An Experimental Investigation On Resonant Laser Ablation Of Metal Sample

Resonant laser ablation with special advantageous of high sensitivity and little sample consumption, plays an important role in archeology, environmental sciences, life sciences, and other industrial application as a technique to detect trace elements. Resonant laser ablation (RLA) is a two-step process, occurring within a pulse of a tunable laser, in which the leading edge of the laser pulse ablates the surface of the solid sample to produce neutral atoms or molecules that are then resonantly ionized by the trailing edge of the same pulse. The process contains the two steps in which the low temperature plasma produced by ablation of sample and the resonant multiphoton ionization of atom or molecule in the plasma are performed within a single laser pulse.This paper is divided into three chapters.In chapter one, the basic concepts of resonant laser ablation technique and its development are introduced. In chapter two, the basic principle of RLA technique is described, including the formation mechanism and the dynamics characters of laser induced plasma, the principle of resonant laser ionization, selection rules, and resonant laser ablation mass spectroscopy. The principle of time of flight mass spectrometer is also presented briefly.In the last chapter, RLA mass spectra in Ni sample are investigated by time of flight mass spectrometer. The mail contents are as followings. (1) The brief description of our experimental setup and measurement method. (2) The measurement and assignment of RLA mass spectra of Ni element in Ni sample within the range of 281.5-286nm. Thirteen RLA spectral lines measured are produced by the resonant multiphoton ionization of Ni and Fe atoms. (3) Tow RLA spectral lines of FeI 281.83nm and 282.41 nm are selected to study the influence of ablation laser power on the spectral line intensity. The experimental results show that the intensity of the RLA spectra line increases with the increase of the laser power. But they have different amplitude of the enhancement of line intensity. Some reasonable discussions on the above results are presented. (4) From the measurement of the intensity of the tow spectral lines mentioned above at different time delay ranged from 22.3us to 24.3us, the spatial evolution property of the resonant laser ionization spectra in Ni sample were finally explored and analyzed.