Diffusion of Water Molecules in Quantum Crystals

Moore, Brendan; Djuricanin, Pavle; Momose, Takamasa

doi:10.1021/acs.jpclett.8b02943

Cited by 6 publications

(6 citation statements)

References 45 publications

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“…Moore and co‐workers recently demonstrated that the photodissociation of proteogenic amino acids in the singlet state yields products such as imine derivatives and CO 2 [2] . This formation primarily occurs from HOCO+RCHNH 2 radicals.…”

Section: Resultsmentioning

confidence: 99%

“…Recent investigations by Moore and colleagues have shed light on the UV photodissociation of specific proteogenic amino acids at 193 and 213 nm, leading to fundamental discoveries concerning the nature of the resulting photoproducts [1,2] . Notably, the irradiation of Alanine, Glycine, Leucine, Proline, and Serine produces amino radical (RCHNH 2 ) and hydroxycarbonyl radical (HOCO).…”

Section: Introductionmentioning

confidence: 99%

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Role of Triplet States in the Photolysis of Proteogenic Amino Acids

Guerra,

Rodríguez‐Núñez,

Ensuncho

2023

ChemPhysChem

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This investigation delves into the UV photodissociation of pivotal amino acids (Alanine, Glycine, Leucine, Proline, and Serine) at 213 nm, providing insights into triplet‐state deactivation pathways. Utilizing a comprehensive approach involving time‐dependent density functional calculations (TD‐DFT), multi‐configurational methods, and ab‐initio molecular dynamics (AIMD) simulations, we scrutinize the excited electronic states (T1, T2, and S1) subsequent to 213 nm excitation. Our findings demonstrate that α‐carbonyl C−C bond‐breaking in triplet states exhibits markedly lower barriers than in singlet states (below 5.0 kcal mol−1). AIMD simulations corroborate the potential involvement of triplet states in amino acid fragmentation, underscoring the significance of accounting for these states in photochemistry. Chemical bonding analyses unveil distinctive patterns for S1 and T1 states, with the asymmetric redistribution of electron density characterizing the C−C breaking in triplet states, in contrast to the symmetric breaking observed in singlet states. This research complements recent experimental discoveries, enhancing our comprehension of amino acid reactions in the interstellar medium.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of Triplet States in the Photolysis of Proteogenic Amino Acids

Guerra,

Rodríguez‐Núñez,

Ensuncho

2023

ChemPhysChem

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“…While the large D G values bolster the notion discussed in ref of enhanced Al atom recombination/reaction occurring near pH 2 crystallite grain boundaries during sample deposition, they do not impact the mobility of Al atoms trapped in the grain interiors. Indeed, recent MIS studies of the aggregation of small molecules (e.g., HF and H 2 O) in low temperature pH 2 solids report measurements performed on a timescale of days, not milliseconds. , Finally, the coefficient of self-diffusion in liquid H 2 only reaches D ≈ 0.9 × 10 –4 cm 2 /s near the boiling point at T = 20 K, while radioactive tracer measurements on 85 Kr in liquid H 2 indicate D ≈ 1.5 × 10 –4 cm 2 /s at T = 20 K …”

Section: Resultsmentioning

confidence: 99%

“…Indeed, recent MIS studies of the aggregation of small molecules (e.g., HF and H 2 O) in low temperature pH 2 solids report measurements performed on a timescale of days, not milliseconds. 36,37 Finally, the coefficient of self-diffusion in liquid H 2 only reaches D ≈ 0.9 × 10 −4 cm 2 /s near the boiling point at T = 20 K, 38 while radioactive tracer measurements on 85 Kr in liquid H 2 indicate D ≈ 1.5 × 10 −4 cm 2 /s at T = 20 K. 39 Thus, our calculated lower limit on the diffusion coefficient of D > 6 × 10 −4 cm 2 /s is not consistent with Al atom diffusion in solid or even liquid pH 2 . Because this value rests on a single observation, it should rightly be viewed with much skepticism.…”

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confidence: 99%

Catastrophic Recombination/Reaction of Aluminum Atoms in Cryogenic Parahydrogen Solids

Fajardo

2019

J. Phys. Chem. A

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We report the results from experiments testing the limits of chemical energy storage in Al-atom-doped cryogenic parahydrogen (pH 2 ) solids produced by codeposition of Al vapor and pH 2 gas. These results map out three regimes of behavior. As described in the immediately preceding companion manuscript, for target Al atom concentrations, [Al] target ≲ 200 parts-per-million (ppm), the Al/pH 2 solids are optically transparent and primarily contain isolated Al atoms, with a small admixture of Al x H y molecules formed by Al atom recombination/reaction. For [Al] target ≳ 500 ppm, the depositions fail immediately, producing highly optically scattering solids with evidence of extensive Al atom recombination/reaction. For intermediate [Al] target concentrations, near-threshold metastable transparent solids are formed which suffer catastrophic recombination/reaction as they grow past some critical thickness. Analysis of these catastrophic events using a minimal two parameter model [Jackson. J. Chem. Phys. 1959, 31, 722−729] yields a critical Al atom concentration near [Al] ≈ 280 ppm and an Al atom diffusion length ≈ 100 μm. While this diffusion length appears unphysically large, it is roughly compatible with even larger 300− 900 μm wavelengths of spatial inhomogeneities visible in images of a remnant postrecombination sample. This spatial pattern is evocative of Turing structures or perhaps the structures sometimes formed upon phase separation; however, the actual mechanism for morphogenesis remains undetermined. The largest achieved Al atom concentrations of [Al] ≈ 300 ppm are roughly two orders-of-magnitude lower than those required for advanced chemical propulsion applications.

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“…In terms of more classical guest species like an oxygen atom, even less is known. Further complicating our understanding of guest diffusion in solid p-H 2 is that both HF and H 2 O have been reported to quantum-diffuse in solid p-H 2 . This was unexpected, and there still is no definitive explanation of how the HF and H 2 O molecules diffuse through the p-H 2 matrix host.…”

Section: Introductionmentioning

confidence: 99%

Infrared Spectroscopic Studies of Oxygen Atom Quantum Diffusion in Solid Parahydrogen

et al. 2023

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The thermally induced diffusion of atomic species in noble gas matrices was studied extensively in the 1990s to investigate low-temperature solid-state reactions and to synthesize reactive intermediates. In contrast, much less is known about the diffusion of atomic species in quantum solids such as solid parahydrogen (p-H2). While hydrogen atoms were shown to diffuse in normal-hydrogen solids at 4.2 K as early as 1989, the diffusion of other atomic species in solid p-H2 has not been reported in the literature. The in situ photogeneration of atomic oxygen, by ArF laser irradiation of an O2-doped p-H2 solid at 193 nm, is studied here to investigate the diffusion of O(3 P) atoms in a quantum solid. The O(3 P) atom mobility is detected by measuring the kinetics of the O(3 P) + O2 → O3 reaction after photolysis via infrared spectroscopy of the O3 reaction product. This reaction is barrierless and is thus assumed to be diffusion-controlled under these conditions such that the reaction rate constant can be used to estimate the oxygen atom diffusion coefficient. The O3 growth curves are well fit by single exponential expressions allowing the pseudo-first-order rate constant for the O(3 P) + O2 → O3 reaction to be extracted. The reaction rates are affected strongly by the p-H2 crystal morphology and display a non-Arrhenius-type temperature dependence consistent with quantum diffusion of the O(3 P) atom. The experimental results are compared to H(2 S) atom reaction studies in p-H2, analogous studies in noble gas matrices, and laboratory studies of atomic diffusion in astronomical ices and surfaces.

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Diffusion of Water Molecules in Quantum Crystals

Cited by 6 publications

References 45 publications

Role of Triplet States in the Photolysis of Proteogenic Amino Acids

Role of Triplet States in the Photolysis of Proteogenic Amino Acids

Catastrophic Recombination/Reaction of Aluminum Atoms in Cryogenic Parahydrogen Solids

Infrared Spectroscopic Studies of Oxygen Atom Quantum Diffusion in Solid Parahydrogen

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