The Density Matrix via Few Dominant Observables: The Quantum Interference in the Isotope Effect for Atto-Pumped N2

In our paper a compact representation of the density as a function of a few observables is examined for the coupled electron-nuclear dynamics unfolding on three electronic states. The time-evolution of the density, populations and coherences, is accurately captured by the time-evolution of only nine coefficients, the Lagrange multipliers of these observables. We use a specific example of the isotope effect in atto-pumped N₂ to show that both classical and quantal effects of mass are well reproduced by this compact description. Simple analytical results for the surprisal are given, which allows a factorization of these two effects.