Ultrafast x-ray pulses and stimulated emission in the x-ray range

2021 ◽  
Author(s):  
Nina Rohringer
Keyword(s):  
Stimulated Emission ◽  
X Ray

scholarly journals Correlating STED and synchrotron XRF nano-imaging unveils cosegregation of metals and cytoskeleton proteins in dendrites

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Florelle Domart ◽  
Peter Cloetens ◽  
Stéphane Roudeau ◽  
Asuncion Carmona ◽  
Emeline Verdier ◽  
...  
Keyword(s):  
Trace Metals ◽  
Neuronal Plasticity ◽  
Hippocampal Neurons ◽  
Molecular Mechanisms ◽  
Memory Formation ◽  
Stimulated Emission ◽  
X Ray ◽  
Nano Imaging ◽  
Zinc Chelation ◽  
Synaptic Level

Zinc and copper are involved in neuronal differentiation and synaptic plasticity but the molecular mechanisms behind these processes are still elusive due in part to the difficulty of imaging trace metals together with proteins at the synaptic level. We correlate stimulated-emission-depletion microscopy of proteins and synchrotron X-ray fluorescence imaging of trace metals, both performed with 40 nm spatial resolution, on primary rat hippocampal neurons. We reveal the co-localization at the nanoscale of zinc and tubulin in dendrites with a molecular ratio of about one zinc atom per tubulin-αβ dimer. We observe the co-segregation of copper and F-actin within the nano-architecture of dendritic protrusions. In addition, zinc chelation causes a decrease in the expression of cytoskeleton proteins in dendrites and spines. Overall, these results indicate new functions for zinc and copper in the modulation of the cytoskeleton morphology in dendrites, a mechanism associated to neuronal plasticity and memory formation.

Growth and Characterization of Deep UV Emitter Structures Grown on Single Crystal Bulk AlN Substrates

2002 ◽  
Vol 743 ◽  
Author(s):  
X. Hu ◽  
R. Gaska ◽  
C. Chen ◽  
J. Yang ◽  
E. Kuokstis ◽  
...  
Keyword(s):  
Quantum Well ◽  
Single Crystal ◽  
Multiple Quantum Well ◽  
Blue Shift ◽  
Stimulated Emission ◽  
Localized States ◽  
Light Sources ◽  
Multiple Quantum ◽  
X Ray ◽  
Deep Uv

ABSTRACTWe report on high Al-content AlGaN-based deep UV emitter structures grown over single crystal, slightly off c-axis (5.8 degrees) bulk AlN substrates. AlN/AlGaN multiple quantum well (MQW) structures with up to 50% of Al in the well material were grown by using low-pressure MOCVD and characterized by using X-ray, AFM, SEM and photoluminescence techniques. Two light sources, one at 213 nm wavelength for selective excitation of quantum well layers and another one at 193 nm to excite both wells and barriers, were exploited. A weak temperature dependence (from 8 K to 300 K) of the luminescence intensity and the absence of blue-shift of the luminescence peak with increasing excitation intensity pointed to a low density of localized states, in a good agreement with the X-ray data, which indicated very high quality of these MQW structures.The most striking result was observation of stimulated emission at wavelength as short as 258 nm in Al0.5Ga0.5N/AlN MQWs grown on bulk AlN single crystals.

scholarly journals Physical conditions and chemistry of molecular gas in galactic centers

2013 ◽  
Vol 9 (S303) ◽  
pp. 15-28
Author(s):  
Susanne Aalto
Keyword(s):  
Milky Way ◽  
Stimulated Emission ◽  
Molecular Gas ◽  
Nuclear Activity ◽  
X Ray ◽  
Physical Conditions ◽  
Luminous Galaxies ◽  
Mass Outflow ◽  
Driving Source ◽  
Luminous Infrared Galaxy

AbstractStudying the molecular phase of the interstellar medium in galaxy nuclei is fundamental for the understanding of the onset and evolution of star formation and the growth of supermassive black holes. We can use molecules as observational tools exploiting them as tracers of chemical, physical and dynamical conditions. The molecular physical conditions in galaxy centers show large variety among galaxies, but in general the average gas densities (traced by e.g. HCN) and temperatures (probed by e.g. H2CO, NH3) are greater than in their disks. Molecular gas and dust is being funneled to the centers of galaxies by spiral arms, bars, and interactions - and one example of this is the minor merger NGC1614. Gas surface densities are also greater in galaxy nuclei and in extreme cases they become orders of magnitudes larger than what we find in the center of our own Milky Way. We can use IR excited molecular emission to probe the very inner regions of galaxies with deeply obscured nuclei where N(H2)>1024 cm−2 - for example the luminous infrared galaxy (LIRG) NGC4418. Abundances of key molecules such as HCN, HCO+, HNC, HC3N, CN, H3O+ are important tools in identifying the nature of buried activity and its evolution. Standard astrochemical scenarios (including X-ray Dominated regions (XDRs) and Photon Dominated Regions (PDRs)) are briefly discussed in this review and how we can use molecules to distinguish between them. High resolution studies are often necessary to separate effects of excitation and radiative transfer from those of chemistry - one example is absorption and effects of stimulated emission in the ULIRG Arp220. The nuclear activity in luminous galaxies often drives outflows and winds and in some cases molecular gas is being entrained in the outflows. Sometimes the molecular gas is carrying the bulk of the momentum. We can study the structure and physical conditions of the molecular gas to constrain the mass outflow rates and the evolution and nature of the driving source and two examples are discussed here: NGC1377 and Mrk231.

scholarly journals A self-terminating X-ray amplifying medium: Kinetics of K-shell photoionization and stimulated emission

2000 ◽  
Vol 18 (1) ◽  
pp. 49-57
Author(s):  
F.N. CHUKHOVSKII ◽  
U. TEUBNER ◽  
I. USCHMANN ◽  
E. FÖRSTER
Keyword(s):  
Emission Cross Section ◽  
Input Pulse ◽  
Stimulated Emission ◽  
Resonant Medium ◽  
Photon Flux ◽  
Stage Model ◽  
Two Stage ◽  
Effective Lifetime ◽  
X Ray ◽  
Amplifying Effect

A two-stage model for achieving X-ray amplifying action on photoionized K-transitions pumped by the soft X-ray broadband flux from laser-produced plasma is treated. A simple pumping criterion is considered by the analysis of the positive gain-length product for the two-stage model of innershell transitions (0) → (3) and (2) → (1). The incident photon flux integrated over the effective lifetime T21 of an innershell transition (2) → (1) is related to the photoionization coefficient μ03(ph), stimulated emission cross section σ21(stim), and the effective gainlength L(eff) ≃ 0.63/μ03(abs), where μ03(abs) is the absorption coefficient of a pump soft X-ray radiation. Numerical estimates for the feasibility of K-shell X-ray amplification are given for C, F, Na, Ti, and Sn. For the example of an exponential X-ray carrier pulse (XCP) propagating through a resonant medium, an amplifying effect depending on the ratio of the input pulse temporal bandwidth τband to the effective lifetime T21 is investigated. It is shown that for an XCP with a finite bandwidth τband the logarithm of an energy gain, ln[U(z)], falls below a linear relation with z and thus, from the viewpoint of maximum amplifying effect bandwidths τband with τband/T21 > 1 are preferable. The requirements for achieving X-ray K-shell photoionization amplification for C are discussed in more detail. PACS numbers: 32.80.Hd, 42.50.Md, 42.55.Vc, 42.65.Re, 52.25.Nr.

scholarly journals Quantum effects in laser-beam Compton interaction and stimulated electron-positron annihilation in a strong field

2004 ◽  
Vol 22 (4) ◽  
pp. 479-484
Author(s):  
I.V. SMETANIN ◽  
K. NAKAJIMA
Keyword(s):  
Laser Beam ◽  
Laser Cooling ◽  
Strong Field ◽  
Quantum Effects ◽  
Pulse Generation ◽  
Stimulated Emission ◽  
X Ray ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
Klein Gordon

Quantum effects in spontaneous and stimulated Compton laser-beam interactions are considered in the frame of the Klein–Gordon theory. We derive a quantum kinetic equation to describe the laser cooling of electron beams. Nonlinear theory of coherent π-pulse generation in the quantum X-ray Compton FEL is presented. A scheme of coherent stimulated annihilation of electron-positron pairs and stimulated emission of γ-ray photons is proposed.

scholarly journals Correlating STED and synchrotron XRF nano-imaging unveils the co-segregation of metals and cytoskeleton proteins in dendrites

2019 ◽  
Author(s):  
Florelle Domart ◽  
Peter Cloetens ◽  
Stéphane Roudeau ◽  
Asuncion Carmona ◽  
Emeline Verdier ◽  
...  
Keyword(s):  
Trace Metals ◽  
Neuronal Plasticity ◽  
Hippocampal Neurons ◽  
Molecular Mechanisms ◽  
Memory Formation ◽  
Stimulated Emission ◽  
X Ray ◽  
Nano Imaging ◽  
Zinc Chelation ◽  
Synaptic Level

AbstractZinc and copper are involved in neuronal differentiation and synaptic plasticity but the molecular mechanisms behind these processes are still elusive due in part to the difficulty of imaging trace metals together with proteins at the synaptic level. We correlate stimulated emission depletion (STED) microscopy of proteins and synchrotron X-ray fluorescence (SXRF) imaging of trace metals, both performed with 40 nm spatial resolution, on primary rat hippocampal neurons. We achieve a detection limit for zinc of 14 zeptogram (10-21 g) per pixel. We reveal the co-localization at the nanoscale of zinc and tubulin in dendrites with a molecular ratio of about one zinc atom per tubulin-αβ dimer. We observe the co-segregation of copper and F-actin within the nano-architecture of dendritic protrusions. In addition, zinc chelation causes a decrease in the expression of cytoskeleton proteins in dendrites and spines. Overall, these results indicate new functions for zinc and copper in the modulation of the cytoskeleton morphology in dendrites, a mechanism associated to neuronal plasticity and memory formation.

High-intensity x-ray spectra and stimulated emission from laser plasmas

1972 ◽  
Vol 5 (5) ◽  
pp. 315-318 ◽  
Author(s):  
T.C. Bristow ◽  
M.J. Lubin ◽  
J.M. Forsyth ◽  
E.B. Goldman ◽  
J.M. Soures
Keyword(s):  
High Intensity ◽  
Stimulated Emission ◽  
X Ray ◽  
Laser Plasmas

scholarly journals Люминесценция и стимулированное излучение поликристаллических пленок Cu(In,Ga)Se-=SUB=-2-=/SUB=-, осажденных методом магнетотронного напыления

2018 ◽  
Vol 52 (10) ◽  
pp. 1120
Author(s):  
И.Е. Свитенков ◽  
В.Н. Павловский ◽  
Е.В. Луценко ◽  
Г.П. Яблонский ◽  
В.Я. Ширипов ◽  
...  
Keyword(s):  
Thin Films ◽  
Laser Pulses ◽  
Stimulated Emission ◽  
Structural Quality ◽  
Optical Parameters ◽  
Nitrogen Laser ◽  
Nonradiative Recombination ◽  
X Ray ◽  
Recombination Centers ◽  
Emission Threshold

AbstractThe stimulated emission of Cu(In,Ga)Se_2 alloy thin films formed by magnetron-assisted sputtering onto a sodium-fluoride layer deposited onto a molybdenum layer on a glass substrate is observed. The structural and optical parameters of the films are determined by scanning electron microscopy, local X-ray spectral microanalysis, X-ray structural analysis, and low-temperature luminescence ( T = 10 K) measurements in the range of excitation levels of 1.6–75 kW cm^–2 provided by nanosecond nitrogen-laser pulses. The stimulated emission threshold corresponds to ~25 kW cm^–2. Comparative analysis of the emission of Cu(In,Ga)Se_2 thin films suggests that the introduction of sodium results in significant improvement of the structural quality, specifically, in a decrease in the density of energy states in the band tails and in a decrease in the concentration of nonradiative-recombination centers.

A beamline-compatible STED microscope for combined visible-light and X-ray studies of biological matter

2019 ◽  
Vol 26 (4) ◽  
pp. 1144-1151
Author(s):  
Marten Bernhardt ◽  
Jan-David Nicolas ◽  
Markus Osterhoff ◽  
Haugen Mittelstädt ◽  
Matthias Reuss ◽  
...  
Keyword(s):  
Cardiac Tissue ◽  
Stimulated Emission ◽  
X Rays ◽  
Full Field ◽  
X Ray ◽  
Biological Matter ◽  
Cell Tissue ◽  
Close Proximity ◽  
Optical Table ◽  
Nano Imaging

A dedicated stimulated emission depletion (STED) microscope had been designed and implemented into the Göttingen Instrument for Nano-Imaging with X-rays (GINIX) at the synchrotron beamline P10 of the PETRA III storage ring (DESY, Hamburg). The microscope was installed on the same optical table used for X-ray holography and scanning small-angle X-ray scattering (SAXS). Scanning SAXS was implemented with the Kirkpatrick–Baez (KB) nano-focusing optics of GINIX, while X-ray holography used a combined KB and X-ray waveguide optical system for full-field projection recordings at a defocus position of the object. The STED optical axis was aligned (anti-)parallel to the focused synchrotron beam and was laterally displaced from the KB focus. This close proximity between the STED and the X-ray probe enabled in situ combined recordings on the same biological cell, tissue or any other biomolecular sample, using the same environment and mounting. Here, the instrumentation and experimental details of this correlative microscopy approach are described, as first published in our preceding work [Bernhardt et al. (2018), Nat. Commun. 9, 3641], and the capabilities of correlative STED microscopy, X-ray holography and scanning SAXS are illustrated by presenting additional datasets on cardiac tissue cells with labeled actin cytoskeleton.

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