Department of Chemistry, University of California, Davis, California 95616, USA.
J Chem Phys. 2012 Apr 7;136(13):134302. doi: 10.1063/1.3696897.
The time-slice velocity-map ion imaging and the resonant four-wave mixing techniques are combined to study the photodissociation of NO in the vacuum ultraviolet (VUV) region around 13.5 eV above the ionization potential. The neutral atoms, i.e., N((2)D(o)), O((3)P(2)), O((3)P(1)), O((3)P(0)), and O((1)D(2)), are probed by exciting an autoionization line of O((1)D(2)) or N((2)D(o)), or an intermediate Rydberg state of O((3)P(0,1,2)). Old and new autoionization lines of O((1)D(2)) and N((2)D(o)) in this region have been measured and newer frequencies are given for them. The photodissociation channels producing N((2)D(o)) + O((3)P), N((2)D(o)) + O((1)D(2)), N((2)D(o)) + O((1)S(0)), and N((2)P(o)) + O((3)P) have all been identified. This is the first time that a single VUV photon has been used to study the photodissociation of NO in this energy region. Our measurements of the angular distributions show that the recoil anisotropy parameters (β) for all the dissociation channels except for the N((2)D(o)) + O((1)S(0)) channel are minus at each of the wavelengths used in the present study. Thus direct excitation of NO by a single VUV photon in this energy region leads to excitation of states with Σ or Δ symmetry (ΔΩ = ±1), explaining the observed perpendicular transition.
时间切片速度映射离子成像和共振四波混合技术相结合，研究了真空紫外（VUV）区域中高于电离势 13.5eV 左右的 NO 光解。通过激发 O((1)D(2)) 或 N((2)D(o)) 的自电离线，或 O((3)P(0,1,2)) 的中间里德堡态，探测中性原子，即 N((2)D(o))、O((3)P(2))、O((3)P(1))、O((3)P(0)) 和 O((1)D(2))。在这个区域中，已经测量了 O((1)D(2)) 和 N((2)D(o)) 的旧和新自电离线，并给出了它们的更新频率。产生 N((2)D(o)) + O((3)P)、N((2)D(o)) + O((1)D(2))、N((2)D(o)) + O((1)S(0)) 和 N((2)P(o)) + O((3)P) 的光解通道都已被识别。这是第一次使用单个 VUV 光子在这个能量区域研究 NO 的光解。我们对各向异性参数（β）的测量表明，除了 N((2)D(o)) + O((1)S(0)) 通道之外，所有解离通道的β在本研究中使用的每个波长下均为负值。因此，在这个能量区域中，单个 VUV 光子直接激发 NO 导致激发具有Σ或Δ对称性（ΔΩ = ±1）的状态，这解释了观察到的垂直跃迁。
