## 3 Results
### Tunable NIR Pump
The tuning of the NIR pulses towards the shorter wavelength region (1335 nm) caused the change in the maximally enhanced harmonic order in the case of the TCP (H28, 1335 nm  
Figure 4: Raw images of harmonic spectra in the case of 1370 nm and 685 nm pumps of tin-containing plasmas. Upper panel: Plasma produced on the tin bulk target at the fluence F = 1.4 J cm\({}^{-2}\). Middle panel: Plasma produced on the Sn nanoparticle (NP) target at the fluence F = 1.4 J cm\({}^{-2}\). Bottom panel: Plasma produced on the Sn NP target at the fluence F = 2 J cm\({}^{-2}\). “W.A.” and “S.A.” correspond to weak and strong ablation of the Sn-containing target. and 668 nm pumps, third panel) and allowed for the generation of a higher yield of this harmonic compared with the neighboring ones. Similar studies were performed in the case of Sn NP LIP. The application of nanoparticles was a part of our efforts to demonstrate the fact that the presence of tin in plasma does not necessarily guarantee the enhancement of a single harmonic. The decrease of oscillator strength of ionic transitions, as well as the detuning of transitions, can cause the difference in the nonlinear optical response of this medium. Meanwhile, the expectation in the application of NPs was related to the stronger effect of single harmonic enhancement, while our studies showed the reverse effect. The distribution of the harmonic spectrum was notably changed as soon as we ablated the Sn NP target. One can assume similar conditions for the resonance enhancement of H29 in this aggregated structure. However, in the case of the SCP of Sn NP LIP, we did not observe this process. At the used fluence of heating pulses (1.5 J cm\({}^{-2}\)), we did not see a strengthening of this harmonic, which points out the insignificant amount of the ionic tin component during the disintegration of Sn NPs in these conditions of ablation, independently of the wavelength of NIR DP. Specifically, the experimental observations were as follows. The fourth panel from the top of Figure 5A shows the harmonic line-out in the case of the SCP (1320 nm) of the plasma produced on the tin NP powder. Only a few harmonics up to H19 generated at these conditions in the studied spectral range (38-89 nm). The optimization of plasma formation and stronger NIR pulses tuned towards 1350 nm allowed for achieving the harmonics up to H33 (fifth panel). At these conditions, no enhancement of the harmonic lying close to the 47 nm region was achieved. The tunings of the DP (1370 nm) also did not result in the generation of enhanced harmonics in the 47 nm region (sixth panel). Finally, the seventh panel shows HHG using the TCP (1320 nm and 660 nm) of the plasma produced  
Figure 5: **(A)** Line-outs of harmonic spectra generated in the plasmas produced on the bulk tin and tin NP powder using tunable near-infrared (NIR) driving pulses. First panel from the top: SCP (1355 nm) of the plasma produced on the bulk Sn. Second panel: TCP (1355 nm and 678 nm) of the plasma produced on the bulk Sn. Third panel: TCP (1335 nm and 668 nm) of the plasma produced on the bulk Sn. Fourth panel: SCP (1320 nm) of the plasma produced on the tin NP powder. Fifth panel: SCP (1350 nm) of the plasma produced on the tin NP powder. Sixth panel: SCP (1370 nm) of the plasma produced on the tin NP powder. Seventh panel: TCP (1320 nm and 660 nm) of the plasma produced on the tin NP powder. **(B)** TEM images of deposited tin NPs during ablation of nanoparticle powder at an optimal fluence of HP. The black markers correspond to 200 nm (upper panel) and 20 nm (bottom panel). on the tin NP powder. Again, we did not see the specific feature of single harmonic enhancement in the above-mentioned XUV range, but rather observed the gradual decay of harmonic yield down to H32. An insignificantly larger yield of H28 shown in this panel may indicate the involvement of the resonance process in the generation of this harmonic (similar to the raw image shown in the middle panel of Figure 4 in the case of 1370 nm and 685 nm pumps).