X-rays

Nature and origin of X-rays

Interaction of X-rays with atoms

Energy Levels for a one electron atom

Energy levels for multielectron atoms

Ene

rgy

Sca

le (

log)

Electronic Transition to inner electron levels

Partial energy level diagram showing common transitions leading to X–radiation.

The most intense lines are indicated by the widest arrows

The orbital shells are labelled as K for n=1, L for n=2, M for n=3.

Some Experimental Data

Generation of X-Rays

Mo

e-

AccelleratingVoltage V

X-ray emission process

Inner shell ionization

Radiative de-excitation

Auger Emission

Auger electron emission following inner shell ionisation

Fluorescence Yield for K and L shells

Probability of a core hole in the K or L shell being filled by a radiative process

X-ray emission from a Silver targetIntensity

Characteristic Silver emission lines are over imposed on a continuous radiation background (Bremsstrahlung radiation) due to deceleration of high-energy electrons.

The three curves are in dependence from the electron accelerating voltage V

X–ray emission from a Mo and Cu target

X-ray absorption

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I t = I0e−μ m ρx

It = incidentIo = transmitted X-ray intensitym = mass absorption coefficient (characteristic of the absorber)= density, andx = thickness of absorber.

X-ray absorption by lead

K

L

M

Absorption edges

Use of absorption edge as a filter to provide effectively monochromatic X-rays