 88Br populated in the β decay of 88Se have been studied by means of βγ and γ γ spectroscopy methods. Neutron-rich parent 88Se nuclei were produced with proton-induced fission of 238U using the Ion Guide Isotope Separator On-Line (IGISOL) method and separated from contaminants using a dipole magnet and the coupled JYFLTRAP Penning trap at the Accelerator Laboratory of the University of Jyvaskyl ¨ a. The level scheme ¨ of 88Br has been constructed and log f t values of levels were determined. The ground-state spin of 88Br is now firmly determined to be 1−. Low-energy levels in 88Br were interpreted as members of the πp3/2(νd5/2) 3, πp−1 3/2(νd5/2) 3, πf −1 5/2 (νd5/2) 3, and…