c=======================================================================
c     This subroutine computes dipole matrix elements for 1-D
c     quantum systems.  It is currently set up for the system
c
c     H0 = p**2/(2*m) - V0*x,  x < L (infinite wall at L)
c
c     This routine is used in the 'accel' program (accel.f)
c=======================================================================
      subroutine dipole(minst,maxst,E,x)

         implicit none

         integer ist, jst

c-----------------------------------------------------------------------
c     minst: minimum state in basis
c     maxst: maximum "
c     E: vector containing energy eigenvalues
c     x: array containing dipole matrix elements
c-----------------------------------------------------------------------
         integer minst, maxst
         real*8 E(minst: maxst)
         real*8 x(minst:maxst,minst:maxst)

c-----------------------------------------------------------------------
c     Common block for communication with accel.f, getE.f, fcn.f
c-----------------------------------------------------------------------
         include 'fcn.inc'

c-----------------------------------------------------------------------
c     Compute dipole matrix elements
c-----------------------------------------------------------------------
         do ist = minst,  maxst
            do jst = minst, maxst
               if (ist .eq. jst) then
                  x(jst,ist) = -2.0d0*E(ist)/(3.0d0*V0)
               else
                  x(jst,ist) = -V0/(m*(E(jst)-E(ist))**2)
               end if
            end do
         end do

         return

      end