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1. The metallo-formate anions, M(CO ₂ ) ⁻ , M = Ni, Pd, Pt, formed by electron-induced CO ₂ activation

   https://doi.org/10.1039/c9cp01915d  

   Liu, Gaoxiang; Ciborowski, Sandra M.; Zhu, Zhaoguo; Chen, Yinlin; Zhang, Xinxing; Bowen, Kit H. (May 2019, Physical Chemistry Chemical Physics)

   The metallo-formate anions, M(CO 2 ) − , M = Ni, Pd, and Pt, were formed by electron-induced CO 2 activation. They were generated by laser vaporization and characterized by a combination of mass spectrometry, anion photoelectron spectroscopy, and theoretical calculations. While neutral transition metal atoms are normally unable to activate CO 2 , the addition of an excess electron to these systems led to the formation of chemisorbed anionic complexes. These are covalently bound, formate-like anions, in which their CO 2 moieties are significantly reduced. In addition, we also found evidence for an unexpectedly attractive interaction between neutral Pd atoms and CO 2 . 

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2. Photoelectron Velocity Map Imaging Spectroscopy of the Beryllium Trimer and Tetramer

   Jaffe, Noah B; Stanton, John F; Heaven, Michael C (September 2023, The journal of physical chemistry letters)

   Computational studies of small beryllium clusters (BeN) predict dramatic, nonmonotonic changes in the bonding mechanisms and per-atom cohesion energies with increasing N. To date, experimental tests of these quantum chemistry models are lacking for all but the Be2 molecule. In the present study, we report spectroscopic data for Be3 and Be4 obtained via anion photodetachment spectroscopy. The trimer is predicted to have D3h symmetric equilibrium structures for both the neutral molecule and the anion. Photodetachment spectra reveal transitions that originate from the X2A2″ ground state and the (1)2A1′ electronically excited state. The state symmetries were assigned on the basis of anisotropic photoelectron angular distributions. The neutral and anionic forms of Be4 are predicted to be tetrahedral. Franck−Condon diagonal photodetachment was observed with a photoelectron angular distribution consistent with the expected Be4−X2A1 → Be4X1A1 transition. The electron affinities of Be3 and Be4 were determined to be 11363 ± 60 and 13052 ± 50 cm−1, respectively 

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3. State selective preparation and nondestructive detection of trapped O2+

   https://doi.org/10.1063/5.0244447  

   Singh, Ambesh Pratik; Mitchell, Michael; Henshon, Will; Hartman, Addison; Lunstad, Annika; Kuzhan, Boran; Hanneke, David (February 2025, The Journal of Chemical Physics)

   The ability to prepare molecular ions in selected quantum states enables studies in areas such as chemistry, metrology, spectroscopy, quantum information, and precision measurements. Here, we demonstrate (2 + 1) resonance-enhanced multiphoton ionization (REMPI) of oxygen, both in a molecular beam and in an ion trap. The two-photon transition in the REMPI spectrum is rotationally resolved, allowing ionization from a selected rovibrational state of O2. Fits to this spectrum determine spectroscopic parameters of the O2d1Πg state and resolve a discrepancy in the literature regarding its band origin. The trapped molecular ions are cooled by co-trapped atomic ions. Fluorescence mass spectrometry nondestructively demonstrates the presence of the photoionized O2+. We discuss strategies for maximizing the fraction of ions produced in the ground rovibrational state. For (2 + 1) REMPI through the d1Πg state, we show that the Q(1) transition is preferred for neutral O2 at rotational temperatures below 50 K, while the O(3) transition is more suitable at higher temperatures. The combination of state-selective loading and nondestructive detection of trapped molecular ions has applications in optical clocks, tests of fundamental physics, and control of chemical reactions. 

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4. Simulated and Experimental Time-Resolved Photoelectron Spectra of the Intersystem Crossing Dynamics in 2-Thiouracil

   https://doi.org/10.3390/molecules23112836  

   Mai, Sebastian; Mohamadzade, Abed; Marquetand, Philipp; González, Leticia; Ullrich, Susanne (November 2018, Molecules)

   We report time-dependent photoelectron spectra recorded with a single-photon ionization setup and extensive simulations of the same spectra for the excited-state dynamics of 2-thiouracil (2TU) in the gas phase. We find that single-photon ionization produces very similar results as two-photon ionization, showing that the probe process does not have a strong influence on the measured dynamics. The good agreement between the single-photon ionization experiments and the simulations shows that the norms of Dyson orbitals allow for qualitatively describing the ionization probabilities of 2TU. This reasonable performance of Dyson norms is attributed to the particular electronic structure of 2TU, where all important neutral and ionic states involve similar orbital transitions and thus the shape of the Dyson orbitals do not strongly depend on the initial neutral and final ionic state. We argue that similar situations should also occur in other biologically relevant thio-nucleobases, and that the time-resolved photoelectron spectra of these bases could therefore be adequately modeled with the techniques employed here. 

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5. Charge distributions and oxidation states in Mn-based oxidants from ab initio molecular dynamics simulation

   Colin Crago, Shifa Zhong§ (August 2021, Chemosphere)

   null (Ed.)

   We used ab initio molecular dynamics simulations to address Mn oxidation states in different Mn systems. We first develop a correlation between Mn partial atomic charge and the oxidation state, based on results of 31 simulations on known Mn aqueous complexes. The results collapse to a master curve; the dependence of partial atomic charge on oxidation state weakens with increasing oxidation state, which concurs with a previously proposed feedback effect. This correlation is then used to address oxidation states in Mn systems used as oxidants. Simulations of MnO2 polymorphs immersed in water give average oxidation states (AOS) in excellent agreement with experimental results, in that b-MnO2 has the highest AOS, a-MnO2 has an intermediate AOS, and d-MnO2 has the lowest AOS. Furthermore, the oxidation state varies substantially with the atom’s environment, and these structures include Mn(III) and Mn(V) species that are expected to be active. In regard to the MnO4−/HSO3−/O2 system that has been shown to be a highly effective oxidant, we propose a novel Mn complex that could give rise to the oxidative activity, where Mn(III) is stabilized by sulfite and dissolved O2 ligands. Our simulations also show that the O2 would be activated to O22- in this complex under acidic conditions, and could lead to the formation of OH radicals that serve as oxidants. 

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