We show that the collision time may be interpreted as the time average of a flux-flux correlation function. This interpretation leads quantum mechanically to a complex time whose real part is identical to the usual definition as provided by F. T. Smith. The imaginary part is identical, in the semiclassical limit, to the imaginary time associated with tunneling.

• Received 20 April 1984

DOI:https://doi.org/10.1103/PhysRevLett.53.115