Nitrogen oxides are delivered to our atmosphere from both biogenic and anthropogenic sources and affect a great deal of atmospheric chemistry e.g., the depletion of ozone. To understand the physical properties of nitrogen monoxide (NO), photoelectron spectroscopy experiments in conjunction with computational methods are used to map part of the potential energy surface of nitric oxide and its anion. Low and high energy NO anions are created in an electron impact source and isolated via mass spectrometry, where photoelectron spectra are captured via velocity map imaging (VMI). Theoretical spectra are produced at various ion temperatures using ezSpectrum software, which calculates the Franck-Condon factors using Gaussian09 optimizations of equilibrium geometry, harmonic frequencies, and normal mode vectors. Comparing the theoretical and experimental spectra, the experimental temperature is observed to vary from 300 K to over 1000 K as a function of ion source energy. The coupling of software with experimental VMI spectra also provides electron affinity, bond energy, and vibrational details of NO.To improve temperature control, our group has recently installed a linear ion trap to the existing mass spectrometer, allowing for the storage of ions and, via helium damping gas, the cooling of these ions over time. The rate of cooling can be calculated by taking VMI spectra for various holding times in the ion trap. In addition, the ion trap provides the opportunity for reactivity studies of these compounds by seeding the helium gas with a reactant neutral. As reactions occur, the product branching and rate constants of the reactions can be determined for various temperatures. Collectively, these studies aim to provide fundamental research into gas phase reactivity and energetics with applications in atmospheric studies emulating both Earth and the Martian atmosphere.

Photoelectron spectroscopy experiments for the determination of electronic structure and reactivity of atmospheric ions: Ion trapping for improved temperature control

255th National Meeting (2018)

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