Description Of Excited-state Dynamics Research Articles

Chemistry without the Born-Oppenheimer approximation.

Chemistry without the Born-Oppenheimer approximation.

Toward a Quantitative Description of Radical Photoinitiator Structure–Reactivity Correlations

The fundamental influence of the structure and substitution of radical photoinitiators was investigated via a trifold combination of pulsed-laser polymerization with subsequent electrospray-ionization mass spectrometry (PLP-ESI-MS), femtosecond transient absorption (fs-TA) spectroscopy, and quantum chemistry. For the first time, a library of benzoin-derived photoinitiators with varied substitution patterns was synthesized. In the PLP-ESI-MS study, different photoinitiators were compared pairwise in so-called cocktail experiments, enabling the direct comparison of their initiation efficiency. In the fs-TA experiments, the transient response was observed after UV excitation in the visible spectral region, allowing for a description of excited state dynamics, which was analyzed with the aid of TD-DFT calculations. Ab initio calculations were undertaken to determine the reactivity of the radical fragments generated from these photoinitiators and to quantify the influence of various substituents on the rate of...

Quantum state and process tomography of energy transfer systems via ultrafast spectroscopy

The description of excited state dynamics in energy transfer systems constitutes a theoretical and experimental challenge in modern chemical physics. A spectroscopic protocol that systematically characterizes both coherent and dissipative processes of the probed chromophores is desired. Here, we show that a set of two-color photon-echo experiments performs quantum state tomography (QST) of the one-exciton manifold of a dimer by reconstructing its density matrix in real time. This possibility in turn allows for a complete description of excited state dynamics via quantum process tomography (QPT). Simulations of a noisy QPT experiment for an inhomogeneously broadened ensemble of model excitonic dimers show that the protocol distills rich information about dissipative excitonic dynamics, which appears nontrivially hidden in the signal monitored in single realizations of four-wave mixing experiments.