ADAS Subroutine r8gav

      function r8gav(u, gam2, n0)

C-----------------------------------------------------------------------
C
C  ***************** FORTRAN77 REAL*8 FUNCTION: R8GAV ******************
C
C  PURPOSE: CALCULATES TOTAL GAUNT FACTOR FOR FREE-FREE AND
C  QUASI-CONTINUOUS FREE-BOUND TRANSITIONS
C
C  INPUT
C      U=HV/KT  WHERE HV IS PHOTON ENERGY
C               AND KT IS ELECTRON TEMPERATURE (ENERGY UNITS)
C      GAM2=Z*Z*IH/KT  WHERE Z IS TARGET ION CHARGE
C                      AND IH IS THE RYDBERG ENERGY
C      N0       IS THE FIRST BOUND LEVEL TO BE INCLUDED IN THE
C               INTEGRAL
C  OUTPUT
C      GAV=MAXWELLIAN AVERAGED GAUNT FACTOR.
C
C
C  AUTHOR   : L D Horton
C  DATE     : 24-06-1997
C
C
C
C  VERSION  : 1.1
C  DATE     : 02-03-2005
C  MODIFIED : Martin O'Mullane
C                - First version in central ADAS.
C                - Make implicit none.
C
C  VERSION  : 1.2
C  DATE     : 15-03-2006
C  MODIFIED : Allan Whiteford
C                - Removed external giii statement.
C
C  VERSION  : 1.3
C  DATE     : 22-06-2006
C  MODIFIED : Martin O'Mullane
C                - Removed redundant external gbf statement.
C
C  VERSION  : 1.4                          
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              GAM2,        U