7,247 research outputs found
Uniqueness of the group Fourier transform on certain nilpotent Lie groups
In this article, we prove that if the group Fourier transform of certain
integrable functions on the Heisenberg motion group (or step two nilpotent Lie
groups) is of finite rank, then the function is identically zero. These results
can be thought as an analogue to the Benedicks theorem that dealt with the
uniqueness of the Fourier transform of integrable functions on the Euclidean
spaces.Comment: update
Electric dipole polarizabilities of alkali metal ions from perturbed relativistic coupled-cluster theory
We use the perturbed relativistic coupled-cluster theory to compute the
static electric dipole polarizabilities of the singly ionized alkali atoms,
namely, Na, , Rb, Cs and Fr. The computations use the
Dirac-Coulomb-Breit Hamiltonian with the no-virual-pair approximation and we
also estimate the correction to the static electric dipole polarizability
arising from the Breit interaction.Comment: 8 pages, 3 figures and 9 tables. arXiv admin note: text overlap with
arXiv:1210.547
Electric dipole polarizability of alkaline-Earth-metal atoms from perturbed relativistic coupled-cluster theory with triples
The perturbed relativistic coupled-cluster (PRCC) theory is applied to
calculate the electric dipole polarizabilities of alkaline Earth metal atoms.
The Dirac-Coulomb-Breit atomic Hamiltonian is used and we include the triple
excitations in the relativistic coupled-cluster (RCC) theory. The theoretical
issues related to the triple excitation cluster operators are described in
detail and we also provide details on the computational implementation. The
PRCC theory results are in good agreement with the experimental and previous
theoretical results. We, then, highlight the importance of considering the
Breit interaction for alkaline Earth metal atoms.Comment: 13 pages, 11 figures, 9 tables, Minor changes, References update
Triple excitations in perturbed relativistic coupled-cluster theory and Electric dipole polarizability of groupIIB elements
We use perturbed relativistic coupled-cluster (PRCC) theory to compute the
electric dipole polarizabilities of Zn, Cd and Hg. The computations
are done using the Dirac-Coulomb-Breit Hamiltonian with Uehling potential to
incorporate vacuum polarization corrections. The triple excitations are
included perturbatively in the PRCC theory, and in the unperturbed sector, it
is included non-perturbatively. Our results of , for all the three
elements, are in excellent agreement with the experimental data. The other
highlight of the results is the orbital energy corrections from Breit
interactions. In the literature we could only get the data of Hg {E. Lindroth
et al., J. Phys. B 22, 2447 (1989)} and are near perfect match with our
results. We also present the linearized equations of the cluster amplitudes,
including the triple excitations, with the angular factors.Comment: With minor corrections, 17 pages, 4 figures and 8 table
Electric dipole polarizability from perturbed Relativistic Coupled-Cluster Theory: application to Neon
We develop a method based on the relativistic coupled-cluster theory to
incorporate a perturbative interaction to the no-pair Dirac-Coulomb atomic
Hamiltonian. The method is general and suitable to incorporate any perturbation
Hamiltonian in a many electron atom or ion. Using this perturbed relativistic
coupled-cluster (PRCC) theory we calculate the electric dipole polarizability,
, of Neon. The linearized PRCC results are in very good agreement with
the experimental value. However, the results of the nonlinear PRCC shows larger
uncertainty but it is consistent with the observations from earlier works.Comment: 6 pages, 8 table
Electric dipole polarizabilities of doubly ionized alkaline Earth metal ions from perturbed relativistic coupled-cluster theory
Using perturbed relativistic coupled-cluster (PRCC) theory we compute the
ground state electric dipole polarizability, , of doubly ionized
alkaline earth metal ions , , ,
and . In the present work we use the
Dirac-Coulomb-Breit atomic Hamiltonian and we also include the Uehling
potential, which is the leading order term in the vacuum polarization
corrections. We examine the correction to the orbital energies arising from the
Uehling potential in the self-consistent field calculations as well as
perturbatively. Our results of are in very good agreement with the
experimental data, and we observe a change in the nature of the orbital energy
corrections arising from the vacuum polarization as we go from
to Ra.Comment: 10 pages, 12 table
Electric dipole polarizability of group-IIIA ions using PRCC: Large correlation effects from nonlinear terms
We compute the ground-state electric dipole polarizability of group-IIIA ions
using the perturbed relativistic coupled-cluster (PRCC) theory. To account for
the relativistic effects and QED corrections, we use the Dirac-Coulomb-Breit
Hamiltonian with the corrections from the Uehling potential and the
self-energy. The effects of triple excitations are considered perturbatively in
the PRCC. Our PRCC results for are good in agreement with the previous
theoretical results for all the ions. From our computations we find that the
nonlinear terms in PRCC have significant contributions and must be included to
obtain the accurate value of for group-IIIA ions. For the correction
from the Breit interaction, we find that it is largest for Al and decreases
as we go towards the heavier ions. The corrections from the vacuum polarization
and the self-energy increase from lighter to heavier ions.Comment: 12 pages, 2 figures, 10 table
Sb concentration dependent structural and resistive properties of polycrystalline Bi-Sb alloys
Polycrystalline Bi-Sb alloys have been synthesized over a wide range of
antimony concentration (8 at% to 20 at%) by solid state reaction method. In
depth structural analysis using X-Ray diffraction (XRD) and temperature
dependent resistivity measurement of synthesized samples have been performed.
XRD data confirmed single phase nature of polycrystalline samples and revealed
that complete solid solution is formed between bismuth and antimony. Rietveld
refinement technique, utilizing MAUD software, has been used to perform detail
structural analysis of the samples and lattice parameters of synthesized Bi-Sb
alloys have been estimated. Lattice parameter and unit cell volume decreases
monotonically with increasing antimony content. The variation of lattice
parameters with antimony concentration depicts a distinct slope change beyond
12 at% Sb content sample. Band gap has been estimated from the thermal
variation of resistivity data, with the 12% Sb content sample showing maximum
value. It has been observed that, with increasing antimony concentration the
transition from direct to indirect gap semiconductor is intimately related to
the variation of the estimated lattice parameters. Band diagram for the
polycrystalline Bi-Sb alloy system has also been proposed.Comment: To be published in J. Applied Physic
Evolution of texture and microstructure during accumulative roll bonding of aluminum AA5086 alloy
In the present investigation, a strongly bonded strip of an
aluminium-magnesium based alloy AA5086 is successfully produced through
accumulative roll bonding (ARB). A maximum of up to eight passes has been used
for the purpose. Microstructural characterization using electron backscatter
diffraction (EBSD) technique indicates the formation of submicron sized
(~200-300 nm) subgrains inside the layered microstructure. The material is
strongly textured where individual layers possess typical FCC rolling texture
components. More than three times enhancement in 0.2% proof stress (PS) has
been obtained after 8 passes due to grain refinement and strain hardeningComment: 13 pages, 9 figure
A new multi line-cusp magnetic field plasma device (MPD) with variable magnetic field for fundamental plasma studies
One of the fundamental problems is the understanding of physics of
electrostatic and electromagnetic fluctuations in multi-scale plasma
turbulence. Especially so, in continuously connected plasma regions with
varying degree of magnetization. Examples range from multiscale plasmas in
Magnetron-like devices to astrophysical plasmas confined by magnetic dipole
structures, solar wind driven collision-less and weakly collisional plasmas
around Earth, to mention a few. Such plasmas are dominated by both electron
scale and ion scale physics as well as finite beta effects. To investigate such
processes in laboratory experiments requires excellent control of continuously
connected regions of nearly zero plasma beta with finite beta regions as well
as the gradient length scales of mean density and temperatures. To address some
of these phenomena at laboratory scale, a new multi-line cusp configured plasma
device (MPD) consisting of electromagnets with core material has been
constructed with a capability to experimentally control the relative volume
fractions of magnetized to unmagntized plasma volume as well as accurate
control on the gradient length scales of mean density and temperature profiles.
The hot tungsten cathode produced Argon plasma in the MPD has been
characterised using single Langmuir probes. Argon plasma has been produced in
the device over a wide range of pressure 5 x 10-5 mBar to 1 x 10-3 mBar,
achieving plasma density range from 109 to 1011cm-3 and temperature in the
range 1eV to 8eV
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