72 research outputs found
Investigation of slow collisions for (quasi) symmetric heavy systems: what can be extracted from high resolution X-ray spectra
We present a new experiment on (quasi) symmetric collision systems at
low-velocity, namely Ar ions ( a.u.) on gaseous Ar and N
targets, using low- and high-resolution X-ray spectroscopy. Thanks to an
accurate efficiency calibration of the spectrometers, we extract absolute X-ray
emission cross sections combining low-resolution X-ray spectroscopy and a
complete determination of the ion beam - gas jet target overlap. Values with
improved uncertainty are found in agreement with previous results
\cite{Tawara2001}. Resolving the whole He-like Ar Lyman series from
to 10 with our crystal spectrometer enables to determine precisely the
distribution of the electron capture probability and the
preferential level of the selective single-electron capture.
Evaluation of cross sections for this process as well as for the contribution
of multiple-capture is carried out. Their sensitivity to the
-distribution of levels populated by single-electron capture is
clearly demonstrated, providing a stringent benchmark for theories. In
addition, the hardness ratio is extracted and the influence of the decay of the
metastable state on this ratio is discussed
Characterization of a CCD array for Bragg spectroscopy
The average pixel distance as well as the relative orientation of an array of
6 CCD detectors have been measured with accuracies of about 0.5 nm and 50
rad, respectively. Such a precision satisfies the needs of modern crystal
spectroscopy experiments in the field of exotic atoms and highly charged ions.
Two different measurements have been performed by illuminating masks in front
of the detector array by remote sources of radiation. In one case, an aluminum
mask was irradiated with X-rays and in a second attempt, a nanometric quartz
wafer was illuminated by a light bulb. Both methods gave consistent results
with a smaller error for the optical method. In addition, the thermal expansion
of the CCD detectors was characterized between -105 C and -40 C.Comment: Submitted to Review of Scientific Instrument
Suppression of the thermal hysteresis in magnetocaloric MnAs thin film by highly charged ion bombardment
We present the investigation on the modifications of structural and magnetic
properties of MnAs thin film epitaxially grown on GaAs induced by slow highly
charged ions bombardment under well-controlled conditions. The ion-induced
defects facilitate the nucleation of one phase with respect to the other in the
first-order magneto-structural MnAs transition with a consequent suppression of
thermal hysteresis without any significant perturbation on the other structural
and magnetic properties. In particular, the irradiated film keeps the giant
magnetocaloric effect at room temperature opening new perspective on magnetic
refrigeration technology for everyday use
Relativistic calculations of pionic and kaonic atoms hyperfine structure
We present the relativistic calculation of the hyperfine structure in pionic
and kaonic atoms. A perturbation method has been applied to the Klein-Gordon
equation to take into account the relativistic corrections. The perturbation
operator has been obtained \textit{via} a multipole expansion of the nuclear
electromagnetic potential. The hyperfine structure of pionic and kaonic atoms
provide an additional term in the quantum electrodynamics calculation of the
energy transition of these systems. Such a correction is required for a recent
measurement of the pion mass
High Resolution He-like Argon And Sulfur Spectra From The PSI ECRIT
We present new results on the X-ray spectroscopy of multicharged argon,
sulfur and chlorine obtained with the Electron Cyclotron Resonance Ion Trap
(ECRIT) in operation at the Paul Scherrer Institut (Villigen, Switzerland). We
used a Johann-type Bragg spectrometer with a spherically-bent crystal, with an
energy resolution of about 0.4 eV. The ECRIT itself is of a hybrid type, with a
superconducting split coil magnet, special iron inserts which provides the
mirror field, and a permanent magnetic hexapole. The high frequency was
provided by a 6.4 GHz microwave emitter. We obtained high intensity X-ray
spectra of multicharged F-like to He-like argon, sulfur and chlorine with one
1s hole. In particular, we observed the 1s2s^{3}S_1 \to 1s^2^{1}S_0 M1 and
1s2p^{3}P_2 \to 1s^2^{1}S_0 M2 transitions in He-like argon, sulfur and
chlorine with unprecedented statistics and resolution. The energies of the
observed lines are being determined with good accuracy using the He-like M1
line as a reference
Magnetic properties changes of MnAs thin films irradiated with highly charged ions
We present the first investigation on the effect of highly charged ion
bombardment on a manganese arsenide thin film. The MnAs films, 150 nm thick,
are irradiated with 90 keV Ne ions with a dose varying from
to ions/cm. The structural and
magnetic properties of the film after irradiation are investigated using
different techniques, namely, X-ray diffraction, magneto-optic Kerr effect and
magnetic force microscope. Preliminary results are presented. From the study of
the lattice spacing, we measure a change on the film structure that depends on
the received dose, similarly to previous studies with other materials.
Investigations on the surface show a strong modification of its magnetic
properties
Primary processes: from atoms to diatomic molecules and clusters
International audienceThis article presents a short review of the main progresses achieved at the GANIL facilities during the last thirty years in the field of ion-atom and ion-diatomic molecule collisions. Thanks to the wide range of projectile energies and species available on the different beam lines of the facility, elementary processes such as electron capture, ionization and excitation have been extensively studied. Beside primary collision mechanisms, the relaxation processes of the collision partners after the collision have been another specific source of interest. Progresses on other fundamental processes such as Young type interferences induced by ion-molecule collisions or shake off ionization resulting from nuclear beta decay are also presented. 1. Introduction For the electronic structures of atoms and molecules, precise theoretical knowledge and high-resolution experimental data are available. But the complete understanding of dynamic processes in atomic collisions remains a challenge, due to large theoretical problems in describing time-dependent many-particle reactions, and to experimental difficulties in performing complete experiments in which all relevant quantities are accessible. Elementary collisions involving ions, atoms and molecules play an important role in many gaseous and plasma environments, where they provide both the heating and cooling mechanisms. The study of such collisions is thus not only of fundamental importance, it is also essential for the understanding of large-scale systems such as astrophysical plasmas, planetary atmospheres, gas discharge lasers, semiconductor processing plasmas, and fusion plasmas. Collisions between ions and atoms (or simple molecules) give also access to the elementary processes responsible for energy transfer in ion-matter and ion-biological molecule collisions. Complete knowledge of these elementary processes is thus of primordial importance for ion induced modification of materials as well as for radiolysis, radiotherapy and biological damages due to radiation exposure
Conditional probability and interferences in generalized measurements with or without definite causal order
International audienceIn the context of generalized measurement theory, the Gleason-Busch theorem assures the unique form of the associated probability function. Recently, in Flatt et al. Phys. Rev. A 96, 062125 (2017), the case of subsequent measurements has been treated, with the derivation of the Lu ̈ders rule and its generalization (Kraus update rule). Here we investigate the special case of subsequent measurements where an intermediate measurement is a composition of two measurements (a or b) and the case where the causal order is not defined (a and b or b and a). In both cases interference effects can arise. We show that the associated probability cannot be written univocally, and the distributive property on its arguments cannot be taken for granted. The two probability expressions correspond to the Born rule and the classical probability; they are related to the intrinsic possibility of obtaining definite results for the intermediate measurement. For indefinite causal order, a causal inequality is also deduced. The frontier between the two cases is investigated in the framework of generalized measurements with a toy model, a Mach-Zehnder interferometer with a movable beam splitter
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