## 1 Introduction
In the field of laser synthesis and the processing of colloids, the interaction mechanism of a laser beam with the material being placed in liquid for a certain laser fluence mainly depends on the following: In the field of laser synthesis and the processing of colloids, the interaction mechanism of a laser beam with the material being placed in liquid for a certain laser fluence mainly depends on the following: in the case of a bulk material (target) that is immersed in the liquid, the laser pulse duration in relation to the electron\(-\)phonon coupling time constant of the material; in the case of a material in the form of micro/nanoparticles (M/NPs) that are suspended in the liquid, it also depends on the particle size through the dependence of the absorption and scattering cross-sections of the particle on it, which in turn determines the amount of energy that is absorbed by the particle [16]. Thus, in the case of a fs laser irradiation, for a certain laser fluence, for particles whose size is such that the energy that is absorbed by them lies close to that corresponding to their ablation threshold, they are ablated via a Coulomb explosion (particle disintegration due to the buildup of electrostatic charge); meanwhile, for particles whose size is such that the energy that is absorbed by them is much larger than that corresponding to their ablation threshold, they are ablated via photothermal surface vaporization (heating-melting-vaporization). Laser ablation of a bulk target material (A) in an NP colloidal solution of another material (B) usually leads to the synthesis of core-shell NPs of the B@A type because the NPs of B act as the nucleation sites for the ablated material A [17]. Optical spectroscopy of the photon emission from electronically excited plasma plume species (atoms, ions, or molecules) during the expansion of the plume, which is termed as laser-induced breakdown spectroscopy (LIBS), and particularly time-resolved dynamics help to provide information about the formation of plasma plume species and the chemistry of the plume and allow for the determination of characteristic parameters of the plume, such as plasma temperature and electron density, that critically determine the mechanisms of synthesis of NPs or NMs and other species by laser ablation of a bulk target material [18]. From an LIBS analysis of the temporal evolution of the Swan band of C\({}_{2}\) molecules and that of the continuum background radiation during ns UV laser ablation (5 ns/355 nm/10 Hz/80 mJ) of pyrolytic graphite in water that lead to the synthesis of NDs, it was concluded that the NMs were growing in a very narrow temporal window at the early stages of the plasma process (time \(<\) 125 ns) and during the fulfilment of the thermodynamic conditions of pressure and temperature in the plume for diamond growth [19]. Nanosecond laser ablation of graphite in water using a UV wavelength (193 nm) leads to the production of mostly NDs that also have much smaller sizes when compared with those created by ablation using an IR wavelength (1040 nm) where, additionally to the NDs, other carbon-based nanostructures such as C\({}_{8}\) and \(n\)-diamond are also produced [20]. This study deals with the fs laser ablation of a bulk graphite target in water for NM and polyyne synthesis. Although there are a large number of papers in the literature about the formation of polyynes by laser ablation in liquids, there is still not any direct experimental evidence reported about their formation by the fs laser ablation of a bulk graphite target in water. The produced solutions were analyzed using UV-vis absorption spectroscopy. The solutions dried out on glass substrates were analyzed using X-ray diffraction (XRD) and Raman spectroscopy and on carbon-coated copper grids using transmission electron microscopy (TEM). The optical emission spectra of the ablation plume were measured using LIBS. The results are discussed and compared with results from relevant literature studies.