content_image/347647.jpg content_image/347648.jpg content_image/347649.jpg content_image/347650.jpg content_image/347651.jpg content_image/347652.jpg content_image/347653.jpg content_image/347654.jpg content_image/347655.jpg content_image/347656.jpg
<img src='content_image/347647.jpg'>

In a similar way for the second and third term of Eq. (16), we obtain 

<img src='content_image/347648.jpg'>

<img src='content_image/347649.jpg'>

where 

<img src='content_image/347650.jpg'>

<img src='content_image/347651.jpg'>

The calculation of the emissivity can be more easily performed by expressing the latest integrals in terms of the Fermi integral, which is defined as [33] 

where α = m e $_{KT}$, β = µ e KT and x = E $_{KT}$. 

With these definitions, Eq. (26) becomes 

therefore 

From (28), (29) and (30), Eqs. (24) and (25) are expressed as 

<img src='content_image/347652.jpg'>

<img src='content_image/347653.jpg'>

<img src='content_image/347654.jpg'>

<img src='content_image/347655.jpg'>

<img src='content_image/347656.jpg'>

