Search results for "Excitation"
showing 10 items of 1290 documents
Shape Coexistence in the Neutron-Deficient Even-EvenHg182−188Isotopes Studied via Coulomb Excitation
2014
Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0(+) states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0(+) state was noted in Hg-182; 184. The results are compared to beyond mean field and interacting-boson based models and i…
Soliplasmon excitations at metal/dielectric/Kerr structures
2009
We present novel optical phenomena based on the existence of a new type of quasi-particle excitation in metal/dielectric/Kerr structures. We discuss the possibility of excitation of surface plasmon polaritons via spatial solitons in these systems.
Lifetime of the 4D 3/2 and 4D 5/2 metastable states in Sr II
1987
Sr+ ions were confined in a r.f. quadrupole trap for times of the order of 30 min. The metastable 4D states were populated via laser excitation of the 5P states. The weak quadrupole transition rate into the 5S 1/2 ground state at 674 and 687 nm was deduced from observation of the exponential decay. At background pressures above 10−7 mbar the radiative decay is dominated by collisional quenching. Extrapolation of the observed decay rate to zero background pressure yields the radiative lifetimes. At pressures around 10−6 mbar fine structure mixing collisions between the 4D states have been observed, which lead to corrections of the extrapolated lifetimes. As the final result we obtain 395±38 …
Zones of soft and hard self-excitation in gyrotrons: Generalized approach
2020
It is known that the gyrotron theory is developed in a general form that allows one to draw many important conclusions about gyrotron operation, which are valid for gyrotrons operating in arbitrary modes, at arbitrary frequencies, and driven by electron beams with different voltages and currents. One of important issues in this theory is the analysis of possible start-up scenarios, i.e., the methods allowing, first, to excite the desired mode prior to competitors in the region of soft self-excitation of this mode and, then, drive it into the zone of hard self-excitation where, as a rule, the operation with high efficiency is possible. So far, in all studies, these zones of soft and hard sel…
Studies of pear-shaped nuclei using accelerated radioactive beams
2013
There is strong circumstantial evidence that certain heavy, unstable atomic nuclei are ‘octupole deformed’, that is, distorted into a pear shape. This contrasts with the more prevalent rugby-ball shape of nuclei with reflection-symmetric, quadrupole deformations. The elusive octupole deformed nuclei are of importance for nuclear structure theory, and also in searches for physics beyond the standard model; any measurable electric-dipole moment (a signature of the latter) is expected to be amplified in such nuclei. Here we determine electric octupole transition strengths (a direct measure of octupole correlations) for short-lived isotopes of radon and radium. Coulomb excitation experiments we…
Exploring the Physical Limits of Saturation Contrast in Magnetic Resonance Imaging
2012
International audience; Magnetic Resonance Imaging has become nowadays an indispensable tool with applications ranging from medicine to material science. However, so far the physical limits of the maximum achievable experimental contrast were unknown. We introduce an approach based on principles of optimal control theory to explore these physical limits, providing a benchmark for numerically optimized robust pulse sequences which can take into account experimental imperfections. This approach is demonstrated experimentally using a model system of two spatially separated liquids corresponding to blood in its oxygenated and deoxygenated forms.
Single Ion Thermal Wave Packet Analyzed Via Time-Of-Flight Detection
2021
Abstract A single 40Ca ion is confined in the harmonic potential of a Paul trap and cooled to a temperature of a few mK, with a wave packet of sub-μm spatial and sub-m s−1 velocity uncertainty. Deterministically extracted from the Paul trap, the single ion is propagating over a distance of 0.27 m and detected. By engineering the ion extraction process on the initial wave packet, theoretically modeling the ion trajectories, and studying experimentally the time-of-flight distribution, we directly infer the state of the previously trapped ion. This analysis allows for accurate remote sensing of the previous motional excitation in the trap potential, both coherently or incoherently. Our method …
Random quasi-phase-matched second-harmonic generation in periodically poled lithium tantalate
2010
We observe second harmonic generation via random quasi-phase-matching in a 2.0 micron periodically poled, 1-cm-long, z-cut lithium tantalate. Away from resonance, the harmonic output profiles exhibit a characteristic pattern stemming from a stochastic domain distribution and a quadratic growth with the fundamental excitation, as well as a broadband spectral response. The results are in good agreement with a simple model and numerical simulations in the undepleted regime, assuming an anisotropic spread of the random nonlinear component. (C) 2010 Optical Society of America
Experimental Investigation of Random Vibration Control Through Dry Friction
1997
The purpose of this experimental investigation is to measure the response statistics in the presence of base friction and other friction sources. The experimental model emulates a one-floor building supported on four leaf springs, subjected to band limited random excitation. Two different types of model base are considered, a friction base and a frictionless base. In both cases friction can also be applied at two sides of the model’s main mass against the direction of its motion. Excitation and response transducer signals are processed to estimate excitation and response statistics in the presence and in the absence of top mass friction. Measured statistics include mean squares, autocorrela…
A Novel Method for the Measurement of Half-Lives and Decay Branching Ratios of Exotic Nuclei
2019
A novel method for simultaneous measurement of masses, Q-values, isomer excitation energies, half-lives and decay branching ratios of exotic nuclei has been demonstrated. The method includes first use of a stopping cell as an ion trap, combining containment of precursors and decay-recoils for variable durations in a cryogenic stopping cell (CSC), and afterwards the identification and counting of them by a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). Feasibility has been established by recording the decay and growth of $^{216}$Po and $^{212}$Pb (alpha decay) and of $^{119m2}$Sb (t$_{1/2}$ = 850$\pm$90 ms) and $^{119g}$Sb (isomer transition), obtaining half-lives and bran…