Dynamics of the biased two-level system in metals

We study the influence of conduction electrons on spectral and dynamical properties of the biased two-level system using path-integral methods. The structure factor for inelastic neutron scattering is calculated in the case of weak coupling (K{}1) and for a special value of the coupling strength (K=1/2). The effect of interbounce interactions is systematically taken into account at low temperatures, thus removing shortcomings of the dilute-bounce-gas approximation. The method and results are relevant also for the ``macroscopic-quantum-coherence'' problem.