Unformatted text preview: there are additional energy sources (beyond photoionization) for the electron population. The quantity in square brackets is often denoted by q 12 . There exists a relation between Ω for a single term and that for a set of closely spaced levels if S=0 or J=0 . This means that certain line ratios are fixed by statistical weights in the atoms  the ratio of photon numbers in the lines is the ratio of statistical weights, and the ratio of line intensities is this value modified by the ratio of frequencies. This accounts for the (nearly) 3:1 ratios in line pairs such as [O III] λ4959,5007 Å, [N II] λ 6548,6583 Å, and [O I] &lambda 6300,6363 Å....
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This note was uploaded on 11/10/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.
 Fall '10
 EmilyHoward
 Astronomy

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