c===========================================================================
c     fitting formula for e-e bremsstrahlung gaunt factor
c
c                 n_e
c      g_e-e= ------------ theta_e J(theta_e,u)
c              n_j (Z_j)^2
c                     
c                      Sqrt(3)
c      J(theta_e,u)=------------- u^2 exp(u) I(theta_e,u)
c                   10 Sqrt(2)Pi
c
c                  /
c     J(theta_e) = | exp(-u)J(theta_e,u)du
c                  /
c
c                   Sqrt(3)     / 
c               = ------------- | u^2 exp(u) I(theta_e,u)
c                 10 Sqrt(2)Pi  /
c
c     We give an analytic fitting formula for J(theta_e).
c     The range of the fitting is
c
c                 -4.0 <= log theta_e <=-1.3
c     
c     Function jfit(logth) returns the fitting result 
c                                                 of J(log(theta_e)). 
c 
c===========================================================================
      real*8 function jfit(logth)
      implicit real*8(a-z)
      real b(1:11)
      data b/
     $     2.21564E+00,1.83879E-01,-1.33575E-01,5.89871E-02,    
     $     -1.45904E-02,-7.10244E-04,2.80940E-03,-1.70485E-03,     
     $     5.26075E-04,9.94159E-05,-1.06851E-04/     
      theta=(logth+2.65d0)/1.35d0
      jfit=  b(1)
     *     +b(2)*theta   
     *     +b(3)*theta**2d0 
     *     +b(4)*theta**3d0  
     *     +b(5)*theta**4d0   
     *     +b(6)*theta**5d0   
     *     +b(7)*theta**6d0   
     *     +b(8)*theta**7d0  
     *     +b(9)*theta**8d0   
     *     +b(10)*theta**9d0  
     *     +b(11)*theta**10d0   
      return
      end