High-Resolution Photoelectron Spectroscopy of Cryogenically Cooled NO₃̅

Abstract

High-resolution anion photoelectron spectra of cryogenically cooled NO 3ˉ anions obtained using slow photoelectron velocity-map imaging are presented and provide new insight into the vibronic structure of the corresponding neutral radical. A combination of improved spectral resolution, measurement of energy-dependent intensity effects, temperature control, and comparison to theory allows for full assignment of the vibronic features observed in this spectrum. We obtain a refined electron affinity of 3.9289( 14) eV for NO 3 . Further, the appearance of Franck-Condon forbidden transitions from vibrationally cold anions to neutral states with excitation along the NO 3 v 4 mode confirms that these features arise from vibronic coupling with the excited state of NO 3 and are not hot bands as has been suggested. Together, the suite of experimental and simulated results provides clear evidence that the v 3 fundamental of NO 3 resides near 1050 cm −1 , addressing a long-standing controversy surrounding this vibrational assignment. File list (2) download file view on ChemRxiv NO3_SI.pdf (208.75 KiB) download file view on ChemRxiv NO3_FINAL.pdf (722.77 KiB)

Photoelectron spectroscopy of cryogenically cooled NiO2¯ via slow photoelectron velocity-map imaging

“…Consequently, spectra for the "B" peaks can be obtained closer to photodetachment threshold, where cryo-SEVI resolution is improved, leading to narrower features as was observed in the cryo-SEVI spectra of the indenyl and nitrate anions. 66,69 As such, we are able to refine our determined value for the v2 bending mode of NiO2 from the position of B1 as 120(7) cm -1 .…”

“…coupling to an excited electronic state with the appropriate symmetry. 29,[64][65][66] Briefly, two vibronic states, a and b, can mix through HT-coupling provided their electronic and vibrational symmetries elec Γ and vib Γ , respectively, satisfy 63 , each an admixture of the two zero-order vibronic levels. Thus, if detachment to state b is FC-allowed, then detachment to state a0 becomes allowed, but will display the electronic character of state b.…”

“…The disparity in near-threshold cross-section between the "A" and "B" features is a tell-tale sign of HT coupling in cryo-SEVI spectra, 29,[64][65][66] as this indicates that "B" features correspond to detachment with lower values of l than the "A" features, reflecting the electronic character of the u ∏ electronic state that lends intensity to these transitions. Consequently, spectra for the "B" peaks can be obtained closer to photodetachment threshold, where cryo-SEVI resolution is improved, leading to narrower features as was observed in the cryo-SEVI spectra of the indenyl and nitrate anions.…”

Accurate quantum dynamics simulation of the photodetachment spectrum of the nitrate anion (NO3−) based on an artificial neural network diabatic potential model

“…A very recent experiment from the same group tried to resolve at least some questions regarding the X state. 80 By cryogenic cooling, some hot bands of the original spectrum could be removed, which allows us to focus on the remaining unexpected features more clearly. Unfortunately, a corresponding experiment for the à state is not available yet.…”

“…Several attempts to simulate this experiment have been published over the years. 64,[71][72][73]80 While the X state could be simulated reasonably well even in the first attempt, 64 the à state took a lot more effort and required a lot of development to obtain a sufficiently accurate PES model. 73,[81][82][83][84] Further development enables us now to use a PES model of unprecedented accuracy to simulate the corresponding spectra.…”