1,071 research outputs found
Nature of nuclear rings in unbarred galaxies: NGC 7742 and NGC 7217
We have studied the unbarred Sb galaxy with a nuclear star-forming ring, NGC
7742, by means of 2D spectroscopy, long-slit spectroscopy, and imaging, and
have compared the results with the properties of another galaxy of this type,
NGC 7217, which is studied by us earlier. Both galaxies have many peculiar
features in common: each has two global exponential stellar disks with
different scalelengths, each possesses a circumnuclear inclined gaseous disk
with a radius of 300 pc, and each has a global counterrotating subsystem,
gaseous one in NGC 7742 and stellar one in NGC 7217. We suggest that past minor
merger is the probable cause of all these peculiarities, including appearance
of the nuclear star-forming rings without global bars; the rings might be
produced as resonance features by tidally induced oval distortions of the
global stellar disks.Comment: Accepted to AJ, 11 PS/EPS figures (5 figures were added in color
Time- and frequency-domain polariton interference
We present experimental observations of interference between an atomic spin
coherence and an optical field in a {\Lambda}-type gradient echo memory. The
interference is mediated by a strong classical field that couples a weak probe
field to the atomic coherence through a resonant Raman transition. Interference
can be observed between a prepared spin coherence and another propagating
optical field, or between multiple {\Lambda} transitions driving a single spin
coherence. In principle, the interference in each scheme can yield a near unity
visibility.Comment: 11 pages, 5 figure
Magnetization in AIIIBV semiconductor heterostructures with the depletion layer of manganese
The magnetic moment and magnetization in GaAs/GaInAs/GaAs
heterostructures with Mn deluted in GaAs cover layers and with atomically
controlled Mn -layer thicknesses near GaInAs-quantum well (3 nm)
in temperature range T=(1.8-300)K in magnetic field up to 50 kOe have been
investigated. The mass magnetization all of the samples of
GaAs/GaInAs/GaAs with Mn increases with the increasing of the
magnetic field that pointed out on the presence of low-dimensional
ferromagnetism in the manganese depletion layer of GaAs based structures. It
has been estimated the manganese content threshold at which the ferromagnetic
ordering was found.Comment: 8 pages, 3 figure
Very High Mach Number Electrostatic Shocks in Collisionless Plasmas
The kinetic theory of collisionless electrostatic shocks resulting from the
collision of plasma slabs with different temperatures and densities is
presented. The theoretical results are confirmed by self-consistent
particle-in-cell simulations, revealing the formation and stable propagation of
electrostatic shocks with very high Mach numbers (), well above the
predictions of the classical theories for electrostatic shocks.Comment: 6 pages, submitted to Phys. Rev. Let
Pulse area theorem in a single mode waveguide and its application to photon echo and optical memory in Tm3+:Y3Al5O12
We derive the area theorem for light pulses interacting with inhomogeneously
broadened ensemble of two-level atoms in a single-mode optical waveguide and
present its analytical solution for Gaussian-type modes, which demonstrates the
significant difference from the formation of pulses by plane waves. We
generalize this theorem to the description of photon echo and apply it to the
two-pulse (primary) echo and the revival of silenced echo (ROSE) protocol of
photon echo quantum memory. For the first time, we implemented ROSE protocol in
a single-mode laser-written waveguide made of an optically thin crystal
. The experimental data obtained are satisfactorily
explained by the developed theory. Finally, we discuss the obtained
experimental results and possible applications of the derived pulse area
approach
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