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Chapter 11: Plasma physics 59 2. The Doppler broadening is caused by the thermal motion of the particles: Δ λ λ = 2 c ± 2ln(2) kT i m i This broadening results in a Gaussian line proFle: k ν = k 0 exp( - [2 ln 2( ν - ν 0 ) / Δ ν D ] 2 ) , with k the coefFcient of absorption or emission. 3. The Stark broadening is caused by the electric Feld of the electrons: Δ λ 1 / 2 = ² n e C ( n e ,T e ) ³ 2 / 3 with for the H- β line: C ( n e ,T e ) 3 · 10 14 ˚ A - 3 / 2 cm - 3 . The natural broadening and the Stark broadening result in a Lorentz proFle of a spectral line: k ν = 1 2 k 0 Δ ν L / [( 1 2 Δ ν L ) 2 +( ν - ν 0 ) 2 ] . The total line shape is a convolution of the Gauss- and Lorentz proFle and is called a Voigt profle . The number of transitions p q is given by n p B pq ρ and by n p n hf ± σ a c ² = n p ( ρ d ν /h ν ) σ a c where d ν is the line width. Then follows for the cross section of absorption processes: σ a = B pq h ν /cd ν . The background radiation in a plasma originates from two processes:
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This note was uploaded on 01/30/2011 for the course PHYSICS 208 taught by Professor Ye during the Spring '10 term at Blinn College.

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