The significance of hydrogen bonding in electron solvation processes in ethanol-n-hexane liquid mixtures

Monte-Carlo programs are well recognized for their ability to model electron beam interactions with samples, and to incorporate boundary conditions such as compositional or surface variations which are difficult to handle analytically. This success has been especially powerful for modelling X-ray emission and the backscattering of high energy electrons. Secondary electron emission has proven to be somewhat more difficult, since the diffusion of the generated secondaries to the surface is strongly geometry dependent, and requires analytical calculations as well as material parameters. Modelling of secondary electron yield within a Monte-Carlo framework has been done using multiple scattering programs, but is not readily adapted to the moderately complex geometries associated with samples such as microelectronic devices, etc.This paper reports results using a different approach in which simplifying assumptions are made to permit direct and easy estimation of the secondary electron signal from samples of arbitrary complexity. The single-scattering program which performs the basic Monte-Carlo simulation (and is also used for backscattered electron and EBIC simulation) allows multiple regions to be defined within the sample, each with boundaries formed by a polygon of any number of sides. Each region may be given any elemental composition in atomic percent. In addition to the regions comprising the primary structure of the sample, a series of thin regions are defined along the surface(s) in which the total energy loss of the primary electrons is summed. This energy loss is assumed to be proportional to the generated secondary electron signal which would be emitted from the sample. The only adjustable variable is the thickness of the region, which plays the same role as the mean free path of the secondary electrons in an analytical calculation. This is treated as an empirical factor, similar in many respects to the λ and ε parameters in the Joy model.

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Urea-Catalyzed Functionalization of Unactivated C–H Bonds

10.26434/chemrxiv.11886789.v1 ◽

2020 ◽

Cited By ~ 2

Author(s):

Alex L. Bagdasarian ◽

Stasik Popov ◽

Benjamin Wigman ◽

Wenjing Wei ◽

woojin lee ◽

...

Keyword(s):

Hydrogen Bonding ◽

Organic Synthesis ◽

High Energy ◽

Acid Catalysts ◽

Potential Utility ◽

New Paradigm ◽

Lewis Acid Catalysts ◽

Reaction Conditions ◽

Highly Active ◽

Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp2 carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.

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Urea-Catalyzed Functionalization of Unactivated C–H Bonds

10.26434/chemrxiv.11886789 ◽

2020 ◽

Author(s):

Alex L. Bagdasarian ◽

Stasik Popov ◽

Benjamin Wigman ◽

Wenjing Wei ◽

woojin lee ◽

...

Keyword(s):

Hydrogen Bonding ◽

Organic Synthesis ◽

High Energy ◽

Acid Catalysts ◽

Potential Utility ◽

New Paradigm ◽

Lewis Acid Catalysts ◽

Reaction Conditions ◽

Highly Active ◽

Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp2 carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.

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Structure and hydrogen bonding of the hydrated selenite and selenate ions in aqueous solution

Dalton Transactions ◽

10.1039/c3dt53468e ◽

2014 ◽

Vol 43 (17) ◽

pp. 6315-6321 ◽

Cited By ~ 22

Author(s):

Lars Eklund ◽

Ingmar Persson

Keyword(s):

Aqueous Solution ◽

Hydrogen Bonding ◽

Free Electron ◽

Electron Pair ◽

Bound Water ◽

Water Molecules ◽

Hydration Sphere ◽

Free Electron Pair

The selenite ion has an asymmetric hydration sphere with loosely electrostatically bound water molecules outside the free electron pair.

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Imaging at an x-ray absorption edge using free electron laser pulses for interface dynamics in high energy density systems

Review of Scientific Instruments ◽

10.1063/1.4982166 ◽

2017 ◽

Vol 88 (5) ◽

pp. 053501 ◽

Cited By ~ 5

Author(s):

M. A. Beckwith ◽

S. Jiang ◽

A. Schropp ◽

A. Fernandez-Pañella ◽

H. G. Rinderknecht ◽

...

Keyword(s):

Energy Density ◽

Absorption Edge ◽

Free Electron ◽

Free Electron Laser ◽

Laser Pulses ◽

High Energy ◽

High Energy Density ◽

Interface Dynamics ◽

X Ray ◽

X Ray Absorption

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Ionization Dosimetry Principles for Conventional and Laser-Driven Clinical Particle Beams

International Journal of Women’s Health Care ◽

10.33140/ijwhc/03/02/00004 ◽

2018 ◽

Vol 3 (2) ◽

Keyword(s):

Ionizing Radiation ◽

Heavy Particle ◽

Absorbed Dose ◽

High Energy ◽

Particle Energy ◽

Particle Accelerators ◽

Carbon Ions ◽

Particle Beams ◽

Radiation Fields ◽

Number Of Particles

In this paper after mentioning the clinical radiation fields of 20 keV-450 MeV/u, they are characterized by the number of particles and their energy. Particle energy is the quantity that determines radiation penetration at the depth at which the tumor is situated (Fig. 1). The number of particles (or beam intensity) is the second major quantity that assures the administration of the absorbed dose in the tumor. The first application shows the radiation levels planned for various radiation fields. Prior to interacting with the medium, the intensity (or energy fluence rate) allows the determination of energy density, energy, power and relativistic force. In the interaction process, it determines the absorbed dose, kerma and exposure. Non-ionizing radiations in the EM spectrum are used as negative energy waves to accelerate particles charged into special installations called particle accelerators. The particles extracted from the accelerator are the source of the corpuscular radiation for high-energy radiotherapy. Of these, light particle beams (electrons and photons) for radiotherapy are generated by betatron, linac, microtron, and synchrotron and heavy particle beams (protons and heavy ions) are generated by cyclotron, isochronous cyclotron, synchro-cyclotron and synchrotron. The ionization dosimetry method used is the ionization chamber for both indirectly ionizing radiation (photons and neutrons) and for directly ionizing radiation (electrons, protons and carbon ions). Because the necessary energies for hadrons therapy are relatively high, 50-250 MeV for protons and 100-450 MeV/u for carbon ions, the alternative to replace non-ionizing radiation with relativistic laser radiation for generating clinical corpuscular radiation through radiation pressure acceleration mechanism (RPA) is presented.

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