subroutine expinx(x,em1)
c     ========================
c
c expinx is a subroutine to calculate the value of e1, the exponential
c integral or em1=x*expo(x)*e1 at the point x.  the polynomial
c expressions that are used come from abromowitz and stegen
c
c     a modification of Tim Kallman's XSTAR routine
c
c
      INCLUDE 'IMPLIC.FOR'
      if(x.gt.1.) then
         b1=9.5733223454
         b2=25.6329561486
         b3=21.0996530827
         b4=3.9584969228
         c1=8.5733287401
         c2=18.0590169730
         c3=8.6347608925
         c4=0.2677737343
         em1=x**4+c1*x**3+c2*x*x+c3*x+c4
         em1=em1/(x**4+b1*x*x*x+b2*x*x+b3*x+b4)
       else
         a0=-0.57721566
         a1=0.99999193
         a2=-0.24991055
         a3=0.05519968
         a4=-0.00976004
         a5=0.00107857
         if(x.gt.0) then
            e1= a0+a1*x+a2*x*x+a3*x**3+a4*x**4+a5*x**5-log(x)
          else
            e1=-a0+a1*x+a2*x*x+a3*x**3+a4*x**4+a5*x**5-log(-x)
         end if
         em1=e1*x*expo(x)
      end if
      return
      end