2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/150592We calculate the probability distribution of the matrix Q = -i \hbar S^{-1} dS/dE for a chaotic system with scattering matrix S at energy E. The eigenvalues τ_j of Q are the so-called proper delay times, introduced by E. P. Wigner and F. T. Smith to describe the time-dependence of a scattering process. The distribution of the inverse delay times turns out to be given by the Laguerre ensemble from random-matrix theory.4 pages, RevTeX; to appear in Phys. Rev. LettChaotic DynamicsMesoscale and Nanoscale Physicstext