We deal with the following Cauchy problem for a Schrödinger equation: D t u − Δu + n j=1 a j (t, x)D x j u + b(t, x)u = 0, u(0, x) = g(x). We assume a decay condition of type |x| −σ , σ ∈ (0, 1), on the imaginary part of the coefficients a j of the convection term for large values of |x|. This condition is known to produce a unique solution with Gevrey regularity of index s ≥ 1 and loss of an infinite number of derivatives with respect to the data for every s ≤ 1 1−σ. In this paper, we consider the case s > 1 1−σ , where, in general, Gevrey ill-posedness holds. We explain how the space where a unique solution exists depends on the decay and regularity of an initial data in H m , m ≥ 0. As a by-product, we show that a decay condition on data in H m produces a solution with (at least locally) the same regularity as the data, but with an expected different behavior as |x| → ∞.