Mechanisms Of Pulsed Laser Ablation Research Articles

Laser Intensity Effect on Polyyne Synthesis in Liquid Hydrocarbons

Laser synthesis of polyyne molecules C2nH2 (n > 2) in liquid hydrocarbons is a complex process in which intense pulsed radiation decomposes the initial carbon-containing substance (the hydrocarbon solvent itself or the solid carbon particles in a suspension). Notwithstanding the fact that the mechanism of pulsed laser ablation in liquids (PLAL) is widely accepted, the effect of the laser parameters on laser-driven polyyne formation is still not understood in detail. Here, we report a study of the polyyne yield as a function of the laser field intensity and exposure dose. Several carbon-containing liquids, including pure n-hexane, pure ethanol, and graphite powder suspended in ethanol, were treated with tightly focused picosecond IR radiation (wavelength of 1064 nm, pulse duration of 10 ps). The synthesis rate was characterized by UV-vis optical absorption spectroscopy. The yields of the polyynes were found to vary in exact accordance with the value of the absorbed laser energy, following specific nonlinear or linear laws. The influence of the laser intensity on the partial concentration of polyynes in the solution was analyzed.

On the mechanism of pulsed laser ablation of phthalocyanine nanoparticles in an aqueous medium

Laser ablation of phthalocyanine nanoparticles has potential for cancer treatment. The ablation is accompanied by the formation of microbubbles and the sublimation of nanoparticles. This was investigated in a liquid medium simulating tissue using optical-acoustic and spectral-luminescent methods. The thresholds for the appearance of microbubbles have been determined as a function of nanoparticle size. For the minimal size particles (80 nm) this threshold is equal to about 20–25 mJ cm−2 and for the maximal size particles (230 nm) this threshold is equal to about 7 mJ cm−2. It was estimated that the particle temperature at which bubbles arise is near 145 °С.

Radiation mechanism of pulsed laser ablation of metal Al

Time-resolved measurement of plasma emission spectra by pulsed XeCl excimer laser ablation of Al under different conditions is reported. The experimental results show that plasma emission spectra are composed of atomic spectrum, univalent ion spectrum and continuous radiation. The atomic spectrum intensity and duration is most significant, the next is the univalent ion spectrum, the continuous radiation is weakest. The detailed mechanism of species excitation is discussed. The continuum radiation comes from electron bremsstrahlung and recombination of electron and ion, the primary atomic and univalent ion excitation originate from recombination of ion and electron. The experimental results are qualitatively explained with the mechanism.

Mechanisms of Pulsed Laser Ablation of Biological Tissues

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Mechanisms of pulsed laser ablation of biological tissues.

Author(s): Vogel, Alfred; Venugopalan, Vasan | Abstract: The mechanisms of pulsed laser ablation of biological tissues were studied. The transiently empty space created between the fiber tip and the tissue surface improved the optical transmission to the target and thus increased the ablation efficiency. It was found that the structure and morphology also affect the energy transport among tissue constituents.

Time‐Resolved Quadrupole Mass Spectrometric Studies on Pulsed Laser Ablation of TiO2

Pulsed laser ablation of TiO2 at 355 nm and 532 nm has been investigated using an angleand time‐resolved quadrupole mass spectrometric technique. The major ablated species include O (m/e = 16), O2 (m/e = 32), Ti (m/e = 48), TiO (m/e = 64) and TiO2 (m/e = 80). The time‐of‐flight (TOF) spectra of ablated species are measured for the ionic and neutral ablated species, and they can be fitted by a Maxwell – Boltzmann (M – B) distribution with a center‐of‐mass velocity. The measured angular distributions of the ionic species (O+ and Ti+) and the neutral species (O and Ti) can be fitted with cos⁡nθ and a cos⁡θ + (1 − a)cos⁡nθ, respectively. In addition, a continuous wave oxygen molecular beam is introduced into the ablated plume, and the enhancement of the signal intensities of TiO is observed. It implies that the ablated Ti atoms/ions species can react with ambient oxygen molecules in the gas phase. In the meanwhile, the physicochemical mechanism of pulsed laser ablation of TiO2 is discussed.

Pulsed laser ablative deposition of thin metal films

Abstract Different mechanisms of pulsed laser ablation and ablative deposition of thin metal films at various fluences are discussed. The window for clear ablation, i.e. the fluence range in which the film is completely removed without any damage of the supporting substrate and the window for best quality printing are determined.

Calorimetric and acoustic study of ultraviolet laser ablation of polymers

Calorimetric and acoustic studies of the mechanism of pulsed laser ablation of a polymer at the wavelengths of 193, 248, and 308 nm are reported. The results are mutually consistent and provide insight into the ablation mechanism.