143,048 research outputs found
Temperature and pressure-induced spin-state transitions in LaCoO3
We report the continuous variation of the spin moment of cobalt in LaCoO3
across its temperature and pressure-induced spin transitions evidenced with
K\beta emission spectra. The first thermal transition is best described by a
transition to an orbitally nondegenerate intermediate spin (S=1) state. In
parallel, continuous redistribution of the 3d electrons is also indicated by
partial fluorescence yield X-ray absorption spectra. At high pressure, our
study confirms that the material becomes low spin between 40 and 70 kbar at
room temperature
Optical pumping effect in absorption imaging of F=1 atomic gases
We report our study of the optical pumping effect in absorption imaging of
Na atoms in the hyperfine spin states. Solving a set of rate
equations for the spin populations in the presence of a probe beam, we obtain
an analytic expression for the optical signal of the absorption imaging.
Furthermore, we verify the result by measuring the absorption spectra of
Na Bose-Einstein condensates prepared in various spin states with
different probe beam pulse durations. The analytic result can be used in the
quantitative analysis of spinor condensate imaging and readily applied to
other alkali atoms with nuclear spin such as Rb.Comment: 6 pages, 4 figure
Infrared study of spin crossover Fe-picolylamine complex
Infrared (IR) absorption spectroscopy has been used to probe the evolution of
microscopic vibrational states upon the temperature- and photo-induced spin
crossovers in [Fe(2-picolylamine)3]Cl2EtOH (Fe-pic). To overcome the small
sizes and the strong IR absorption of the crystal samples used, an IR
synchrotron radiation source and an IR microscope have been used. The obtained
IR spectra of Fe-pic show large changes between high-spin and low-spin states
for both the temperature- and the photo- induced spin crossovers. Although the
spectra in the temperature- and photo-induced high-spin states are relatively
similar to each other, they show distinct differences below 750 cm-1. This
demonstrates that the photo-induced high-spin state involves microscopically
different characters from those of the temperature-induced high-spin state. The
results are discussed in terms of local pressure and structural deformations
within the picolylamine ligands, and in terms of their possible relevance to
the development of macroscopic photo-induced phase in Fe-pic.Comment: 6 pages (text) and 6 figures,submitted to J. Phys. Soc. Jp
The Fermi edge singularity of spin polarized electrons
We study the absorption spectrum of a two-dimensional electron gas (2DEG) in
a magnetic field. We find that that at low temperatures, when the 2DEG is spin
polarized, the absorption spectra, which correspond to the creation of spin up
or spin down electron, differ in magnitude, linewidth and filling factor
dependence. We show that these differences can be explained as resulting from
creation of a Mahan exciton in one case, and of a power law Fermi edge
singularity in the other.Comment: 4 pages, 4 figures, published in Phys. Rev. Let
First-principles calculation of x-ray dichroic spectra within the full-potential linearized augmented planewave method: An implementation into the Wien2k code
X-ray absorption and its dependence on the polarization of light is a
powerful tool to investigate the orbital and spin moments of magnetic materials
and their orientation relative to crystalline axes. Here, we present a program
for the calculation of dichroic spectra from first principles. We have
implemented the calculation of x-ray absorption spectra for left and right
circularly polarized light into the Wien2k code. In this package, spin-density
functional theory is applied in an all-electron scheme that allows to describe
both core and valence electrons on the same footing. The matrix elements, which
define the dependence of the photo absorption cross section on the polarization
of light and on the sample magnetization, are computed within the dipole
approximation. Results are presented for the L2,3 and M4,5 egdes of CeFe2 and
compared to experiments
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