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1.
Hyperfine structure and isotope shifts in five optical
transitions: 424.5 nm (
–
), 537.2 nm (
–
), 554.5 nm
(
–
), 560.9 nm
(
–
) and 666.0 nm
(
–
)
of Pb II have been measured. As a light source the discharge tube was used.
The hyperfine structure measurements were
performed using metallic isotope 207Pb. For isotope shifts
measurements natural lead was used. The high resolution spectral apparatus consisted of a silver
coated Fabry-Perot etalon and a grating spectrograph combined
with a CCD camera used as a detector. In the analysis of the
spectra a computer simulation technique was used. The hyperfine
structure observations yielded the splitting constants A for
seven levels of Pb II. The isotope shift studies enabled to
separate the mass and the field shifts and to determine values of
changes of the mean square nuclear charge radii. 相似文献
2.
S. H. Li C. Wang J. S. Liu X. X. Wang R. X. Li G. Q. Ni Z. Z. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,34(1-3):215-218
Using time-of-flight spectrometry, the interaction of intense femtosecond
laser pulses with argon clusters has been studied by measuring the energy
and yield of emitted ions. With two different supersonic nozzles, the
dependence of average ion energy
on cluster size
in a large range of
has been measured. The experimental results indicate that
when the cluster size
, the average ion
energy
Coulomb explosion is the
dominant expansion mechanism. Beyond this size, the average ion energy gets
saturated gradually, the clusters exhibit a mixed Coulomb-hydrodynamic
expansion behavior. We also find that with the increasing gas backing
pressure, there is a maximum ion yield, the ion yield decreases as the gas
backing pressure is further increased. 相似文献
3.
We present new experimental data on the highly excited levels in mercury using the two-step laser excitation and optogalvanic detection technique in conjunction with a RF discharge cell. The 6s7s 3S1 intermediate level has been accessed from the 6s6p 3P2 metastable level that is collisionally populated in the mercury discharge in the presence of a buffer gas at a pressure of about 1 Torr. Two beams fromtwo different dye lasers pumped with a common excimer laser were passed through the discharge cell containing mercury vapors. The first laser was tuned to 6s7s 3S1 level whereas the second laser was scanned covering the wavelength region between 544-458 nm. We have observed the 6snp 3P0 (
), 6snp
(
), 6snp
(
) and 6snp
) Rydberg series. The 6snp
Rydberg series to such high n-value has been reported for the first time. The first ionization potential of mercury is determined from the 6snp
Rydberg series as 84184.15
0.05 cm-1. Some collisionally induced parity forbidden transitions have also been located that are identified as 6sns
(
) series.Received: 5 November 2003, Published online: 20 January 2004PACS:
31.50.-x Potential energy surfaces - 32.30.Jc Visible and ultraviolet spectra - 32.80.Rm Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) 相似文献
4.
Resonant active-to-active (
), as well as active-to-sterile (
) neutrino (
) oscillations can take place during the core bounce of a supernova collapse. Besides, over this phase, weak magnetism increases the antineutrino (
) mean free path, and thus its luminosity. Because the oscillation feeds mass-energy into the target
species, the large mass-squared difference between the species (
) implies a huge amount of energy to be given off as gravitational waves (
erg s-1), due to anisotropic but coherent
flow over the oscillation length. This asymmetric
-flux is driven by both the spin-magnetic and the universal spin-rotation coupling. The novel contribution of this paper stems from (1) the new computation of the anisotropy parameter
-0.01, and (2) the use of the tight constraints from neutrino experiments as SNO and KamLAND, and the cosmic probe WMAP, to compute the gravitational-wave emission during neutrino oscillations in supernovae core collapse and bounce. We show that the mass of the sterile neutrino
that can be resonantly produced during the flavor conversions makes it a good candidate for dark matter as suggested by Fuller et al. , Phys. Rev. D 68, 103002 (2003). The new spacetime strain thus estimated is still several orders of magnitude larger than those from
diffusion (convection and cooling) or quadrupole moments of neutron star matter. This new feature turns these bursts into the more promising supernova gravitational-wave signals that may be detected by observatories as LIGO, VIRGO, etc., for distances far out to the VIRGO cluster of galaxies.Received: 26 November 2003, Revised: 26 February 2004, Published online: 3 June 2004 相似文献
5.
X. Z. Cai C. Zhong W. Q. Shen Y. G. Ma H. Y. Zhang Y. B. Wei J. G. Chen W. Guo K. Wang G. L. Ma X. F. Zhou 《The European Physical Journal A - Hadrons and Nuclei》2004,20(2):263-267
,
and
have been calculated via the BUU model with soft EOS and 0.8 times of
. The density distribution without any adjustable parameters which comes from the RMF model has been introduced into the BUU calculation to replace the normally used one-parameter square-type distribution. The calculated results can reproduce the experimental data well for both halo- and stable-nuclei-induced reactions. Here
or
is calculated as the difference between
of halo nucleus and core nucleus, by assuming
. It indicates that this assumption works very well at high energy in the BUU calculation. More experimental measurements are necessary to test the validity of this assumption at intermediate energy.Received: 12 June 2003, Revised: 29 September 2003, Published online: 27 April 2004PACS:
24.10.-i Nuclear reaction models and methods - 25.60.Dz Interaction and reaction cross-sections - 25.60.Gc Breakup and momentum distributions - 27.20. + n
相似文献
6.
The position of high-energy critical minimum in elastic electron-argon scattering was investigated both experimentally and theoretically. Differential cross-sections (DCSs) were measured as a function of both incident electron energy (40-150 eV) and scattering angle (
), in small steps around the critical minimum. The position of the high-energy critical minimum in elastic electron-argon scattering was experimentally found to be at
eV and
. To cover the energy and angular ranges of the present experiment, relevant relativistic ab initio calculations were carried out, based on the Dirac-Hartree-Fock method with the exchange calculated exactly. Target polarization is described by an ab initio potential taken from relativistic polarized orbital calculations. The calculated position of the high-energy critical minimum is
eV,
. It was shown that even slight difference of fixed scattering angle close to the critical point could affect significantly the energy dependent DCS. Discussion of behavior of DCS in the vicinity of the critical minimum was performed including convolution analysis in both energy and angle.Received: 31 October 2003, Published online: 20 April 2004PACS:
31.15.Ar Ab initio calculations - 34.80.Bm Elastic scattering of electrons by atoms and molecules 相似文献
7.
The distorted wave Born approximation (DWBA) with the spin averaged static exchange potential has been used to calculate the triple differential cross-sections (TDCSs) for Ne (2s
2) ionization by electron impact in coplanar to perpendicular plane symmetric geometry at 110.5 eV incident electron energy. The present theoretical results at gun angles
(coplanar symmetric geometry) and
(perpendicular plane geometry) are in satisfactory agreement with the available experimental data. A deep interference minimum appears in the TDCS in the coplanar symmetric geometry and a strong peak at scattering angle
caused by the single collision mechanism has been observed in the perpendicular plane geometry. The TDCSs at the gun angles
, and
are predicted.Received: 16 July 2002, Published online: 22 July 2003PACS:
34.80.Gs Molecular excitation and ionization by electron impact - 34.80.Dp Atomic excitation and ionization by electron impact 相似文献
8.
A pair
of interacting Kerr oscillators treated as a master coupler sending chaotic or hyperchaotic signals to its slave copy
is considered. We synchronize a with A and b with B through two communication channels
and
. The effect of synchronization is non-simultaneous, the pairs
and
have different times of synchronization. It is possible to synchronize an individual pair, for example,
when its communication channel
is turned off, provided that the second channel for the pair
is turned on. The resulted synchronization is termed induced. The efficiencies of the presented synchronization precesses are studied.Received: 20 February 2003, Published online: 29 April 2003PACS:
05.45.Xt Synchronizations; coupled oscillators - 05.45.Pq Numerical simulations of chaotic systems - 42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics 相似文献
9.
The effects of the open boundaries on the dynamical behavior of the optimal velocity traffic flow models with a delay time
allowing the car to reach its optimal velocity is studied using numerical simulations. The particles could enter the chain with a given injecting rate probability
, and could leave the system with a given extracting rate probability
. In the absence of the variation of the delay time
, it is found that the transition from unstable to metastable and from metastable to stable state occur under the effect of the probabilities rates
and
. However, for a fixed value of
, there exist a critical value of the extraction rate
above which the wave density disappears and the metastable state appears and a critical value
above which the metastable state disappears while the stable state appears.
and
depend on the values of
and the variation of the delay time
. Indeed
and
increase when increasing
and/or decreasing
. The flow of vehicles is calculated as a function of
,
and
for a fixed value of
. Phase diagrams in the (
) plane exhibits four different phases namely, unstable, metastable, stable. The transition line between stable phase and the unstable one is curved and it is of first order type. While the transition between stable (unstable) phase and the metastable phase are of second order type. The region of the metastable phase shrinks with increasing the variation of the delay time
and disappears completely above a critical value
.Received: 23 July 2003, Published online: 8 December 2003PACS:
05.50. + q Lattice theory and statistics (Ising, Potts, etc.) - 64.60.Cn Order-disorder transformations; statistical mechanics of model systems - 75.30.Kz Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.) - 82.20.Wt Computational modeling; simulation 相似文献
10.
A study of Z-boson pair production in e + e- annihilation at center-of-mass energies between 190 GeV and 209 GeV is reported. Final states containing only leptons, (
and
), quark and lepton pairs, (
,
) and only hadrons (
) are considered. In all states with at least one Z boson decaying hadronically, lifetime, lepton and event-shape tags are used to separate
pairs from
final states. Limits on anomalous ZZ
and ZZZ couplings are derived from the measured cross sections and from event kinematics using an optimal observable method. Limits on low scale gravity with large extra dimensions are derived from the cross sections and their dependence on polar angle.Received: 14 July 2003, Published online: 18 December 2003 相似文献
11.
M. Z.M. Kamali K. Ratnavelu Y. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):267-279
The recent theoretical work by Bartlett et al. [J. Phys. B 38, L95 (2005)] and the latest measurements on the reduced Stokes parameters
,
and
for 54.4 eV electron impact excitation of the 2p state atomic hydrogen by Williams and Mikosza [J. Phys. B 39, 4113 (2006)] has motivated the present work. A coupled-channel-optical calculation with 9 and 12 atomic states supplemented
with the continuum optical potentials for the stronger coupling channels has been performed. The calculated n = 2 and n =
3 differential cross sections and the reduced Stokes parameters are comparable with the state-of-the art calculations. There is closer agreement between the present calculations and the experimental measurements for the reduced
Stokes parameters
and
in the n = 2p excitation at 54.4 eV. The present CCO calculations also display good accord with the limited experimental
data for the reduced Stokes parameters in the n=3p excitation. 相似文献
12.
production in
interactions has been detected via its decays into
,K
+
K
-
K
+
K
- and
in the data taken with the DELPHI detector at LEP1 and LEP2 energies. The two-photon radiative width averaged over all observed decay channels is
= 13.9
2.0 (stat.)
1.4(syst.)
2.7 (BR) keV. No direct decay channel
has been observed. An upper limit
< 5.5 keV at 95% confidence level has been evaluated for this decay mode.Received: 3 July 2003, Published online: 7 November 2003 相似文献
13.
A. Ehresmann W. Kielich L. Werner Ph. V. Demekhin D. V. Omel''yanenko V. L. Sukhorukov K.-H. Schartner H. Schmoranzer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):235-246
Dispersed fluorescence from fragments formed after the de-excitation of the
1s-1π* resonances of N*O and NO* has been
measured in the spectral range of 118–142 nm. This range is dominated by
lines of atomic nitrogen and oxygen fragments and by the
bands in the NO+ ion which result from the participator Auger decay of the 1s-1π* resonances.
Ab-initio calculations of the transition probabilities between vibrational
levels during the reaction NO
N*O
⇒ NO
were used to explain the observed intensity dependence for the
fluorescence bands on the exciting-photon energy across
the resonances and on both v′ and v′′
vibrational quantum numbers. The multiplet structure of the 1s-1π* resonance and lifetime vibrational interference explain the observed exciting-photon energy dependence of the
fluorescence
intensity. A strong spin-orbit coupling between singlet and triplet states
of NO+ is proposed to reduce additional cascade population of the
state via radiative transitions from the
and
states and to explain
remaining differences between measured and calculated integral fluorescence
intensities. 相似文献
14.
The anomalous weak dipole moments of the
lepton are measured in a data sample collected by ALEPH from 1990 to 1995 corresponding to an integrated luminosity of 155 pb-1. Tau leptons produced in the reaction
at energies close to the
mass are studied using their semileptonic decays to
,
,
or
. The real and imaginary components of both the anomalous weak magnetic dipole moment and the CP-violating anomalous weak electric dipole moment,
,
,
and
, are measured simultaneously by means of a likelihood fit built from the full differential cross section. No evidence of new physics is found. The following bounds are obtained (95% CL):
,
,
, and
.Received: 25 September 2002, Published online: 29 August 2003 相似文献
15.
Di-jet production is studied in collisions of quasi-real photons at e + e- centre-of-mass energies
from 189 to 209 GeV at LEP. The data were collected with the OPAL detector. Jets are reconstructed using an inclusive
-clustering algorithm for all cross-section measurements presented. A cone jet algorithm is used in addition to study the different structure of the jets resulting from either of the algorithms. The inclusive di-jet cross-section is measured as a function of the mean transverse energy
of the two leading jets, and as a function of the estimated fraction of the photon momentum carried by the parton entering the hard sub-process,
, for different regions of
. Angular distributions in di-jet events are measured and used to demonstrate the dominance of quark and gluon initiated processes in different regions of phase space. Furthermore the inclusive di-jet cross-section as a function of
and
is presented, where
is the jet pseudo-rapidity. Different regions of the
-
-space are explored to study and control the influence of an underlying event. The results are compared to next-to-leading order perturbative QCD calculations and to the predictions of the leading order Monte Carlo generator PYTHIA.Received: 20 December 2002, Published online: 17 October 2003 相似文献
16.
H. Prakash P. Kumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):359-363
We study amplitude-squared squeezing of the Hermitian operator Zθ=Z1
cosθ+Z2 sin θ, in the most general superposition state
, of two coherent states
and
. Here operators Z1,2 are defined by
, a is annihilation operator, θ is angle, and
complex numbers C1,2 , α, β are arbitrary and only
restriction on these is the normalization condition of the state
. We define the condition for a state
to be amplitude-squared squeezed for the operator Zθ
if squeezing parameter
, where N=a+a and
. We find
maximum amplitude-squared squeezing of Zθ in the superposed
coherent state
with minimum value 0.3268 of the
parameter S for an infinite combinations with α- β= 2.16
exp [±i(π/4) + iθ/2],
and with
arbitrary values of (α+β) and θ. For this minimum
value of squeezing parameter S, the expectation value of photon number can
vary from the minimum value 1.0481 to infinity. Variations of the parameter
S with different variables at maximum amplitude-squared squeezing are also
discussed. 相似文献
17.
We explore CP violation in
decay processes in the presence of the anomalous right-handed
and
couplings. The complex anomalous top coupling can be a source of new CP violation and may lead to a deviation of the observed weak phase in
decays, which accounts for the present disagreement of the observed
between
and
decays. Direct CP violation is also predicted.
Received: 27 November 2002, Revised: 28 March 2003, Published online: 2 June 2003 相似文献
18.
Gyürky Gy. Fülöp Zs. Somorjai E. Kiss G. Rolfs C. 《The European Physical Journal A - Hadrons and Nuclei》2004,20(2):355-358
The absolute strengths of the
keV resonance in the
reaction and of the
keV resonance in the
reaction have been measured to
meV and
meV, respectively, in good agreement with previous values. These resonances can be used to measure the absolute acceptance of the recoil separator ERNA to a precision of about 10%.Received: 12 December 2003, Revised: 10 February 2004, Published online: 3 August 2004PACS:
24.30.-v Resonance reactions - 25.40.Lw Radiative capture - 26.20. + f Hydrostatic stellar nucleosynthesis 相似文献
19.
Multi-ring signatures of
appearance via the oscillation
are formulated for a water Cherenkov detector. These signatures are appropriate for long-baseline neutrino experiments operating at relatively high neutrino energies
GeV that emphasize the matter effect. The NC background is less for selected multi-ring events than for 1e-like events, and may be directly estimated from the data. Our results suggest that best sensitivity to
and to the sign of
can be reached with baselines over some 6000 km.Received: 14 April 2003, Revised: 19 June 2003, Published online: 26 September 2003M.A. Kubantsev: Now at Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA 相似文献
20.
Measurements of on-shell ZZ production are described, using data from the DELPHI experiment at LEP in e
+
e
- collisions at centre-of-mass energies between 183 and 209 GeV, corresponding to an integrated luminosity of about 665 pb-1. Results obtained in each of the final states
,
,
,
,
, l
+
l
-
l
+
l
-, and
(with
) are presented. The measured production cross-sections are consistent with the Standard Model expectations. These results update and supersede those already published at 183 and 189 GeV.Received: 3 March 2002, Revised: 28 May 2003, Published online: 19 September 2003 相似文献