Laser matter interaction
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Laser-matter interaction depends on laser parameters as well as materials physical and chemical properties. The material response to the laser light depends on laser conditions and material properties. The material will respond differently to different intensities of laser light.
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Laser matter interaction
The document discusses laser matter interaction and provides an overview of lasers. It defines what a laser is, the mechanism of stimulated emission that allows lasers to function, and the typical components of a laser. It also describes how lasers interact with and affect various materials, including semiconductors, solids, and gases. Several types of lasers are outlined such as diode lasers, gas lasers, fiber lasers, and crystal lasers.
X ray Photoelectron Spectroscopy (XPS)
X-ray photoelectron spectroscopy (XPS) or Electron spectroscopy for chemical analysis (ESCA) is used to investigate the chemistry at the surface of the samples. The basic mechanism behind an XPS instrument is that the photons of a specific energy are used to excite the electronic states of atoms at and just below the surface of the sample.
There are several areas suited to measurement by XPS:
1. Elemental composition
2. Empirical formula determination
3. Chemical state
4. Electronic state
5. Binding energy
6. Layer thickness in the upper portion of surfaces
XPS has many advantages, such as it is is good for identifying all but two elements, identifying the chemical state on surfaces, and is good with quantitative analysis. XPS is capable of detecting the difference in the chemical state between samples. XPS is also able to differentiate between oxidations states of molecules.
XPS has also some limitations, for instance, samples for XPS must be compatible with the ultra high vacuum environment. XPS is limited to measurements of elements having atomic numbers of 3 or greater, making it unable to detect hydrogen or helium. XPS spectra also take a long time to obtain. The use of a monochromator can also reduce the time per experiment.
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Raman scattering involves the inelastic scattering of photons by phonons in a crystal. When a photon interacts with a crystal, it may be scattered with no change in energy (Rayleigh scattering), or a change in energy may occur through the creation or annihilation of a phonon (Raman scattering). The intensity ratio of anti-Stokes to Stokes Raman lines depends on temperature and can be used to determine phonon population. Raman spectroscopy provides information about phonon modes in crystals through observation of Raman peaks and their intensities and temperature dependence.
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Laser matter interaction
The document discusses laser matter interaction and provides an overview of lasers. It defines what a laser is, the mechanism of stimulated emission that allows lasers to function, and the typical components of a laser. It also describes how lasers interact with and affect various materials, including semiconductors, solids, and gases. Several types of lasers are outlined such as diode lasers, gas lasers, fiber lasers, and crystal lasers.
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1. Elemental composition
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This document discusses the interactions between x-rays and matter. There are three main interactions - photoelectric effect, Compton scattering, and coherent scattering. The photoelectric effect occurs when a photon ejects an inner shell electron from an atom. This produces characteristic x-rays and leaves the atom ionized. Compton scattering involves the deflection of photons by outer shell electrons, producing scattered radiation. At diagnostic energies, Compton scattering is the most common interaction. The photoelectric effect dominates for high atomic number materials and low energy x-rays. These two interactions are most important in diagnostic radiology, while coherent scattering, pair production and photodisintegration occur at higher energies.
INTERACTION OF IONIZING RADIATION WITH MATTER
The document discusses the interaction of ionizing radiation with matter. It describes the main interaction processes including photoelectric effect, Compton scattering, and pair production. For radiation therapy, Compton scattering is the most important interaction as it allows high energy beams to penetrate tissue more uniformly depositing dose. The photoelectric effect is more significant for diagnostic radiology due to its dependence on atomic number.
Atomic and nuclear physics
The document discusses several topics in atomic and nuclear physics including:
1) The photoelectric effect describes how light shining on a metal surface can eject electrons. Compton scattering demonstrates that X-rays lose energy when scattered by electrons, showing the particle nature of light.
2) X-rays are produced when high-energy electrons collide with atoms, either ejecting inner electrons or through braking radiation when deflected by the nucleus.
3) Light exhibits both wave and particle properties in experiments like the photoelectric effect, Compton scattering, and the Young's interference experiment, known as wave-particle duality.
4) Electrons falling between energy levels emit photons with energy equal to the level difference
Interaction of ionizing
Ionizing radiation interacts with matter by ejecting electrons through processes like ionization and excitation. The three main interaction processes between photons and atoms are the photoelectric effect, Compton effect, and pair production. The probability of each interaction depends on the photon energy and atomic number of the absorbing material. Charged particles like electrons and protons mainly interact through ionization and excitation via radiative collisions.
Basic Interactions Between X Rays and Matter
X-rays can interact with matter through various processes. The most common interactions in diagnostic radiology are the photoelectric effect, Compton scattering, and coherent scattering. In the photoelectric effect, an incoming x-ray photon ejects an inner shell electron, leaving behind characteristic radiation. Compton scattering involves x-ray photon deflection by a free electron, producing scatter radiation. Coherent scattering changes a photon's direction but not its energy. These interactions have different probabilities depending on the photon energy and the electron binding energy.
Intercation with matter
X-rays can interact with matter through various interactions such as coherent scattering, photoelectric effect, Compton scattering, pair production, and photodisintegration. The photoelectric effect and Compton scattering are the most important interactions for diagnostic x-rays. The photoelectric effect accounts for about 75% of interactions and results in the emission of characteristic x-rays. Compton scattering accounts for about 20% of interactions and scatters x-rays without energy loss, producing scatter radiation. The interaction that occurs depends on the photon energy and the atomic number of the absorbing material.
Molecular luminescence spectrometry
This document discusses molecular fluorescence and phosphorescence spectroscopy. It provides details on:
- The processes of fluorescence, where emission occurs from an excited singlet state, and phosphorescence, where emission occurs from an excited triplet state.
- Factors that influence fluorescence and phosphorescence intensities like quantum yield, transition types (π->π* vs π->n), molecular structure, and competing deactivation processes.
- How excitation and emission spectra are obtained and related to the energy of electronic state transitions.
- Applications of photoluminescence spectroscopy like determining material band gaps and quality.
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The cost of acquiring information by natural selection
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
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Speaker: Diego Blas (IFAE/ICREA)
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Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
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学校原件一模一样【微信：741003700 】《(salfor毕业证书)索尔福德大学毕业证》【微信：741003700 】学位证，留信认证（真实可查，永久存档）原件一模一样纸张工艺/offer、雅思、外壳等材料/诚信可靠,可直接看成品样本，帮您解决无法毕业带来的各种难题！外壳，原版制作，诚信可靠，可直接看成品样本。行业标杆！精益求精，诚心合作，真诚制作！多年品质 ,按需精细制作，24小时接单,全套进口原装设备。十五年致力于帮助留学生解决难题，包您满意。
本公司拥有海外各大学样板无数，能完美还原。
1:1完美还原海外各大学毕业材料上的工艺：水印，阴影底纹，钢印LOGO烫金烫银，LOGO烫金烫银复合重叠。文字图案浮雕、激光镭射、紫外荧光、温感、复印防伪等防伪工艺。材料咨询办理、认证咨询办理请加学历顾问Q/微741003700
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Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
Summary Of transcription and Translation.pdf
Hello Everyone Here We are Sharing You with The process of protien Synthesis in very short points you will be Able to understand It Very well
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDS
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
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Alternate Wetting and Drying - Climate Smart Agriculture
Alternate Wetting and Drying - Climate Smart AgricultureInternational Food Policy Research Institute- South Asia Office
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Aleš Zamuda: Randomised Optimisation Algorithms in DAPHNE .
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https://ashpc.eu/
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The cost of acquiring information by natural selection
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Laser matter interaction
- 2. “INTRODUCTION” The interaction mechanism between laser light and matter depend on: • Laser parameters, • Material’s properties.
- 3. “LIGHT PROPAGATION IN MATERIAL” Light-matter interaction causes different effects i.e. coherent scattering, photoelectric effect, Compton Effect, pair production.
- 4. “Coherent scattering” 1. Incoming photon interacts with outer orbital electron; 2. The incoming photon gives up its all energy to electron which makes the electron excited; 3. The excited electron gives up its excess energy in different direction in the form of phonon of same energy as incident photon.
- 5. “Photoelectric effect” In the process, emission an electron from the atom takes place when photon strikes to atom.
- 6. “Compton Effect” It is scattering of photon by a charged particle. Photon interacts with the free electron whose energy is less than the incident photon, electron receives energy from the photon and emitted at some angle ϴ where the reduced energy photon scattered at angle Φ from an atom.
- 7. “Pair production” A high energy photon interacts with the nucleus of an atom. The photon disappears and its energy is converted into matter in the form of two particles i.e. electrons and positron.
- 8. “Energy absorption mechanism” • In liquid and gases, light can induces electronic, vibrational, and rotational transitions within single molecules.
- 9. “Energy absorption mechanism” • In solids, the specific mechanisms by which the absorption occurs will depend on the type of material. Metals, Insulators and semiconductors.
- 10. “Laser matter interaction” The process starts with material excitation. If the excitation energy is instantaneously transformed into heat, then such process is Photo- thermal. If the photon energy is high enough, laser-light excitation can result in direct bond breaking such a process is Photo-chemical. Photo- physical ablation shall describe a process in which both thermal and non-thermal mechanisms contribute to the overall ablation rate. Thermally or non-thermally process generate defects, stresses, and volume changes in the material which then results in material's ablation and the formation of plasma.
- 11. “Photo-thermal process” When the laser-induced excitation rate is low in comparison to the thermalization rate, such processes are called photo- thermal process. In thermal process the excitation energy is instantaneously transformed into heat. The temperature rise can result in thermal material ablation with or without melting.
- 12. “Photo-chemical processes” When the laser induced excitation rate is high in comparison to the thermalization rate, such processes are referred as photochemical processes. In this case laser-light excitations can result in direct bond breaking. The process can take place without any change in surface temperature.
- 13. “Photo-physical processes” When photo-thermal and photo-chemical processes contribute in overall processing rate such processes are referred as photo- physical processes.
- 14. “Material response” The material response will depend on the particular material system and the laser processing conditions.
- 16. “conclusion” Laser matter interaction depends on laser parameters as well as materials physical and chemical properties. Laser matters interaction cause different energy losses and effects i.e. coherent scattering, photoelectric effect, Compton Effect, and pair production. Energy absorption mechanism of laser light by determined by the electrons transition, in insulators and semiconductors inter-band and in metals intra-band transition. Processing of laser light can be done by different phenomena's which includes photo-thermal, photo-chemical and photo- physical processes. The material response to the laser light depends on laser conditions and material properties. Material will respond differently at different intensities of laser light. The laser light parameters and the material's properties the combination of all these characteristics offers wide range of applications.