Approximate formula for the asymptotic polarization for passage across two overlapping spin resonances

The formula for the asymptotic level of polarization, when the beam energy in a synchrotron is accelerated uniformly across a single isolated depolarizing spin resonance, is given by the well-known Froissart–Stora formula. There is no analytical closed-form solution in the case of passage across two (or more) overlapping spin resonances. We present an approximate analytical closed-form formula for the asymptotic level of polarization for the passage across two overlapping spin resonances. We also present a quantitative criterion for the domain of applicability of our formula.