Onset of charge interaction in strong-field photoemission from nanometric needle tips

Abstract Strong-field photoemission from nanostructures and the associated temporally modulated currents play a key role in the development of ultrafast vacuum optoelectronics. Optical light fields could push their operation bandwidth into the petahertz domain. A critical aspect of their functionality in the context of applications is the impact of charge interaction effects. Here, we investigated the photoemission and photocurrents from nanometric tungsten needle tips exposed to carrier-envelope phase (CEP)-controlled few-cycle laser fields. We report a characteristic rapid increase in the intensity-rescaled cutoff energies of emitted electrons beyond a certain intensity value. By comparison with simulations, we identify this feature as the onset of charge-interaction dominated photoemission dynamics. Our results are anticipated to be relevant also for the strong-field photoemission from other nanostructures, including photoemission from plasmonic nanobowtie antennas used in CEP-detection and for PHz-scale devices.

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Nonadiabatic Coulomb effects in strong-field ionization in circularly polarized laser fields

Physical Review A ◽

10.1103/physreva.88.013421 ◽

2013 ◽

Vol 88 (1) ◽

Cited By ~ 58

Author(s):

Jivesh Kaushal ◽

Olga Smirnova

Keyword(s):

Strong Field ◽

Field Ionization ◽

Laser Fields ◽

Circularly Polarized ◽

Strong Field Ionization ◽

Coulomb Effects

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Experimental Investigation and Statistical Approach to Wear Characterization of Plasma Nitrided AISI 4140 Steel-A Case Study

Manufacturing and Industrial Engineering ◽

10.12776/mie.v15i1-2.804 ◽

2017 ◽

Vol 15 (1-2) ◽

Author(s):

Santosh V. Bhaskar ◽

Hari N. Kudal

Keyword(s):

Plasma Nitriding ◽

Interaction Effects ◽

Wear Volume ◽

Effective Parameters ◽

Operational Parameters ◽

Sliding Speed ◽

Aisi 4140 Steel ◽

Study Results ◽

Aisi 4140 ◽

The Impact

<p>Components of forming tool dies such as draw ring, ejector pin use AISI 4140 as material for their manufacturing. The integrity of the die cutting tools is essential to achieve adequate product quality. In present study, the influence of plasma nitriding (PN) on the wear behav-iour of AISI 4140 steel was investigated. Full factorial experimental design technique was used to study the main effects and the interaction effects between operational parameters and the response variable. The control factors at their two levels (-1 and +1) were: applied load (4.905N and 14.715N), sliding speed (3.14 m/s and 5.23 m/s), and sliding distance (500m and 1000m).The parameters were coded as A, B, and C, consecutively, and were investigated at two levels (-1 and +1). Response selected was Wear Volume Loss (WVL). The effects of in-dividual variables and their interaction effects for dependent variables, namely, WVL were determined. The process of selecting significant factors, based on statistical tools, is illustrat-ed. Analysis of Variance (ANOVA) was performed to know the impact of individual factors on the WVL. Untreated and PN treated AISI 4140 specimens were investigated using field emission Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray (EDX) analyzer. Finally diagnostics tools were used to check adequacy of the model in terms of assumptions of ANOVA. ‘Design Expert-7’ and ‘Minitab 17’ softwares were used in the study. Results of statistical analysis indicate that the most effective parameters in the WVL were load and sliding speed. The interaction between load and sliding speed was the most influencing interaction. Results of regression analysis indicate regression coefficient (R2) to be above 90% which suggests good predictability of the model. ‘Predicted-R2’ and ‘Adjusted-R2’, found to be in good agreement with R2, for both the materials under investigation. More-over, results of SEM microscopy suggest PN to be an effective technique to reduce wear.</p>

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Perturbative deflection angle, gravitational lensing in the strong field limit and the black hole shadow

The European Physical Journal C ◽

10.1140/epjc/s10052-021-09026-7 ◽

2021 ◽

Vol 81 (3) ◽

Author(s):

Junji Jia ◽

Ke Huang

Keyword(s):

Gravitational Lensing ◽

Deflection Angle ◽

Strong Field ◽

Distance Effect ◽

Critical Value ◽

Field Limit ◽

Perturbative Method ◽

The Deflection Angle ◽

The Impact ◽

Strong Field Limit

AbstractA perturbative method to compute the deflection angle of both timelike and null rays in arbitrary static and spherically symmetric spacetimes in the strong field limit is proposed. The result takes a quasi-series form of $$(1-b_c/b)$$ ( 1 - b c / b ) where b is the impact parameter and $$b_c$$ b c is its critical value, with coefficients of the series explicitly given. This result also naturally takes into account the finite distance effect of both the source and detector, and allows to solve the apparent angles of the relativistic images in a more precise way. From this, the BH angular shadow size is expressed as a simple formula containing metric functions and particle/photon sphere radius. The magnification of the relativistic images were shown to diverge at different values of the source-detector angular coordinate difference, depending on the relation between the source and detector distance from the lens. To verify all these results, we then applied them to the Hayward BH spacetime, concentrating on the effects of its charge parameter l and the asymptotic velocity v of the signal. The BH shadow size were found to decrease slightly as l increases to its critical value, and increase as v decreases from light speed. For the deflection angle and the magnification of the images however, both the increase of l and decrease of v will increase their values.

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