\label{fig:cs-spectrum} Spectrum of one-dimensional complex-scaled single-particle Hamiltonian with potential \(v(x) = 3(x^2 - 2) \mathrm{e}^{-x^2 / 4}\) and \(\theta=0.5\). The lowest-energy resonance, here located close to the origin, does not lie exactly on the real axis but has an imaginary part of about \(-10^{-5}\).