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Table C.1
Physical quantities.
| Symbol | Meaning | units (cgs) |
|
|
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| μ | Direction cosine (μ = cos(θ)) | |
| T | Temperature | K |
| n k | Total density of species k | cm-3 |
| n i | Density in an energy level labeled by i | cm-3 |
| f i | Relative density (fi = ni/nk) | |
| x i | Weighted relative density (xi = fi/gi) | |
| g i | Statistical weight of level i | |
| ν | Frequency | Hz |
| I ν | Specific intensity | erg s-1 cm-2 sr-1 Hz-1 |
|
Mean intensity | erg s-1 cm-2 Hz-1 |
| τ ν | Optical depth | |
| τ V | Optical depth at 500 nm | |
| S ν | Source function | erg s-1 cm-2 sr-1 Hz-1 |
| B ν | Planck function | erg s-1 cm-2 sr-1 Hz-1 |
| χ ν | Monochromatic extinction | cm-1 |
| η ν | Monochromatic emissivity | erg s-1 cm-3 sr-1 Hz-1 |
| β ν | Escape probability | |
| A ul | Einstein coefficient for spontaneous de-excitation | s-1 |
| B ij | Einstein coefficient for stimulated (de)excitation | erg-1 cm2 Hz |
| C ij | Rate for collisional (de)excitation | cm3 s-1 |
|
Normalized line profile of the transition i → j | Hz-1 |
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