Advances (2016–2017) in Quantum Chemistry of the Excited State (QCEX) are presented
in this book chapter focusing firstly on developments of methodology and excited-state
reaction-path computational strategies and secondly on the applications of QCEX to
study light–matter interaction in distinct fields of biology, (nano)-technology, medicine
and the environment. We highlight in this contribution developments of static and
dynamic electron-correlation methods and methodological approaches to determine
dynamical properties, recent examples of the roles of conical intersections, novel DNA
spectroscopy and photochemistry findings, photo-sensitisation mechanisms in biological
structures and the current knowledge on chemi-excitation mechanisms that give rise to
light emission (in the chemiluminescence and bioluminescence phenomena).