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由Nd:YAG激光器三倍频,输出波长为λ=355 nm(28 169 cm~(-1))的激光光解NO_2分子产生的氧原子,通过共振增强多光子电离(REMPI resonance enhanced multiphoto ionization)及飞行时间(TOF time of flight)质谱技术,获得了自旋-轨道精细能级分辨的氧原子O(2 p~3P_J~″=2,1,0)离子谱.氧离子信号强度与UV电离激光能量(λ≈226 nm)之间的关系能用三次方曲线很好拟合,它表明光解产物氧原子是通过(2+1)多光子吸收过程而被电离的.由离子信号得到的氧原子基态三个自旋-轨道支能级布居比f_1=I(~3P_1)/I(~3P_2)与fo=I(~3P_0)/I(~3P_2)分别为0.54±0.09和0.20±0.04,并且在不同的光解激光能量下其布居比保持不变.这一比值与统计分布计算的值为0.6和0.2一致(即统计分布~3P_2:~3P_1:~3P_0=1:0.6:0.2).这是由于样品(NO_2)在较低的压力下(1.33×10~(-4)Pa)和极短的光解-电离时间范围内(10~(-8)s),产物O(~3P_J~″)支能级间几乎不可能发生碰撞能量转移,因此,氧原子三个自旋-轨道角动量分裂能级布居O(~3P_J~″=2,1,0)是统计分布的.
The oxygen atoms generated by NO 2 were photodissociated by a laser with a wavelength of λ = 355 nm (28169 cm -1) by the triplet frequency of Nd: YAG laser. By resonance enhanced multiphoton ionization (MIP) And TOF time of flight mass spectrometry, the ion spectra of oxygen atoms O (2 p ~ 3P_J ~ “= 2,1,0) resolved by spin-orbit fine level energy were obtained. The signal intensities of oxygen ions and UV ionization The relationship between laser energy (λ≈226 nm) can be fitted well by a cubic curve, which shows that the photolytic oxygen atom is ionized by the (2 + 1) multiphoton absorption process. The ion signal The three spin-orbital energy levels of the atomic oxygen atoms were 0.54 ± 0.09 and 0.20 ± (f 3), respectively 0.04, and its dwelling ratio remained the same under different photolysis laser energy, which was consistent with the statistical distribution of 0.6 and 0.2 (that is, the statistical distribution of ~ 3P_2: ~ 3P_1: ~ 3P_0 = 1: 0.6: 0.2), which is due to the fact that the product O (NO 2) is at a low pressure (1.33 × 10 -4 Pa) and an extremely short photolysis-ionization time (10 -8 s) (~ 3P_J ~ ”) branch level is almost impossible to collide Therefore, the splitting energy levels of the three spin-orbital angular momentums of oxygen atoms are statistically distributed (~ 3P_J ~ "= 2,1,0).