Spectral shift function for the Stark operator in the large coupling constant limit

Let H be the Stark operator in $\mathbb{R}^{3}$ and let V=V(x) be a non-negative potential which decays at infinity as |x|^−l for a sufficiently large l>0. The spectral shift function for the pair of operators H+tV, H is studied in the asymptotic regime t→∞. The leading term of the asymptotics is obtained; the result is in agreement with the phase space volume considerations.