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20.   Spectral Line Shapes, Widths, and Shifts

Observed spectral lines are always broadened, partly due to the finite resolution of the spectrometer and partly due to intrinsic physical causes. The principal physical causes of spectral line broadening are Doppler and pressure broadening. The theoretical foundations of line broadening are discussed in Atomic, Molecular, & Optical Physics Handbook, Chaps. 19 and 57, ed. by G.W.F. Drake (AIP, Woodbury, NY, 1996).

Values of Stark-broadening parameter α1/2 for the Hβ line of hydrogen (4861 ) for various temperatures and electron densities.

  Ne (cm-3)
 
T(K) 1015 1016 1017 1018

  5 000 0.0787 0.0808 0.0765 ...
10 000 0.0803 0.0840 0.0851 0.0781
20 000 0.0815 0.0860 0.0902 0.0896
30 000 0.0814 0.0860 0.0919 0.0946


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