30 research outputs found
Quantum chaos in multicharged ions and statistical approach to the calculation of electron-ion resonant radiative recombination
We show that the spectrum and eigenstates of open-shell multicharged atomic
ions near the ionization threshold are chaotic, as a result of extremely high
level densities of multiply excited electron states ( in
Au^{24+}) and strong configuration mixing. This complexity enables one to use
statistical methods to analyse the system. We examine the dependence of the
orbital occupation numbers and single-particle energies on the excitation
energy of the system, and show that the occupation numbers are described by the
Fermi-Dirac distribution, and temperature and chemical potential can be
introduced. The Fermi-Dirac temperature is close to the temperature defined
through the canonical distribution. Using a statistical approach we estimate
the contribution of multielectron resonant states to the radiative capture of
low-energy electrons by Au^{25+} and demonstrate that this mechanism fully
accounts for the 10^2 times enhancement of the recombination over the direct
radiative recombination, in agreement with recent experimental observations.Comment: Amended version, 19 pages, including 9 figures, REVTEX, to appear in
the Australian Journal of Physics, vol. 52, No. 3 (1999
Can We Apply Statistical Laws to Small Systems? the Cerium Atom
It is shown that statistical mechanics is applicable to quantum systems with
finite numbers of particles, such as complex atoms, atomic clusters, etc.,
where the residual two-body interaction is sufficiently strong. This
interaction mixes the unperturbed shell-model basis states and produces
``chaotic'' many-body eigenstates. As a result, an interaction-induced
equilibrium emerges in the system, and temperature can be introduced. However,
the interaction between the particles and their finite number can lead to
prominent deviations of the equilibrium occupation numbers distribution from
the Fermi-Dirac shape. For example, this takes place in the cerium atom with
four valence electrons, which was used to compare the theory with realistic
numerical calculations.Comment: 4 pages, Latex, two figures in eps-forma
Statistics of electromagnetic transitions as a signature of chaos in many-electron atoms
Using a configuration interaction approach we study statistics of the dipole
matrix elements (E1 amplitudes) between the 14 lower odd states with J=4 and
21st to 100th even states with J=4 in the Ce atom (1120 lines). We show that
the distribution of the matrix elements is close to Gaussian, although the
width of the Gaussian distribution, i.e. the root-mean-square matrix element,
changes with the excitation energy. The corresponding line strengths are
distributed according to the Porter-Thomas law which describes statistics of
transition strengths between chaotic states in compound nuclei. We also show
how to use a statistical theory to calculate mean squared values of the matrix
elements or transition amplitudes between chaotic many-body states. We draw
some support for our conclusions from the analysis of the 228 experimental line
strengths in Ce [J. Opt. Soc. Am. v. 8, p. 1545 (1991)], although direct
comparison with the calculations is impeded by incompleteness of the
experimental data. Nevertheless, the statistics observed evidence that highly
excited many-electron states in atoms are indeed chaotic.Comment: 16 pages, REVTEX, 4 PostScript figures (submitted to Phys Rev A
Chaos and localization in the wavefunctions of complex atoms NdI, PmI and SmI
Wavefunctions of complex lanthanide atoms NdI, PmI and SmI, obtained via
multi-configuration Dirac-Fock method, are analyzed for density of states in
terms of partial densities, strength functions (), number of principal
components () and occupancies (\lan n_\alpha \ran^E) of single
particle orbits using embedded Gaussian orthogonal ensemble of one plus
two-body random matrix ensembles [EGOE(1+2)]. It is seen that density of states
are in general multi-modal, 's exhibit variations as function of the
basis states energy and 's show structures arising from localized
states. The sources of these departures from EGOE(1+2) are investigated by
examining the partial densities, correlations between , and
\lan n_\alpha \ran^E and also by studying the structure of the Hamiltonian
matrices. These studies point out the operation of EGOE(1+2) but at the same
time suggest that weak admixing between well separated configurations should be
incorporated into EGOE(1+2) for more quantitative description of chaos and
localization in NdI, PmI and SmI.Comment: There are 9 figure
Interaction-Driven Equilibrium and Statistical Laws in Small Systems. The Cerium Atom
It is shown that statistical mechanics is applicable to isolated quantum
systems with finite numbers of particles, such as complex atoms, atomic
clusters, or quantum dots in solids, where the residual two-body interaction is
sufficiently strong. This interaction mixes the unperturbed shell-model
(Hartree-Fock) basis states and produces chaotic many-body eigenstates. As a
result, an interaction-induced statistical equilibrium emerges in the system.
This equilibrium is due to the off-diagonal matrix elements of the Hamiltonian.
We show that it can be described by means of temperature introduced through the
canonical-type distribution. However, the interaction between the particles can
lead to prominent deviations of the equilibrium distribution of the occupation
numbers from the Fermi-Dirac shape. Besides that, the off-diagonal part of the
Hamiltonian gives rise to the increase of the effective temperature of the
system (statistical effect of the interaction). For example, this takes place
in the cerium atom which has four valence electrons and which is used in our
work to compare the theory with realistic numerical calculations.Comment: 25 pages, RevTeX, 5 figures in ps-format. Submitted to Phys. Rev.
Wigner Random Banded Matrices with Sparse Structure: Local Spectral Density of States
Random banded matrices with linearly increasing diagonal elements are
recently considered as an attractive model for complex nuclei and atoms. Apart
from early papers by Wigner \cite{Wig} there were no analytical studies on the
subject. In this letter we present analytical and numerical results for local
spectral density of states (LDOS) for more general case of matrices with a
sparsity inside the band. The crossover from the semicircle form of LDOS to
that given by the Breit-Wigner formula is studied in detail.Comment: Misprints are corrected and stylistic changes are made. To be
published in PR
Short time decay of the Loschmidt echo
The Loschmidt echo measures the sensitivity to perturbations of quantum
evolutions. We study its short time decay in classically chaotic systems. Using
perturbation theory and throwing out all correlation imposed by the initial
state and the perturbation, we show that the characteristic time of this regime
is well described by the inverse of the width of the local density of states.
This result is illustrated and discussed in a numerical study in a
2-dimensional chaotic billiard system perturbed by various contour deformations
and using different types of initial conditions. Moreover, the influence to the
short time decay of sub-Planck structures developed by time evolution is also
investigated.Comment: 7 pages, 7 figures, published versio
Electron recombination with multicharged ions via chaotic many-electron states
We show that a dense spectrum of chaotic multiply-excited eigenstates can
play a major role in collision processes involving many-electron multicharged
ions. A statistical theory based on chaotic properties of the eigenstates
enables one to obtain relevant energy-averaged cross sections in terms of sums
over single-electron orbitals. Our calculation of the low-energy electron
recombination of Au shows that the resonant process is 200 times more
intense than direct radiative recombination, which explains the recent
experimental results of Hoffknecht {\em et al.} [J. Phys. B {\bf 31}, 2415
(1998)].Comment: 9 pages, including 1 figure, REVTe
Π€Π°ΡΠΌΠ°ΠΊΠΎΠΊΠΈΠ½Π΅ΡΠΈΡΠ΅ΡΠΊΠΈΠ΅ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΡ Π»Π΅ΠΊΠ°ΡΡΡΠ²Π΅Π½Π½ΡΡ Π²Π΅ΡΠ΅ΡΡΠ², ΠΌΠ΅ΡΠ°Π±ΠΎΠ»ΠΈΠ·ΠΈΡΡΠ΅ΠΌΡΡ ΠΈΠ·ΠΎΡΠ΅ΡΠΌΠ΅Π½ΡΠΎΠΌ ΡΠΈΡΠΎΡ ΡΠΎΠΌΠ° P450 CYP2C9
The role of cytochrome P450 isoforms CYP2C9 and in the metabolism of losartan described. Losartan pharmacokinetics data in humans and laboratory animals are presented. Examples of drug-drug interactions of substrate marker losartan of CYP2C9 of with different drugs are given. The results of studies of the effects of afobazole, an inducer (rifampicin) and inhibitors (fluconazole) in effective doses on the pharmacokinetics of losartan.ΠΠΏΠΈΡΠ°Π½Π° ΡΠΎΠ»Ρ ΡΠΈΡΠΎΡ
ΡΠΎΠΌΠ° Π 450 ΠΈ Π΅Π³ΠΎ ΠΈΠ·ΠΎΡΠΎΡΠΌΡ CYP2C9 Π² ΠΌΠ΅ΡΠ°Π±ΠΎΠ»ΠΈΠ·ΠΌΠ΅ Π»ΠΎΠ·Π°ΡΡΠ°Π½Π°. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ Π΄Π°Π½Π½ΡΠ΅ ΠΎ ΡΠ°ΡΠΌΠ°ΠΊΠΎΠΊΠΈΠ½Π΅ΡΠΈΠΊΠΈ Π»ΠΎΠ·Π°ΡΡΠ°Π½Π° Ρ Π»Π°Π±ΠΎΡΠ°ΡΠΎΡΠ½ΡΡ
ΠΆΠΈΠ²ΠΎΡΠ½ΡΡ
ΠΈ ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ°. ΠΠΏΠΈΡΠ°Π½Ρ ΠΏΡΠΈΠΌΠ΅ΡΡ ΠΌΠ΅ΠΆΠ»Π΅ΠΊΠ°ΡΡΡΠ²Π΅Π½Π½ΠΎΠ³ΠΎ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΡ ΡΡΠ±ΡΡΡΠ°ΡΠ½ΠΎΠ³ΠΎ ΠΌΠ°ΡΠΊΠ΅ΡΠ° CYP2C9 - Π»ΠΎΠ·Π°ΡΡΠ°Π½Π° Ρ ΡΠ°Π·Π»ΠΈΡΠ½ΡΠΌΠΈ Π»Π΅ΠΊΠ°ΡΡΡΠ²Π΅Π½Π½ΡΠΌΠΈ Π²Π΅ΡΠ΅ΡΡΠ²Π°ΠΌΠΈ. ΠΡΠΈΠ²Π΅Π΄Π΅Π½Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ Π²Π»ΠΈΡΠ½ΠΈΡ Π°ΡΠΎΠ±Π°Π·ΠΎΠ»Π°, ΠΈΠ½Π΄ΡΠΊΡΠΎΡΠ° (ΡΠΈΡΠ°ΠΌΠΏΠΈΡΠΈΠ½Π°) ΠΈ ΠΈΠ½Π³ΠΈΠ±ΠΈΡΠΎΡΠ° (ΡΠ»ΡΠΊΠΎΠ½Π°Π·ΠΎΠ»Π°) Π² ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΡΡ
Π΄ΠΎΠ·Π°Ρ
Π½Π° ΡΠ°ΡΠΌΠ°ΠΊΠΎΠΊΠΈΠ½Π΅ΡΠΈΠΊΡ Π»ΠΎΠ·Π°ΡΡΠ°Π½Π°