Slanger Tom G, Hwang Eunsook S, Bartlett Nate C-M, Kalogerakis Konstantinos S
Center for Geospace Studies , SRI International , Menlo Park , California , United States.
J Phys Chem A. 2018 Oct 18;122(41):8114-8125. doi: 10.1021/acs.jpca.8b07469. Epub 2018 Oct 9.
Collisional removal of electronic energy from O in the low-lying aΔ state is typically an extremely slow process for the v = 0 level. In this study, we report results on the deactivation of O( aΔ, v = 1-3) in collisions with O and CO. Ozone photodissociation in the 200-310 nm Hartley band is the source of O( a, v), and resonance-enhanced multiphoton ionization is used to probe the vibrational-level populations. Deactivation of the a( v = 1-3) levels in collisions with O at 300 K is fast, with rate coefficients of (5.6 ± 1.1) × 10, (3.6 ± 0.4) × 10, and (1.9 ± 0.4) × 10 cm s (2σ) for v = 1, 2, and 3, respectively. The relaxation process appears to involve a near-resonant electronic energy transfer pathway analogous to that observed in vibrationally excited O( bΣ). With CO collider gas, the removal rate coefficient at 300 K is (1.8 ± 0.4) × 10 and (4.4 ± 0.6) × 10 cm s (2σ) for v = 1 and 2, respectively. Despite the small mole fraction of O in the atmospheres of Mars and Venus, O is at least as important as CO in the final stages of collisional relaxation within the O vibrational-level manifold.
对于处于低激发态aΔ的氧原子，从v = 0能级通过碰撞去除电子能量通常是一个极其缓慢的过程。在本研究中，我们报告了O(aΔ, v = 1 - 3)与O和CO碰撞时的失活结果。200 - 310 nm哈特利波段的臭氧光解离是O(a, v)的来源，并且采用共振增强多光子电离来探测振动能级的布居。在300 K下，O(aΔ, v = 1 - 3)与O碰撞时的失活很快，对于v = 1、2和3，速率系数分别为(5.6 ± 1.1)×10、(3.6 ± 0.4)×10和(1.9 ± 0.4)×10 cm³ s⁻¹(2σ)。弛豫过程似乎涉及一条近共振电子能量转移途径，类似于在振动激发的O(bΣ)中观察到的情况。对于CO碰撞气体，在300 K下，v = 1和2时的去除速率系数分别为(1.8 ± 0.4)×10和(4.4 ± 0.6)×10 cm³ s⁻¹(2σ)。尽管在火星和金星大气中O的摩尔分数很小，但在O振动能级多重态内的碰撞弛豫的最后阶段，O至少与CO一样重要。
