## 4 Discussion
CNF plasma showed optimum delay at 300 ns (Figure 4a, green line with empty circles) and similar to C\({}_{60}\) cutoff (21 st order, Figure 4b). We assume that plasma from CNF ablation was less fragmented compared to MW CNT despite the higher HP energy used there (3 m) vs. 2 m). Earlier reported TOFMS spectra have demonstrated the similarities between the MW CNT and CNF, with the presence of small carbon C\({}_{n}\) fragments (with \(n\) varied up to 20) and no ions higher than low-sized carbon clusters in the mass spectra up to 5000 mass/charge units [25]. Additionally, the emission from ablated MW CNT and C\({}_{60}\) targets showed almost similar spectra (Figure 2), with strong relative lines for CIII and CIV transitions. We can suppose that, in the case of MW CNT, the fragmentation process induces the appearance of small-sized carbon molecules and clusters inducing the larger cutoff, since at short delay (100 ns, Figure 4a) the integrated harmonic signal from MW CNT plasma exceeds that from bulk C LIP. Plasma spectra for CNF demonstrate the most contradictive result, with strong relative CI transition line, which indirectly points out to the presence of large number of neutral carbon atoms, but without extending the HHG cutoff. TOFMS is a natural and obvious way to precisely determine the mass-to-charge state of the ablation plume. Notice that the main goal of present research was to study high-order harmonics generation from the plasmas generated on the graphite, fullerenes, carbon nanotubes, carbon nanofibers, diamond nanoparticles, and graphene targets. Meantime, the joint application of HHG and TOFMS facilities in a single set of experiments is hardly to be achieved. Earlier studies, which combined the data revealed from above facilities, were performed separately, which did not allow for a conclusive argument for the similarity of the plasma formation conditions in these two sets of experiments. Meanwhile, we demonstrate that the HHG approach allows for analyzing the dynamics of plasma spreading out from ablated surface thus revealing some interesting peculiarities hardly obtainable in the case of TOFMS approach. Our present research, as well as earlier reported studies of harmonic generation in laser-induced plasmas, enabled a demonstration of the attractive features of the high-order nonlinear spectroscopy of these species. The HHG spectra generated in the plasmas produced on the graphene sheets and diamond nanoparticles are shown on the right column of Figure 3. The harmonic yields from GR and DN was multiplied by a factor of 2 to make them more visible and, in order to compare with other spectra. Both plasmas allowed the generation of weaker harmonics compared to the other four samples. The delay dynamics in the case of GR (Figure 4a, solid pink line with filled rhombuses) indicated the presence of large fragments in LIP, with maximal harmonic yield observed at 300 ns delay. The delay dynamics curve is more flattened with respect to the above-discussed materials, with comparable integrated harmonic yield in the range of 100 ns to 700 ns. We attribute this pattern of delay dynamics to the wide distribution of GR's pieces possessing different velocities centered at -1 \(\times\) 10\({}^{3}\) m/s. The harmonic spectrum changed at optimum delay (Figure 4b) and showed the cutoff at 23 rd order, and the enhanced 11 th and 13 th harmonics (Figure 3, left column, black line). We attribute this increase in harmonic yield to the arrival of large-sized fragments of graphene to the interaction area. Among all studied materials, DNs have the largest crystal lattice energy. This characteristic can explain, to some extent, the better survival of DNs in the plasmas produced by the heating pulses. This may also explain why DNs showed relatively extended optimum delay (500 ns; Figure 4a, dark yellow line with empty rhombuses).