Spectroscopic measurements of the plasma plume induced during laser ablation of graphite J.Hoffman 1 , M.Jedynski 1 , W. Mróz 2 , A.Prokopiuk 2 , Z. Szymanski 1 1 Institute of Fundamental Technological Research, Świętokrzyska 21, 00-049 Warsaw, Poland 2 Institute of Optoelectronics of Military University of Technology, ul.Kaliskiego 2, 00-908 Warsaw, Poland Plasma plume induced by laser ablation of a graphite target is studied. An excimer ArF laser operates at the wavelength of 193 nm with the pulse energy of ~440 mJ and 20 ns pulse duration. The laser fluence is 7 J⋅cm -2 . The plasma expands in a chamber evacuated to a background pressure of 3×10 -8 bar. The emission spectra of the plasma plume are registered with the use of a spectrograph and an Andor iStar ICCD camera. The electron densities of ~1.6×10 24 ÷ 2×10 22 m -3 are determined from the Stark broadening of the Ca II and Ca I lines at distances 0.1÷10 mm from the target. The electron temperature is determined from the ratio of intensities of the 2509.12 C II ionic line and the 2478.56 Å C I atomic line. Close to the target the temperature of 19 kK is found.The expansion of the plasma plume is studied using the time of flight method. Velocities of the order of 10 4 m/s are found. 1. Introduction Pulsed laser deposition is well-established method of deposition of thin films on different substrates. The particles ablated from a target owing to laser-target interaction form a plasma plume and subsequently are deposited on a substrate. The mechanism of plasma formation and expansion consists of three stages. During the interaction of the laser beam with a material the target is heated to temperature exceeding the boiling temperature and some times also the critical temperature. The characteristic time of the target temperature rise varies from 1 nanosecond to some hundreds nanoseconds. At the same moment begins the process of ablation. In the second stage the ablated particles are heated by the remaining part of the laser pulse to the temperatures of some tens of kK and form a plasma plume. The characteristic time of plasma heating is 10-100 nanoseconds depending on the intensity of the laser beam and quantum energy [2]. Next the expansion of the plasma plume takes place. In this paper plasma plume induced by laser ablation is studied. 2.Experiment Graphite target irradiation was performed using an excimer ArF laser. The laser operated at the wavelength of 193 nm with the pulse energy of ~400 mJ and 20 ns pulse duration. The laser fluence was 9.5 J⋅cm -2 . The plasma expanded in a chamber evacuated to a background pressure of 3×10 -8 bar. Plasma parameters are studied as a function of a distance from the target. Schematic diagram of the experimental setup used to register the emission spectra of the laser- induced plasma is shown in figure 1. vacuum chamber target substrate laser beam plasma plume gas inlet rotating lens window heated spectrograph/ monochromator ICCD camera PMT window movable lens Fig.1 Schematic diagram of the experimental arrangement