The Nature of Quantum States Created by One Photon Absorption: Pulsed Coherent vs. Pulsed Incoherent Light

TL;DR

This study compares the effects of pulsed incoherent solar-like light and ultrashort coherent light on molecular electronic states, revealing significant differences in wave functions and coherence decay relevant to natural processes.

Contribution

It provides a detailed analysis of how different light sources influence molecular excited states and coherence, highlighting differences relevant to natural phenomena like photosynthesis.

Findings

Excited wave functions differ qualitatively based on light source.

Electronic coherence decays faster under incoherent light.

Ultrafast coherent excitation does not replicate natural solar-induced dynamics.

Abstract

We analyze electronically excited nuclear wave functions and their coherence when subjecting a molecule to the action of natural, pulsed incoherent solar-like light, and to that of ultrashort coherent light assumed to have the same center frequencies and spectral bandwidths. Specifically, we compute the spatio-temporal dependence of the excited wave packets and their electronic coherence for these two types of light sources, on different electronic potential energy surfaces. The resultant excited state wave functions are shown to be qualitatively different, reflecting the light source from which they originated. In addition, electronic coherence is found to decay significantly faster for incoherent light than for coherent ultrafast excitation, for both continuum and bound wave packets. These results confirm that the dynamics observed in studies using ultrashort coherent pulses are not relevant to naturally occurring solar-induced processes such as photosynthesis and vision.