Classical mechanical analysis of the experimental high-energy spectrum of the sodium trimer molecule

Classical mechanics is used to compute the low-resolution spectrum of ${\mathrm{Na}}_3$ in the classically chaotic regime. Excellent agreement between the numerical simulation and experiment enables an assignment of the experimental coarse-grained spectrum, which is based not on periodic orbits but on weakly unstable, reduced dimension, quasiperiodic motion. In contrast to previous work on similar systems, there is no need to use a semiclassical approximation based on the Gutzwiller summation formula.