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1.
We report on the experimental study of the excitation mechanism of fluorescence in a 10000-ppm wt. Tm+3-doped ZBLAN fiber. Visible (at 453 nm and 480 nm) and near-infrared (∼800 nm) radiations were studied under excitation at
1.064 μm. The up-conversion mechanisms responsible are investigated, based on experimental data. The results show that the3
H
4 and the 1
D
2 levels are predominantly excited by ion-ion cross-relaxation processes.
Received: 19 August 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +41/31-631-3765, E-mail: Reda.El-Agmy@iap.unibe.ch 相似文献
2.
C. Pahl S. Bethke O. Biebel S. Kluth J. Schieck 《The European Physical Journal C - Particles and Fields》2009,64(4):533-547
Predictions of analytical models for hadronisation, namely the dispersive model, the shape function and the single dressed
gluon approximation, are compared with moments of hadronic event shape distributions measured in e+e− annihilation at centre-of-mass energies between 14 and 209 GeV. In contrast to Monte Carlo models for hadronisation, analytical
models require to adjust only two universal parameters, the strong coupling and a second quantity parametrising non-perturbative
corrections. The extracted values of α
S are consistent with the world average and competitive with previous measurements. The variance of event shape distributions
is compared with predictions given by some of these models. Limitations of the models, probably due to unknown higher order
corrections, are demonstrated and discussed. 相似文献
3.
Walter Bonivento 《Czechoslovak Journal of Physics》1999,49(2):49-60
A large number of measurement related to spin was performed during the last decade at the e + e ? colliders LEP and SLC providing important information on the dynamics of high energy interactions. In this paper three main topics will be covered: the measurements of the electroweak couplings, the study of fragmentation dynamics and the search for physics beyond the Standard Model. 相似文献
4.
J.?G.?Due?as N.?Gutierrez R.?Martínez F.?Ochoa 《The European Physical Journal C - Particles and Fields》2009,60(4):653-659
We analyse the possibilities to detect a new Z
′ boson in di-electron events at Tevatron and LHC in the framework of the 331 model with right-handed neutrinos. We also study
other fermions and Higgs events as final state at LHC. Using
collision data collected by the CDF II detector at Fermilab Tevatron, we find that the 331 Z
′ boson is excluded with masses below 920 GeV. For an integrated luminosity of 100 fb−1 at LHC, and considering a central value
GeV, we obtain the invariant-mass distribution in the process pp→Z
′→e
+
e
−, where a huge peak, corresponding to 800 signal events/(20 GeV), is found above the SM background. The number of di-electron
events vary from 50000 to 2400 in the mass range of
–2000 GeV. We also obtain branching ratios and cross sections in other fermion and Higgs channels at LHC, where a heavy top
quark T exhibits the biggest ratio with m
T
=300 GeV. 相似文献
5.
Large amounts of hyperpolarized 3He gas with high nuclear polarization rates are required for use in neutron spin filters or nuclear magnetic resonance imaging of human lung. Very high efficiency can be obtained by metastability exchange optical pumping using multimode lasers to excite the [
2
]3S-[
2
]3P transition at 1083 nm. Broadband ytterbium-doped tunable fiber lasers have been designed for that particular application. Different options for the architecture of the fiber oscillator are presented and compared. Emphasis is given to a linear cavity configuration that includes a high reflectivity fiber mirror and a low reflectivity tunable fiber Bragg grating. Optical measurements are performed to finely characterize the spectral behavior of the lasers. Atomic response is also quantitatively probed to assess the optimal design of the oscillator for optical pumping. Multimode operation matching the 2 GHz Doppler-broadened helium resonance line and tunability over more than 200 GHz are demonstrated. Boosting the output of this fiber laser with a Yb-doped fiber power amplifier, all-fiber devices are built to provide robust, high-power turnkey sources at 1083 nm for improved production of laser polarized 3He. PACS 42.60.-v; 42.55.Wd; 32.80.Bx 相似文献
6.
Bose-Einstein correlations (BEC) between final state particles in the reaction
have been studied. Data corresponding to a total integrated luminosity of 550 pb-1, recorded by the DELPHI detector at centre-of-mass energies ranging from 189 to 209 GeV, were analysed. An indication for
inter-W BEC between like-sign particles has been found at the level of 2.4 standard deviations of the combined statistical
and systematic uncertainties.
Received: 11 January 2005, Revised: 13 July 2005, Published online: 13 September 2005
This paper is dedicated to the late Frans Verbeure.
Frans was a very active member of the DELPHI collaboration and its QCD
and WW working groups. The loss of Frans touched us all deeply. 相似文献
7.
B. Di Micco 《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):125-127
In this report the measurement of the η mass is presented. The analysis has been performed on 450pb^-1 of data collected in
the years 2001 and 2002. The measured value is m
η = (547.874±0.07stat±0.029syst) MeV.
Original article based on material presented at HADRON 2007. 相似文献
8.
We present a numerical model of Er3+–Tm3+–Pr3+-co-doped fiber amplifier pumped with 980 nm laser for the first time, to the best of our knowledge. The rate and power propagation
equations are solved numerically to analyze the effects of the pump power and active ion concentrations on the gains at 1310,
1470, 1530, 1600, 1650 nm windows. The results show that with pump power of 200 mW and when Pr3+, Tm3+, Er3+ concentrations are around 2.0×1024, 3.0×1024, 1.5×1024 (ions/m3), respectively, the signals at 1470, 1530, 1600 nm may be nearly equally amplified with gain of 11–12.0 dB in the active
fiber with length of 11.0 m, and the signals at 1310, 1470 and 1600 nm windows may be nearly equally amplified with gain of
12.0 dB in the active gain medium with length of 15.0 m. With pump power of 300 mW, the signals at 1470, 1530, 1600 nm may
be nearly equally amplified with a gain of 16.0 dB in the active medium with a length of 15.0 m. 相似文献
9.
K.-M. Källman M. Brenner V.Z. Goldberg T. Lönnroth P. Manngård A.E. Pakhomov V.V. Pankratov 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):159-169
The excitation function and angular distributions of elastic α-particle scattering on 28Si have been measured in the laboratory energy range 6-28 MeV using a backscattering technique on a thick target, yielding
a continuous energy distribution. More than 200 narrow states are observed, with widths in the range ∼ 30-100 keV at excitation
energies E
* = 13-32 MeV. Angular distributions at backward angles were measured, and angular momentum values of more than 83 states have
been deduced. The analysis gives spin-parities J
π, α-partial widths Γα and reduced widths of the narrow high-lying resonant states in 32S. The experimentally observed states display both the negative- and the positive-parity rotational-like sequences with seemingly
no parity splitting, a finding which is at variance with most potential-model predictions. The deduced effective moment of
inertia indicates a more extended structure than the ground-state configuration. The observed strength of each ℓ-value is
analyzed in terms of an underlying split doorway state of Lorentzian form, which yields an interpretation as fragmented rotational
α + 28Si states.
Received: 26 June 2000 / Accepted: 16 September 2002 / Published online: 4 February 2003
RID="a"
ID="a"e-mail: kkallman@abo.fi
RID="b"
ID="b"Present address: Swedish Polytechnic, FIN-65200 Vasa, Finland.
Communicated by D. Guerreau 相似文献
10.
11.
A. V. Derbin A. I. Egorov I. A. Mitropol’sky V. N. Muratova D. A. Semenov E. V. Unzhakov 《The European Physical Journal C - Particles and Fields》2009,62(4):755-760
A search for resonant absorption of 14.4 keV solar axions by a 57Fe target was performed. The Si(Li) detector placed inside the low-background setup was used to detect the γ-quanta appearing in the deexcitation of the 14.4 keV nuclear level: A+57Fe→57Fe*→57Fe+γ. The new upper limit for the hadronic axion mass has been obtained of m
A
≤159 eV (95% c.l.) (S=0.5, z=0.56). 相似文献
12.
X. Liu S. Ye Y. Qiao G. Dong B. Zhu D. Chen G. Lakshminarayana J. Qiu 《Applied physics. B, Lasers and optics》2009,96(1):51-55
In the present paper, we investigate the near-infrared (NIR) luminescence of Tb3+–Yb3+ codoped lanthanum borogermanate (LBG) glasses under visible and ultraviolet light excitation. The results indicate that NIR
quantum cutting occurs through cooperative energy transfer from Tb3+ to Yb3+ ions when only 4f
8 levels of Tb3+ ions are excited in the wavelength region of 300–490 nm. The highest quantum efficiency under the excitation 5
D
4 level of Tb3+ at 484 nm is 146%. Ultraviolet excitation that populates the charge transfer band (CTB) of Yb3+ near 270 nm does not result in quantum cutting as the fast nonradiative decay from CTB to 2
F
5/2 level dominates. These materials are expected to be used as a converting layer for silicon solar cells to enhance their efficiency
by splitting each high-energy photon into two NIR photons. 相似文献
13.
Yu. B. Burkatovskaya V. M. Bystritsky G. N. Dudkin A. R. Krylov A. S. Lysakov S. Gazi J. Huran B. A. Nechaev V. N. Padalko A. B. Sadovsky Yu. G. Tuleushev M. Filipowicz A. V. Philippov 《Physics of Particles and Nuclei Letters》2016,13(2):190-197
The cross section of the reaction D(4He, γ)6Li with titanium and zirconium deuterides as targets is measured for incident 4He+ ion energies of 30 and 36 keV, respectively. The ion beam is generated by a Hall pulsed plasma accelerator. For the first time, upper limits on the cross section of the reaction D(4He, γ)6Li at ultralow energies are imposed (at 90% confidence level): σ ≤ 1.2 × 10?35 cm2 for the TiD2 target and E(4He+) = 30 keV, and σ ≤ 7 × 10?36 cm2 for the ZrD2 target and E(4He+) = 36 keV 相似文献
14.
The frequency of 127I2 hyperfine component a3 of the P(13) 43-0 transition at 514.6 nm has been measured with an optical clockwork based on a femtosecond laser frequency comb generator. The measured frequency at an iodine pressure of 0.12 Pa is 67.3(0.75) kHz higher than the value of 582490603.38(15) MHz, adopted by the CIPM in 2003 [9] but is in a good agreement with the value measured by [29]. In our experiment we used H-maser reference frequency located at BNM-SYRTE Observatoire de Paris and transported to our laboratory by a 43 km optical fibre link. PACS 06.20.-f; 06.20.Fn; 06.30.Bp; 06.30.Ft 相似文献
15.
N. Rakov L. A. Gómez D. J. Rátiva G. S. Maciel 《Applied physics. B, Lasers and optics》2009,94(2):199-202
Upconversion (UC) emission in thulium (Tm3+) and neodymium (Nd3+) co-doped aluminum oxide ceramic powders prepared by combustion synthesis was investigated at room temperature using a continuous
wave laser operating at 800 nm. Our sample containing Tm3+ (1 wt.%) did not show any UC emission but our sample co-doped with Tm3+ and Nd3+ in 1:2 wt.% proportion presented blue (∼480 nm) UC intensity more than one order of magnitude larger than our sample co-doped
with Tm3+ and Nd3+ in 1:1 wt.% proportion. X-ray diffraction data showed the presence of α-Al2O3 and REAlO3 (RE=Tm or Nd) crystalline phases in co-doped powders, while the singly doped powder has only α-Al2O3 phase. Our results show that the UC emission efficiency of Tm3+ and the host crystalline structure can be tailored by manipulating the Nd3+ doping concentration. 相似文献
16.
L. González-Sánchez E. Bodo F. A. Gianturco 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):65-72
An ab initio computed potential energy surface is employed to
evaluate the interaction of the OH+(3Σ -) molecule with
4He(1S) atom and an analytic fitting of the raw points is
directly employed in quantum scattering calculations at ultralow
collision energies. The Hund's case (b) chosen to handle the
spin-rotation coupling allows to extract from the numerous inelastic
cross sections the relative importance of pure “spin flip" vis-à-
vis rotational cooling cross sections. The final rates of all the
above processes as a function of the initial |N〉 state are
analysed in detail and possible propensity rules are discussed. 相似文献
17.
N. N. Kalmykov G. V. Kulikov V. P. Sulakov Yu. A. Fomin 《Moscow University Physics Bulletin》2009,64(5):536-540
Data on muon and electron components of extensive air showers (EAS) (obtained with the EAS MSU array) were used to derive
the primary cosmic ray (PCR) mass composition. It is shown that for energies beyond the knee at energy 3 × 1015 eV the abundance of heavy nuclei increases with energy. But at energies above 1017 eV the abundance of light nuclei starts to grow. The primary cosmic ray spectrum in the range 1015–1018 eV is analyzed. It is shown that at energies above 1017 eV the additional component appears and it differs from the bulk of Galactic cosmic rays generated by shocks in SN remnants. 相似文献
18.
P. Dubé A. A. Madej J. E. Bernard L. Marmet A. D. Shiner 《Applied physics. B, Lasers and optics》2009,95(1):43-54
In this paper, we describe in detail a narrow linewidth and frequency-stable laser source used to probe the 5s
2
S
1/2–4d
2
D
5/2 clock transition of the 88Sr+ optical frequency standard. The performance of the laser system is investigated with studies of its frequency drift rates
and with high resolution spectra of the 88Sr+ clock transition. The observed short-term drift rates are typically in the range of 10 to 23 mHz/s, and the current long-term
drift rate is 13.9(3) mHz/s. The laser stability, after subtraction of linear drifts, reaches 5×10−16 at an averaging time of 3000 s. This high level of stability is attributed for the most part to stabilization of the reference
cavity at the temperature where the coefficient of linear thermal expansion crosses zero. An upper bound for the laser linewidth
is given by the observation of a Fourier-transform limited resonance of 4.3 Hz (Δν/ν=1×10−14) on the 88Sr+ clock transition. The effective averaging time during the linewidth measurements was about 100 s. 相似文献
19.
20.
Using 160GeV muon scattering data collected with the COMPASS experiment at CERN, the exclusive production of ωπ0 via virtual photons was studied. Selective population of a peak around 1250MeV is observed. Possible contributions from spin-parity
1- are searched for, inspecting decay angular correlations. In particular, the orientation of the ω decay plane may allow a
distinction from the 1+
b
1(1235) state. Our observation is compared with indications of a (1250) in annihilation and in γp .
Original article based on material presented at HADRON 2007. 相似文献