The spectrum of background radiation in the interstellar medium

In 1994, I published a composite background radiation field from radio frequencies to the H I Lyman limit in the far ultraviolet ( Black 1994).   This was done in the context of an assessment of energy budgets in diffuse molecular clouds.  In order to provide a more detailed explanation of how this spectrum was constructed, I provide  here  some current notes in PDF format.  A brief description and table of the spectrum are provided   here   in ASCII format. 

John H. Black
Onsala Space Observatory
2002 January 28
revised 2005 December 14