Abstract：Resonance ionization spectroscopy (RIS) is an important technique for trace analyses. In the present paper, based on the population rate equations, “2+1”, “1+1” and “1+1+1” multiphoton resonant ionization processes of Mn atom are studied by computer simulation. The phenomena and the threshold condition of saturated excitation and ionization processes are discussed. The threshold laser intensities for saturated ionization of Mn atom with different RIS schemes are calculated. With the typical Q-switched laser duration of 10 ns, the obtained saturation threshold laser intensity for the ionization steps in all the resonant ionization processes of Mn is about 108 W·cm-2 with the exception of the “1+1” resonant ionization of Mn which is 3 orders of magnitude lower. The obtained threshold laser intensity for the saturated excitation steps is about 102-103 W·cm-2 in “1+1” and “1+1+1” ionization processes. It is also shown that the threshold laser intensity required for saturated excitation and ionization processes turns smaller with the laser duration prolonged.
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