Atomic line width
- 1. Presentation On: Atomic Line width & Uncertainty principle • Definition • Profile Of an atomic line • Importance Of Atomic line width • Sources of line broadening • Uncertainty principle Contents: 1
- 2. Atomic Line Width • Line width or effective line width of an atomic absorption or emission line is defined as its width in wavelength unit when measured at one half of the maximum signal. • An atomic line should have small(or zero) line width since transition between two quantum states requires an exact amount of energy. • Several phenomena however cause line broadening so that all atomic lines have finite width. 2
- 3. Profile of an atomic line: 3
- 4. Importance of atomic line width: • Width of atomic line are quite important in atomic spectroscopy • Narrow lines in atomic and emission spectra reduce the possibility of interference due to overlapping line. • Line width are extremely important in the design of instruments for atomic emission spectroscopy. 4
- 5. Sources of line broadening: • The uncertainty effect • The Doppler effect • The pressure effect • Electric & magnetic field effect 5
- 6. Line broadening from the uncertainty effect: • Spectral lines always have finite width because the life time of one or both transition states are finite, which leads to uncertainties in the transition times and to line broadening as consequence of the uncertainty principle. • Transition between two states would approach zero only if the life time of two states approached infinity. • Although the lifetime of a ground states electron is long, the lifetimes of excited states are generally short( typically 10^-7 to 10^-8 sec) 6
- 7. Example: 7
- 8. Solution: 8