共查询到20条相似文献,搜索用时 156 毫秒
1.
M. Barat J.C. Brenot H. Dunet J.A. Fayeton Y.J. Picard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):271-276
An experimental study of the dissociation of the heteronuclear Na ion by collisions with He and H2 targets at a collision energy of 2.4 keV is presented. The use of a technique based on the measurement of the velocity vectors
of the fragments allows investigating in detail the two basic dissociation mechanisms: impulsive and electronic. In the present
asymmetric case, one is able to assess the relative role of close encounters with each of the Na+ and atomic cores of the molecule. Electronic transitions at a surface crossing are proposed to explain processes which happens
in close collisions between the core and the He target.
Received: 3 October 1997 / Revised: 1 December 1997 / Accepted: 16 January 1998 相似文献
2.
M.L. Gardel R. Vandenbosch B.P. Henry C. Cooper D.I. Will 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):79-81
The destruction cross-section for 22.5 and 50 keV C1- , for 10 and 50 keV C8
1- and for 50 and 75 keV C60
1- clusters in collisions with H2 has been measured by an attenuation method. The destruction of the cluster anions is dominated by electron detachment rather
than fragmentation and is of the order of the geometric cross-section. The cross-sections vary little with bombarding energy.
Received: 16 September 1998 / Received in final form: 23 February 1999 相似文献
3.
Y. Torii N. Shiokawa T. Hirano T. Kuga Y. Shimizu H. Sasada 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):239-242
We utilized a blue-detuned Laguerre-Gaussian (doughnut) laser beam to trap cold rubidium atoms by optical dipole force. ”Pulsed”
polarization gradient cooling was applied to the trapped atoms to suppress the trap loss due to heating caused by random photon
scattering of the trapping light. In this trap about 108 atoms were initially captured and the trap lifetime was 1.5 s, which was consistent with losses due to background gas collisions.
This trap can readily be applied to atom guiding, compression, and evaporative cooling.
Received: 10 July 1997 / Received in final form: 5 January 1998 / Accepted: 16 January 1998 相似文献
4.
A. Fioretti E. Arimondo A. Crubellier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):219-225
The measurements of fine-structure changing collisions in a cesium magneto-optical trap, reported in a previous work [A. Fioretti
et al., Phys. Rev. A 55, R3999 (1997)], are reanalyzed within a model based on the flux enhancement effect, which takes place in cold atomic collisions.
In the present analysis, we consider the cooperative effect of the long-range and the shorter-range excitation by the strong
trap laser. We evidence also the important role of the hyperfine structure of the Cs2 molecular levels asymptotically connected to the ground-state and excited-state dissociation limits.
Received 22 July 1999 and Received in final form 4 May 2000 相似文献
5.
S. Martin J. Bernard L. Chen A. Denis J. Désesquelles 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):1-6
Electron capture by Ar8+ in collisions with C60 fullerene has been investigated using coincident measurements of the number n of ejected electrons, the mass and charge of multicharged Cr+
60
recoil ions and their fragments Ci+
m and the final charge state of outgoing projectiles Ar(8-s)+ (). The number of captured electrons r is the sum of the numbers of stabilized and emitted electrons: r
=
n
+
s. The ratio n
/
s decreases by a factor three with s increasing from 1 to 7 showing that the multiply excited states populated by capture of a large number of electrons are rather
stable against auto-ionisation. Each kinetic energy spectrum of Ar+ and Ar2+ projectiles is composed of two peaks which we attribute to collisions “inside” and “outside” the C60 cage. The measured energy shift of the projectile keV is consistent with the corresponding energy loss keV in a carbon foil with an equivalent thickness. Inside collisions are characterized by a strong dissociation of recoil
ions into light monocharged fragments and by a high multiplicity of ejected electrons.
Received: 25 March 1998 / Received in final form and Accepted: 9 June 1998 相似文献
6.
O. Wilhelmi K.-H. Schartner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):79-90
Molecular oxygen O2 was dissociated in collisions with protons and electrons in the intermediate velocity range (p+-energies: 17-800 keV, e--energies: 0.2-2 keV). Fluorescence from excited atomic and singly ionised fragments and from singly ionised molecules was
detected in the VUV and in the visible and near UV spectral range. Highly resolved spectra are presented for the VUV (46-131
nm) and the near UV/visible (340-605 nm) spectral range. Absolute emission cross-sections have been determined for dissociative
ionisation and excitation leading to fluorescence in the VUV. Results are compared with published data.
Received 9 September 1999 and Received in final form
15 December 1999 相似文献
7.
M.W. Mancini A.L. de Oliveira K.M.F. Magalhãaes V.S. Bagnato L.G. Marcassa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):317-322
In an experimental study, the multi-ionisation of metallic clusters (Nan) has been analysed in collisions with light ions in low charge states (H+, He+, He2+, O3+) at collision velocities below 1 a.u. Cluster ions are produced in charge states up to 5+. The average charge of the nano-particles
is found to increase linearly with the variation of projectile velocity and the square of the effective projectile charge,
well in agreement with the electronic stopping power of the bulk material. A fraction of 50% to 30% of the total projectile
energy loss (decreasing with velocity) is transferred into vibrational modes in good agreement with recent theoretical predictions.
Received 8 November 2000 and Received in final form 26 January 2001 相似文献
8.
A. Morozov B. Krylov G. Gerasimov R. Hallin A. Arnesen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):379-385
The origins of spectral structures that appear close to the Xe resonance line at 146.96 nm in absorption spectra of Kr gas
with an admixture of Xe are discussed in this paper. It is shown that these structures can result from bound-bound and bound-free
transitions in the Xe-Kr molecule between the ground state and the 1(3P1) excited state, which both are weakly-bound. The depth of the excited state is estimated. An introduction of a hump on the
1(3P1) state internuclear potential is suggested.
Received 15 December 1999 and Received in final form 20 February 2000 相似文献
9.
L.G. Marcassa R.A.S. Zanon S. Dutta J. Weiner O. Dulieu V.S. Bagnato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):317-321
Using a technique that consists in ionizing atoms out of the 5P
1/2
fragments originated in the cold collision process, we have measured the contribution of the fine structure changing collision
(FS) to the total trap loss rate of cold 85Rb. Our results show that FS contribution is responsible for about 4% of the total trap loss. This result should stimulate
new theoretical discussions involving exoergic cold collisions.
Received 26 October 1998 and Received in final form 2 February 1999 相似文献
10.
V. Vescoli J. Favand F. Mila L. Degiorgi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):149-154
The validity of the optical sum rules has been addressed eversince and was always matter of debate. Particularly controversial
is the proof that the partial sum rules can be extended to both optical conductivity and energy loss function. We show in this paper that for both transverse
(optical conductivity) and longitudinal (energy loss function) absorption processes the corresponding sum rule can be theoretically
established and through appropriate conditions for the integration limits exactly verified. We also focus our attention on
the one-dimensional case within the microscopic Hubbard model. An application of these concepts to the quasi one-dimensional
systems, for which we have chosen the organic (TMTSF)2PF6 material, will also be presented.
Received: 19 December 1997 / Received in final form: 9 March 1998 / Accepted: 23 March 1998 相似文献
11.
O. Toulemonde F. Studer A. Barnabé A. Maignan C. Martin B. Raveau 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):159-167
The XAS study at Cr, Co, Ni and Mn K-edges was performed for the doped CMR manganites Ln0.5Ca0.5Mn1-xBxO3 with Ln=La, Nd, Sm and B= Cr, Co, Ni (), on the samples that were studied previously for their ferromagnetic-metallic to antiferromagnetic-insulator transition.
We observed that the formal charges of the doping elements are Ni2+, Co2+ and Cr3+. It is also evidenced that the average formal charge of the manganese is increased after doping, in agreement with the charge
compensation keeping “O3” stoichiometry. These results suggest that the doping elements participate directly to the band structure.
Received: 9 January 1998 / Received in final form: 6 April 1998 / Accepted: 7 April 1998 相似文献
12.
E. Rastelli A. Tassi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(3):285-289
Dipolar spin-spin interactions play a crucial role as for the magnetic order in the compounds of the RBa2Cu3O6+x family, (R = Dy, Er, Nd). However, inelastic neutron scattering data observed in ErBa2Cu3O7 can be explained only if exchange interactions in addition to dipolar ones are taken into account.
Received: 12 January 1998 / Received in final form: 26 March 1998 / Accepted: 10 April 1998 相似文献
13.
K. Orlovsky V. Grushevsky A. Ekers 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):133-146
We present results of theoretical studies of the non-resonant excitation transfer in Rb(7S) + Rb(5S) and Rb(5D) + Rb(5S) collisions
at thermal collision energies. Rb2 adiabatic molecular terms correlating with the 5S+7S, 5S+5D and 5P+5P states of separated atoms were calculated for internuclear
distances R > 20 a.u. using asymptotic approximation. Mechanisms of collisional population and quenching of the 5D state were treated
on the basis of the computed molecular terms, and the respective cross-sections were calculated. Theoretical cross-sections
are in good agreement with the experimental values at thermal collision energies ( K).
Received 13 November 1998 and Received in final form 22 November 1999 相似文献
14.
V.P. Dyakonov M.T. Borowiec A. Jedrzejczak M. Górska N.A. Doroshenko E. Zubov Yu. Bukhantsev T. Zayarnyuk H. Szymczak 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):9-14
Magnetic phase transition in the CsDyW2O8 magnet has been studied by means of low temperature specific heat C
(
T
) measurements. The magnetic ordering temperature of the Dy3+ sublattice was established to be 1.34 K. The experimental results indicate on the antiferromagnetic character of interactions
between Dy3+ ions. The behavior of the C
(
T
) dependencies above and below T
N
is discussed in frames of different theoretical models. The measurements data on temperature and field dependencies of magnetization
are used to calculate the exchange and dipole-dipole interactions energy and to determine the possible magnetic structure
of the ground state.
Received 7 January 2002 / Received in final form 15 May 2002 Published online 7 September 2002 相似文献
15.
We show how Fermi liquid theory results can be systematically recovered using a renormalization group (RG) approach. Considering
a two-dimensional system with a circular Fermi surface, we derive RG equations at one-loop order for the two-particle vertex
function in the limit of small momentum () and energy () transfer and obtain the equation which determines the collective modes of a Fermi liquid. The density-density response function
is also calculated. The Landau function (or, equivalently, the Landau parameters F
l
s
and F
l
a
) is determined by the fixed point value of the -limit of the two-particle vertex function (). We show how the results obtained at one-loop order can be extended to all orders in a loop expansion. Calculating the quasi-particle
life-time and renormalization factor at two-loop order, we reproduce the results obtained from two-dimensional bosonization
or Ward Identities. We discuss the zero-temperature limit of the RG equations and the difference between the Field Theory
and the Kadanoff-Wilson formulations of the RG. We point out the importance of n-body () interactions in the latter.
Received: 27 June 1997 / Received in final form: 17 December 1997 / Accepted: 26 January 1998 相似文献
16.
E. Chappel M.D. Núñez-Regueiro F. Dupont G. Chouteau C. Darie A. Sulpice 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):609-614
Magnetisation measurements up to 23 T and submillimeter wave ESR in the frequency region 48-380 GHz have been performed on
NaNiO2 powders at low temperature. Also typical spectra above the Néel temperature are shown. At 4 K the magnetisation shows a spin-flop transition at 1.8 T and saturation at 10 T. /Ni confirms the low spin state of the Ni3+ ions. The susceptibility exhibits a maximum at K with and K. NaNiO2 is an A-type antiferromagnet: we derive K and K for the interactions between Ni ions within and between adjacent layers, respectively. The AFMR spectra yield an energy
gap of 52.5 GHz, in agreement with the spin-flop value derived from the magnetisation. The anisotropy of the g factor observed at 100 K with can be attributed to the Jahn-Teller effect for Ni3+ ions in the low spin state, which stabilises the occupation. We finally comment on the isomorphic controversial Li1-xNi1+xO2 compound.
Received 9 March 2000 and Received in final form 13 July 2000. 相似文献
17.
N. Magnani G. Amoretti A. Baraldi R. Capelletti 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):79-84
The experimental values of the energy levels of Er3+, Dy3+, and Nd3+ in BaY2F8 were fitted to a single-ion Hamiltonian containing free-ion and crystal-field interactions. The crystal-field parameters
so evaluated were then analyzed by using Newman's Superposition Model. The agreement between the two sets of parameters is
good, provided a possible distortion of the F- polyhedron around the rare-earth site is taken into account. The effects of a possible displacement of the rare-earth ion
substituting for Y3+ are also evaluated.
Received 14 May 2002 / Received in final form 12 July 2002 Published online 17 September 2002 相似文献
18.
A. Knipp W. Langel H. Mutka E. Knözinger 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):109-117
Inelastic neutron scattering spectra at 17 meV and 68 meV incident energies of molecular hydrogen adsorbed on vapour deposited
substrates of pure CO2, 90:10 and 50:50 CO2:Kr are reported. The ortho-para transition is shifted from 14.7 meV in the free H2-molecule to 9.4 meV in a presumably commensurate ortho-H2 monolayer on the CO2 surface. The quadrupole-quadrupole interaction of ortho-H2 molecules with the CO2 substrate results in a strongly anisotropic potential. In addition to rotations the dynamics of this layer comprise a local
Einstein mode and phonons in resonance with the substrate, giving rise to intense multiphonon transitions. Quasielastic scattering
on warmer samples is assigned to a liquidlike adsorption layer, in which the H2 rotations are strongly perturbed.
Received: 15 October 1996 / Revised: 25 August 1997 / Accepted: 24 October 1997 相似文献
19.
E.A. Alipieva S.I. Karabasheva 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(3):291-294
The non-linear Voigt effect has been studied in He discharge under resonance laser interaction with the He transition. The range of non-linear signal existence was determined. The contribution of the lower and upper states to
the overall signal was analyzed. The cross-section for depolarizing collisions with ground state He atoms was estimated for
the 33
D
2,3
He state.
Received: 16 June 1998 / Received in final form: 14 December 1998 相似文献
20.
E. Leber S. Barsotti I.I. Fabrikant J.M. Weber M.-W. Ruf H. Hotop 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):125-131
Using a high resolution ( meV) laser photoelectron attachment method, we have studied the formation of (CO 2)
q
− ions (q = 4−22) in collisions of low energy electrons (1−180 meV) with (CO2)
N
() clusters. The previously reported “zero energy resonance”, observed at much larger electron bandwidths, actually consists
of several narrow vibrational Feshbach resonances of the type [(CO 2)
N
−1CO which involve a vibrationally-excited molecular constituent ( denotes vibrational mode) and a diffuse electron weakly bound to the cluster by long range forces. The resonances occur at
energies below those of the vibrational excitation energies of the neutral clusters [(CO 2)
N
−1CO ]; the redshift rises with increasing cluster ion size q by about 12 meV per unit; these findings are recovered by a simple model calculation for the size dependent binding energies.
The size distribution in the cluster anion mass spectrum, resulting from attachment of very slow electrons, mainly reflects
the amount of overlap of solvation-shifted vibrational resonances with zero energy; the cluster anion size q is identical with or close to that of the attaching neutral cluster.
Received 11 January 2000 and Received in final form 10 April 2000 相似文献