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1.
The electron terms are constructed for oxygen dimer ions at large ion-atom distances taking into account a certain scheme of summation of electron momenta on the basis of a hierarchy of various ion-atom interactions. Because the number of interaction types exceeds that in the Hund scheme, a realistic hierarchy of interactions and corresponding quantum numbers of the diatomic ion are outside the Hund coupling scheme. Electron terms are evaluated for the oxygen dimer ion in the case where the ground and first excited states of an atom and an ion belong to the respective valence electron shells p4 and p3 and correspond to the range of separations that determine the cross sections of resonant charge exchange in plasma. These electron terms allow us to calculate the partial and average cross sections for resonant charge exchange involving an oxygen ion and atom in the ground and first excited states in the range of collision energies of interest for oxygen plasmas. The specific features of electron terms of the oxygen ion dimer and the cross section of electron transfer are analyzed. 相似文献
2.
B. M. Smirnov 《Journal of Experimental and Theoretical Physics》2003,97(3):493-504
The coupling of electron momenta is considered for the resonant charge exchange process in slow collisions. Because the electron transfer in this process occurs at large distances between the colliding atomic particles, where ion-atom interactions are relatively weak, we can separate different types of interaction and find the character of coupling of the electron momenta in the quasi-molecule, consisting of the colliding ion and its atom, for real collision pairs. Since the real number of interaction types for colliding particles exceeds that used in the classical Hund coupling scheme, there are intermediate cases of momentum coupling outside the standard Hund scheme. This occurs for the resonant charge exchange involving halogens and oxygen where the quantum numbers of the quasi-molecule in the course of the electron transfer are the total momenta J and j of the colliding ion and atom and the projection M or MJ of the atom orbital or total momentum on the quasi-molecule axis. The ion-atom exchange interaction potential is independent of the ion fine state, and under these conditions, the resonant charge exchange process is not entangled with the rotation of electron momenta, as in case “a” of the Hund coupling. The partial cross section of the resonant charge exchange process depends on quantum numbers of the colliding particles. The average cross sections depend weakly on the coupling scheme. 相似文献
3.
B. M. Smirnov 《Journal of Experimental and Theoretical Physics》2001,92(6):951-959
The asymptotic resonant charge exchange theory is developed for slow collisions of atoms and ions with valent p-electrons. Because of a small rotation angle of the molecular axis in the course of the p-electron transition, the resonant charge exchange cross section is not sensitive to the rotational energy of colliding particles, and the cross sections are nearly equal for cases “a”, “b”, and “d” of the Hund coupling, and also for cases “c” and “e” of the Hund coupling. The cross sections of the resonant charge exchange process are evaluated under various conditions and for various elements of the periodical table with p-electron shells of atoms and ions. 相似文献
4.
The electronic density of states, spin-splittings and atomic magnetic moments of SmCO7-compound have been studied using spin-polarized MS-Xα method. The results show that a few of electrons are transferred to
Sm(5d0) orbital because of orbital hybridization between Sm and Co atoms in the compound. The exchange interactions between 3d and
5d electrons lead to the magnetic coupling between Sm and Co, and therefore, result in the long-range ferromagnetic order
inside the SmCo7 compound. There are negative exchange couplings occurring at some levels, which weakens the strength of average coupling
around Co lattice. So, the Curie temperature and Co-moment of SmCo7-decrease distinctly compared with pure Co. Compared with SmCo5 compound, the disordered substitution of Co-Co “dumbbell-atom” pairs for Sm changes the local environment of Co lattice,
which makes the 2e site bear negative magnetic moment. The strength of hybridization near Fermi level weakens and the free
energy of the compound increases obviously. Thus, SmCo7 is a metastable compound at room temperature. Considering the localization of 4f electrons and a few of 5d electrons arising
from the orbital hybridization, the magnetic moment of Sm atom will be 1.61μB in SmCo7 compound, which is in agreement with the experimental values of Sm3+ ion-moment and Sm atom-moment in metals. 相似文献
5.
F.O. Talbot J.P. Simons 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):389-398
Mass-resolved resonant two photon ionisation (R2PI) and infrared ion dip spectra have been recorded for 4-phenylimidazole
(4PI) and its singly and multiply hydrated clusters 4PI(H2O)n = 0 - 4, under supersonic expansion conditions. In the case of 4PI(H2O)0,1, it has also been possible to record infrared spectra in both the ground (S0) and excited (S1) states. Combining the experimental data with the results of ab initio calculations has led to the structural assignment of each cluster. In each case, the water molecules bind primarily to the
NH site of the imidazole ring. Clusters with n≥ 2 incorporate linear water chains, in which the proton donating terminus bridges either to the π-electron system (n = 2) or to the >N: atom site (n = 3, 4) on the imidazole ring. Despite the creation of a “water wire”, connecting the donor and acceptor sites of imidazole,
there is no evidence of proton transfer in either the ground or excited state.
Received 20 December 2001 Published online 13 September 2002 相似文献
6.
A.A. Zvyagin A. Klümper J. Zittartz 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):25-36
The exactly solvable model of supersymmetric t - J chains (STJC) of correlated electrons with next-nearest-neighbour (NNN) interactions is proposed and studied. The model with
interactions between nearest neighbours and NNN interactions in one chain can also be considered as a two-chain model with
zigzag-like coupling between the chains. The NNN interaction (coupling between chains) causes the onset of additional Dirac
seas for low-lying charge and/or spin excitations. These Dirac seas change the low-energy (conformal) behavior of the model.
The filling of those seas depends on the values of the NNN coupling (interactions between chains), external magnetic field
and applied voltage. We identify the new ground state phases which appear due to the NNN as incommensurate ones. The NNN coupling
in the incommensurate phases induces spontaneous magnetization and/or spontaneous filling of the Dirac sea for charge excitations
(“spontaneous charge ordering”). The onset of this order implies a first order quantum phase transition driven by the field
with hysteresis phenomena.
Received 13 September 2000 相似文献
7.
M. Combescot 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(3):289-303
We reconsider the procedure
developed for atoms a few decades ago by Girardeau, in the light of
the composite-boson many-body theory we recently proposed. The
Girardeau's procedure makes use of a so called “unitary Fock-Tani
operator” which in an exact way transforms one composite bound
atom into one bosonic “ideal” atom. When used to transform the
Hamiltonian of interacting atoms, this operator generates an extremely
complex set of effective scatterings between ideal bosonic atoms and free
fermions which makes the transformed Hamiltonian impossible to write
explicitly, in this way forcing to some truncation. The scatterings
restricted to the ideal-atom subspace are shown to read rather simply in
terms of the two elementary scatterings of the composite-boson many-body
theory, namely, the energy-like direct interaction scatterings
— which describe fermion interactions without fermion exchange — and
the dimensionless Pauli scatterings — which describe fermion exchanges
without fermion interaction. We here show
that, due to a fundamental difference in the scalar products of
elementary and composite bosons, the Hamiltonian expectation
value for N ground state atoms
obtained by staying in the ideal-atom subspace and working
with boson operators only, differ from the exact ones even for N = 2 and
a mapping to the ideal-atom subspace performed, as advocated, from
the fully antisymmetrical atomic state, i.e., the state which obeys the
so-called “subsidiary condition”. This shows that, within this
Girardeau's procedure too, we cannot completely forget the underlying
fermionic components of the particles if we want to correctly describe
their interactions. 相似文献
8.
The Landau-Herring method is used to derive an analytic expression for the one-electron exchange interaction of a polar molecule
with its positively charged ion, induced by a σ-electron. Analogously to the classical Van der Pole method, the exchange interaction
potential is averaged over the rotational states of colliding particles. The resonant charge-transfer cross section is calculated,
and the effect of the dipole moments of the core on the cross section is analyzed. It is shown that allowance for the dependence
of the exchange potential on the orientation of the dipole moments relative to the molecular axis may change the dependence
of the cross section on the velocity of colliding particles, which is typical of the resonant charge exchange, from the resonance
to the quasi-resonance dependence. 相似文献
9.
Vladimir Kalitvianski 《Central European Journal of Physics》2009,7(1):1-11
We show that the electrostatic potential of an atomic nucleus “seen” by a fast charged projectile at short distances is quantum
mechanically smeared due to nucleus motion around the atomic center of inertia. For example, the size of the “positive charge
cloud” in the Hydrogen ground state is much larger than the proper proton size. For target atoms in excited initial states,
the effect is even larger. The elastic scattering at large angles is generally weaker than the Rutherford scattering since
the effective potential at short distances is softer than the Colombian one due to a natural “cutoff”. In addition, the large-angle
scattering leads to target atom excitations due to pushing the nucleus (⇒ inelastic processes). The Rutherford cross section
is in fact inclusive rather than elastic. These results are analogous to those from QED. Non-relativistic atomic calculations
are presented. The difference and the value of these calculations arise from nonperturbatively (exact) nucleus “dressing”
that immediately leads to correct physical results and to significant technical simplifications. In these respects a nucleus
bound in an atom is a simple but rather realistic model of a “dressed” charge in the QFT. This idea is briefly demonstrated
on a real electron model (electronium) which is free from infinities.
相似文献
10.
A. A. Makarov 《Applied physics. B, Lasers and optics》1982,29(4):287-290
For the detection of the rare radioactive isotope41Ca, the possibilities of the earlier-proposed initial-state enrichment by continuous-wave laser radiation are examined. It is shown that the enrichment 1014 of 3d-states of the ion Ca II can be reached. As the method of enriched-state detection, the process of resonant charge exchange is analysed. For a further increase of the selectivity, the repetition of the cycle initial state enrichment plus resonant charge exchange is discussed. 相似文献
11.
A.K. Kolezhuk H.-J. Mikeska 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):543-550
We study the “mixed spin” isotropic ladder system having S=1 spins on one leg and S=1/2 spins on the other, with general-type exchange interactions between spins on neighboring rungs. A set of model Hamiltonians
with exact ground states in the form of a certain matrix product wave function is obtained. We show that sufficiently strong
frustration can lead to exotic singlet ground states with infinite (exponential) degeneracy. We also list a couple of rather
simple models with nontrivial ground states, including a model with only bilinear exchange.
Received: 2 December 1997 / Accepted: 28 January 1998 相似文献
12.
A. B. Voitkiv 《Journal of Experimental and Theoretical Physics》1997,85(6):1074-1080
Ionization of hydrogen and helium atoms is studied for the case of “soft” collisions with highly charged fast ions with v≲Z≪v2 and v≫v
0, where Z is the ion charge, v is the collision velocity, and v
0∼1 is the characteristic velocity of the electron in the ground state of the atom. Analytical expressions are derived for
the singly and doubly differential cross section for ionization of a hydrogen atom accompanied by the ejection of a slow electron
v
e≲v
0, where v
e is the velocity of the ejected electron with respect to the recoil ion). The results are generalized to the case of single
ionization of helium. It is shown that soft collisions provide the main contribution to the hydrogen ionization cross section
and for all practical purposes determine the cross section for single ionization of helium. The asymmetry in the angular distribution
of the ejected slow electrons and the properties of momentum exchange in such collisions are discussed. Finally, a formula
for the cross section for single ionization of helium is proposed.
Zh. éksp. Teor. Fiz. 112, 1966–1977 (December 1997) 相似文献
13.
Relativistic analytical expressions are derived for the electric quadrupole moment induced by the hyperfine interaction of the electron with the nucleus of a hydrogen-like atom in the ns1/2 and np1/2 states. The magnetic dipole and electric quadrupole hyperfine interactions are taken into account. The calculations are performed using the generalized virial relationships for the Dirac equation in a central field. The dependences of the electric quadrupole moment on the nuclear charge Z and the principal quantum number n are analyzed. The induced quadrupole moments are compared with the nuclear quadrupole moments. 相似文献
14.
Ion transport and focusing in radio-frequency (rf) quadrupole channels filled with a buffer gas at an intermediate pressure
(100–1000 Pa) are studied theoretically through numerical simulation based on a combined model of ion-molecule interactions.
The simulations uncovered specific effects that appear in the considered gas pressure range: “quasi-absolute” stability of
motion of small-mass ions and radial boundedness of the ion focusing region. 相似文献
15.
Donato Bini Christian Cherubini Simonetta Filippi Andrea Geralico 《General Relativity and Gravitation》2009,41(12):2781-2795
An exact solution of Einstein’s equations representing the static gravitational field of a quasi-spherical source endowed
with both mass and mass quadrupole moment is considered. It belongs to the Weyl class of solutions and reduces to the Schwarzschild
solution when the quadrupole moment vanishes. The geometric properties of timelike circular orbits (including geodesics) in
this spacetime are investigated. Moreover, a comparison between geodesic motion in the spacetime of a quasi-spherical source
and non-geodesic motion of an extended body also endowed with both mass and mass quadrupole moment as described by Dixon’s
model in the gravitational field of a Schwarzschild black hole is discussed. Certain “reciprocity relations” between the source
and the particle parameters are obtained, providing a further argument in favor of the acceptability of Dixon’s model for
extended bodies in general relativity. 相似文献
16.
Miron Ya. Amusia Arkadiy S. Baltenkov Larissa V. Chernysheva 《Central European Journal of Physics》2008,6(1):14-25
We demonstrate rather interesting manifestations of co-existence of resonance features in characteristics of the photoionization
of 3d-electrons in Xe, Cs and Ba endohedral atoms. It is shown that for all of the considered atoms the reflection by the fullerene
shell of photoelectrons produced by the 3d subshell photoionization affects greatly partial photoionization cross-sections of 3d
5/2 and 3d
3/2 levels and respective angular anisotropy parameters, both dipole and non-dipole adding to all of them additional maximums
and minimums. The results obtained demonstrate distinctive differences between the three atoms. The calculations are performed
treating the 3/2 and 5/2 electrons as electrons of different kinds with their spins “up” and “down”. The effect of the C60 shell is accounted for in the frame of the “orange” skin potential model. It is essential that in the considered photon frequency
region the presented resonance features are not affected by the C60polarization.
相似文献
17.
R. Thissen P. Lablanquie R.I. Hall M. Ukai K. Ito 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):335-342
Photoionization of rare gas clusters in the innervalence shell region has been investigated using threshold photoelectron
and photoion spectrometers and synchrotron radiation. Two classes of states are found to play an important role: (A) valence
states, correlated to dissociation limits involving an ion with a hole in its innervalence ns shell, (B) Rydberg states correlated to dissociation limits involving an ion with a hole in its outervalence np shell plus an excited neutral atom. In dimers, class A states are “bright”, that is, accessible by photoionization, and serve
as an entrance step to form the class B “dark” states; this character fades as the size of the cluster increases. In the dimer,
the “Mulliken” valence state is found to present a shallow potential well housing a few vibrational levels; it is predissociated by the
class B Rydberg states. During the predissociation a remarkable energy transfer process is observed from the excited ion that
loses its innershell electron to its neutral partner.
Received: 10 February 1998 / Revised: 17 July 1998 / Accepted: 31 July 1998 相似文献
18.
Different laser devices working as “atom diodes” for ultra-cold atoms
have been proposed recently. They transmit ground state level atoms coming
from
one side, say from the left, but reflect them when they come from the other
side.
We present and compare some of these models.
In all of them spontaneous decay is included
as an irreversible element which avoids backwards motion after the atom has
crossed the diode.
We also review the proposal of a cooling method based on an
“atom diode”. 相似文献
19.
W. Hanke M.L. Kiesel M. Aichhorn S. Brehm E. Arrigoni 《The European physical journal. Special topics》2010,188(1):15-32
One central challenge in high-T
c superconductivity (SC) is to derive a detailed understanding for the specific role of the Cu-d
x2-y2 and O-p
x,y
orbital degrees of freedom. In most theoretical studies an effective one-band Hubbard (1BH) or t-J model has been used. Here,
the physics is that of doping into a Mott-insulator, whereas the actual high-T
c cuprates are doped charge-transfer insulators. To shed light on the related question, where the material-dependent physics
enters, we compare the competing magnetic and superconducting phases in the ground state, the single- and two-particle excitations
and, in particular, the pairing interaction and its dynamics in the three-band Hubbard (3BH) and 1BH-models. Using a cluster
embedding scheme, i.e. the variational cluster approach (VCA), we find which frequencies are relevant for pairing in the two
models as a function of interaction strength and doping: in the 3BH-models the interaction in the low- to optimal-doping regime
is dominated by retarded pairing due to low-energy spin fluctuations with surprisingly little influence of inter-band (p-d
charge) fluctuations. On the other hand, in the 1BH-model, in addition a part comes from “high-energy” excited states (Hubbard
band), which may be identified with a non-retarded contribution. We find these differences between a charge-transfer and a
Mott insulator to be renormalized away for the ground-state phase diagram of the 3BH- and 1BH-models, which are in close overall
agreement, i.e. are “universal”. On the other hand, we expect the differences - and thus, the material dependence to show
up in the “non-universal” finite-T phase diagram (T
c-values). 相似文献
20.
W. M. Reiff E. H. Witten J. Takacs J. H. Zhang C. C. Torardi 《Hyperfine Interactions》1990,56(1-4):1723-1728
The extremes of single ion slow paramagnetic relaxation and cooperative 3D-antiferromagnetic order are exemplified in a series
of structurally characterized complexes based on the anhydrous FeCl3-α-di-imine system. “Soft” Cl−Cl contacts, C−C (π-π) and hydrogen bonding interactions are found to lead to surprisingly strong
magnetic exchange among five and six coordinate high-spin iron III monomers. The latter form the building blocks of novel
“double chain” polymer magnets held together via the preceding “weak” interactions. 相似文献