共查询到20条相似文献,搜索用时 31 毫秒
1.
G. Stancari S. N. Atutov R. Calabrese L. Corradi A. Dainelli C. de Mauro A. Khanbekyan E. Mariotti P. Minguzzi L. Moi S. Sanguinetti L. Tomassetti S. Veronesi 《The European physical journal. Special topics》2007,150(1):389-392
Francium is one of the best candidates for atomic parity
nonconservation (APNC) and for the search of permanent electric
dipole moments (EDMs). APNC measurements test the weak force
between electrons and nucleons at very low momentum transfers. They
also represent a unique way to detect weak nucleon-nucleon
interactions. EDMs are instead related to the time-reversal
symmetry. Preliminary to these fundamental measurements are
precision studies in atomic spectroscopy and the development of
magneto-optical traps (MOT), which partially compensate for the lack
of stable Fr isotopes. At LNL Legnaro, francium is produced by
fusion of 100-MeV 18O with 197Au in a thick target,
followed by evaporation of neutrons from the compound nucleus.
Francium diffuses inside the hot target (1200 K) and is surface
ionized for injection at 3 keV in an electrostatic beamline.
Typically, we produce 1×106 (210Fr ions)/s for a
primary flux of 1.5×1012 particles/s. We have studied
Fr yields as a function of primary beam energy, intensity, and
target temperature. Information on the efficiency of bulk
diffusion, surface desorption and ionization is deduced. The beam
then enters a Dryfilm-coated cell, where it is neutralized on a
heated yttrium plate. The escape time of neutral Fr (diffusion +
desorption) is approximately 20 s at 950 K, as measured with a
dedicated setup. In the MOT, we use 6 orthogonal Ti:sapphire laser
beams for the main pumping transition and 6 beams from a stabilized
diode repumper. Fluorescence from trapped atoms is observed with a
cooled CCD camera, in order to reach noise levels from stray
light equivalent to approximately 50 atoms. Systematic tests are
being done to improve the trapping efficiency. We plan to further
develop Fr traps at LNL; in parallel, we will study APNC and EDM
techniques and systematics with stable alkalis at Pisa, Siena, and
Ferrara. 相似文献
2.
Nuclear magnetic moments provide a sensitive test of nuclear wave functions, in particular those of neutrons, which are not
readily obtainable from other nuclear data. These are taking added importance by recent proposals to study parity non-conservation
(PNC) effects in alkali atoms in isotopic series. By taking ratios of the PNC effects in pairs of isotopes, uncertainties
in the atomic wave functions are largely cancelled out at the cost of knowledge of the change in the neutron wave function.
The Bohr–Weisskopf effect (B–W) in the hyperfine structure interaction of atoms measures the influence of the spatial distribution
of the nuclear magnetization, and thereby provides an additional constraint on the determination of the neutron wave function.
The added great importance of B–W in the determination of QED effects from the hfs in hydrogen-like ions of heavy elements,
as measured recently at GSI, is noted. The B–W experiments require precision measurements of the hfs interactions and, independently,
of the nuclear magnetic moments. A novel atomic beam magnetic resonance (ABMR) method, combining rf and laser excitation,
has been developed for a systematic study and initially applied to stable isotopes. Difficulties in adapting the experiment
to the ISOLDE radioactive ion beam, which have now been surmounted, are discussed. A first radioactive beam measurement for
this study, the precision hfs of 126Cs, has been obtained recently. The result is 3629.515(∼0.001) MHz. The ability of ABMR to determine with high precision nuclear
magnetic moments in free atoms is a desideratum for the extraction of QED effects from the hfs of the hydrogen-like ions.
We also point out manifestations of B–W in condensed matter and atomic physics.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
G.D. Sprouse S. Aubin E. Gomez J.S. Grossman L.A. Orozco M.R. Pearson M. True 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):239-242
The alkali element francium has a simple electronic structure, and copious amounts of a wide range of isotopes can be produced
in present and future rare isotope facilities. The atomic parity violating weak interaction in Fr is 18 times larger than
in Cs, which makes it one of the best candidates to search for the effects of the weak interaction and its isotopic dependence.
Atomic trapping methods now offer new ways to study these atoms with precision, and we will discuss some of our recent measurements
with trapped Fr atoms. Future measurements of the spin-independent weak interaction can be used to test the standard model,
but advances in atomic theory and improved understanding of the neutron distribution in nuclei are needed to make progress.
We have made precise hyperfine-anomaly measurements in Fr and have shown that they are sensitive to the radial distribution
of the neutron magnetization. Measurements of this type can help to constrain the neutron distributions. Future measurements
of the spin-dependent weak interaction should allow extraction of the nuclear anapole moments for a sequence of isotopes,
and allow separation of the neutron and proton weak interactions between hadrons.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
4.
M. Marchetto Z. T. Ang K. Jayamanna R. E. Laxdal A. Mitra V. Zvyagintsev 《The European physical journal. Special topics》2007,150(1):241-242
ISAC at TRIUMF is a world-class facility for the production and post-acceleration of radioactive ion beams (RIB).
Commissioned in 2002 the ISAC I linear accelerator serves three different beam lines delivering
both stable and radioactive species.
Two of them are permanent experiments (DRAGON and TUDA); the third one is a general purpose station (GPS).
The maximum energy we can reach in ISAC I is 1.8 MeV/u.
ISAC II is a phased upgrade of the ISAC facility. The beam coming from ISAC I is injected at 1.5 MeV/u into
a new superconducting LINAC. In `Phase I' the LINAC adds 20 MV to the beam energy
and 20 MV more will be added in `Phase II'.
The paper will give an overview of both the ISAC I and ISAC II accelerators.
Operational experience with accelerating RIBs in ISAC I is summarized.
First ISAC II commissioning results are presented. 相似文献
5.
S. Aubin J. A. Behr R. Collister V. V. Flambaum E. Gomez G. Gwinner K. P. Jackson D. Melconian L. A. Orozco M. R. Pearson D. Sheng G. D. Sprouse M. Tandecki J. Zhang Y. Zhao 《Hyperfine Interactions》2013,214(1-3):163-171
We present a method for measuring the nuclear anapole in a string of francium isotopes. The anapole is a parity non-conserving electromagnetic moment that enables parity-forbidden transitions between ground state hyperfine levels of an atom. The experiment is run by the FrPNC collaboration and relies on a beam of artificially-produced francium from the ISAC facility at TRIUMF. 相似文献
6.
P. Bricault 《The European physical journal. Special topics》2007,150(1):227-232
The ISAC facility at TRIUMF utilizes up to 100 μA from the 500 MeV H- cyclotron to produce the RIB using the Isotopic Separation On Line (ISOL) method. The ISAC-I facility comprised the RNB production
target stations, the mass separator and the beam delivery to low energy area and to a room temperature linear accelerator
composed of a 4-rod RFQ and an inter-digital H type structure Drift Tube LINAC. ISAC-I linear accelerator can provide beam
from A = 3 to 30 amu with an energy range from 0.15 to 1.5 A MeV.
Since the beginning of operations target development program has been to increase proton beam currents on targets. Now we
routinely operate our target at 50 to 85 μA and recently we have operated our target at 100 μA. Other developments are in
place to add other ion sources, laser, FEBIAD and ECRIS to the actual surface ion source. The last two five year plans were
mainly devoted to the construction of a heavy ion superconducting LINAC (ISAC-II), that will upgrade the mass and the energy
range from 30 to 150 and 1.5 to 6.5 A MeV, respectively.
We are now commissioning the medium β section and first experiment is scheduled for the fall 2006. 相似文献
7.
A. Gorelov J.A. Behr D. Melconian M. Trinczek P. Dubé O. Häusser U. Giesen K.P. Jackson T. Swanson J.M. D'Auria M. Dombsky G. Ball L. Buchmann B. Jennings J. Dilling J. Schmid D. Ashery J. Deutsch W.P. Alford D. Asgeirsson W. Wong B. Lee 《Hyperfine Interactions》2000,127(1-4):373-380
Laser trapping and cooling techniques are now being applied to the study of nuclear β-decay at several labs. A magneto-optical
trap (MOT) provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and
be detected in coincidence with the β. This allows reconstruction of the neutrino momentum, and the deduction of the β-v correlation in a more direct fashion than previously possible. In addition, the nuclei can be polarized by atomic techniques,
opening a new class of spin correlation measurements to test the degree to which parity is maximally violated in the weak
interaction. Our present experiment has detected several hundred thousand recoil-β+ coincidences from the 0+ → 0+ pure Fermi decay of 38mK, produced at the on-line isotope separators TISOL and ISAC at TRIUMF. Our goal is to set constraints on non-Standard Model
scalar bosons competitive with high-energy colliders and more conventional β-v correlation experiments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Harun R. Yazar 《Pramana》2008,70(5):805-815
In this work, we analyse the positive parity of states of odd-mass nucleus within the framework of interacting boson-fermion
model. The result of an IBFM-1 multilevel calculation with the 2d5/2, 1g7/2, 3s1/2, 2d3/2 and 1h11/2, single particle orbits is reported for the positive parity states of the odd-mass nucleus 125–129Xe. Also, an IBM-1 calculation is presented for the low-lying states in the even-even 124–128Xe core nucleus. The energy levels and B(E2) transition probabilities were calculated and compared with the experimental data. It was found that the calculated positive
parity low-spin state energy spectra of the odd-mass 125–129Xe isotopes agree quite well with the experimental data.
相似文献
9.
Pierre G. Bricault Friedhelm Ames Marik Dombsky Peter Kunz Jens Lassen 《Hyperfine Interactions》2014,225(1-3):25-49
The present status of the ISAC facility for rare isotopes beams after its first 10 years of operation is presented. Planning for the ISAC facility started in 1985 with the Parksville workshop on radioactive ion beams (Buchmann and D’Auria 1985). It was put on halt by the KAON proposal and planning was only resumed in 1993 after the cancellation of KAON. The ISAC facility was built to satisfy the scientific need for accelerated beams of rare isotopes for use in applications such as nuclear physics, nuclear astrophysics, atomic and condensed matter physics as well as medicine. At the time of the ISAC proposal submission, a number of facilities were either planned or under construction. In order to have an impact in the field, the requirements and specifications for the driver beam intensity on target was set to 100 μA, 500 MeV protons, which for ISAC results in a driver beam power of 50 kW. 相似文献
10.
M. Seliverstov A. Andreyev N. Barré H. De Witte D. Fedorov V. Fedoseyev S. Franchoo J. Genevey G. Huber M. Huyse U. Köster P. Kunz S. Lesher B. Marsh B. Roussière J. Sauvage P. Van Duppen Yu. Volkov 《Hyperfine Interactions》2006,171(1-3):225-231
Mean-square charge radii and magnetic moments have been measured for the neutron deficient lead isotopes, 182–190Pb. The measurement was performed at the ISOLDE online mass separator, using the in-source resonance ionization spectroscopy
technique. The wavelength of the first excitation step for the resonance ionization laser ion source (RILIS) was scanned over
the resonance(s) whilst the α- and γ-ray spectra from the decay of the Pb isotopes were recorded as a function of the wavelength. The isotope shift and, in the
case of odd-A isotopes, the hyperfine splitting were deduced. The rms-charge radii of the very neutron deficient Pb isotopes follow the
smooth trend of the heavier isotopes. This finding indicates a spherical shape for the lead ground states at the neutron mid-shell
(N = 104), where the excitation energy of the oblate 0+ state in the even isotopes reaches its minimum. 相似文献
11.
The multiplicity fluctuations of the produced pions were studied using scaled variance method in 16O–AgBr interactions at 2.1 AGeV, 24Mg–AgBr interactions at 4.5 AGeV, 12C–AgBr interactions at 4.5 AGeV, 16O–AgBr interactions at 60 AGeV and 32S–AgBr interactions at 200 AGeV at two different binning conditions. In the first binning condition, the rapidity interval
was varied in steps of one centring about the central rapidity until it reached 14. In the second case, the rapidity interval
was increased in steps of 1.6 up to 14.4. Multiplicity distributions and their scaled variances were presented as a function
of the dependence on the rapidity width for both the binning conditions. Multiplicity fluctuations were found to increase
with the increase of rapidity interval and later found to saturate at larger rapidity window for all the interactions and
in both the binning conditions. Multiplicity fluctuations were found to increase with the energy of the projectile beam. The
values of the scaled variances were found to be greater than one in all the cases in both the binning conditions indicating
the presence of correlation during the multiparticle production process in high-energy nucleus–nucleus interactions. Experimental
results were compared with the results obtained from the Monte Carlo simulated events for all the interactions. The Monte
Carlo simulated data showed very small values of scaled variance suggesting very small fluctuations for the simulated events.
Experimental results obtained from 16O–AgBr interactions at 60 AGeV and 32S–AgBr interactions at 200 AGeV were compared with the events generated by Lund Monte Carlo code (FRITIOF model). FRITIOF
model failed to explain the multiplicity fluctuations of pions emitted from 16O–AgBr interactions at 60 AGeV for both the binning conditions. However, the experimental data agreed well with the FRITIOF
model for 32S–AgBr interactions at 200 AGeV. 相似文献
12.
Rydberg hydrogen atom in the presence of uniform magnetic and quadrupolar electric fields 总被引:1,自引:0,他引:1
Laser cooling and trapping offers the possibility of confining a sample of radioactive atoms in free space. Here, we address the question of how best to take advantage of cold atom properties to perform the observation of as highly forbidden a line as the 6S-7S Cs transition for achieving, in the longer term, atomic parity violation (APV) measurements in radioactive alkali isotopes. Another point at issue is whether one might do better with stable, cold atoms than with thermal atoms. To compensate for the large drawback of the small number of atoms available in a trap, one must take advantage of their low velocity. To lengthen the time of interaction with the excitation laser, we suggest choosing a geometry where the laser beam exciting the transition is colinear to a slow, cold atomic beam, either extracted from a trap or prepared by Zeeman slowing. We also suggest a new observable physical quantity manifesting APV, which presents several advantages: specificity, efficiency of detection, possibility of direct calibration by a parity conserving quantity of a similar nature. It is well adapted to a configuration where the cold atomic beam passes through two regions of transverse, crossed electric fields, leading both to differential measurements and to strong reduction of the contributions from the M1-Stark interference signals, potential sources of systematics in APV measurements. Our evaluation of signal-to-noise ratios shows that with available techniques, measurements of transition amplitudes, important as required tests of atomic theory, should be possible in 133Cs with a statistical precision of 10-3 and probably also in Fr isotopes for production rates of
Fr atoms s-1. For APV measurements to become realistic, some practical realization of the collimation of the atomic beam as well as multiple passages of the excitation beam matching the atomic beam looks essential.Received: 5 March 2003, Published online: 17 July 2003PACS:
32.80.Ys Weak-interaction effects in atoms - 32.70.Cs Oscillator strengths, lifetimes, transition moments - 32.80.Pj Optical cooling of atoms; trapping - 39.90.+d Other instrumentation and techniques for atomic and molecular physicsS. Sanguinetti: Also at E. Fermi Physics Dept., Pisa Univ., Pisa, Italy. 相似文献
13.
The position and momentum space information entropies of weakly interacting trapped atomic Bose–Einstein condensates and spin-polarized
trapped atomic Fermi gases at absolute zero temperature are evaluated. We find that sum of the position and momentum space
information entropies of these quantum systems containing N atoms confined in a D( ≤ 3)-dimensional harmonic trap has a universal form as St(D) = N(a D - b lnN) S_\mathrm{t}^{(D)} = N(a D - b \ln N) , where a ≃ 2.332 and b = 2 for interacting bosonic systems and a ≃ 1.982 and b = 1 for ideal fermionic systems. These results obey the entropic uncertainty relation given by Beckner, Bialynicki-Birula
and Myceilski. 相似文献
14.
C. G. Barham S. S. Alghamdi A. Bhagwat M. Booth I. S. Grant M. Lindroos J. Rikovska B. D. D. Singleton N. J. Stone P. M. Walker 《Hyperfine Interactions》1992,75(1-4):431-438
Assignments for the principal Nilsson configuration in light β+-decaying bromine isotopes were proposed in a contribution to the OLNO-1 conference. These assignments were made on the basis
of magnetic moments derived from the temperature dependence of anisotropies in daughter Se isotopes observed in the DOLIS-COLD
facility at Daresbury. Anisotropy measurements have since been extended to a lower base temperature in74m
Br and72g
Br decay, leading to more stringent limits on the ground state moment of72Br. The proposed π[312]3/2 configuration for75Br has also now been confirmed by a measurement of the sign of its magnetic moment. This was done by observing the β-asymmetry
in75Br decay using high purity Si detectors mounted within the dilution refrigerator. 相似文献
15.
Absolute frequency and isotope shift measurements of the cooling transition in singly ionized indium
Y. H. Wang R. Dumke J. Zhang T. Liu A. Stejskal Y. N. Zhao Z. H. Lu L. J. Wang Th. Becker H. Walther 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):307-311
We report greater than two orders of magnitude improvements in the absolute frequency and isotope shift measurements of the
In+ 5s2
1S0 (F = 9/2)–5s5p 3P1 (F = 11/2) transition near 230.6 nm. The laser-induced fluorescence from a single In+ in a radio-frequency trap is detected. The fourth-harmonic of a semiconductor laser is used as the light source. The absolute
frequency is measured with the help of a frequency comb referenced to a Cs atomic clock. The resulting transition frequencies
for isotopes 115In+ and 113In+ are measured to be 1 299 648 954.54(10) MHz and 1 299 649 585.36(16) MHz, respectively. The deduced cooling transition frequency
difference is 630.82(19) MHz. By taking into account of the hyperfine interaction, the isotope shift is calculated to be 695.76(1.68) MHz. 相似文献
16.
Lorenz Willmann Klaus Jungmann Cornelis J. G. Onderwater Rob G. E. Timmermans Hans W. Wilschut 《Hyperfine Interactions》2012,211(1-3):39-43
Discrete symmetries tested in high precision atomic physics experiments provide guidance to model building beyond the Standard Model (SM). Here experimental opportunities arise for searches for permanent electric dipole moments (EDMs) and measurements of atomic parity violation (APV). Heavy atoms are favorable for such experiments since symmetry violating effects in atoms increase faster than the third power of the nuclear charge Z. Of special interest are isotopes of the heavy alkaline earth element radium (Z=88) since they offer large enhancement factors for EDMs and provide a new experimental road towards high precision measurements of atomic parity violation. These opportunities are exploited at the TRIμP facility at KVI, Groningen. 相似文献
17.
M.C. Fujiwara J.M. Bailey G.A. Beer J.L. Beveridge J.L. Douglas T.M. Huber R. Jacot‐Guillarmod P. Kammel S.K. Kim P.E. Knowles A.R. Kunselman M. Maier V.E. Markushin G.M. Marshall C.J. Martoff G.R. Mason F. Mulhauser A. Olin C. Petitjean T.A. Porcelli J. Zmeskal 《Hyperfine Interactions》1997,106(1-4):257-264
The emission of muonic tritium atoms from a thin film of hydrogen isotopes into vacuum was observed. The time and position
of the muon decays were measured by tracking the decay electron trajectory. The observations are useful both for testing the
theoretical cross sections for muonic atomic interactions, and producing an atomic beam of slow μ-t with a controllable energy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
J. Söding D. Guéry-Odelin P. Desbiolles F. Chevy H. Inamori J. Dalibard 《Applied physics. B, Lasers and optics》1999,69(4):257-261
We have measured the three-body decay of a Bose–Einstein condensate of rubidium (87Rb) atoms prepared in the doubly polarized ground state F=m
F
=2. Our data are taken for a peak atomic density in the condensate varying between 2×1014 cm-3 at initial time and 7×1013 cm-3, 16 s later. Taking into account the influence of the uncondensed atoms on the decay of the condensate, we deduce a rate
constant for condensed atoms L=1.8 (±0.5) ×10-29 cm6 s-1. For these densities we did not find a significant contribution of two-body processes such as spin dipole relaxation.
Received: 24 November 1998 / Revised version: 26 June 1999 / Published online: 8 September 1999 相似文献
19.
The effect of plasticizer and TiO2 nanoparticles on the conductivity, chemical interaction and surface morphology of polymer electrolyte of MG49–EC–LiClO4–TiO2 has been investigated. The electrolyte films were successfully prepared by solution casting technique. The ceramic filler,
TiO2, was synthesized in situ by sol-gel process and was added into the MG49–EC–LiClO4 electrolyte system. Alternating current electrochemical impedance spectroscopy was employed to investigate the ionic conductivity
of the electrolyte films at 25 °C, and the analysis showed that the addition of TiO2 filler and ethylene carbonate (EC) plasticizer has increased the ionic conductivity of the electrolyte up to its optimum
level. The highest conductivity of 1.1 × 10−3 Scm−1 was obtained at 30 wt.% of EC. Fourier transform infrared spectroscopy measurement was employed to study the interactions
between lithium ions and oxygen atoms that occurred at carbonyl (C=O) and ether (C-O-C) groups. The scanning electron microscopy
micrograph shows that the electrolyte with 30 wt.% EC posses the smoothest surface for which the highest conductivity was
obtained. 相似文献
20.
HADI ESLAMIZADEH 《Pramana》2012,78(2):231-236
Data on shape isomer yield for α + 235U reaction at Ea lab = E_\alpha ^{\rm lab} =\,\,20–29 MeV are analysed in the framework of a combined dynamical–statistical model. From this analysis, information on the
double humped fission barrier parameters for some Pu isotopes has been obtained and it is shown that the depth of the second
potential well should be less than the results of statistical model calculations. 相似文献