In order to solve multidimensional tunneling problems that cannot be treated by the normal instanton techniques, we introduce the path decomposition expansion formalism, and show its usefulness by solving three generic examples: the symmetric and asymmetric double well, and the decay problem. The technique allows us to handle excited states and backscattering effects in nonseparable potentials.

• Received 24 February 1984

DOI:https://doi.org/10.1103/PhysRevLett.53.411