engleski

Dual pulse laser ablation studied by cavity ring-down spectroscopy

Dual pulse laser ablation is recently attracting attention related to applications such as laser induced breakdown spectroscopy or production of nanoparticles. Depending on the time delay between laser pulses large increase of light emission or particle production rate was observed. However, details of dual laser ablation processes and plume dynamics are still not completely understood. Dual pulse laser ablation might be interesting technique to apply for efficient production of cold molecules. We have performed study of the plume content by using direct absorption method having this application in mind. Laser ablation was performed within the vacuum chamber which could be evacuated by means of a roots pump system yielding final pressures of about 10&#8315; &sup3 ; ; Torr. For ablation we have used two Nd-YAG lasers (Brilliant 350 mJ at 1064 nm and Brio 100 mJ at 1064 nm). Laser pulses were triggered and synchronized by means of a digital delay generator. For CRDS we have used an excimer (LPX 105E Lambda Physik) pumped dye laser (LPD 3002E Lambda Physik) working with a Rhodamine B dye. The laser pulse duration was about 15 ns and bandwidth about 6 GHz. Targets were mounted on an X-Y translation stage to allow precise positioning (100 mm) and were also rotated to avoid drilling. Details of CRDS arrangement were described in more details previously [1]. Lasers, digital delay generator and oscilloscope were controlled by a PC computer using a homemade LabVIEW program which also allows analyses of CRDS ringdown signal in various time windows [2]. In the present work we have studied dual laser ablation in the parallel laser beam configuration. As a test case targets of manganese or titanium were used and atomic spectra measured in the wavelength range around 630 nm. Results show clear increase (tenfold) of atomic absorptions for the case of dual laser ablation compared to single laser absorptions. We have explored CRDS potential (simultaneous determination of particles densities and velocities [3]), for study of dynamics of the plume depending on the time delay between laser pulses and the buffer gas environment. Preliminary results showed high potential of the dual laser ablation for the efficient production of molecules and particles. References (optional) [parindent]<LaTeX>\parindent</LaTeX>=0ptReferences[smallbreak]<LaTeX>\smallbreak </LaTeX> [1] N. Krstulović, I. Labazan, S. Milošević, Eur. Phys. D 37 209-215 (2006). [2] I. Labazan and S. Milošević, J. Phys. D: Appl. Phys. 37 2975-2980 (2004). [3] I. Labazan and S. Milošević, Phys. Rev. A 68 032901 (2003).

dual-laser ablation; cavity ring-down spectroscopy

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