# IR Pulsed Laser Ablation of Carbon Materials in High Vacuum
## 5 Conclusions  
In this paper, the IR-pulsed laser ablation of graphite and other types of carbon targets in high vacuum is presented. Laser ablation occurs using a low laser intensity of the order of \(3\times 10^{9}\) W/cm\({}^{2}\), with a 3 ns pulse duration and 100 mJ pulse energy. These parameters are sufficient to produce a highly dense and hot carbon plasma, with a density of the order of \(10^{17}\) atoms/cm\({}^{3}\) and a temperature of the order of 30 eV or more.  
Different carbon targets have been employed to study the plasma dependence on their density and on their binding energy, finding that the ablation yield is inversely proportional to the mass and to the binding energy.  
Measurements have been conducted using the TOF of emitted ions along the normal to the target surface, obtaining C ion maximum energies of about 1.7 keV, charge states from C1+ up to C4+, and Boltzmann ion energy distributions, which are shifted toward higher energy, increasing their charge state, according to the literature [29]. The average ion acceleration measured in the non-equilibrium plasma is about 200 eV per charge state. Such energetic ions enable the formation of adherent carbon thin films on substrates, the aggregation of C atoms, and the generation of C nanoparticles in liquids.  
The angular emission distribution of C atoms has highlighted a wide distribution in the case of HOPG, glassy carbon, and vegetal carbon ablation and a narrower distribution in the case of emission from graphite and active carbon. By increasing the angle with respect to the normal direction, the emitted atoms and ions decrease in yield and energy, and the emitted photons also decrease.  
The ablation yield has been evaluated for the different ablated targets, indicating a maximum ablation yield of 96.14 \(\upmu\)g/pulse in the case of vegetable carbon and a minimum value of 0.46 \(\upmu\)g/pulse in the case of glassy carbon, while that relating to graphite is intermediate, taking the value of 14.41 \(\upmu\)g/pulse.  
The results of this study could be useful for different purposes, such as being able to better control the laser photo-deposition of thin carbon films on different substrates, generating high-density carbon aggregates, and creating carbon nanoparticles and C-dots in liquids. The literature reports excellent results for thin carbon films deposited on silicon [39], the generation of diamond-like materials using the laser ablation of HOPG targets [16], and C-dot generation in phosphate-buffered saline solutions [38]. Further investigations are in progress on these last cited processes.  
**Author Contributions:** Conceptualization, L.T. and M.C.; methodology, L.T.; software, M.C and A.T.; formal analysis, L.T., M.C. and A.T.; investigation, L.T., M.C. and A.T.; data curation, M.C. and A.T.; writing--original draft preparation, L.T.; writing--review and editing, A.T.; supervision, L.T.; project administration, L.T. and M.C.; funding acquisition, M.C. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The research has been carried out at the CANAM (Centre of Accelerators and Nuclear Analytical Methods) infrastructure LM 2015056. This publication was funded by OP RDE, MEYS, Czech Republic, under the project CANAM OP, grant number CZ.02.1.01/0.0/0.0/16_013/0001812 and by long-term conceptual development project of the NUCLEAR INSTITUTE OF THE CZECH ACADEMY OF SCIENCES, grant number RVO 61389005. This work was also supported by the CZECH SCIENCE FOUNDATION, under the project GACR No. 23-06702S.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data is contained within the article.  
**Conflicts of Interest:** The authors declare no conflicts of interest.