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.

Timing of repeated movements: Test of a two-stage model

1997 ◽  
Author(s):  
Saul Sternberg ◽  
Teresa Pantzer
Keyword(s):  
Stage Model ◽  
Two Stage

Nonlinear dynamics of pulsating detonation wave with two-stage chemical kinetics in the shock-attached frame

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Yaroslava E. Poroshyna ◽  
Aleksander I. Lopato ◽  
Pavel S. Utkin
Keyword(s):  
Wave Propagation ◽  
Detonation Wave ◽  
Model Comparison ◽  
Approximation Order ◽  
Transition Regime ◽  
Stage Model ◽  
Two Stage ◽  
One Dimensional ◽  
Kinetics Of ◽  
Detonation Wave Propagation

Abstract The paper contributes to the clarification of the mechanism of one-dimensional pulsating detonation wave propagation for the transition regime with two-scale pulsations. For this purpose, a novel numerical algorithm has been developed for the numerical investigation of the gaseous pulsating detonation wave using the two-stage model of kinetics of chemical reactions in the shock-attached frame. The influence of grid resolution, approximation order and the type of rear boundary conditions on the solution has been studied for four main regimes of detonation wave propagation for this model. Comparison of dynamics of pulsations with results of other authors has been carried out.

scholarly journals Temperature-Dependent Stimulated Emission Cross-Section in Nd3+:YLF Crystal

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 431
Author(s):  
Giorgio Turri ◽  
Scott Webster ◽  
Michael Bass ◽  
Alessandra Toncelli
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Room Temperature ◽  
Radiative Decay ◽  
Emission Cross Section ◽  
Spectroscopic Properties ◽  
Stimulated Emission ◽  
Different Temperatures ◽  
Stimulated Emission Cross Section ◽  
Semi Empirical

Spectroscopic properties of neodymium-doped yttrium lithium fluoride were measured at different temperatures from 35 K to 350 K in specimens with 1 at% Nd3+ concentration. The absorption spectrum was measured at room temperature from 400 to 900 nm. The decay dynamics of the 4F3/2 multiplet was investigated by measuring the fluorescence lifetime as a function of the sample temperature, and the radiative decay time was derived by extrapolation to 0 K. The stimulated-emission cross-sections of the transitions from the 4F3/2 to the 4I9/2, 4I11/2, and 4I13/2 levels were obtained from the fluorescence spectrum measured at different temperatures, using the Aull–Jenssen technique. The results show consistency with most results previously published at room temperature, extending them over a broader range of temperatures. A semi-empirical formula for the magnitude of the stimulated-emission cross-section as a function of temperature in the 250 K to 350 K temperature range, is presented for the most intense transitions to the 4I11/2 and 4I13/2 levels.

scholarly journals Correction to: Identifying resting locations of a small elusive forest carnivore using a two-stage model accounting for GPS measurement error and hidden behavioral states

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Dalton J. Hance ◽  
Katie M. Moriarty ◽  
Bruce A. Hollen ◽  
Russell W. Perry
Keyword(s):  
Measurement Error ◽  
Stage Model ◽  
Two Stage ◽  
Gps Measurement ◽  
Behavioral States

An amendment to this paper has been published and can be accessed via the original article.

Two-stage model for estimating the spatiotemporal distribution of hourly PM1.0 concentrations over central and east China

2019 ◽  
Vol 675 ◽  
pp. 658-666 ◽  
Author(s):  
Wei Wang ◽  
Feiyue Mao ◽  
Bin Zou ◽  
Jianping Guo ◽  
Lixin Wu ◽  
...  
Keyword(s):  
Spatiotemporal Distribution ◽  
East China ◽  
Stage Model ◽  
Two Stage

Emotion Expressions

2011 ◽  
Vol 20 (6) ◽  
pp. 407-408 ◽  
Author(s):  
Azim F. Shariff ◽  
Jessica L. Tracy
Keyword(s):  
Historical Perspective ◽  
Empirical Work ◽  
Stage Model ◽  
Two Stage ◽  
Cultural Symbols ◽  
Expression Of Emotions ◽  
Complete Story

We appreciate Barrett’s (2011, this issue) comments and her discussion of how our two-stage model is and is not consistent with Darwin’s views on the evolution of emotion expressions. Like many pioneering books, Darwin’s The Expression of Emotions in Man and Animals represents a flurry of novel and revolutionary, yet often inconsistent, ideas, which lend themselves to different readings. However, while the historical perspective Barrett provides is useful, the scientific conversation on emotion expressions has evolved since Darwin. Here, we briefly discuss why the two alternative explanations Barrett offers for the origins of emotion expressions—expressions as cultural symbols and/or as evolutionary byproducts—are both untenable in light of existing research. We also note that although evidence for our two-stage model is currently incomplete, our goal was not to tell a complete story. Instead, we sought to offer the best emerging explanation for the existing research and provide a path for future empirical work that can test it.

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