X-ray Fluorescence Essay Example | Topics and Well Written Essays - 1500 words

X-ray Fluorescence - Essay Example J. Moseley number elements in 1913 through the observation of K-line transitions as observed in X-ray spectrum. This formed the basis of element identification through X-ray fluorescence spectroscopy by considering the relationship between the atomic number and the frequency. X-Ray fluorescence, XRF refers to the emission of characteristic secondary, also referred to as fluorescent X-rays by bombarding a material with X-rays at high energy or gamma rays so that the material gets excited. The wavelength of X-rays range between 50 and 100 A related to energy in the relationship: E = h? where h is Planck constant, 6.62 * 10-24 and ? is the frequency in Hertz. High energy X-rays would be required for XRF as the soft X-rays get absorbed by the target element, with the absorption edges depending on ionisation energies of the respective electrons, unique to each element. While the energy dispersive XRF, EDXRF methodology detects all elements from Na through to U, the wavelength dispersive X RF, WDXRF detects down to Be (Shackley 34). How XRF Works When the atoms of the target material absorb the high energy photons from the X-rays or gamma-rays, the electrons at the inner shell would be ejected from the atom transforming them to photoelectrons. As a result, the atom would be left at an excited state having a vacancy in its inner shell. The outer shell electrons would then fall into this resultant vacancy in the process emitting photons whose energy equals the difference in energy between the two states. It would be appreciated that each element has its unique energy level set, implying that each element would emit characteristic pattern of X-rays unique to itself which Sharma (527) refers to as characteristic X-rays. With increase in the concentration of the corresponding element, there would also be an increase in the X-ray intensity. This phenomenon also applies in the quantitative analysis of elements through the production of optical emission spectra. With characte ristic X-rays resulting from transition between the energy levels in an atom, the electrons that transition from energy level Ei to Ej would emit X-rays with energy Ex = Ei – Ej. With each element having unique atomic energy level set, a unique X-rays set would be emitted characteristic of the element (Sharma 526). Considering Bohr’s atomic model (see fig. 1), with atomic levels designated as K, L, M and so forth, each with additional sub-shells, a transition between these shells would result in the emission of characteristic X-rays. Fig. 1. Bohr’s atomic model from Sharma (527) As such, M X-ray would result from transition to M shell, so would K X-ray be a result of transition to K shell. K?1 X-ray would result from an electron dropping from M3 shell to fill in a vacancy in the K shell (see fig. 2). The emitted X-ray would have energy EX-ray = EK – EM3. Figure 2: X-ray line labelling from Bounakhla and Tahri (12) Sources According to Bounakhla and Tahri (21), radioisotopes provide the simplest source for configuration since one selects a source that emits X-rays slightly above the target element’s absorption edge energy. They have found wide application due to their stability and smallness in size in the context where monochromatic and continuous sources would be required. It serves well with regard to ruggedness, reliability, simplicity and in the consideration of cost of equipment. For safety, emissions would be limited to approximately 107 photons. The activity would be described in terms of disintegration rates of the radioisotopes where this activity would decrease from initial activity, A0 to final activity At for a duration of time, t. At = A0e(-0.693t/T?) where T? is the

Question answer Essay Example | Topics and Well Written Essays - 2000 words

Question answer - Essay Example Notably, finance minister of State X was present at the signing of the agreement between the two parties and after signing the document, the finance minister added the words â€Å"approved and ratified† and the minister also placed his own signature. Later on, a dispute aroused where OIC initiated a settlement proceeding in accordance with the procedures set out in the joint venture contract specifying both IPF and State X. However, State X argued that settlement tribunal has no jurisdiction over it. The major case issue is that whether State X can be excused from participating in the suit or not. With regard to the case, it can be stated that State X cannot be excused from participating in the suit. As the common law of contract in Australia affirms that any third party benefitting from the contractual agreement is liable to sue the other major party under the contractual agreement and vice versa. Nonetheless, privity of contract states that only the major parties entering in to the contractual agreement has the right to sue each other if any dispute arises. Simultaneously, the doctrine of privity of contract denies any obligations or liabilities to third party1. However, the doctrine of privity states that the major party has the right to sue the third party benefiting from the contract. ... over the performance of IPF, it cannot be denied that any action performed by IPC is governed by and taken with the active participation of State X2. Thus, the action of IPC cannot be distinguished from State X. In addition, State X also affirmed the contract by providing its approval and rectification as well as the finance minister of State X placed his signature to the contractual agreement which provided an evidence of State X’s involvement to the contractual agreement entered between OIC and IPF. At the same time, it can be argued that finance minister of State X was endorsing the contract but he was not making government as a party to the contract entered. Despite this aspect, it can be stated that State X should not be excused from participating in the suit. Additionally, the arbitration tribunal has sole power to involve State X in the suit. QUESTION 2: Considering the case of the Republic of Argentina et al v. Weltover Inc. et al., The United States used the Foreign S overeign Immunities Act of 1996 to bring suit against Argentina for a default on bond repayment. According to Foreign Sovereign Immunities Act 1996, statutory method can be ascertained from the United States courts to acquire jurisdiction over non-US sovereign. It offers that any person in the United States can seek for jurisdiction for disputes resulting from business transactions to non-US sovereign. It immunises non-U.S. states from jurisdiction of US court unless any exceptional scenario applies. Accordingly, Supreme Court of the USA has characterised â€Å"commercial activity† as the most important exception. This exception provides the verdict regarding which party can apply for lawsuit against the non-US sovereign in the US court. As part of a plan to stabilise petitioner, the Republic of