Data for spin quantum beats in pump push spectroscopy

Spin quantum beats prove the quantum nature of reactions involving radical pairs, the key species of spin chemistry. However, such quantum beats remain hidden to transient-absorption-based optical observation because the spin hardly affects the radical pairs’ absorption properties. We succeeded in demonstrating such quantum beats in the photo-induced charge separated state (CSS) of an electron-donor-acceptor dyad by using two laser pulses, one for pumping the sample, and another one, with variable delay, for further exciting the CSS to a higher electronic state, wherein ultrafast recombination to distinct, optically detectable products of singlet or triplet multiplicity occurs. This represents a spin quantum measurement of the spin state of the CSS at the time instant of the second (push) pulse.