Matrix Isolation Spectroscopy and Nuclear Spin Conversion of Propyne Suspended in Solid Parahydrogen

Strom, Aaron; Gutiérrez-Quintanilla, Alejandro; Chevalier, Michèle; Čeponkus, Justinas; Crépin, C.; Anderson, David T.

doi:10.1021/acs.jpca.0c02900

Cited by 5 publications

(1 citation statement)

References 65 publications

(175 reference statements)

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“…This behavior can be explained by nuclear spin statistics: symmetric tops with three equivalent hydrogens, such as CH 3 CCH, have two different spin symmetriesnamely, A and E. The A states correlate with the transitions with K=0, 3, 6, 9, ..., whereas the E states correspond to the remaining transitions, such as K=1, 2, 4, 5, ... (e.g. Strom et al 2020). Those states have relative statistical weights of A:E = 2:1 (Herzberg 1945), and therefore the population distribution of the transitions at higher temperatures will favor the K=3 states.…”

Section: Relative Intensitiesmentioning

confidence: 99%

A spectral survey of CH3CCH in the Hot Molecular Core G331.512-0.103

Santos,

Bronfman,

Mendoza

et al. 2022

Preprint

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A spectral survey of methyl acetylene (CH 3 CCH) was conducted toward the hot molecular core/outflow G331.512-0.103. Our APEX observations allowed the detection of 41 uncontaminated rotational lines of CH 3 CCH in the frequency range between 172-356 GHz. Through an analysis under the local thermodynamic equilibrium assumption, by means of rotational diagrams, we determined.05 for an extended emitting region (∼10 ). The relative intensities of the K=2 and K=3 lines within a given K-ladder are strongly negatively correlated to the transitions' upper J quantum-number (r=-0.84). Pure rotational spectra of CH 3 CCH were simulated at different temperatures, in order to interpret this observation. The results indicate that the emission is characterized by a non-negligible temperature gradient with upper and lower limits of ∼45 and ∼60 K, respectively. Moreover, the line widths and peak velocities show an overall strong correlation with their rest frequencies, suggesting that the warmer gas is also associated with stronger turbulence effects. The K=0 transitions present a slightly different kinematic signature than the remaining lines, indicating that they might be tracing a different gas component. We speculate that this component is characterized by lower temperatures, and therefore larger sizes. Moreover, we predict and discuss the temporal evolution of the CH 3 CCH abundance using a two-stage zero-dimensional model of the source constructed with the three-phase Nautilus gas-grain code.

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Section: Relative Intensitiesmentioning

confidence: 99%

A spectral survey of CH3CCH in the Hot Molecular Core G331.512-0.103

Santos,

Bronfman,

Mendoza

et al. 2022

Preprint

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Spatial Diffusion of Hydrogen Atoms in Normal and Para-Hydrogen Molecular Films at Temperature 0.7 K

Sheludiakov,

Wetzel,

Lee

et al. 2024

J Low Temp Phys

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Hydrogen atom quantum diffusion in solid parahydrogen: The H + N2O → cis-HNNO → trans-HNNO reaction

Mutunga

Olenyik

Strom

et al. 2021

The Journal of Chemical Physics

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The diffusion and reactivity of hydrogen atoms in solid parahydrogen at temperatures between 1.5 K and 4.3 K are investigated by high-resolution infrared spectroscopy. Hydrogen atoms are produced within solid parahydrogen as the by-products of the 193 nm in situ photolysis of N2O, which induces a two-step tunneling reaction, H + N2O → cis-HNNO → trans-HNNO. The second-order rate constant for the first step to form cis-HNNO is found to be inversely proportional to the N2O concentration after photolysis, indicating that the hydrogen atoms move through solid parahydrogen via quantum diffusion. This reaction only readily occurs at temperatures below 2.8 K, not due to an increased rate constant for the first reaction step at low temperatures but rather due to an increased selectivity to the reaction. The rate constant for the second step of the reaction mechanism involving unimolecular isomerization is shown to be independent of the N2O concentration as expected. The inverse concentration dependence of the rate constant for the reaction step that involves the hydrogen atom demonstrates clearly that quantum diffusion influences the reactivity of the hydrogen atoms in solid parahydrogen, which does not have an analogy in classical reaction kinetics.

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Matrix Isolation Spectroscopy and Nuclear Spin Conversion of Propyne Suspended in Solid Parahydrogen

Cited by 5 publications

References 65 publications

A spectral survey of CH3CCH in the Hot Molecular Core G331.512-0.103

A spectral survey of CH3CCH in the Hot Molecular Core G331.512-0.103

Spatial Diffusion of Hydrogen Atoms in Normal and Para-Hydrogen Molecular Films at Temperature 0.7 K

Hydrogen atom quantum diffusion in solid parahydrogen: The H + N2O → cis-HNNO → trans-HNNO reaction

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