1. E /eV
2. sigma /cm²

• B8: R. K. Janev, J. J. Smith, F. Aumayr, D. Wutte, M. Schneider, H. P. Winter, J. Schweizer, "Atomic collision database for Li beam interaction with fusion plasmas", IAEA, Vienna 267 (1993). [https://www-nds.iaea.org/publications/indc/indc-nds-0267/]

c
c##############################################################################
c
      subroutine neexh2(pe, pcf, kncf, pxs, kermsg)
c
c     this is a subroutine to calculate cross sections (cm[2])
c     versus energy (ev) for electron impact excitation.
c
c     pe = collision energy in ev
c
c     pcf(1) = threshold energy (ev), eth.
c     pcf(2-7) = parameters for fit to the cross section
c
c     kermsg = blank if no errors
c
c     pxs = cross section in cm[2]
c
c------------------------------------------------------------------------
c
      double precision pe, pcf, pxs
      double precision cstr, ryd, ksq, x, alog, u , ucont, eth
c
      dimension pcf(7)
      character*(*) kermsg
c
      data ryd/13.6d0/
c
      eth = pcf(1)
      if(pe .ge. eth) then
        kermsg = ' '
      else
        pxs = 0.0d0
        return
      endif
c
        ksq= pe/ryd
        etrans = eth/ryd
        x=ksq/etrans
        xsq = x*x
        xsq2 = xsq*xsq
        alog = 0.0d0
c
        if (pcf(6) .ne. zero) alog = pcf(6) * dlog (x)
        cstr = alog + pcf(2) + pcf(3)/x + pcf(4)/xsq + pcf(5)/(x*xsq)
c
        u = (pe - eth) / eth
        ucont = ( u / (u + 1.0d0)) ** pcf(7)
        pxs =   5.984e-16 *  ucont * cstr / pe
c
      return
      end