共查询到20条相似文献,搜索用时 15 毫秒
1.
B. Ketzer T. von Egidy F.J. Hartmann C. Maierl R. Pohl J. Eades E. Widmann T. Yamazaki M. Kumakura N. Morita R.S. Hayano M. Hori T. Ishikawa H.A. Torii I. Sugai D. Horváth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):305-316
The quenching of metastable states of antiprotonic helium by collisions with hydrogen and deuterium molecules was studied.
A systematic investigation of the delayed annihilation time spectra at various H2 and D2 admixture ratios at the ppm level revealed characteristic changes of their shape, which indicated a strong principal and
orbital quantum number dependent quenching of levels in both cases. Applying a laser spectroscopy technique to measure the
lifetimes of individual states and cascades we deduced H2 and D2 quenching cross-sections for the states (n, l )= (39, 35) and (37, 34). These cross-sections establish for D2 molecules the strong increase of the quenching efficiency with increasing principal quantum number n of the state under investigation previously reported for the case of H2 admixtures. Our experiments indicate that the low-n state (37, 34) is somewhat less affected by D2 than by H2, while the high-n state (39, 35) is equally quenched by both isotopes.
Received 2 October 2000 相似文献
2.
M. Mizusaki Y. Morishima B.B. Raju F.M. Winnik 《The European physical journal. E, Soft matter》2001,5(1):105-115
Steady-state fluorescence spectroscopy and isothermal titration calorimetry (ITC) have been used to study the aggregation
in aqueous solutions of poly-(2-acrylamido)-2-methylpropanesulfonic acids, sodium salt mono-endcapped with either N,N-di-n-octadecyl or N-4-[(1-pyrenyl)butyl]-N-n-octadecyl which were prepared by free radical polymerization of 2-(acrylamido)-2-methylpropane sulfonic acid (AMPS) initiated
with the azo compounds, 4,4'-azobis{cyano-N,N-di-n-octadecyl}pentanamide and 4,4'-azobis{cyano-N,N-[4-(1-pyrenyl)butyl]-n-octadecyl}pentanamide, respectively. Both techniques indicate the occurrence of multimolecular aggregates in solutions of
the polymers in water and in 0.2 M NaCl. The concentration range for aggregation is about 1-14 mmol AMPS l-1 (0.5-2.7 g l-1) in 0.2 M NaCl and the enthalpy of micellization, estimated from ITC data, is ∼100 J [mol AMPS]-1. The accessibility of the chromophores to neutral molecules and to cationic species was assessed by quenching of fluorescence
with nitromethane and thallium nitrate, respectively. The association of the mono-endcapped polymers is compared to that of
PAMPS derivatives carrying hydrophobic groups randomly attached along the chain.
Received 7 August 2000 and Received in final form 26 October 2000 相似文献
3.
K. Kossert M. Camen F. Wissmann J. Ahrens J.R.M. Annand H.-J. Arends R. Beck G. Caselotti P. Grabmayr O. Jahn P. Jennewein M.I. Levchuk A.I. L'vov J.C. McGeorge A. Natter V. Olmos de León V.A. Petrun'kin G. Rosner M. Schumacher B. Seitz F. Smend A. Thomas W. Weihofen F. Zapadtka 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):259-273
Differential cross-sections for quasi-free Compton scattering from the proton and neutron bound in the deuteron have been
measured using the Glasgow/Mainz photon tagging spectrometer at the Mainz MAMI accelerator together with the Mainz [48]cm
;SPMOslash; × [64]cm NaI(Tl) photon detector and the G?ttingen SENECA recoil detector. The data cover photon energies ranging from [200]MeV
to [400]MeV at θLAB
γ = 136.2°. Liquid deuterium and hydrogen targets allowed direct comparison of free and quasi-free scattering from the proton. The neutron
detection efficiency of the SENECA detector was measured via the reaction p(γ,π+
n). The “free” proton Compton scattering cross-sections extracted from the bound proton data are in reasonable agreement with
those for the free proton which gives confidence in the method to extract the differential cross-section for free scattering
from quasi-free data. Differential cross-sections on the free neutron have been extracted and the difference of the electromagnetic
polarizabilities of the neutron has been determined to be αn - βn = 9.8±3.6(stat)+2.1
-1.1(syst)±2.2(model) in units of [10-4]fm
3. In combination with the polarizability sum αn + βn = 15.2±0.5 deduced from photoabsorption data, the neutron electric and magnetic polarizabilities, αn = 12.5±1.8(stat)+1.1
-0.6(syst)±1.1(model) and βn = 2.7±1.8(stat)+0.6
-1.1(syst)±1.1(model) are obtained. The backward spin polarizability of the neutron was determined to be γ(n)
π = (58.6±4.0)×10-4
fm
4.
Received: 21 August 2002 / Accepted: 16 October 2002 / Published online: 11 February 2003
RID="a"
ID="a"Part of the Doctoral Thesis.
RID="b"
ID="b"Present address: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig.
RID="a"
ID="a"Part of the Doctoral Thesis.
RID="b"
ID="b"Present address: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig.
RID="c"
ID="c"Part of the Habilitation Thesis.
RID="d"
ID="d"e-mail: schumacher@physik2.uni-goettingen.de
Communicated by Th. Walcher 相似文献
4.
S. Michimasa S. Kubono S.H. Park T. Teranishi Y. Yanagisawa N. Imai Zs. Fülöp X. Liu T. Minemura C.C. Yun J.M. D'Auria K.P. Jackson 《The European Physical Journal A - Hadrons and Nuclei》2002,14(3):275-278
Differential cross-sections of the 24Mg(p, t)22Mg reaction were measured at 34.68 MeV for the states near the proton threshold at 5.502 MeV in 22Mg. Among them, the new states at 5.962, 6.046, 6.246 and 6.323 MeV, which were reported previously, have been confirmed.
Angular distributions for these states were analyzed by distorted-wave Born-approximation calculations to deduce the spins
and parities. The angular distribution for the 5.714 MeV state, which is considered to be most crucial for the stellar reaction
21Na(p, γ)22Mg, has been found to be consistent with J
π = 2+ assignment. The 6.046 MeV state is newly assigned to have J
π = 0+, and the 5.962 MeV state is tentatively assigned to have J
π = (1-). These two states will also play an important role for 22Mg production in novae.
Received: 7 March 2002 / Accepted: 7 May 2002 相似文献
5.
C. Signorini M. Mazzocco G.F. Prete F. Soramel L. Stroe A. Andrighetto I.J. Thompson A. Vitturi A. Brondi M. Cinausero D. Fabris E. Fioretto N. Gelli J.Y. Guo G. La Rana Z.H. Liu F. Lucarelli R. Moro G. Nebbia M. Trotta E. Vardaci G. Viesti 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):249-253
Large cross-section reaction channels were measured in the systems 6Li( 7Li) + 208Pb with high statistical accuracy at 5(3) energies around the Coulomb barrier from 29 to 39 MeV. These channels were assigned
(mainly) to the breakup of 6Li, very loosely bound, into α + d and to the breakup of 5Li, produced by n-transfer to the target, into α + p and to similar processes with 7Li beam. The cross-sections with 6Li, S
α = 1.475 MeV, are systematically larger than the 7Li ones. This reflects, most likely, the higher binding energy of 7Li, S
α = 2.468 MeV. Theoretical predictions for the 6Li + 208Pb system which include for 6Li breakup to continuum states within a continuum discretized coupled-channels approach (CDCC) and resonant breakup plus n-transfer
with DWBA reproduce the angular distribution shapes but still underestimate the cross-sections by a factor ∼ 3.
Received: 15 January 2001 / Accepted: 3 March 2001 相似文献
6.
Yu.N. Lobach A.D. Efimov A.A. Pasternak 《The European Physical Journal A - Hadrons and Nuclei》1999,6(2):131-140
Lifetimes of excited states in 110Cd have been measured by the Doppler shift attenuation method in the reaction (α,2nγ) at E
α= 25 MeV. Lifetime values for 8 states and lifetime limits for 3 states were obtained. The band structures of 110Cd have been interpreted in terms of a modified version of the interacting boson model (IBM + 2 q.p.). The calculations explain
well the excitation energies and electromagnetic transition probabilities up to J
π= 16+, except for the 10+
1 state. The structural features are discussed in terms of collective and two quasiparticle excitations.
Received: 20 March 1999 / Revised version: 28 May 1999 相似文献
7.
T.S. Jensen V.E. Markushin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):261-270
The deexcitation of exotic hydrogen atoms in highly excited states in collisions with hydrogen molecules has been studied
using the classical-trajectory Monte Carlo method. The Coulomb transitions with large change of principal quantum number n have been found to be the dominant collisional deexcitation mechanism at high n. The molecular structure of the hydrogen target is shown to be essential for the dominance of transitions with large Δn. The external Auger effect has been studied in the eikonal approximation. The resulting partial wave cross-sections are consistent
with unitarity and provide a more reliable input for cascade calculations than the previously used Born approximation.
Received 28 May 2002 Published online 15 October 2002
RID="a"
ID="a"e-mail: thomas@physik.unizh.ch 相似文献
8.
V.V. Anisovich A.V. Sarantsev 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):229-258
We present the results of the current analysis of the partial wave IJ
PC = 00+ + based on the available data for meson spectra ( ππ, KˉK,ηη,η,ππππ). In the framework of the K-matrix approach, the analytical amplitude has been reconstructed in the mass region 280 MeV < < 1900 MeV. The following scalar-isoscalar states are seen: comparatively narrow resonances f
0(980), f
0(1300), f
0(1500), f
0(1750) and the broad state f0(1200-1600). The positions of the amplitude poles (masses and total widths of the resonances) are determined as well as pole
residues (partial widths to meson channels ππ, KˉK,ηη,η,ππππ). The fitted amplitude gives us the positions of the K-matrix poles (bare states) and the values of bare-state couplings to meson channels thus allowing the quark-antiquark nonet
classification of bare states. On the basis of the obtained partial widths to the channels ππ, KˉK,ηη,η, we estimate the quark/gluonium content of f
0(980), f
0(1300), f
0(1500), f
0(1750), f0(1200-1600). For f
0(980), f
0(1300), f
0(1500) and f
0(1750), their partial widths testify the qˉq origin of these mesons though being unable to provide precise evaluation of the possible admixture of the gluonium component
in these resonances. The ratios of the decay coupling constants for the f0(1200-1600) support the idea about the gluonium nature of this broad state.
Received: 14 May 2002 / Accepted: 20 August 2002 / Published online: 11 February 2003
RID="a"
ID="a"e-mail: anisovic@thd.pnpi.spb.ru
Communicated by A. Sch?fer 相似文献
9.
10.
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
11.
A. Hader A. Memsouk Y. Boughaleb 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):315-319
We have studied the scaling properties of diffusion fronts by numerical calculations based on the mean field approach in the
context of a lattice gas model, performed in a triangular lattice. We find that the height-height correlation function scales
with time t and length l as C(l, t) ≈l
α
f (t/l
α/β) with α = 0.62±0.01 and β = 0.39±0.02. These exponent values are identical to those characterising the roughness of the diffusion
fronts evolving through a square lattice [1,2], thus confirming their universality.
Received 14 November 2001 / Received in final form 20 April 2002 Published online 31 July 2002 相似文献
12.
D. Sohler Zs. Dombrádi J. Blomqvist J. Cederkäll J. Huijnen M. Lipoglavšek M. Palacz A. Atac C. Fahlander H. Grawe A. Johnson A. Kerek W. Klamra J. Kownacki A. Likar L.-O. Norlin J. Nyberg J. Persson D. Seweryniak G. de Angelis P. Bednarczyk D. Foltescu D. Jerrestam S. Juutinen E. Mäkelä M. de Poli H.A. Roth T. Shizuma Ö. Skeppstedt G. Sletten J. Timár S. Törmänen M. Weiszflog 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):171-175
Excited states of 99Ag were populated via the 50Cr + 58Ni (261 MeV) reaction using the NORDBALL detector array equipped with charged-particle and neutron detector systems for reaction
channel separation. On the basis of the measured γγ-coincidence relations and angular distribution ratios a significantly
extended level scheme has been constructed up to E
x ∼ 7.8 MeV and I = 35/2. The experimental results were described within the framework of the shell model. Candidates for states fully aligned
in the πg
9/2
-3ν(d
5/2, g
7/2)2 valence configuration space were found at 4109 and 6265 keV.
Received: 18 June 2002 / Accepted: 11 October 2002 / Published online: 4 February 2003
RID="a"
ID="a"e-mail: sohler@atomki.hu
Communicated by J. ?yst? 相似文献
13.
H. Iwasaki T. Motobayashi H. Akiyoshi Y. Ando N. Fukuda H. Fujiwara Zs. Fülöp K. I. Hahn Y. Higurashi M. Hirai I. Hisanaga N. Iwasa T. Kijima A. Mengoni T. Minemura T. Nakamura M. Notani S. Ozawa H. Sagawa H. Sakurai S. Shimoura S. Takeuchi T. Teranishi Y. Yanagisawa M. Ishihara 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):55-58
Experimental studies on in-beam γ-ray spectroscopy using a 12Be radioactive beam are presented. Inelastic scattering of the neutron-rich 12Be nucleus on 208Pb, 12C, and (CH2)n targets has been studied by measuring de-excitation γ-rays in coincidence with scattered particles. The level schemes and
transition probabilities are determined for low-lying excited states in 12Be. The present paper presents a brief review of the spectroscopic results, which may be associated with the N = 8 shell quenching near the drip line.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
14.
R. Ferrini G. Guizzetti M. Patrini A. Parisini L. Tarricone B. Valenti 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):449-458
In0.49Ga0.51P films, both undoped and doped n- and p-type (up to 1018 cm-3), were grown lattice matched on GaAs substrates, with different miscut angles, by Metal-Organic Vapour Phase Epitaxy (MOVPE)
at different temperatures. The shift of the fundamental gap E0, caused by “ordering effect” was measured as a function of temperature by photoluminescence. The complex refractive index
= n + ik and the dielectric function = ɛ
1 + iɛ
2 at room temperature were determined from 0.01 to 5.5 eV by using complementary data from fast-Fourier-transform far-infrared
(FFT-FIR), dispersive, and ellipsometric spectroscopies. The effect of the native oxide was accounted for and the self-consistency
of the optical functions was checked in the framework of the Kramers-Kronig causality relations. In the restrahlen region
the dielectric function was well fitted by classical Lorentz oscillators; in the transparent region below E0, the refractive index was modelled by a Sellmeier dispersion relation; in the interband region the dielectric function was
well reproduced by analytical lineshapes associated to seven critical points. Thus parametrized analytical expressions were
obtained for the optical functions all over the spectral range, without discontinuities, to be used in the modelling and characterization
of multi-layer structures, also on opaque substrates.
Received 13 December 2001 Published online 25 June 2002 相似文献
15.
Y. Fujita H. Fujita T. Adachi G.P.A. Berg E. Caurier H. Fujimura K. Hara K. Hatanaka Z. Janas J. Kamiya T. Kawabata K. Langanke G. Martınez-Pinedo T. Noro E. Roeckl Y. Shimbara T. Shinada S.Y. van der Werf M. Yoshifuku M. Yosoi R.G.T. Zegers 《The European Physical Journal A - Hadrons and Nuclei》2002,13(4):411-418
Under the assumption that isospin is a good quantum number, symmetry is expected for the transitions from the ground states
of T = 1, T
z = ±1 nuclei to the common excited states of the T
z = 0 nucleus situated between the two nuclei. The symmetry can be studied by comparing the strengths of Gamow-Teller (GT)
transitions obtained from a (p, n)-type charge-exchange reaction on a target nucleus with T
z = 1 with those from the β-decay of the T
z = - 1 nucleus. The A = 58 system is the heaviest for which such a comparison is possible. As a part of the symmetry study, we measured the GT
transitions from 58Ni (T
z = 1) to 58Cu (T
z = 0) by using the zero-degree (3
He, t) reaction at 150 MeV/nucleon. With the achieved resolution of 50 keV, many hitherto unresolved GT states have been identified.
The GT transition strengths were obtained for states up to 8 MeV excitation, i.e., near to the Q window limitation ( Q
EC = 9.37 MeV) of the β-decay from 58Zn (T
z = - 1) to 58Cu. The strength distribution is compared with that from shell-model calculations.
Received: 24 November 2001 / Accepted: 30 January 2002 相似文献
16.
The cross-sections for the reactions of muonium (anti-muonium) production in the high-energy electron (positron) scattering
by nuclei e
-(e
+) + Z↦Z + M
0(ˉM) + μ-(μ+) are calculated in dependence on energy and polarization of the initial electron (positron) and polarization of the final
μ-(μ+)-meson. Since this is a coherent phenomenon the cross-sections are proportional to Z2. For Z ∼ 100, due to the factor Z2, the cross-sections are large enough to be measured at the energies available for the HERA Collider at DESY. The results
are discussed in connection with a test of CPT invariance.
Received: 24 September 2002 / Accepted: 12 March 2003 / Published online: 27 May 2003 相似文献
17.
18.
I. Dillmann M. Hannawald U. Köster V.N. Fedoseyev A. Wöhr B. Pfeiffer D. Fedorov J. Shergur L. Weissman W.B. Walters K.-L. Kratz 《The European Physical Journal A - Hadrons and Nuclei》2002,13(3):281-284
Production yields and β-decay half-lives (T
1/2) of very neutron-rich indium isotopes were determined at CERN/ISOLDE using isobaric selectivity of a resonance-ionization
laser ion-source. Beta-delayed neutron (βdn) multiscaling measurements have yielded improved T
1/2 for 206(6) ms 132In, 165(3) ms 133In and 141(5) ms 134In. With 92(10) ms 135In, a new r-process nuclide has been identified which acts as an important “waiting point” in the In isotopic chain for neutron
densities in the range n
n≃ 1024-1026 n/cm3, where the r-matter flow has already passed the A≃ 130 abundance peak region.
Received: 17 January 2002 / Accepted: 30 January 2002 相似文献
19.
H.W. Dannhausen E.J. Durwen H.M. Fischer M. Leneke W. Niehaus F. Takasaki 《The European Physical Journal A - Hadrons and Nuclei》2001,11(4):441-455
The differential cross-section for the reaction γp↦π +
n was measured using the bremsstrahlung beam of the Bonn 2.5 GeV electron synchrotron. The pions were detected and momentum
analysed in a multichannel magnet spectrometer. Data reduction resulted in 1278 measured cross-sections which are presented
as energy distributions at six laboratory angles between 180° and 95°. The range of laboratory photon energies extended from
0.3 to 2.1 GeV. The statistical accuracy is better than 3 percent, the systematic error is about 5 percent. The data are compared
with other experimental results and predictions of a phenomenological analysis. These cross-sections are the result of a measurement
program which was started in the seventies. Further results will be reported in forthcoming publications.
Received: 2 February 2000 / Accepted: 14 August 2001 相似文献
20.
A. Johansson M.K. Raarup Z.S. Li V. Lokhnygin D. Descamps C. Lyngå E. Mevel J. Larsson C.-G. Wahlström S. Aloise M. Gisselbrecht M. Meyer A. L'Huillier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):3-11
A pump-probe technique has been applied for measuring the lifetimes and absolute photoionization cross-sections of excited
He states. The 1s2p 1P and 1s3p 1P states of He are excited by using the 13th and the 14th harmonic, respectively, of a tunable 70 ps dye laser generated in
a Kr gas jet. The states are ionized after a varying time delay, by absorption of probe photons with energies between 1.6
and 4.5 eV. Lifetimes of τ(1s2p) = 0.57 ns and τ(1s3p) = 1.76 ns are determined with a precision of about 15%. A significant enhancement of the number of ions present in the lifetime
curves at zero time delay for pressures above 6×10-5 mbar is attributed to direct two-photon ionization of He in combination with AC Stark broadening of the excited state and
absorption of the XUV light in the medium. Absolute photoionization cross-sections from the He 1s2p 1P and He 1s3p 1P states in the threshold region are determined by measuring the saturation of the ionization process with a precision of
∼ 25%. In addition, the variation of the relative orientation between the polarization vectors of the pump and probe beams
enables the determination of partial photoionization cross-sections.
Received 3 June 2002 / Received in final form 14 August 2002 Published online 22 October 2002
RID="a"
ID="a"Present address: Department of Biophysics, Leiden University, 2333 CA Leiden, The Netherlands.
RID="b"
ID="b"Present address: Continuum Electro-Optics Inc., 3150 Central Expressway, Santa Clara, CA 95051, USA.
RID="c"
ID="c"Present address: CEA/DRECAM/SPAM, CEN Saclay, 91105 Gif-sur-Yvette, France.
RID="d"
ID="d"Present address: Department of Physics, National University of Rwanda, Butare, Rwanda.
RID="e"
ID="e"Present address: CELIA, Université Bordeaux 1, 33405 Talence, France.
RID="f"
ID="f"Present address: MAX-Lab, Lund University, Box 118, 221 00 Lund, Sweden.
RID="g"
ID="g"e-mail: anne.lhuillier@fysik.lth.se 相似文献