Universality in escape from a modulated potential well

We show that the rate of activated escape $W$ from a periodically modulated potential displays scaling behavior versus modulation amplitude $A$. For adiabatic modulation of an optically trapped Brownian particle, measurements yield $\ln W\propto (A_{\mathrm{c}}-A{)}^{\mu }$ with $\mu =1.5$. The theory gives $\mu =3\mathrm{/}2$ in the adiabatic limit and predicts a crossover to $\mu =2$ scaling as $A$ approaches the bifurcation point where the metastable state disappears.