Johnston M David, Pearson Wright L, Wang Greg, Metz Ricardo B
Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
Rev Sci Instrum. 2018 Jan;89(1):014102. doi: 10.1063/1.5012896.
We present the details of a fast ion velocity map imaging mass spectrometer that is capable of imaging the photofragments of trap-cooled (≥7 K) ions produced in a versatile ion source. The new instrument has been used to study the predissociation of NO produced by electric discharge and the direct dissociation of Al formed by laser ablation. The instrument's resolution is currently limited by the diameter of the collimating iris to a value of Δv/v = 7.6%. Photofragment images of NO show that when the predissociative state is changed from Σ(200) to Σ(300) the dominant product channel shifts from a spin-forbidden ground state, N (S) + NO(v = 5), to a spin-allowed pathway, N(D) + NO. The first photofragment images of Al confirm the existence of a directly dissociative parallel transition (Σ ← Σ) that yields products with a large amount of kinetic energy. D of ground state Al (Σ) measured from these images is 138 ± 5 kJ/mol, which is consistent with the published literature.
我们介绍了一种快速离子速度成像质谱仪的详细情况，该仪器能够对在通用离子源中产生的阱冷却（≥7 K）离子的光碎片进行成像。这台新仪器已被用于研究放电产生的NO的预解离以及激光烧蚀形成的Al的直接解离。目前，该仪器的分辨率受准直光阑直径限制，为Δv/v = 7.6%。NO的光碎片图像表明，当预解离态从Σ(200)变为Σ(300)时，主要产物通道从自旋禁戒的基态N(S) + NO(v = 5)转变为自旋允许的途径N(D) + NO。Al的首张光碎片图像证实了存在一种直接解离的平行跃迁（Σ←Σ），该跃迁产生具有大量动能的产物。从这些图像测得的基态Al(Σ)的D为138±5 kJ/mol，这与已发表的文献一致。
