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Characteristic and Bremsstrahlung Radiation

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Characteristic and Bremsstrahlung Radiation

Post by Joshua on Tue Sep 08, 2009 4:13 pm

Characteristic x-rays
are emitted from heavy elements when their electrons make transitions
between the lower atomic energy levels. The characteristic x-rays
emission which shown as two sharp peaks in the illustration at left
occur when vacancies are produced in the n=1 or K-shell of the atom
and electrons drop down from above to fill the gap. The x-rays
produced by transitions from the n=2 to n=1 levels are called K-alpha
x-rays, and those for the n=3->1 transiton are called K-beta
x-rays.


Transitions to the n=2 or L-shell
are designated as L x-rays (n=3->2 is L-alpha, n=4->2 is
L-beta, etc. ). The continuous distribution of x-rays which forms the
base for the two sharp peaks at left is called
"bremsstrahlung"
radiation
.



X-ray production typically involves
bombarding a metal target in an
x-ray
tube
with
high speed electrons which have been accelerated by tens to hundreds
of kilovolts of potential. The bombarding electrons can eject
electrons from the inner shells of the atoms of the metal target.
Those vacancies will be quickly filled by electrons dropping down
from higher levels, emitting x-rays with sharply defined frequencies
associated with the difference between the atomic energy levels of
the target atoms.


The frequencies of the
characteristic x-rays can be predicted from the Bohr model . Moseley
measured the frequencies of the characteristic x-rays from a large
fraction of the elements of the periodic table and produces a plot of
them which is now called a
"Moseley
plot"
.


Characteristic x-rays are used for
the investigation of crystal structure by x-ray diffraction. Crystal
lattice dimensions may be determined with the use of
Bragg's
law
in a
Bragg
spectrometer
.





"Bremsstrahlung" means
"braking radiation" and is retained from the original
German to describe the radiation which is emitted when electrons are
decelerated or "braked" when they are fired at a metal
target. Accelerated charges give off electromagnetic radiation, and
when the energy of the bombarding electrons is high enough, that
radiation is in the
x-ray
region of the
electromagnetic
spectrum
.
It is characterized by a continuous distribution of radiation which
becomes more intense and shifts toward higher frequencies when the
energy of the bombarding electrons is increased. The curves above are
from the 1918 data of Ulrey, who bombarded tungsten targets with
electrons of four different energies.

The bombarding electrons can also
eject electrons from the inner shells of the atoms of the metal
target, and the quick filling of those vacancies by electrons
dropping down from higher levels gives rise to sharply defined
characteristic
x-rays
.
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Joshua

Posts : 9
Join date : 2009-08-19
Age : 40

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Re: Characteristic and Bremsstrahlung Radiation

Post by renien on Fri Oct 02, 2009 5:21 pm

sir josh..
gud aftie..
sir pumunta po kmi friday ng hapon dito sa school pero wla kdaw.. sir remind kunalang ung adjustment sa grade namin ni Ms. celestial..Ms. Muyco po to sir.. 2 points po ung sa akin..kasi bka di na po ako mka balik dito bukas.. salamat sir...
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renien

Posts : 9
Join date : 2009-09-15

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