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1. Roaming pathways and survival probability in real-time collisional dynamics of cold and controlled bialkali molecules

   https://doi.org/10.1038/s41598-021-90004-0  

   Kłos, Jacek; Guan, Qingze; Li, Hui; Li, Ming; Tiesinga, Eite; Kotochigova, Svetlana (May 2021, Scientific Reports)

   Abstract Perfectly controlled molecules are at the forefront of the quest to explore chemical reactivity at ultra low temperatures. Here, we investigate for the first time the formation of the long-lived intermediates in the time-dependent scattering of cold bialkali$$^{23}\hbox {Na}^{87}$$ ${}^{23}{\text{Na}}^{87}$Rb molecules with and without the presence of infrared trapping light. During the nearly 50 nanoseconds mean collision time of the intermediate complex, we observe unconventional roaming when for a few tens of picoseconds either NaRb or$$\hbox {Na}_2$$ ${\text{Na}}_2$and$$\hbox {Rb}_2$$ ${\text{Rb}}_2$molecules with large relative separation are formed before returning to the four-atom complex. We also determine the likelihood of molecular loss when the trapping laser is present during the collision. We find that at a wavelength of 1064 nm the$$\hbox {Na}_2\hbox {Rb}_2$$ ${\text{Na}}_2{\text{Rb}}_2$complex is quickly destroyed and thus that the$$^{23}\hbox {Na}^{87}$$ ${}^{23}{\text{Na}}^{87}$Rb molecules are rapidly lost. 

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2. Single Spot Rb‐Sr Isochron Dating of Biotite by LA‐MC‐ICP‐MS / MS

   https://doi.org/10.1111/ggr.12518  

   Cruz‐Uribe, Alicia M.; Craig, Grant; Garber, Joshua M.; Paul, Bence; Arkula, Cemil; Bouman, Claudia (July 2023, Geostandards and Geoanalytical Research)

   Laser ablation tandem mass spectrometry is a burgeoning field forin situRb‐Sr geochronology. Here, we determined simultaneous isotope ratios of⁸⁷Sr/⁸⁶Sr and⁸⁷Rb/⁸⁶Sr in metamorphic biotite from western Maine, using an ESL™ imageGEO™193 excimer laser ablation system coupled to a Thermo Scientific™ Neoma™ MC‐ICP‐MS/MS. Measurements were made on Faraday cups with Rb⁺at mass 87; Sr isotopes were reacted with SF₆gas and measured as SrF⁺at masses 103–107. Twenty‐two laser spots in biotite from a single sample yield a traditional Rb‐Sr isochron date of 289 ± 6 Ma. Time‐resolved signals reveal significant zoning in⁸⁷Sr/⁸⁶Sr and⁸⁷Rb/⁸⁶Sr within single spot analyses, which were used to construct single spot isochrons. Individual laser spots contain multiple isochronous subpopulations; some spots contain up to three distinct Rb‐Sr isochrons that are decoupled from variations in Rb/Sr. Thirty‐five isochron dates were determined using this sub‐spot approach, with⁸⁷Sr/⁸⁶Sr intercepts that systematically vary with Rb‐Sr date; two‐point isochrons were calculated for individual integrations (n= 780) based on these variable intercepts. Both methods yield age peaks at 303, 270 and 240 Ma. These data suggest that the Rb‐Sr system has the potential to record multiple heating, cooling or fluid‐alteration events spanning ~ 100 My within small domains in single biotite crystals. 

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3. Combined Crossed Molecular Beams and Ab Initio Study of the Bimolecular Reaction of Ground State Atomic Silicon (Si; ³ P) with Germane (GeH ₄ ; X ¹ A ₁ )

   https://doi.org/10.1002/cphc.202100235  

   Krasnoukhov, Vladislav_S; Azyazov, Valeriy_N; Mebel, Alexander_M; Doddipatla, Srinivas; Yang, Zhenghai; Goettl, Shane; Kaiser, Ralf_I (June 2021, ChemPhysChem)

   Abstract The chemical dynamics of the elementary reaction of ground state atomic silicon (Si;³P) with germane (GeH₄; X¹A₁) were unraveled in the gas phase under single collision condition at a collision energy of 11.8±0.3 kJ mol⁻¹exploiting the crossed molecular beams technique contemplated with electronic structure calculations. The reaction follows indirect scattering dynamics and is initiated through an initial barrierless insertion of the silicon atom into one of the four chemically equivalent germanium‐hydrogen bonds forming a triplet collision complex (HSiGeH₃;³i1). This intermediate underwent facile intersystem crossing (ISC) to the singlet surface (HSiGeH₃;¹i1). The latter isomerized via at least three hydrogen atom migrations involving exotic, hydrogen bridged reaction intermediates eventually leading to the H₃SiGeH isomeri5. This intermediate could undergo unimolecular decomposition yielding the dibridged butterfly‐structured isomer¹p1(Si(μ‐H₂)Ge) plus molecular hydrogen through a tight exit transition state. Alternatively, up to two subsequent hydrogen shifts toi6andi7, followed by fragmentation of each of these intermediates, could also form¹p1(Si(μ‐H₂)Ge) along with molecular hydrogen. The overall non‐adiabatic reaction dynamics provide evidence on the existence of exotic dinuclear hydrides of main group XIV elements, whose carbon analog structures do not exist. 

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4. Spectroscopic Evidence of Hyponitrite Radical Intermediate in NO Disproportionation at a MOF‐Supported Mononuclear Copper Site

   https://doi.org/10.1002/anie.202015359  

   Sun, Chenyue; Yang, Luming; Ortuño, Manuel A.; Wright, Ashley M.; Chen, Tianyang; Head, Ashley R.; López, Núria; Dincă, Mircea (March 2021, Angewandte Chemie International Edition)

   Abstract Dianionic hyponitrite (N₂O₂²⁻) is often proposed, based on model complexes, as the key intermediate in reductive coupling of nitric oxide to nitrous oxide at the bimetallic active sites of heme‐copper oxidases and nitric oxide reductases. In this work, we examine the gas‐solid reaction of nitric oxide with the metal–organic framework Cu^I‐ZrTpmC* with a suite of in situ spectroscopies and density functional theory simulations, and identify an unusual chelating N₂O₂^.−intermediate. These results highlight the advantage provided by site‐isolation in metal–organic frameworks (MOFs) for studying important reaction intermediates, and provide a mechanistic scenario compatible with the proposed one‐electron couple in these enzymes. 

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5. Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N ₂ O

   https://doi.org/10.1002/anie.201909137  

   Abucayon, Erwin G.; Khade, Rahul L.; Powell, Douglas R.; Zhang, Yong; Richter‐Addo, George B. (October 2019, Angewandte Chemie International Edition)

   Abstract Some bacterial heme proteins catalyze the coupling of two NO molecules to generate N₂O. We previously reported that a heme Fe–NO model engages in this N−N bond‐forming reaction with NO. We now demonstrate that (OEP)Co^II(NO) similarly reacts with 1 equiv of NO in the presence of the Lewis acids BX₃(X=F, C₆F₅) to generate N₂O. DFT calculations support retention of the Co^IIoxidation state for the experimentally observed adduct (OEP)Co^II(NO⋅BF₃), the presumed hyponitrite intermediate (P^.+)Co^II(ONNO⋅BF₃), and the porphyrin π‐radical cation by‐product of this reaction, and that the π‐radical cation formation likely occurs at the hyponitrite stage. In contrast, the Fe analogue undergoes a ferrous‐to‐ferric oxidation state conversion during this reaction. Our work shows that cobalt hemes are chemically competent to engage in the NO‐to‐N₂O conversion reaction. 

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