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X-ray soec

QuestionAnswer
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