Lawrence Berkeley National Laboratory

© 2016 IOP Publishing Ltd. We present the simultaneous study of laser-induced plasma emission spectroscopy and high-order harmonic generation (HHG) from laser-ablated graphite plume. Time resolved evolution of carbon species in the ablation plume is investigated, revealing a clear abundance of C2 molecules under conditions optimal for graphite HHG. We also compare the high-order harmonic spectra with the photoionization cross-section of C2 molecules, which shows good agreement between the two. Our observations provide strong evidence that C2 molecules contribute to intense graphite HHG. Furthermore, properties of C2 molecules are investigated at different time periods of plasma evolution, and we identify the laser-ablation conditions for optimum harmonics yield.