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1. Experimental study of the proton-transfer reaction C + H 2 + → CH + + H and its isotopic variant (D 2 + )

   https://doi.org/10.1039/D0CP04810K  

   Hillenbrand, Pierre-Michel ; Bowen, Kyle P. ; Dayou, Fabrice ; Miller, Kenneth A. ; de Ruette, Nathalie ; Urbain, Xavier ; Savin, Daniel W. ( December 2020 , Physical Chemistry Chemical Physics)

   We report absolute integral cross section (ICS) measurements using a dual-source merged-fast-beams apparatus to study the titular reactions over the relative translational energy range of E r ∼ 0.01–10 eV. We used photodetachment of C − to produce a pure beam of atomic C in the ground electronic 3 P term, with statistically populated fine-structure levels. The H 2 + and D 2 + were formed in an electron impact ionization source, with well known vibrational and rotational distributions. The experimental work is complemented by a theoretical study of the CH 2 + electronic system in the reactant and product channels, which helps to clarify the possible reaction mechanisms underlying the ICS measurements. Our measurements provide evidence that the reactions are barrierless and exoergic. They also indicate the apparent absence of an intermolecular isotope effect, to within the total experimental uncertainties. Capture models, taking into account either the charge-induced dipole interaction potential or the combined charge-quadrupole and charge-induced dipole interaction potentials, produce reaction cross sections that lie a factor of ∼4 above the experimental results. Based on our theoretical study, we hypothesize that the reaction is most likely to proceed adiabatically through the 1 4 A′ and 1 4 A′′ states of CH 2 + via the reaction C( 3 P) + H 2 + ( 2 Σ+g) → CH + ( 3 Π) + H( 2 S). We also hypothesize that at low collision energies only H 2 + ( v ≤ 2) and D 2 + ( v ≤ 3) contribute to the titular reactions, due to the onset of dissociative charge transfer for higher vibrational v levels. Incorporating these assumptions into the capture models brings them into better agreement with the experimental results. Still, for energies ≲0.1 eV where capture models are most relevant, the modified charge-induced dipole model yields reaction cross sections with an incorrect energy dependence and lying ∼10% below the experimental results. The capture cross section obtained from the combined charge-quadrupole and charge-induced dipole model better matches the measured energy dependence but lies ∼30–50% above the experimental results. These findings provide important guidance for future quasiclassical trajectory and quantum mechanical treatments of this reaction. 

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2. Pendant Alkyl and Aryl Groups on Tin Control Complex Geometry and Reactivity with H 2 /D 2 in Pt(SnR 3 ) 2 (CNBu t ) 2 (R = Bu t , Pr i , Ph, Mesityl)

   https://doi.org/10.1021/ja511295h  

   Koppaka, Anjaneyulu ; Zhu, Lei ; Yempally, Veeranna ; Isrow, Derek ; Pellechia, Perry J. ; Captain, Burjor ( January 2015 , Journal of the American Chemical Society)
3. Isomer-specific cryogenic ion vibrational spectroscopy of the D 2 tagged Cs + (HNO 3 )(H 2 O) n=0–2 complexes: ion-driven enhancement of the acidic H-bond to water

   https://doi.org/10.1039/c9cp06689f  

   Mitra, Sayoni ; Duong, Chinh H. ; McCaslin, Laura M. ; Gerber, R. Benny ; Johnson, Mark A. ( February 2020 , Physical Chemistry Chemical Physics)

   We report how the binary HNO 3 (H 2 O) interaction is modified upon complexation with a nearby Cs + ion. Isomer-selective IR photodissociation spectra of the D 2 -tagged, ternary Cs + (HNO 3 )H 2 O cation confirms that two structural isomers are generated in the cryogenic ion source. In one of these, both HNO 3 and H 2 O are directly coordinated to the ion, while in the other, the water molecule is attached to the OH group of the acid, which in turn binds to Cs + with its –NO 2 group. The acidic OH stretching fundamental in the latter isomer displays a ∼300 cm −1 red-shift relative to that in the neutral H-bonded van der Waals complex, HNO 3 (H 2 O). This behavior is analyzed with the aid of electronic structure calculations and discussed in the context of the increased effective acidity of HNO 3 in the presence of the cation. 

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4. Analysis of the Proton Transfer Bands in the Infrared Spectra of Linear N 2 H + ···OC and N 2 D + ···OC Complexes Using Electric Field-Driven Classical Trajectories

   https://doi.org/10.1021/acs.jpca.0c06756  

   Boutwell, Dalton ; Okere, Onyinye ; Omodemi, Oluwaseun ; Toledo, Alexander ; Barrios, Antonio ; Olocha, Monique ; Kaledin, Martina ( September 2020 , The Journal of Physical Chemistry A)

   null (Ed.)
5. Chemical dynamics study on the gas-phase reaction of the D1-silylidyne radical (SiD; X 2 Π) with deuterium sulfide (D 2 S) and hydrogen sulfide (H 2 S)

   https://doi.org/10.1039/d1cp01629f  

   Goettl, Shane J. ; Doddipatla, Srinivas ; Yang, Zhenghai ; He, Chao ; Kaiser, Ralf I. ; Silva, Mateus X. ; Galvão, Breno R. ; Millar, Tom J. ( June 2021 , Physical Chemistry Chemical Physics)

   The reactions of the D1-silylidyne radical (SiD; X 2 Π) with deuterium sulfide (D 2 S; X 1 A 1 ) and hydrogen sulfide (H 2 S; X 1 A 1 ) were conducted utilizing a crossed molecular beams machine under single collision conditions. The experimental work was carried out in conjunction with electronic structure calculations. The elementary reaction commences with a barrierless addition of the D1-silylidyne radical to one of the non-bonding electron pairs of the sulfur atom of hydrogen (deuterium) sulfide followed by possible bond rotation isomerization and multiple atomic hydrogen (deuterium) migrations. Unimolecular decomposition of the reaction intermediates lead eventually to the D1-thiosilaformyl radical (DSiS) (p1) and D2-silanethione (D 2 SiS) (p3) via molecular and atomic deuterium loss channels (SiD–D 2 S system) along with the D1-thiosilaformyl radical (DSiS) (p1) and D1-silanethione (HDSiS) (p3) through molecular and atomic hydrogen ejection (SiD–H 2 S system) via indirect scattering dynamics in barrierless and overall exoergic reactions. Our study provides a look into the complex dynamics of the silicon and sulfur chemistries involving multiple deuterium/hydrogen shifts and tight exit transition states, as well as insight into silicon- and sulfur-containing molecule formation pathways in deep space. Although neither of the non-deuterated species – the thiosilaformyl radical (HSiS) and silanethione (H 2 SiS) – have been observed in the interstellar medium (ISM) thus far, astrochemical models presented here predict relative abundances in the Orion Kleinmann-Low nebula to be sufficiently high enough for detection. 

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