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Extinction Index
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::

   Extinction Index = {model_name} {float} []

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**Description / Usage**
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This required card is used to specify the model for electrical permittivity when using REFRACTIVE_INDEX model.
Definitions of the input parameters are as follows:

CONSTANT
   Name of the model for constant extinction index
      * <float> -the value 
TABLE
    See TABLE instructions, WAVELENGTH is probably what you want to interpolate with

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**Examples**
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Following are sample cards:

::

   Extinction Index = CONSTANT 1.
   Extinction Index = TABLE 2 WAVELENGTH 0 LINEAR FILE=k.txt

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**Technical Discussion**
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This card is utilized to set the extinction index, used for acoustic and time-harmonic Maxwell.


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**References**
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No References.