281—332nmSO_2^+的光碎片激发谱研究

Study on the photofragment excitation spectrum of SO_2^+ in the range of 281-332nm

在超声分子束条件下 ,利用 380 85nm的电离激光使SO2 分子经由 [3+1]共振增强多光子电离 (REMPI)制备纯净的分子离子SO+2 ( X2 A1 (0 0 0 ) ) ,用另一束解离激光在 2 81— 332nm扫描获得了光解碎片激发 (PHOFEX)谱 .获得的光碎片SO+ 激发谱基本可以归属为SO+2 ( E , D)←SO+2 ( X2 A1 )序列跃迁 .尝试性地标识了 X2 A1 (0 0 0 )到 D电子态弯曲振动能级的跃迁 ,给出 D电子态新的弯曲振动频率ν2 =2 4 1 78± 0 92cm- 1 和非谐常数X2 2 =- 1 71± 0 0 1cm- 1 .结合可见光波长区 (5 6 2— 6 6 4nm)的PHOFEX连续谱讨论了SO+2 的 E , D , C电子态的对称性和它们的预解离动力学 .结果表明 :SO+2 的 E , D , C电子态附近可能存在着两个和解离限SO+ (X2 П ) +O(3Pg)相关、对称性分别为2 A2 ,2 B2 的排斥态α2 A2 和 β2 B2 ,由此得到SO+2 的 E , D , C电子态的对称性分别为 E2 B2 , D2 B1 , C2 A1 , D2 B1 和α2 A2 排斥态的电子 振动耦合、 E2 B2 和 β2 B2 排斥态的电子 电子、电子 振动耦合导致了到SO+ (X2 П) +O(3Pg)的解离 .

With the preparing of SO2+ ((X) over tilde (2) A(1) (000)) by [3+1] multiphoton ionization of the neutral SO2 molecules at 380.85 nm, the photofragment excitation (PHOFEX) spectrum in ultraviolet (UV) (281-332 nm) wavelength range has been obtained. The PHOFEX spectrum in the UV range was assigned essentially to the SO2+ ((E) over tilde,(D) over tilde)<--SO2+ ((X) over tilde (2) A(1)) transitions. The transitions from (x) over tilde (2) A(1) (000) to the bend vibration levels of SO2+ ((D) over tilde) were suggested, new harmonic bend vibrational frequency nu(2)=241.78+/-0.92 cm(-1) and the anharmonicity constant X-22=-1.71+/-0.01 cm(-1) for SO2+ ((D) over tilde) was deduced. By using the SO+ PHOFEX spectra in UV and in visible range (562-664 nm), the symmetry of (E) over tilde, (D) over tilde, (C) over tilde states of SO2+ and the predissociation mechanism of SO2+ ((E) over tilde, (D) over tilde, (C) over tilde) were determined, that is, (i) the symmetry of (E) over tilde, (D) over tilde, (C) over tilde states of SO2+ should be (E) over tilde (2) B-2, (D) over tilde (2) B-1, (C) over tilde (2) A(1) (ii) around (E) over tilde, (D) over tilde, (C) over tilde states there should be two repulsive states of symmetry alpha(2) A(2) and beta(2) B-2 converging to the dissociation limit of SO+(X-2 Pi) + O(P-3(g)), (iii) the couplings between (d) over tilde (2) B-1 and alpha(2) A(2) and between (E) over tilde (2) B-2 and beta(2) B-2 lead to the dissociation to SO+(X-2 Pi) + O(P-3(g)).