Dissipative Equation of Motion for Electromagnetic Radiation in Quantum Dynamics

The dynamical description of the radiative decay an electronically excited state in realistic many-particle systems is unresolved challenge. In present investigation electromagnetic radiation charge density approximated as power dissipated by a classical dipole, to cast emission closed form unitary single-electron theory. This results formalism unprecedented efficiency, critical for ab initio modeling, which exhibits at same time remarkable properties: it quantitatively predicts rates, natural broadening, and absorption intensities. Exquisitely accurate excitation lifetimes are obtained from time-dependent DFT simulations ${\mathrm{C}}^{2+}$, ${\mathrm{B}}^{+}$, Be, 0.565, 0.831, 1.97 ns, respectively, accord with experimental values $0.57\ifmmode\pm\else\textpm\fi{}0.02$, $0.86\ifmmode\pm\else\textpm\fi{}0.07$, 1.77--2.5 ns. Hence, development expands frontiers quantum dynamics, bringing within reach first-principles wealth photophysical phenomena, fluorescence time-resolved spectroscopies.