Perturbative model of transient Circular Dichroism of molecular aggregates

Microscopic, quantum-mechanical models of spectroscopic techniques allow researchers to interpret the information contained within a measured spectrum. Theoretical models of transient circular dichroism (TCD) spectroscopy—an analogue to transient absorption (TA) spectroscopy—are relatively understudied and would aid in the interpretation of signals arising from laboratory TCD measurements. Steady-state CD spectra can report on the chirality induced by electronic coupling between chromophores in molecular aggregates, and it is therefore anticipated that TCD can report on the electronic and orientational dynamics of excitons in molecular aggregates. In this work [1], we derived a perturbative theoretical model of femtosecond TCD spectroscopy, with some similarities and differences to prior works [2-4]. We study the signals that arise from small molecular aggregates including dimers, trimers, and tetramers. The results indicate that TCD can produce new insights into the electronic and structural orientation properties of molecular aggregates.

[1] Arpin and Turner, J. Chem. Phys. 157, 154101 (2022)

[2] Cho, J. Chem. Phys. 119, 7003 (2003).

[3] Abramavicius et al., J. Chem. Phys. 124, 034113 (2006).

[4] Holdaway et al., J. Chem. Phys. 144, 194112 (2016).