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1. Elucidating the nature of the proton radioactivity and branching ratio on the first proton emitter discovered 53mCo

   https://doi.org/10.1038/s41467-023-39389-2  

   Sarmiento, Luis G; Roger, Thomas; Giovinazzo, Jérôme; Brown, B Alex; Blank, Bertram; Rudolph, Dirk; Kankainen, Anu; Alvarez-Pol, Héctor; Raj, Alex Arokia; Ascher, Pauline; et al (December 2023, Nature Communications)

   Abstract The observation of a weak proton-emission branch in the decay of the 3174-keV^53mCo isomeric state marked the discovery of proton radioactivity in atomic nuclei in 1970. Here we show, based on the partial half-lives and the decay energies of the possible proton-emission branches, that the exceptionally high angular momentum barriers,$${{{{{{\mathcal{l}}}}}}}_{{{{{{\rm{p}}}}}}}=9$$ $l_p=9$and$${{{{{{\mathcal{l}}}}}}}_{{{{{{\rm{p}}}}}}}=7$$ $l_p=7$, play a key role in hindering the proton radioactivity from^53mCo, making them very challenging to observe and calculate. Indeed, experiments had to wait decades for significant advances in accelerator facilities and multi-faceted state-of-the-art decay stations to gain full access to all observables. Combining data taken with the TASISpec decay station at the Accelerator Laboratory of the University of Jyväskylä, Finland, and the ACTAR TPC device on LISE3 at GANIL, France, we measured their branching ratios as b_p1= 1.3(1)% and b_p2= 0.025(4)%. These results were compared to cutting-edge shell-model and barrier penetration calculations. This description reproduces the order of magnitude of the branching ratios and partial half-lives, despite their very small spectroscopic factors. 

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2. Strong Evidence for ${}^9\mathrm{N}$ and the Limits of Existence of Atomic Nuclei

   https://doi.org/10.1103/PhysRevLett.131.172501  

   Charity, R J; Wylie, J; Wang, S M; Webb, T B; Brown, K W; Cerizza, G; Chajecki, Z; Elson, J M; Estee, J; Hoff, D_E M; et al (October 2023, Physical Review Letters)

   The boundaries of the Chart of Nuclides contain exotic isotopes that possess extreme proton-toneutron asymmetries. Here we report on two of the most exotic proton-rich isotopes where at least one half of their constitute nucleons are unbound. While the ground state of 8C is a resonance, its first excited state lies in the diffuse borderland between nuclear states and fleeting scattering features. Evidence for 9N, with seven protons and two neutrons, is also presented. This extremely proton-rich system represents the first-known example of a ground-state five-proton emitter. The energies of these states are consistent with theoretical predictions of an open-quantum-system approach. 

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3. Assessment of electron–proton correlation functionals for vibrational spectra of shared-proton systems by constrained nuclear-electronic orbital density functional theory

   https://doi.org/10.1063/5.0243086  

   Yang, Yuzhuo; Zhang, Yuzhe; Yang, Yang; Xu, Xi (December 2024, The Journal of Chemical Physics)

   Proton transfer plays a crucial role in various chemical and biological processes. A major theoretical challenge in simulating proton transfer arises from the quantum nature of the proton. The constrained nuclear-electronic orbital (CNEO) framework was recently developed to efficiently and accurately account for nuclear quantum effects, particularly quantum nuclear delocalization effects, in quantum chemistry calculations and molecular dynamics simulations. In this paper, we systematically investigate challenging proton transfer modes in a series of shared-proton systems using CNEO density functional theory (CNEO-DFT), focusing on evaluating existing electron–proton correlation functionals. Our results show that CNEO-DFT accurately describes proton transfer vibrational modes and significantly outperforms conventional DFT. The inclusion of the epc17-2 electron–proton correlation functional in CNEO-DFT produces similar performance to that without electron–proton correlations, while the epc17-1 functional yields less accurate results, comparable with conventional DFT. These findings hold true for both asymmetrical and symmetrical shared-proton systems. Therefore, until a more accurate electron–proton correlation functional is developed, we currently recommend performing vibrational spectrum calculations using CNEO-DFT without electron–proton correlation functionals. 

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4. Programmable Nuclear-Spin Dynamics in Ti(IV) Coordination Complexes

   https://doi.org/10.1021/acs.inorgchem.0c00244  

   Johnson, Spencer H.; Jackson, Cassidy E.; Zadrozny, Joseph M. (April 2020, Inorganic Chemistry)

   Interstitial patterning of nuclear spins is a nascent design principle for controlling electron spin superposition lifetimes in open-shell complexes and solid-state defects. Herein we report the first test of the impact of the patterning principle on ligand-based nuclear spin dynamics. We test how substitutional patterning of 1H and 79/81Br nuclear spins on ligands modulates proton nuclear spin dynamics in the ligand shell of metal complexes. To do so, we studied the 1H nuclear magnetic resonance relaxation times (T1 and T2) of a series of eight polybrominated catechol ligands and six complexes formed by coordination of the ligands to a Ti(IV) ion. These studies reveal that 1H T1 values can be enhanced in the individual ligands by a factor of 4 (from 10.8(3) to 43(5) s) as a function of substitution pattern, reaching the maximum value for 3,4,6-tribromocatechol. The T2 for 1H is also enhanced by a factor of 4, varying by ∼14 s across the series. When complexed, the impact of the patterning design strategy on nuclear spin dynamics is amplified and 1H T1 and T2 values vary by over an order of magnitude. Importantly, the general trends observed in the ligands also match those when complexed. Hence, these results demonstrate a new design principle to control 1H spin dynamics in metal complexes through pattern-based design strategies in the ligand shell. 

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5. Describing proton transfer modes in shared proton systems with constrained nuclear–electronic orbital methods

   https://doi.org/10.1063/5.0151544  

   Zhang, Yuzhe; Xu, Xi; Yang, Nan; Chen, Zehua; Yang, Yang (June 2023, The Journal of Chemical Physics)

   Proton transfer is crucial in various chemical and biological processes. Because of significant nuclear quantum effects, accurate and efficient description of proton transfer remains a great challenge. In this Communication, we apply constrained nuclear–electronic orbital density functional theory (CNEO-DFT) and constrained nuclear–electronic orbital molecular dynamics (CNEO-MD) to three prototypical shared proton systems and investigate their proton transfer modes. We find that with a good description of nuclear quantum effects, CNEO-DFT and CNEO-MD can well describe the geometries and vibrational spectra of the shared proton systems. Such a good performance is in significant contrast to DFT and DFT-based ab initio molecular dynamics, which often fail for shared proton systems. As an efficient method based on classical simulations, CNEO-MD is promising for future investigations of larger and more complex proton transfer systems. 

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