Galvin T C, Wagner C J, Eden J G
Laboratory for Optical Physics and Engineering, Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801, USA.
J Chem Phys. 2016 Jun 28;144(24):244308. doi: 10.1063/1.4953864.
The diatomic collisional intermediate responsible for the formation of an electronically excited molecule by teratomic recombination has been observed in both the spectral and temporal domains by laser spectroscopy. We report experiments demonstrating thermal Xe(6s[3/2]2)-Xe(5p(6) (1)S0) atomic collision pairs to be the immediate precursor to the formation of Xe2 (∗)(a(3)Σu (+),A(1)Σu (+)) by the three body process: Xe(∗)(6s) + 2Xe ⟶ Xe2 (∗) + Xe, where the asterisk denotes an excited electronic state. Photoassociating Xe(6s)-Xe atomic pairs by free ⟵ free transitions of the collision complex interrupts the production of the electronically excited Xe dimer, thereby suppressing Xe2 spontaneous emission in the vacuum ultraviolet (VUV, λ ∼ 172 nm, A(1)Σu (+)→X(1)Σg (+)). Intercepting Xe(6s)-Xe pairs before the complex is stabilized by the arrival of the third atom in the teratomic collision process selectively depletes the pair population in a specific Franck-Condon region determined by the probe laser wavelength (λ). Measurements of the variation of VUV emission suppression with λ provide a spectral signature of the Xe(6s[3/2]2) - Xe((1)S0) complex and map the probe laser wavelength onto the thermal energy (ϵ″) of the incoming collision pairs.
通过激光光谱法已在光谱和时间域中观测到了通过三原子复合形成电子激发分子的双原子碰撞中间体。我们报告的实验表明，热Xe(6s[3/2]2)-Xe(5p(6) (1)S0)原子碰撞对是通过三体过程形成Xe2 (∗)(a(3)Σu (+),A(1)Σu (+))的直接前体：Xe(∗)(6s) + 2Xe ⟶ Xe2 (∗) + Xe，其中星号表示激发电子态。通过碰撞复合体的自由⟵自由跃迁对Xe(6s)-Xe原子对进行光缔合会中断电子激发的Xe二聚体的产生，从而抑制真空紫外（VUV，λ ∼ 172 nm，A(1)Σu (+)→X(1)Σg (+)）中的Xe2自发发射。在三原子碰撞过程中第三个原子到达使复合体稳定之前拦截Xe(6s)-Xe对，会在由探测激光波长（λ）确定的特定弗兰克-康登区域中选择性地耗尽该对的数量。测量VUV发射抑制随λ的变化提供了Xe(6s[3/2]2) - Xe((1)S0)复合体的光谱特征，并将探测激光波长映射到入射碰撞对的热能（ϵ″）上。
