An important parameter to characterize the scattering matrix S for quantum-chaotic scattering is the width Γcorr of the S-matrix autocorrelation function. We show that the "Weisskopf estimate" d/(2Π)∑ycTc (where d is the mean resonance spacing, Tc with 0≤Tc≤1 the "transmission coefficient" in channel c and where the sum runs over all channels) provides a good approximation to Γcorr even when the number of channels is small. That same conclusion applies also to the cross-section correlation function. © 2011 Elsevier B.V.
Dietz, B., Richter, A., & Weidenmüller, H. A. (2011). Correlation widths in quantum-chaotic scattering. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 697(4), 313–317. https://doi.org/10.1016/j.physletb.2011.02.009