Temporal and spectral control of the X-ray pulses in a resonant medium with a modulated transition frequency

Recently, for the generation of extremely short pulses, a method was proposed for coherent control of the polarization of a medium, based on the excitation of atomic polarization oscillations and their subsequent arrest using a pair of ultra short pulses. The so-called stopped pulse of polarization of the medium, which appears in the interval between its excitation and de-excitation, can be a source of an extremely short radiation pulse. In this paper, the indicated possibility of generating an isolated attosecond ultraviolet pulse in a three-level resonant medium, the parameters of which correspond to a hydrogen atom excited by a pair of unipolar X-ray pulses, is considered theoretically. In this case, the generation mechanism is "antenna", that is, it is caused by the collective spontaneous emission of pre-phased atoms in the absence of a noticeable decay of their free polarization. Key words: collective spontaneous emission, coherent control of atomic polarization, attosecond pulses, unipolar pulses, X-ray pulses, hydrogen atom.

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

Laser and Particle Beams ◽

10.1017/s0263034600181066 ◽

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.

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Multicolor Operation and Spectral Control in a Gain-Modulated X-Ray Free-Electron Laser

Physical Review Letters ◽

10.1103/physrevlett.111.134801 ◽

2013 ◽

Vol 111 (13) ◽

Cited By ~ 57

Author(s):

A. Marinelli ◽

A. A. Lutman ◽

J. Wu ◽

Y. Ding ◽

J. Krzywinski ◽

...

Keyword(s):

Free Electron ◽

Free Electron Laser ◽

X Ray ◽

Spectral Control

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Spectral Control of an X-Ray L -Edge Transition via a Thin-Film Cavity

Physical Review Letters ◽

10.1103/physrevlett.122.123608 ◽

2019 ◽

Vol 122 (12) ◽

Cited By ~ 3

Author(s):

Johann Haber ◽

Jakob Gollwitzer ◽

Sonia Francoual ◽

Martin Tolkiehn ◽

Jörg Strempfer ◽

...

Keyword(s):

Thin Film ◽

X Ray ◽

Spectral Control

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Shaping of X-ray Pulses via Dynamical Control of Their Interaction with a Resonant Medium

Springer Proceedings in Physics - X-Ray Lasers 2018 ◽

10.1007/978-3-030-35453-4_7 ◽

2020 ◽

pp. 45-52

Author(s):

T. Akhmedzhanov ◽

V. Antonov ◽

X. Zhang ◽

K. C. Han ◽

E. Kuznetsova ◽

...

Keyword(s):

Resonant Medium ◽

X Ray ◽

Dynamical Control

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Space and Time Distribution of Hard X-Ray Emission in a Loop at the Beginning of a Flare

International Astronomical Union Colloquium ◽

10.1017/s0252921100025446 ◽

1994 ◽

Vol 144 ◽

pp. 275-277

Author(s):

M. Karlický ◽

J. C. Hénoux

Keyword(s):

Time Distribution ◽

Electron Bombardment ◽

Spatial Evolution ◽

Superthermal Electrons ◽

Flare Loop ◽

X Ray ◽

Superthermal Electron ◽

Flare Loops ◽

Chromospheric Evaporation ◽

Temporal And Spatial

AbstractUsing a new ID hybrid model of the electron bombardment in flare loops, we study not only the evolution of densities, plasma velocities and temperatures in the loop, but also the temporal and spatial evolution of hard X-ray emission. In the present paper a continuous bombardment by electrons isotropically accelerated at the top of flare loop with a power-law injection distribution function is considered. The computations include the effects of the return-current that reduces significantly the depth of the chromospheric layer which is evaporated. The present modelling is made with superthermal electron parameters corresponding to the classical resistivity regime for an input energy flux of superthermal electrons of 109erg cm−2s−1. It was found that due to the electron bombardment the two chromospheric evaporation waves are generated at both feet of the loop and they propagate up to the top, where they collide and cause temporary density and hard X-ray enhancements.

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Some Problems in Understanding the Solar Corona

International Astronomical Union Colloquium ◽

10.1017/s025292110002491x ◽

1994 ◽

Vol 144 ◽

pp. 1-9

Author(s):

A. H. Gabriel

Keyword(s):

Solar Corona ◽

Solar Atmosphere ◽

Theoretical Modelling ◽

Total System ◽

Major Advance ◽

X Ray ◽

Proper Perspective ◽

Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

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White-Light Coronal Structures: Streamers and CMEs

International Astronomical Union Colloquium ◽

10.1017/s0252921100025045 ◽

1994 ◽

Vol 144 ◽

pp. 82

Author(s):

E. Hildner

Keyword(s):

Emission Line ◽

Electron Density ◽

White Light ◽

Coronal Mass Ejections ◽

X Rays ◽

Solar Cycles ◽

Temperature Function ◽

X Ray ◽

Eclipse Observations ◽

Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

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Iron K-Line Emission from X-Ray Binaries

International Astronomical Union Colloquium ◽

10.1017/s0252921100107389 ◽

1988 ◽

Vol 102 ◽

pp. 47-50

Author(s):

K. Masai ◽

S. Hayakawa ◽

F. Nagase

Keyword(s):

Accretion Disk ◽

Radiative Recombination ◽

Characteristic Temperature ◽

Line Emission ◽

Ionization Front ◽

Continuum Radiation ◽

X Ray ◽

Low Mass ◽

X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx> 10 keV is likely due to fluorescence outside the He II ionization front.

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