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1.
A novel d.c. polarization/self-depolarization study and electret-type effect in AgI are reported. AgI pellets of varying thicknesses,
placed between two blocking (graphite) electrodes, were subjected to an external d.c. potential. A state of complete polarization
was attained within ∼10 min, irrespective of the sample thickness. At this state, the potential difference, developed across
the sample pellet as a result of polarization/accumulation of mobile Ag+ ions at the bulk/negative electrode interface, was measured experimentally. The potential difference, obtained immediately
after the removal of the external d.c. source, has been referred to as ‘instant peak potential (Vp)’. As soon as the external voltage source is switched off, a process of self-depolarization is initiated due to the chemical/self
diffusion of polarized mobile Ag+ ions throughout the bulk. ‘Vp’ gives a direct information regarding the extent of mobile ion concentration (n). ‘Vp’ measurements were carried out as a function of temperature and ‘Log Vp vs 1/T’ variation was compared with the ‘Log n vs 1/T’ Arrhenius plot, reported earlier in an entirely independent study.
The two variations are almost analogous. This, in turn, supported as an earlier assertion that the abrupt conductivity increase
in α-AgI, after β→α-phase transition at ∼147 °C, is predominantly due to the excessive increase in ‘n’. Furthermore, it has
also been revealed that the Ag+ ions play another unique role which led to the existence of ‘persistent polarization’ states in AgI. These states are identical
to the ‘electret-type effects’, observed in a number of dielectric materials. The polarization state persisted for very long
time in ‘thermally stimulated polarized’ sample. A detailed investigation of the persistence/retention of polarization in
the thermally-stimulated-polarized sample is reported. 相似文献
2.
Pierre Delahaye Gilles Ban Dominique Durand A.M. Vinodkumar Christian Le Brun Etienne Liénard Franчois Mauger Oscar Naviliat Jerzy Szerypo Bernard Tamain 《Hyperfine Interactions》2001,132(1-4):475-480
New developments in ion cooling and ion bunching allow the trapping of radioactive ions from a low energy beam, in a very
short time scale and with very good efficiency. The performances of Radio Frequency Quadrupole (RFQ) coolers, recently developed
in several laboratories in Europe and USA, are now better known. In the present study, a RFQ device will be used to inject
6He+ ions in a transparent Paul trap. The ion beam will be delivered by the SPIRAL facility at GANIL. The careful measurement
of the β-recoil ion coincidence spectrum is sensitive to the angular correlation parameter a, which depends on the coupling constants of the weak hamiltonian. It should be equal to −1/3 if the interaction is only of
axial vector type (V-A theory). Deviation from this value would imply a new tensor-like interaction involving a new exchange
boson thus introducing new physics beyond the Standard Model.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Optical absorption, thermoluminescence glow and emission spectra of RbBr:Ca2+ and RbBr:OH− have been studied and analysed. It is observed that both Ca2+ and OH− ions enhance theF-centre concentration.F
Z1 band in RbBr:Ca2+ appears at 1.55 eV. TL glow peak corresponding toF
Z1 centre on analysis gives a trap depth of 0.84 eV. OH− ions in the crystal seem to act as TL ‘killers’. Spectral distribution of emission under the glow peaks shows five bands
around 1.5, 1.8, 2.1, 2.5 and 2.9 eV. Probable models of TL mechanism are suggested to explain the observed TL emission bands. 相似文献
4.
The vortex dynamics at microwave frequencies in YBa2Cu3O7-δ (YBCO) films have been studied. We observe a peak in the microwave (4.88 and 9.55 GHz) surface resistance in some films in
magnetic fields up to 0.8 T. This is associated with the ‘peak-effect’ phenomenon and reflects the order-disorder transformation
of the flux line lattice near the transition temperature. Introduction of artificial pinning centers like columnar defects
created as a result of irradiation with 200 MeV Ag ion (at a fluence of 4×1010 ions/cm2) leads to the suppression of the peak in films previously exhibiting ‘peak effect’. 相似文献
5.
Band mixing calculations have been done for24Ne including the two degenerate prolate and oblate Hartree-Fock states and also some particle-hole excited states in the projection
formalism using an interaction obtained by Preedom and Wildenthal. The energy spectrum agrees very well with the experimental
results as well as the exact shell model calculations. Thus the band mixing calculations provide a good approximation to the
lengthy exact shell-model calcuations. In addition they offer a physical insight into the collective nature of the nucleus
as nuclear states are described in terms of only a few ‘intrinsic’ states. 相似文献
6.
High-resolution spectra of the 0–9, 0–10 and 0–11 bands of theA
2II
u
—X
2II
g
system of (16O18O)+ ion have been studied for their rotational structure. This study enables a direct determination of the Λ-doubling parameters
of theA
2II
u
andX
2II
g
states. The model of ‘pure precession’ explains, though not entirely, the Λ-doubling of theX
2II
a
state as arising out of its interaction with theB
2
Σ
g
− state. The Λ-doubling in theA
2II
u
state was found insignificant. 相似文献
7.
A. Kellerbauer G. Bollen J. Dilling S. Henry F. Herfurth H.-J. Kluge E. Lamour D. Lunney R.B. Moore C. Scheidenberger S. Schwarz G. Sikler J. Szerypo 《Hyperfine Interactions》2001,132(1-4):507-511
With the Penning trap mass spectrometer ISOLTRAP, close to 200 nuclides have already been investigated and their masses determined
with a typical relative precision of δm/m=10−7. Recently, ISOLTRAP's beam preparation system was replaced by an RFQ ion beam cooler and buncher. The principle and the characteristics
of this new beam preparation system will be presented. It is planned to use ions of various carbon clusters C+
n
(n>1) as reference ions for mass measurements. Apart from negligible molecular binding energies, these clusters have masses
that are exact multiples of the unified atomic mass unit. This will allow ISOLTRAP to carry out absolute mass measurements
as well as to investigate possible mass-dependent systematic errors. The results of tests of the production, transport, and
trapping of such carbon clusters will be presented.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Fritz Bosch 《Hyperfine Interactions》2006,173(1-3):1-11
Ion storage rings and ion traps provide the very first opportunity to address nuclear beta decay under conditions prevailing
in hot stellar plasmas during nucleosynthesis, i.e. at high atomic charge states. Experiments are summarized that were performed
in this field during the last decade at the ion storage-cooler ring ESR in Darmstadt. Special emphasis is given to the first
observation of bound-state beta decay, where the created electron remains bound in an inner orbital of the daughter atom.
The impact of this specific ‘stellar’ decay mode for s-process nucleosynthesis as well as for nuclear ‘eon clocks’ is outlined. Finally, a new technique, single-ion decay spectroscopy,
is presented, where one observes two-body beta decay characteristics (i.e. orbital electron capture or bound-state beta decay)
of highly charged, single ions for well-defined nuclear and atomic quantum states of both the mother – and the daughter –
ion. 相似文献
9.
The concept of ‘D-Differentiation’, which, in the context of smooth manifolds, generalises Lie and covariant differentiation, is extended to
R
∞ -supermanifolds under the name of ‘Super D-Differentiation’. This is done by defining new (non-linear) mappings, called ‘μ-mappings’ and by relating their non-linearity to the Leibniz rule that a derivation must satisfy when it acts on a tensor
product. The resulting axiomatics, which is basis-independent and coordinate-free, is then expressed in a general basis (not
necessarily holonomic). Super Lie and Super covariant differentiation are, amongst others, special cases of Super D-Differentiation. In particular, the transformation rules for the connection coefficients and the commutation coefficients
of non-holonomic bases are obtained. These special cases are found to be in agreement with the DeWitt Super covariant and
Super Lie derivatives.
相似文献
10.
V. K. Rai 《Applied physics. B, Lasers and optics》2010,100(4):871-874
Experimental results for variations in the lifetime of excited states of Sm3+ ions incorporated in a glassy system with a ‘refractive index’ have been reported. Increasing content of barium carbonate
in the solid host matrix results in a fairly large variation in its refractive index, which provides a way to determine the
local field effects for ions doped in the solid host material. Measurements are observed to be in disagreement with the virtual
cavity model, while they show a reasonable agreement with the real cavity model. 相似文献
11.
O. Engels L. Beck G. Bollen D. Habs G. Marx J. Neumayr U. Schramm S. Schwarz P. Thirolf V. Varentsov 《Hyperfine Interactions》2001,132(1-4):501-505
SHIPTRAP is an electromagnetic transport and trapping system to provide very clean and cold beams of singly-charged recoil
ions from the SHIP facility at GSI. The different components of the system are currently under development in Munich (gas
cell and extraction RFQ) and GSI (Buncher RFQ and Penning traps)[1]. Design and manufacturing of the prototype buffer gas
cell and the extraction RFQ based on a wide range of simulations have been completed. The results of these simulations together
with the first measurements will be reported.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
13.
N. I. Tarantin 《Hyperfine Interactions》2001,132(1-4):439-446
Data on nuclear masses provide a basis for creating and testing various nuclear models. A tandem system comprised of the U-400M
cyclotron, the COMBAS magnetic separator and the mass spectrometric ion trap of an ‘in-flight capture’ type is considered
as a complex for producing of the short-lived nuclei by heavy ions in fragmentation reactions and for precise mass measurement
of this nuclei. The FLNR plan scientific and technical research includes a project DRIBs for producing accelerated beams of
radioactive nuclear reaction products and photofission fragments. This project proposes also precise mass measurements with
the help of ion trap.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
S. Bagchi P. Prem Kiran M.K. Bhuyan S. Bose P. Ayyub M. Krishnamurthy G.R. Kumar 《Applied physics. B, Lasers and optics》2007,88(2):167-173
We present results on hot electron and energetic ion (keV–MeV) generation from polished and nanostructured metallic surfaces
excited by p-polarized, femtosecond laser pulses in the intensity range of 1×1015–1.5×1017 W cm-2. A clear enhancement in the hard X-ray spectrum from nanoparticle-coated surfaces is observed, indicating ‘hotter’ electron
production in nanoparticle-produced plasma until the intensity of 2×1016 W cm-2 is reached. Contrary to the existing perception, we find that the hotter electrons do not lead to hotter ion emission. The
total ion flux and the ion energy integrated over the 4–1400 keV energy range are found to be enhanced by 50% and 16%, respectively,
for nanostructured targets in comparison to those from polished targets. 55% enhancement in yield is observed for ions at
the lower end of the energy range, while hotter ions are actually found to be suppressed by ∼40%. The surface modulations
present on the nanoparticle-coated targets are observed to reduce the maximum energy of the ions and showed an intensity-dependent
increase in the divergence of the ion beam.
PACS 79.20.Ds; 68.47.De; 61.80.Ba; 61.82.Bg; 42.65.Re 相似文献
15.
Reactions such as 25Al(p,γ)26Si are the key to understand the production of 26g
Al and 26m
Al in our galaxy. Experimental results could provide important constraints on nova nucleosynthesis and modelling where 26Al is believed to be produced. To achieve such measurements, high-intensity and high-purity radioactive beams are required.
However, production targets at ISOL-type facilities such as ISAC at TRIUMF produce high-intensity alkali beams by surface
ionization on hot transfer tubes hampering the measurement of isotopes of interest. To overcome this issue, an ion source
combining a segmented linear radiofrequency quadrupole (RFQ) to a laser ion source is being built. Its main function is to
suppress alkali impurities whilst allowing for fast-release of short-lived isotopes. The beam production method, the RFQ/laser
ion source and the removal of alkali contaminants are discussed in this paper. 相似文献
16.
Facing the difficulties associated with the preparation of crystalline ion beams in heavy ion storage rings we propose two
complementary table top schemes to elucidate fundamental issues like stability criteria for moving ion crystals at low velocities.
One is based on a small radio-frequency quadrupole (RFQ) storage ring, where by laser cooling Mg+ ion crystals at rest were observed, but conceptionally modified with additional acceleration electrodes and manufactured
with highest mechanical precision. The other approach suggested here implies the use of an RFQ ion guide for the lateral confinement
of the ions combined with buffer gas viscous damping, which could lead to an ideal starting condition for first time direct
three-dimensional laser cooling in a single pass arrangement.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Chenxia Li Shiqing Xu Rengguang YeDegang Deng Youjie HuaShilong Zhao Songlin Zhuang 《Physica B: Condensed Matter》2011,406(9):1698-1701
Ho3+/Tm3+/Yb3+ tri-doped glass ceramics with white light emitting have been developed and demonstrated. Pumped by 980 nm laser diode (LD), intensive red, green and blue up-conversions (UC) were obtained. The green emission is assigned to Ho3+ ion and the blue emission is assigned to Tm3+ ion, whereas the red emission is the combination contribution of the Ho3+ and Tm3+ ions. The RGB intensities could be adjusted by tuning the rare-earth ion concentration and pump power intensity. Thus, multicolor of the luminescence, including perfect white light with CIE-X=0.329 and CIE-Y=0.342 in the 1931 CIE chromaticity diagram can be obtained in 0.15 Ho3+/0.2Tm3+/3Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals pumped by a single infrared laser diode source of 980 nm at 500 mW. The up-conversion luminescence mechanism of Yb3+ sensitize Ho3+ and Tm3+ ions and the energy transfer from Ho3+ to Tm3+ in oxy-fluoride silicate glass ceramics were analyzed. 相似文献
18.
19.
Guido Zavattini Encrico Calloni 《The European Physical Journal C - Particles and Fields》2009,62(3):459-466
Low energy non-linear QED effects in vacuum have been predicted since 1936 and have been subject of research for many decades.
Two main schemes have been proposed for such a ‘first’ detection: measurements of ellipticity acquired by a linearly polarized
beam of light passing through a magnetic field and direct light–light scattering. The study of the propagation of light through
an external field can also be used to probe for new physics such as the existence of axion-like particles and millicharged
particles. Their existence in nature would cause the index of refraction of vacuum to be different from unity in the presence
of an external field and dependent of the polarization direction of the propagating light. The major achievement of reaching
the project sensitivities in gravitational wave interferometers such as LIGO and VIRGO has opened the possibility of using
such instruments for the detection of QED corrections in electrodynamics and for probing new physics at very low energies.
We show that it is possible to distinguish between various scenarios of new physics in the hypothetical case of detecting
unexpected values. Considering the design sensitivity in the strain of the near future VIRGO+ interferometer leads to a variable
dipole magnet configuration such that B
2
D≥13000 T2 m
for a ‘first’ vacuum non-linear QED detection. 相似文献
20.
Dip N. Mahato R. H. Pink S. R. Badu R. H. Scheicher Archana Dubey H. P. Saha Lee Chow Mahendra K. Mahanti M. B. Huang T. P. Das 《Hyperfine Interactions》2007,174(1-3):15-20
The LPCTrap facility is coupled to the low-energy beam line LIRAT of the SPIRAL source at GANIL (France). The facility comprises
an RFQ trap for beam preparation and a transparent Paul trap for in-trap decay studies. The system has been tested for several
ion species. The Paul trap has been fully characterized for 6Li+ and 23Na+ ions. This characterization together with GEANT4 simulations of the in-trap decay setup (Paul trap and detection system)
has permitted to predict the effect of the size of the ion cloud on the decay study of 6He+. 相似文献