74 research outputs found
Enhanced four-wave mixing via elimination of inhomogeneous broadening by coherent driving of quantum transition with control fields
We show that atoms from wide velocity interval can be concurrently involved
in Doppler-free two-photon resonant far from frequency degenerate four-wave
mixing with the aid of auxiliary electromagnetic field. This gives rise to
substantial enhancement of the output radiation generated in optically thick
medium. Numerical illustrations addressed to typical experimental conditions
are given.Comment: LaTeX2e, hyperref, 7 pages, 5 figures, to appear in PRA 1 august 200
Optical spectroscopic study of the interplay of spin and charge in NaV2O5
We investigate the temperature dependent optical properties of NaV2O5, in the
energy range 4meV-4eV. The symmetry of the system is discussed on the basis of
infrared phonon spectra. By analyzing the optically allowed phonons at
temperatures below and above the phase transition, we conclude that a
second-order change to a larger unit cell takes place below 34 K, with a
fluctuation regime extending over a broad temperature range. In the high
temperature undistorted phase, we find good agreement with the recently
proposed centrosymmetric space group Pmmn. On the other hand, the detailed
analysis of the electronic excitations detected in the optical conductivity,
provides direct evidence for a charge disproportionated electronic
ground-state, at least on a locale scale: A consistent interpretation of both
structural and optical conductivity data requires an asymmetrical charge
distribution on each rung, without any long range order. We show that, because
of the locally broken symmetry, spin-flip excitations carry a finite electric
dipole moment, which is responsible for the detection of direct two-magnon
optical absorption processes for E parallel to the a axis. The charged-magnon
model, developed to interpret the optical conductivity of NaV2O5, is described
in detail, and its relevance to other strongly correlated electron systems,
where the interplay of spin and charge plays a crucial role in determining the
low energy electrodynamics, is discussed.Comment: Revtex, 19 pages, 16 postscript pictures embedded in the text,
submitted to PRB. Find more stuff at
http://www.stanford.edu/~damascel/andreaphd.html or
http://www.ub.rug.nl/eldoc/dis/science/a.damascelli
Low energy excitations and dynamic Dzyaloshinskii-Moriya interaction in -NaVO studied by far infrared spectroscopy
We have studied far infrared transmission spectra of alpha'-NaV2O5 between 3
and 200cm-1 in polarizations of incident light parallel to a, b, and c
crystallographic axes in magnetic fields up to 33T. The triplet origin of an
excitation at 65.4cm-1 is revealed by splitting in the magnetic field. The
magnitude of the spin gap at low temperatures is found to be magnetic field
independent at least up to 33T. All other infrared-active transitions appearing
below Tc are ascribed to zone-folded phonons. Two different dynamic
Dzyaloshinskii-Moriya (DM) mechanisms have been discovered that contribute to
the oscillator strength of the otherwise forbidden singlet to triplet
transition. 1. The strongest singlet to triplet transition is an electric
dipole transition where the polarization of the incident light's electric field
is parallel to the ladder rungs, and is allowed by the dynamic DM interaction
created by a high frequency optical a-axis phonon. 2. In the incident light
polarization perpendicular to the ladder planes an enhancement of the singlet
to triplet transition is observed when the applied magnetic field shifts the
singlet to triplet resonance frequency to match the 68cm-1 c-axis phonon
energy. The origin of this mechanism is the dynamic DM interaction created by
the 68cm-1 c-axis optical phonon. The strength of the dynamic DM is calculated
for both mechanisms using the presented theory.Comment: 21 pages, 22 figures. Version 2 with replaced fig. 18 were labels had
been los
Performance of the CMS Level-1 trigger in proton-proton collisions at √s = 13 TeV
At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-of-mass energy of 13\TeV. During Run 2 (years 2015–2018) the LHC eventually reached a luminosity of 2.1× 10 cms, almost three times that reached during Run 1 (2009–2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016–2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals
Composition and monomer sequence distribution in ternary copolymers tetrafluoroethylene-ethylene-hexafluoropropylene determined by pyrolytic gas chromatography
Rabbinic Judaism's perspective on the first crimes against humanity [Prvi zločini proti človeštvu z vidika rabinskega judovstva]
This article focuses on the first recorded crimes (sins) against humanity in the context of the broader and more fundamental issue of human life's intrinsic value and dignity. An analysis of the views of rabbinic Judaism reveals a network of concepts that are dynamically intertwined. They originate from a strictly monotheistic framework (worldview) of Judaism that helps resolve whether a person is allowed to end his life for the sake of others. Careful analysis and interpretation of the first three acts of violence recorded in the Hebrew Bible (Tanakh) reveal the catastrophic consequences of choosing to end another's life without considering its intrinsic value while ignoring the intrinsic value of the other and his dignity and assuming that humans have the power to decide the fate of another human being, to distance humanity from God (from God's presence), trapping humans in the idolatry of materialism. Moreover, the Hebrew Bible (Tanakh) allows for a factual assessment and distinction between different acts of violence. It offers guidance, protection, and hope, for both victims and perpetrators, in the drama of creation and salvation. © 2021 Roubalová et al., CC BY 4.
Identification of the polymeric base of composite materials using pyrolytic gas chromatography
Determination by pyrolysis gas chromatography of the composition of materials based on styrene copolymers and of blends ABS-polycarbonate
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