ADAS Subroutine r8giiav

      function r8giiav(u, u2, n0)

C-----------------------------------------------------------------------
C
C  **************** FORTRAN77 REAL*8 FUNCTION: R8GIIAV *****************
C
C  PURPOSE: CALCULATE AVERAGED FREE-BOUND GAUNT FACTOR FOR SUMMED
C  CONTRIBUTIONS OF THE HIGH LYING STATES - SUMMERS AND HOOPER EQU. 19
C
C  INPUT
C      U=HV/IH  WHERE HV IS PHOTON ENERGY
C               AND IH IS THE RYDBERG ENERGY
C      U2=K*TE/IH  WHERE TE IS THE ELECTRON TEMPERATURE
C                  AND K IS THE BOLTZMANN CONSTANT
C      N0       IS THE FIRST LEVEL TO BE COUNTED IN THIS
C               QUASI-CONTINUUM
C  OUTPUT
C      GIIAV=AVERAGED FREE-BOUND GAUNT FACTOR.
C
C
C  AUTHOR   : L D Horton
C  DATE     : 24-06-1997
C
C
C  VERSION  : 1.1
C  DATE     : 02-03-2005
C  MODIFIED : Martin O'Mullane
C                - First version in central ADAS.
C
C  VERSION  : 1.3                          
C  DATE     : 10-04-2007
C  MODIFIED : Allan Whiteford
C               - Modified documentation as part of automated
C		  subroutine documentation preparation.
C
C-----------------------------------------------------------------------
C
C-----------------------------------------------------------------------
      INTEGER             N0
      REAL*8              U,           U2