code: def _phiTilde(self, r, N,L):
          
          xi = self._calculateXi(r)
          CC = _C(xi,N,L)
          a = self._a
          phi = nu.zeros((N,L), float)
          n = nu.arange(0,N)[:, nu.newaxis]
          l = nu.arange(0, L)[nu.newaxis,:]
          phi[:,:] = - (r*a)**l/ ((a + r)**(2*l + 1.)) * CC[:,:]* (4*nu.pi)**0.5
          return phi
docs: NAME:
             _phiTilde
          PURPOSE:
             Evaluate phi_tilde as defined in equation 3.10 and 2.25 for 0 <= n < N and 0 <= l < L
          INPUT:
             r - Evaluate at radius r
             N - size of the N dimension
             L - size of the L dimension
          OUTPUT:
             phi tilde 
          HISTORY:
             2016-05-17 - Written - Aladdin