In this paper, we show that
under certain conditions the self-adjoint Schroediner operator −Δn+ V (x) on
L2(Rn), n ≧ 1, has essential spectrum [0,∞). The theorems improve previous results
by permitting V (x) to be more singular locally. The proof employs a factorization
V (x) = A(x)B(x) of the potential.