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X-ray soec
| Question | Answer |
|---|---|
| X-ray wavelength range | 0.0001nm to 10nm |
| Analytical methods based on | 1. emission 2.absorption 3.fluorescence 4.scattering 5.diffraction |
| How x-ray radiation is produced? | 1.primary x-ray radiation produce by bombardment of metal target with high energy electrons 2. secondary x-ray rad.- expsoing material to a beam of primary radiation 3. by the decay of radioactive source 4. from a synchrotrom |
| What kind of spectra does an x-ray produce | Both continuum and line spectra: 1. production of continuum of x-ray radiation only 2. production of a continuum of x-ray radiation on whichh a line spectrum is super-imposed |
| other name for continuum spectra | white radiation; bremsstrahlung |
| what is the continuum characterized by? | short wavelength lambda not(lo) |
| what does lambda not(lo)depend on | Volatage; higher V- shorter lo |
| does lo depend on the target material? | NO! x-ray continuum radiation will be the same from any metal target at particular voltage |
| What are K-series | group of lines at shorter wavelnegth. produced by by elements with smaller atomic number then 23 consists of two line Ka and KB result when electron is ejected for k orbital :n=1 |
| What are l-series | longer wavelength. Consist of three line LB2,LB1, La result when electrons are lost from l-orbitals n=2 |
| When the highest probability of the atom absorbing the radiation occurs? | It occurs when energy of x-ray radiation=energy required to remove electron from the inner orbital KE electron=0 |
| Formula for mass absorption coefficient | ln(Po/P)=mx ln(Po/P)=Mmrx 1.Mm-mass absorption coefficients: independent of the physical and chemical state 2. mass absorption coefficients are additive functions.Mm=wa+ma+wb+mb.... |
| difference between fluorescence and absorption | fluorescence lines occur at slightly longer wavelength than the corresponding adsorption edge. |
| is x-ray fluoresce a destructive technique? | NO |
| what are the requirements for diffraction? | 1. distance between planes of the crystal must be of the same order of magnitude as the wavelength of the x-radiation 2. scattering centers of the crystal must be distributed in a regular manner: MUST BE REGULAR CRYSTAL LATTICE |
| Bragg's Law | nl=3dsinF |
| Detctors in X-ray | 1. Gas-Filled detectors 2. Scintillation counters 3. Semiconductor detectors |
| Type of Gas filled detectors | 1.ionization chamber 2. proportional counter 3. geiger counter |
| different Voltage Regions in the gas-filled tube | 1. Ionization chamber region 2. Proportional counter region 3.Geiger region |
| Ionization chamber region | 1.current is very small 10^-12 to 10^-16; independent of voltage 2. Not very sensitive is not used in x-ray spec |
| Proportional counter region | 1.# of electron increase with applied voltage 2. number of electrons depends on the frequency of x-ray rad 2. deadtime is small |
| Geiger region | 1.number of electrons independent of energy of x-ray rad. 2.deadtime is large 3.not widely used in x-ray spectrometers |
| Scintillation counter | 1.consists of a crystal activated NaI 2. number of photons is proportional to the energy of incident radiation |
| Semiconductor detector consists of these levels: | 1st layer:p-type material. Coated with thin Gold layer protected with beryllium layer 2nd layer: Li-drifted zone. 3rd layer: n-type material coted with layer of AL |
Created by:
K@t
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