共查询到20条相似文献,搜索用时 15 毫秒
1.
P.V. Grujić 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(4):441-450
We calculate rovibronic intrashell spectra of the triply highly excited atomic hydrogen dianion, helium anion and lithium
atom, within a simple semiclassical model. Zero-order electronic energy levels and half-lives are calculated for a number
of principal quantum numbers and approximate thresholds for the appearance of vibronic modes are estimated. Since no quantum-mechanical
and experimental data are available for the highly excited levels (N > 5), where the semiclassical models apply, no comparison with other results are possible at present. The problem of comparing
semiclassical and quantum-mechanical calculations for moderately large quantum numbers, which seem attainable by the present
day experimental technique, has been discussed.
Received: 16 September 1998 / Received in final form: 16 March 1999 相似文献
2.
V. Bystritsky W. Czaplinski N. Popov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):185-191
The deexcitation of excited muonic protium and deuterium in the mixture of hydrogen and helium isotopes is considered. Methods
of experimental determination of the probability of direct atomic muon capture by hydrogen and muon transfer rates from excited
muonic hydrogen to helium are proposed. Theoretical results for the population of the muonic atoms in the ground state, , are compared with the existing experimental data. Results obtained for mixtures are of interest for investigation of nuclear fusion in muonic molecules.
Received: 6 August 1998 / Revised: 1st October 1998 / Accepted: 2 October 1998 相似文献
3.
S.V. Romanov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):217-230
In recent experiments performed at the Paul Scherrer Institute (PSI) measurements were made of the yield of the two-photon transition of the fully-ionized muonic boron formed and quenched in a gaseous mixture of diborane B2H6 and helium. In the present work this yield is calculated for an idealized case of a very low diborane density when the main
2
s state decay modes competing with the two-photon transition are due to the electron transfer from helium to the μ-ion. As
the rate of this transfer depends strongly on the relative velocity, a treatment is needed of the whole kinetics of processes
occurring with the μ-ion in helium. Accordingly, within the optical model with a complex potential constructed before we calculate
cross-sections of the elastic scattering and electron transfer. Then the time evolution of the μ-ion energy is considered
and, finally, the yield is calculated. It proves that at helium pressures Torr this yield may be written in the form: ,where the factor C is greater than unity and increases rapidly with the initial energy E0 which the μ-ion has after its formation in the diborane molecule. Thus measurement of the pressure dependence of allows E0 to be estimated. The results obtained make it possible to suggest a similar parametrization of the PSI data.
Received: 21 October 1997 / Revised: 16 January 1998 / Accepted: 2 March 1998 相似文献
4.
A.K. Das M. Ehara H. Nakatsuji 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):195-200
Excited states of the s, p, and d symmetries up to principal quantum number n = 4 are studied for the first eight members of Ne isoelectronic sequence (Ne to Cl7+) by the SAC-CI (symmetry-adapted-cluster configuration-interaction) method. The valence STO basis sets of Clementi et al. and the optimized excited STO are used by the STO-6G expansion method. The calculated transition energies agree well with
the experimental values wherever available.
Received 26 July 2000 and Received in final form 14 September 2000 相似文献
5.
I.D. Petrov V.L. Sukhorukov E. Leber H. Hotop 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):53-65
The effect of the polarization of the atomic core by the outer electron on near threshold photoionization of excited alkali
atoms Ak(np) (Ak = Na-Cs; n=3-6) is investigated. Partial and total cross-sections for photo-ionization of the np-electron were computed utilizing the configuration interaction technique with Pauli-Fock atomic orbitals (CIPF) and including
the long range core polarization potential (CP). To calculate the core polarization potential the variational principle is
applied. Comparison with previous theoretical results and with available experimental data is made for the total cross-section
, for the electron angular distribution parameter , for the ratio of the reduced electric dipole matrix elements and for the phase shift difference , associated with the d-wave and s-wave continua, respectively. In the comparison, new experimental results for , , and , measured for laser-excited, polarized 39K(4p
3/2) atoms, have been included.
Received 21 July 1999 and Received in final form 14 October 1999 相似文献
6.
T.S. Jensen V.E. Markushin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):165-181
The differential and total cross-sections for the scattering of muonic, pionic, kaonic and antiprotonic hydrogen in excited
states from atomic hydrogen have been calculated for the purpose of atomic cascade calculations. The scattering problem is
treated in a fully quantum mechanical framework which takes the energy shifts and, in the case of the hadronic atoms, the
widths of the ns states into account. The validity of semiclassical approximations is critically examined.
Received 4 December 2001 and Received in final form 4 February 2002 相似文献
7.
A.S. Shalabi M.M. Assem S. Abd El-Aal M.A. Kamel M.M. Abd El-Rahman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(2):181-189
Ab initio calculations were performed for several suggested mechanisms of energy transfer between helium metastable particles and neon.
Optimized geometries and excited-state energies were calculated for neon excited-state complexes and the convergence properties
of the non-additive contributions to the interaction energies were examined. The most probable excitation-transfer mechanism
was found to be based on an energy difference of 0.0674 eV between the triplet excited state of and the singlet excited state of . No theoretical evidence was found for the production of neon singlet excited-state complexes other than 20.0858 to 20.4875
eV by the considered two-, three- and four-body models of energy transfer processes. The energy curves of the reactions involving
the excited-state complexes and are provided and compared with the previously reported experimental results on the reaction . The relation between the probability of energy transfer and laser activity is discussed. The non-additive contribution to
the total interaction energy of the nominated intermediate complex was found to be negligible, pointing to the possibility of constructing model potentials and simulation
of larger systems.
Received: 15 December 1998 / Received in final form: 20 March 1999 相似文献
8.
L.A.A. Nikolopoulos Takashi Nakajima P. Lambropoulos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):297-304
Calculations of intense field (around 1016 W/cm2) single- and double-ionization processes in helium at XUV wavelengths are presented. The laser wavelength is chosen near
the | 2s2p
1
P autoionization structure and the dynamics are explored. Single and double ionization yields, as well as the photoelectron
energy spectrum for photon energies around the autoionization structure are calculated. In the case of a pulse of few femtoseconds
duration, no significant enhancement of the double ionization yield has been found in tuning the photon frequency around the
peak of the resonance. It is also shown that in the case of a long pulse (and hence narrow compared with the relevant autoionization
width), the branching ratio of double to single ionization yield can be relatively enhanced by tuning to the absorption minimum
of the resonance.
Received 19 February 2002 / Received in final form 2 May 2002 Published online 19 July 2002 相似文献
9.
M. Das M. Purkait C. R. Mandal 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):13-18
The Classical Trajectory Monte-Carlo (CTMC) simulation method has been employed to calculate the total electron capture cross-sections
with sub-shell distributions and ionization cross-sections in collision of B
q+
(q=1-4) with ground state atomic hydrogen in the energy range of 10-200 keV/amu. The computed results have been observed to be in
reasonable agreement with other existing theoretical and experimental results over the entire energy region considered.
Received 23 February 1999 and Received in final form 23 May 1999 相似文献
10.
L.B. Madsen L.A.A. Nikolopoulos P. Lambropoulos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):67-79
Ab initio time-dependent (TD) calculations of the behavior of positronium (Ps) under strong subpicosecond laser pulses are presented.
The results are compared with results in H through scaling. It is found that a substantial amount of the population can be
found in excited states after the pulse. In the perturbative regime, generalized multiphoton ionization cross-sections are
extracted from the results of the time-dependent calculations. The generalized cross-sections are used to predict the response
of Ps to nanosecond laser pulses at wavelengths of current experimental interest. Beyond the application to Ps, the generality
of the method for extracting generalized cross-sections from TD nonperturbative calculations is discussed.
Received 8 June 1999 相似文献
11.
V.I. Savichev R. Blümel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):3-12
We present the first thorough theoretical discussion of non-monotonic structure in the temporal behavior of X-ray fluorescence
intensity spectra of muon charge-exchange reactions of the type pμ + Z→p + μZ. Our discussion is based on semiclassical methods; our results are almost entirely analytical. We find that the reported
experimental maxima of muon charge-exchange rates are very close to the theoretical limits. We identify a new quantum mechanism,
quantum impedance matching, which explains observed inelastic transitions close to the Unitarity Limit. We investigate the specific example of the reaction
pμO
8 + in detail using two-center Coulomb adiabatic potential terms. We find that quantum impedance matched higher-order partial-wave
resonances yielding muon-transfer rates close to the Unitarity Limit are responsible for the remarkable non-monotonic structure
in the X-ray fluorescence spectra.
Received 7 January 2002 / Received in final form 15 April 2002 Published online 24 September 2002 相似文献
12.
Zu Wei Yan Xi Xia Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):531-538
A variational theory is proposed to study the surface states of electrons in a semi-infinite ternary mixed crystal, by taking
the effect of electron-surface optical (SO) phonon interaction into account. The energy and the wave function of the electronic
surface-states are calculated. The numerical results of the energies of the surface states of the polarons and the self-trapping
energies are obtained as functions of the composition x and surface potential V0 for several ternary mixed crystal materials. The results show that the electron-phonon interaction lowers the surface-state
levels with the energies from several to scores of meV. It is also found that the self-trapping energy of the surface polaron
has a minimum at some middle value of the composition x. It is indicated that the electron-phonon coupling effect can not be neglected.
Received 4 January 1999 and Received in final form 7 January 2000 相似文献
13.
Ken-Ichiro Imura 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):155-160
Effects of backward scattering between fractional quantum Hall (FQH) edge modes are studied. Based on the edge-state picture
for hierarchical FQH liquids, we discuss the possibility of the transitions between different plateaux of the tunneling conductance
G. We find a selection rule for the sequence which begins with a conductance (m: integer, p: even integer) in units of e
2/h. The shot-noise spectrum as well as the scaling behavior of the tunneling current is calculated explicitly.
Received 5 October 1999 and Received in final form 19 November 1999 相似文献
14.
M.S. Li M. Cieplak 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):787-792
The Go model is extended to the case when the non-native contact energies may be either attractive or repulsive. The folding
temperature is found to increase with the energy of non-native contacts. The repulsive non-native contact energies may lead
to folding at T=0 for some unusual two-dimensional sequences and to reduction in complexity of disconnectivity graphs for local energy minima.
Received 10 May 1999 and Received in final form 13 October 1999 相似文献
15.
L. Szybisz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):733-746
Density functionals proposed in the literature for describing the behaviour of liquid helium at T
=0 K are examined. In so doing, several properties of the ground states of free films of superfluid
4
He are calculated by using zero- and finite-range density functional theories and these results are compared to that computed
with Monte Carlo simulations. We mainly focus the attention on the energy per particle of the slabs, the surface tension and
the width of the liquid-vacuum interfaces, all as a function of the inverse of coverage. The largest differences are found
in the case of the surface widths.
Received 26 July 1999 相似文献
16.
J. Akola A. Rytkönen H. Häkkinen M. Manninen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):93-99
The ionization potential of sodium clusters () at a finite temperature is studied using density functional theory and ab initio molecular dynamics. The threshold regions of the photoionization efficiency curves are deduced from the integrated IP distributions,
which are obtained from the energy eigenvalues of the highest occupied Kohn-Sham states during molecular dynamics by applying
a theoretically well-defined shift. The calculated ionization potentials are directly compared to the experimental values.
The energetically best geometry of Na55 is found to be a slightly distorted icosahedron.
Received 16 April 1999 and Received in final form 6 July 1999 相似文献
17.
F. Vigliotti M. Chergui 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(3):379-390
Higher Rydberg states of NO trapped in rare gas matrices have been studied by inducing Rydberg-Rydberg transitions from the
lowest
Rydberg state and detecting its fluorescence depletion. This technique unravels Rydberg states, which cannot be accessed
by ground state absorption. However, no clear cut Rydberg series show up. The data show a compression of the n-(n + 1) splittings between Rydberg states, as well as of the splittings. The results are rationalised in terms of the quantum defect model and the lack of extended Rydberg series is
due to the compression of high-n Rydberg states in a tiny energy region below the ionisation potential. Finally, fluorescence depletion data of NO trapped
in amorphous sites (the so-called red sites) of solid Ar can be interpreted in terms of the gas phase NO-Ar van der Waals
data. A general discussion on the fate of Rydberg states in van der Waals complexes, in liquids, and in solids is presented
in an attempt to relate the data in these different media.
Received 28 July 1999 and Received in final form 8 November 1999 相似文献
18.
P. Müller B.A. Bushaw W. Nörtershäuser K. Wendt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):33-44
Isotope shifts and hyperfine structure have been measured in 4snp 1 P1 and Rydberg states for all stable calcium isotopes and the radioisotope 41Ca using high-resolution laser spectroscopy. Triple-resonance excitation via
Rydberg state was followed by photoionization with a CO2 laser and mass selective ion detection. Isotope shifts for the even-mass isotopes have been analyzed to derive specific mass
shift and field shift factors. The apparent isotope shifts for 41Ca and 43Ca exhibit anomalous values that are n-dependent. This is interpreted in terms of hyperfine-induced fine-structure mixing, which becomes very pronounced when singlet-triplet
fine-structure splitting is comparable to the hyperfine interaction energy. Measurements of fine-structure splittings for
the predominant isotope 40Ca have been used as input parameters for theoretical calculation of the perturbed hyperfine structure. Results obtained by
diagonalizing the second-order hyperfine interaction matrices agree very well with experimentally observed spectra. These
measurements allow the evaluation of highly selective and sensitive methods for the detection of the rare 41Ca isotope.
Received 17 December 1999 and Received in final form 29 March 2000 相似文献
19.
W. Czapliński A. Kravtsov A. Mikhailov N. Popov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(3):223-227
Nuclear fusion reactions in hydrogen-lithium muonic molecules, (where h=p,d,t) are considered and fusion rates from rotational states J=0 of the molecules are presented. Results obtained depend on the isotopic composition of the molecules and range between
and . The upper limit for fusion rates from rotational states J=0 of hydrogen-helium muonic molecules, and , equal , is also found.
Received: 4 December 1997 / Revised: 30 April 1998 / Accepted: 7 May 1998 相似文献
20.
S. Cebrat A. Pȩkalski 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):687-690
We propose, and solve via Monte-Carlo simulation, a model describing evolution of population subject to harmful mutations. The habitat changes periodically.
The evolution of two, initially identical, populations is compared. One without any external ingerence and the second in which
we eliminate all individuals which are ill-fitted to the changed environment (eugenics). We show that although in the short
run the individuals in the latter are better adapted and live longer, after some more changes of the environment, the populations
with eugenics become extinct, while the others live on.
Received 8 April 1999 相似文献