Three-state Feshbach resonances in the presence of external fields

We present an analytical analysis of Feshbach resonances involving three states in heteronuclear atom-atom collisions in the presence of external static electric and magnetic fields. The Hamiltonian of study involves a resonance coupling between a $p$-wave continuum state and a bound molecular state and a coupling between an $s$-wave continuum state and the $p$-wave continuum state. There is no direct coupling between the $s$-wave scattering state and the bound state of the dimer. The dependence of elastic $s$-wave scattering on the $s$-$p$ and $p$-bound couplings is described.