A TD-CIS study of high-harmonic generation of uracil cation fragments

High-harmonic generation (HHG) spectroscopy was investigated from laser ablation plasmas of uracil targets in the experimental work of Hutchinson et al., [Phys. Chem. Chem. Phys. Comparison of high-order harmonic generation in uracil and thymine ablation plumes, 2013, 15, 12308] and of Lopez-Quintas et al., [Appl. Surf. Sci., Characterization of laser-induced plasmas of nucleobases: Uracil and thymine, 2014, 302, 299]. Inspired by these works we computed HHG spectra of uracil cation fragments by means of real-time time-dependent configuration interaction with single excitations (RT-TD-CIS) and continuum-optimal Gaussian basis sets. We calculated the rotationally-averaged HHG spectra of different cation fragments analysing the relation between HHG, geometry of the fragments (linear/nonlinear) and electron dynamics (bound and continuum energy states). Moreover, to simulate the complexity of a sample containing fragments upon ablation, we calculated weighted-rotationally-averaged HHG spectra where the contribution of each fragment is included through weights assigned accordingly to the experimental mass spectra.