Search results for "Metas"
showing 10 items of 1693 documents
Quantum Stochastic Resonance in a Micromaser
1998
We demonstrate that quantum stochastic resonance allows for the noise-controlled synchronization of quantum jumps between the metastable states of the quantized radiation field in a micromaser. Under readily accessible experimental conditions optimal synchronization is achieved at a finite temperature $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}500\mathrm{mK}$ of the environment.
Many-particle dynamics and intershell effects in Wigner molecules
2011
We apply classical molecular dynamics within the velocity Verlet algorithm to examine the formation dynamics of Wigner crystals in two-dimensional harmonic oscillators. Using a large ensemble of initial conditions as well as different freezing mechanisms, we obtain reliable information on the energies and probabilities of stable and metastable configurations, their formation dynamics, and their stability. Wigner-crystal configurations of up to 30 particles are presented and the dynamics of transition processes, e.g., intershell effects, are analyzed.
Scaling and mean-field-like behaviour in phase separation processes
1985
Extensive Monte Carlo calculations are used to study the still not well understood process of phase separation in binary systems. The results show that for a separation dominated by long-wavelength fluctuations a mean-field description holds in certain concentration regions. This, however, is only true for short times after the system has been brought into a non-equilibrium state. A crucial parameter is the interaction range. It determines the region and the time where the mean field description is valid. At later times the structure factor exhibits dynamical scaling. Scaling is also investigated for the metastable states. The results are applicable to polymer blends with long chains or bin…
Enhanced nuclear Schiff moment in stable and metastable nuclei
2019
Nuclei with static intrinsic octupole deformation or a soft octupole vibrational mode lead to strongly enhanced collective nuclear Schiff? moments. Interaction between electrons and these Schiff moments produce enhanced time reversal (T) and parity (P) violating electric dipole moments (EDM) in atoms and molecules. Corresponding experiments may be used to test CP-violation theories predicting T,P-violating nuclear forces and to search for axions. Nuclear octupole deformations are predicted in many short lived isotopes. This paper investigates octupole deformations in stable and very long lifetime nuclei such as 153Eu, 235U, 237Np and 227Ac, which can ease atomic experiments substantially. T…
Nuclear structure “southeast” ofPb208: Isomeric states inHg208andTl209
2009
The nuclear structure of neutron-rich N>126 nuclei has been investigated following their production via relativistic projectile fragmentation of a E/A=1 GeV U-238 beam. Metastable states in the N=128 isotones Hg-208 and Tl-209 have been identified. Delayed gamma-ray transitions are interpreted as arising from the decay of I-pi=(8(+)) and (17/2(+)) isomers, respectively. The data allow for the so far most comprehensive verification of the shell-model approach in the region determined by magic numbers Z 126.
Isotope shift of182Hg and an update of nuclear moments and charge radii in the isotope range181Hg-206Hg
1986
The technique of collinear fast-beam laser spectroscopy has been used to measure the isotope shifts of the even-even isotopes of Hg (Z=80) in the mass range 182≤A≤198 at the on-line mass separator ISOLDE at CERN. The atomic transition studied (6s 6p 3 P 2- 6s7s 3 S 1,λ=546.1 nm) starts from a metastable state, which is populated in a quasi resonant charge transfer process. The resulting changes in nuclear mean square charge radii show clearly that182Hg follows the trend of the heavier, even, weakly oblate isotopes. Correspondingly the huge odd-even shape staggering in the light Hg isotopes continues and the nuclear shape staggering and shape coexistence persists down to the last isotope inv…
Spectroscopy of excited state positronium
1994
Electric dipole transitions in the microwave range have been induced between the fine-structure levels of positronium in the excited staten=2. As an indication of the transitions, we used the increase in Lyman-α radiation when the metastable 23S1-level is depopulated. The results for the transitions 23S1→23P0,1,2 areΝ 0=18499.65±1.20±4.00 MHz,Ν 1=13012.42 ±0.65±1.54 MHz andΝ 2=8624.38±0.54±1.40 MHz. The first error is statistical and the second systematic. The precision of the present measurement has improved by a factor of 3, compared to previous data. Recent bound state QED-calculations have been extended to the orderR t8 α 4lnα −1. The not yet completely calculated orderR t8 α 4 is estim…
A dense polarized 3He target based on compression of optically pumped gas
1992
Abstract 3 He-gas is spin polarized by the method of optical pumping of metastables and metastability exchange in a low pressure gas discharge. At a pressure of p ≈ 1.5 Torr a volume of 1 l is polarized within about 30 s to a degree of 50% with 300 mW of incident light from an argon-ion laser pumped LNA laser, tuned to the λ = 1.083 μm resonance line. The polarized gas is compressed by a Toepler pump into a target cell of 120 cm 3 volume. In a first attempt a steady state polarization of 30% has been achieved in the target at a pressure of 685 Torr. The paper analyses the essential parameters governing this technique and pilotes its experimental realization.
A highly polarized target for the electron beam at MAMI
2009
Abstract Polarized He 3 from metastability exchange optical pumping (MEOP) is used as an effective polarized neutron target for electron scattering experiments at the MAinz MIcrotron (MAMI). With the present setup an initial polarization of up to 72% has been obtained at the experimental area. A novel calibration technique will be presented which allows the determination of the absolute polarization within a relative uncertainty of 3%.
Determination of helium number densities in high-frequency electrodeless plasma
2010
Abstract The number densities of He first excited states 2 3 S 1 , 2 1 S 0 , 2 3 P 0,1,2 , and 2 1 P 0 were measured by absorption and self-absorption methods. The emission lines in the range 290–730 nm were used to determine the number densities of He metastable and resonant states of inductively coupled high-frequency electrodeless lamps filled with helium at pressure 0.1 Torr. The obtained number densities of helium metastable levels 2 3 S 1 and 2 1 S 0 are 2×10 12 and 3×10 11 cm −3 , respectively. For the 2 3 P 0,1,2 and 2 1 P 0 levels the determined number densities are ten times smaller than that of the metastable levels. Values of number densities from measurements using both method…