以Nd:YAG脉冲激光器的基频1064 nm和二倍频532 nm输出为激发源，获得了一种切、斩两用不锈钢刀具材料在300~500 nm波长区间的激光诱导击穿光谱，通过对谱线的归属，发现该不锈钢材料除包含主要元素Fe，还含有为改善材料特性添加的Cr、Ni、Mo、Nb、Cu、V、Ti及微量杂质元素Gd、Zr、Sm、Pm、Nd等。而文献报道的元素C、Si、N，由于其灵敏谱线波长大部分小于300 nm，所以光谱图中未出现明显对应这些元素的谱线。同时发现随激光脉冲能量的增加，等离子体发射谱线的强度、电子温度、电子数密度均增大，将该现象归因于激光能量增加导致的样品烧蚀量增大及电场强度的增加。相同激光能量的条件下，532 nm激光诱导的等离子体具有更高的电子温度和电子密度。

通过求解光和物质相互作用的速率方程，获得了(1+1)共振增强多光子电离过程中电离几率的解析表达式，以该表达式为基础，理论模拟了激光强度、激光脉宽、碰撞弛豫速率等参量对（1+1）多光子电离几率的影响。发现电离几率随激光强度、激光脉宽的增加而增大，到一定程度达到饱和，激光脉宽越大，电离几率随激光强度增加的速率越快，饱和光强值越小。当光强超过饱和值时，电离几率随激光强度的增加围绕饱和值1振荡，电离几率出现大于1的情况，这一有悖于事实的理论结果表明，由于强激光场和物质的相互作用改变了物质系统的能级结构特征，描述光与物质相互作用的速率方程理论不再适用。理论结果还显示，电离几率随碰撞弛豫速率的增加呈线性规律减小，但变化很小，所以样品气压对多光子电离几率的影响可忽略。

Analytic formula of the efficiency of optical-optical double-color double-resonance multi-photon ionization (OODR-MPI) is derived from the dynamic rate equation about the interaction of photon and material. Based on this formula, the influence of characteristic of the pump and probe laser on the ionization efficiency of (1+2+1) OODR-MPI process is simulated theoretically. It is shown that the pump laser will affect the ionization efficiency by the number control of the molecules excited to the first resonance state. The ionization efficiency is decided by the probe laser directly. Both of the excited molecules and ionization efficiency increase with the intensity and pulse duration of the laser until saturation. It is also found that the longer the delay time of the probe laser to the pump one is, the lower the ionization efficiency would be. The delay time ought to be smaller than the lifetime of the excited molecule in the practical use of the OODR-MPI technique.

The analytic formula of the ionization efficiency in the process of double resonance enhanced multi-photon ionization (DREMPI) is derived from the dynamic rate equation about the interaction of photon and material. Based on this formula, the ionization efficiency and the laser power index versus laser intensity in the DREMPI process of NO molecule, via A2\sum and S2\sum intermediate resonant states, is numerically simulated. It is shown that the ionization efficiency of NO molecule increases with the laser intensity until getting saturation, while the laser power index decreases with the enhancement of the laser intensity and changes to zero at last. The variation of the laser power index with the laser intensity indicates that the ionization efficiency reaches saturation in the one, two, and three excitation steps respectively. It is also found that the narrower the laser pulse duration is, the higher becomes the laser intensity for saturation.

The optical-optical double-resonant multiphoton ionization (OODR-MPI) spectrum of NO2 molecule in the 460-605 nm wavelength region of the probe photon is presented. The mechanism of the OODR-MPI of NO2 molecule is analyzed. The results show that the resonant features can be assigned to the transitions from the first 3s'sigma'g Rydberg intermediate resonant state to the final np'sigma'u Rydberg series. The ionization pathway is NO2(X2A1)-[3h'nu'1]->3s'sigma'g-[h'nu'2]->np'sigma'u-[h'nu'2 or autoionization]->NO2(+)+e. It is found that the converging potential of the np'sigma'u Rydberg series and the quantum defect of np orbit about NO2 are (78803+-14) cm^(-1) and 0.652+-0.014, respectively. The bending vibration frequency of 5p'sigma'u state is determined also.

The multi-photon ionization spectrum of NO in the wavelength region of 575-680 nm is obtained with an optical parameter generator and amplifier (OPG/OPA) pumped by a picosecond Nd:YAG laser as radiation source. The banded structure of the spectrum indicates that NO molecule is ionized in resonant manner and the peaks of the spectrum are assigned to the transition of NO molecule from the ground electronic state to A2'Sigma' (v'=0,1,2,3), E2'Sigma' (v'=0,1,2), F2'Delta' (v'=0,1,2,3) and H2'Sigma' (v'=0,1,2) intermediate resonant ones. The molecule constants about NO (A2'Sigma', E2'Sigma', F2'Delta', H2'Sigma') states are calculated from the center wavelength of the spectrum. It is also found that owing to the special electron configuration of NO, this molecule does not follow the normal transition selection rule of the diatomic molecule during the multi-photon process.