Photoelectron Spectroscopy of cis-Nitrous Acid Anion (cis-HONO‿/sup>)

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• 作者：Allan M. Oliveira ; Julia H. Lehman ; Anne B. McCoy ; W. Carl Lineberger
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：March 17, 2016
• 年：2016
• 卷：120
• 期：10
• 页码：1652-1660
• 全文大小：463K
• ISSN：1520-5215

文摘

We report photoelectron spectra of cis-HONO^– formed from an association reaction of OH^– and NO in a pulsed, plasma-entrainment ion source. The experimental data are assigned to the cis-HONO^– isomer, which is predicted to be the global minimum on the anion potential energy surface. We do not find evidence for a significant contribution from trans-HONO^–. Electron photodetachment of cis-HONO^– with 1613, 1064, 532, 355, and 301 nm photons accesses the ground X̃ ¹A′ (S₀) and excited ã ³A″ (T₁) states of neutral HONO. The photoelectron spectrum resulting from detachment forming cis-HONO (S₀) exhibits a long vibrational progression, dominated by overtones and combination bands involving the central O–N stretching and ONO bending vibrations. This indicates that there is a significant change in the central O–N bond length between cis-HONO^– and cis-HONO (S₀). The electron affinity (EA) of cis-HONO is determined to be 0.356(8) eV. We also report the dissociation energy (D₀) of cis-HONO^–, forming OH^– + NO, as 0.594(9) eV, which is a factor of 4 decrease in the central O–N bond strength compared to neutral cis-HONO. The T₁ state of cis-HONO is shown to be ∼2.3 eV higher in energy than cis-HONO (S₀). Electron photodetachment to form cis-HONO (T₁) accesses a transition state along the HO–NO bond dissociation coordinate. The resulting photoelectron spectrum exhibits broad peaks spaced by the terminal N═O stretching frequency. Electronic structure calculations and photoelectron spectrum simulations reported here show very good agreement with the experimental data.