Rarefied Gas Phase Research Articles

An open source code for two-phase rarefied flows: rarefiedMultiphaseFoam

This paper presents the development and benchmarking tests of an open source code for providing solutions of two-phase rarefied flows. The solver is named in rarefiedMultiphaseFoam and it is developed in OpenFOAM, based on dsmcFoamPlus, which is used for the rarefied gas phase. The solver can produce both steady and transient results for arbitrary 2D/3D two-phase rarefied flows and includes a phase change model for materials that experience melting and solidification processes. The benchmarking tests include momentum and heat exchange between gas phase and solid phases, particle phase change, a converging nozzle that creates a solid particle beam, and transport of solid particles. The tests yield good agreement with analytical and experimental data where available, and are compared to previous numerical results from the literature. Program summaryProgram Title: rarefiedMulitphaseFoamCPC Library link to program files:https://doi.org/10.17632/8vxrc5gsb8.1Licensing provisions: GNU General Public License 3Programming language: C++Nature of problem: rarefiedMultiphaseFoam has been developed to help investigate multiphase problems with rarefied gas and solid phases. The rarefied gas phase is simulated with the direct simulation Monte Carlo (DSMC) method, with both one and two way coupling models available to simulate the momentum and heat transfer between the phases. It provides an easily extended, parallelised, environment.Solution method: rarefiedMultiphaseFoam implements an explicit time-stepping solver with stochastic molecular collisions appropriate for studying rarefied gas flow problems and uses a Green's function model to calculate the energy transfers between phases.

Flying Cages in Traveling Wave Ion Mobility: Influence of the Instrumental Parameters on the Topology of the Host-Guest Complexes.

Supramolecular mass spectrometry has emerged in the last decade as an orthogonal method to access, at the molecular level, the structures of noncovalent complexes extracted from the condensed phase to the rarefied gas phase using electrospray ionization. It is often considered that the soft nature of the ESI source confers to the method the capability to generate structural data comparable to those in the condensed phase. In the present paper, using the ammonium ion/cucurbituril combination as a model system, we investigate using ion mobility and computational chemistry the influence of the instrumental parameters on the topology, i.e., internal versus external association, of gaseous host/guest complex ions. MS and theoretical data are confronted to condensed phase data derived from nuclear magnetic resonance spectroscopy to assess whether the instrumental parameters can play an insidious role when trying to derive condensed phase data from mass spectrometry results. Graphical Abstract ᅟ.

ChemInform Abstract: Gaseous Diphosphorus and Triphosphorus Sulfide: Generation and Identification by Neutralization-Reionization Mass Spectrometry.

Abstract The dissociative ionization by electron impact (70 eV) of tetraphosphorus trisulfide, P4S3, yields [P3S]+ and [PZS]+0 ions whose structures have been investigated by means of Coliisionai Activation (CA) mass spectra. Using the technique of Neutralization-Reionization mass spectrometry (NRMS) it is shown that both ions can be reduced to the corresponding neutral molecules. Thus, triphosphorus sulfide and diphosphorus sulfide are viable molecules in the rarefied gas phase. The results of ab initio MO calculations were used to interpret the experimental findings. Tetrahedral (C3v) and triangular (C2v) structures are proposed for the [P,S]+ and [PZS]+0 ions respectively.

The covalently bound dimer ion HC[dbnd]N[sbnd]C[dbnd]NH[rad]+ and its neutral counterpart

Model chemistry calculations (CBS-QB3 and CBS-APNO methods) and tandem mass spectrometry based experiments indicate that dissociative ionization of 2-methoxy-s-triazine (consecutive losses of CH2O and HCN) yields the elusive covalently bound [H,C,N] dimer ion HCNCNH+, a species of interest in astrochemistry. Neutralization–Reionization Mass Spectrometry (NRMS) experiments indicate that its neutral counterpart, HCNCNH, is a kinetically stable molecule in the rarefied gas-phase.

The covalently bound HC [tbnd]N dimer ions HC [dbnd]N−N [dbnd]CH [rad]+ and HC [dbnd]N−C( [dbnd]N)H [rad]+ are stable species in the gas-phase, but the neutral counterparts are not

Tandem mass spectrometry based experiments and computational chemistry (CBS-QB3/APNO methods) indicate that ionized s-tetrazine eliminates N 2 to yield the elusive linear HC N dimer ion HC N–N CH + ( 1). The ion is stable in the rarefied gas-phase but, as it is generated with considerable internal energy, it readily interconverts with HC N–C( N)H + ( 2), via a 1,2-HCN shift. This more stable HCN dimer ion was generated independently by loss of HCN from ionized s-triazine. Whereas the HN C dimer ion HN C C NH + has a (kinetically) stable neutral counterpart, theory and experiment (neutralization–reionization mass spectrometry) agree that the HC N dimer ions 1 and 2 do not.

The covalently bound HNC dimer ion HN [dbnd]C [dbnd]C [dbnd]NH [rad]+ has a kinetically stable neutral counterpart

Neutralization-reionization mass spectrometry (NRMS) and computational chemistry (CBS-QB3/APNO methods) have been used to show that HN C C NH (ethenediimine) and its isomer H 2N–C–C N (aminocyanocarbene) are generated as kinetically stable molecules in the rarefied gas-phase by one electron reduction of their ionic precursors. One route to the very stable ion HN C C NH + involves loss of HC N from the hydrogen-bridged radical cation [ HN C ⋯ H 2 N – C – C N ] + via a remarkable quid-pro-quo catalysis in which both the ion and the neutral undergo isomerization.

Ionic and neutral mercaptothiocarbonyl: A tandem mass spectrometry and computational study

Dissociative electron ionization (70 eV) of ethyl carbomylmethanedithioate generates m/ z 77 ions of composition [H, C, S 2] +. The collision-induced dissociation (CID) mass spectrum of these ions is consistent with the mercaptothiocarbonyl connectivity HSCS + ( a +). Calculations predict that some of the a + ions may equilibrate with HC(S)S + ( b) + ions prior to dissociation. Neutralization-reionization mass spectrum (NRMS) of these ions confirmed that neutral HSCS is stable in the rarefied gas phase. The relative, dissociation, and isomerization energies for the ions and neutrals studied at B3LYP/6-311G(d,p) and G2/G2(MP2) levels, are used to support and interpret the experimental results.

Generation and characterization of ionic and neutral chloro(hydroxy) phosphanyl [Cl–P–OH] +/[rad] and chloro(thiohydroxy) phosphanyl [Cl–P–SH] +/[rad] in the gas phase by tandem mass spectrometry and computational chemistry

Dissociative electron ionization (70 eV) of diethyl chlorothiophosphate ( I) and ethylphosphonodichloridate ( II) generates moderately abundant m/ z 83 ions of composition [P, Cl, O, H] +. From tandem mass spectrometry experiments and theoretical calculations at the B3LYP/6-31G(d, p), G2, and G2(MP2) levels it is concluded that the majority of the ions have the structure of ClPOH + ( 1a +) and it is separated by high-energy barriers from its isomers HP(O)Cl + ( 1b +), HPOCl + ( 1c +), and OP–ClH ( 1d +). Neutralization–reionization experiments confirm the theoretical prediction that radical 1a is a stable species in the gas phase. The 70 eV electron ionization of ethylphosphonothioic dichloride ( III) yields m/ z 99 ions, predominantly of the structure ClPSH + ( 2a +). This conclusion follows from tandem mass spectrometry experiments and theoretical calculations. The calculations predict that ( 2a +) is separated by high-energy barriers from its isomers HP(S)Cl + ( 2b +), HPSCl + ( 2c +), and SP–ClH ( 2d +). Neutralization–reionization experiments confirmed that 2a radical is a stable species in the rarefied gas phase, which is in agreement with theoretical calculations.

Mutual Diffusion Coefficient in Binary Mixtures and the Lattice Gas Model

A modification of the elementary kinetic theory of a gas mixture in terms of the lattice gas model is proposed. It is assumed that molecules of components of the mixture are spherical and close in size. In calculating the diffusion flux of molecules through a selected plane, instead of the mean thermal velocity of molecules, the mean relative velocity of molecules of components of different types is used. In this case, the flux explicitly depends on the type of component with which a molecule collided last before intersecting the selected plane. The proposed modification allows one to derive an expression for the mutual diffusion coefficient of components of a binary mixture that at low densities of the mixture (as in a rarefied gas phase), is consistent with the expression obtained in the rigorous kinetic theory of gases.

Selenoketene (H2CCSe)+• and selenoketyl cumulene (HCCSe)+ ions and their neutral counterparts: a tandem mass spectrometric and computational study

AbstractDissociative electron ionization (70eV) of selenophene (C4H4Se) generates m/z 106 ions of composition [H2, C2, 80Se]+• and m/z 105 ions of [H, C2, 80Se]+. From tandem mass spectrometric experiments, Density Functional Theory (DFT) and ab initio calculations, it is concluded that these ions have the structure of selenoketene H2CCSe+• (1a+• )and selenoketyl HCCSe+ (2a+) ions respectively. The calculations predict that selenoketene ion 1a+• is separated by high energy barriers from its isomers selenirene (H$\catcode`@=11 \def\overlsqmatrix#1{\null\vbox{\normalbaselines\m@th \ialign{\hfil$##$\hfil&&\quad\hfil$##$\hfil\crcr \mathstrut\crcr\noalign{\kern-\baselineskip} #1\crcr\mathstrut\crcr\noalign{\kern-\baselineskip}}}} \newdimen\rulwidth \def\downsqbrace#1{\setbox1=\hbox{#1} \rulwidth=\wd1\advance \rulwidth by -6pt \raise3pt\hbox{$\overlsqmatrix{\vrule height5pt\kern-0.5pt\raise5pt\hbox to \rulwidth{\hrulefill}\kern-0.5pt\vrule height5pt\cr\noalign{\vskip-3pt}\hbox{#1}\cr\noalign{\vskip-5pt}}$}} \catcode`@=12 \downsqbrace{{\rm CCHS}}$e)+• 1b+•, ethyne selenol (HCCSeH)+• 1c+•, (CCHSeH)+• 1d+• and (CCSeH2)+• 1e+•. The selenoketyl ion 2a+ is separated by high barriers from its isomers (CCHSe)+ 2b+, and (CCSeH)+ 2c+. Neutralization‐reionization mass spectra (NRMS) of these structurally characterized ions confirmed that the corresponding neutral analogues, selenoketene H2CCSe 1a and selenoketyl radical HCCSe 2a• are stable in the rarefied gas phase. The relative, dissociation, and isomerization energies for selenoketene and selenoketyl ions and neutrals studied at B3LYP/6–31G(d,p) and G2/G2(MP2) levels are used to support and interpret the experimental results. Copyright © 2005 John Wiley & Sons, Ltd.

Generation and characterization of ionic and neutral methylene isothiocyanate by a combined tandem mass spectrometry and computational study

AbstractThe heterocumulene, methyleneisothiocyanate ion, CH2NCS+ (1a+), is generated by the dissociative electron ionization of 2‐mercaptoimidazole. This conclusion follows from tandem mass spectrometry experiments and theoretical calculations at the B3LYP/6‐311G** and G2/G2(MP2) levels. The calculations predict that 1a+ is separated by high energy barriers from its isomers CHNCHS (1b+), CHNCSH (1d+), CNCHSH (1e+) and CHNHCS (1f+). The low energy metastable ions 1a+ dissociate by loss of HCN via the pathway 1a+ → 1b+ → HCS+ + HCN. Neutralization‐reionization experiments confirm the theoretical prediction that the hitherto unknown heterocumulene CH2NCS. is a stable species in the rarefied gas phase. Copyright © 2004 John Wiley & Sons, Ltd.

Generation and characterization of ionic and neutral selenocumulene HC 3Se +/[rad] by tandem mass spectrometry and computational study

Dissociative electron ionization (70 eV) of diphenyl diselenide [(C 6H 5Se) 2] generates m/ z 117 ions of composition [H, C 3, 80 Se ] +. The collision-induced dissociation (CID) mass spectrum of these ions are consistent with the selenocumulene connectivity HCCCSe +. Neutralization–reionization mass spectrum (NRMS) of these structurally characterized ions confirmed that the corresponding neutral analog, hitherto unknown hetero cumulene, HCCCSe, is stable in the rarefied gas phase. The relative, dissociation, and isomerization energies for the ions and neutrals studied at B3LYP/6-31G(d,p) and B3LYP/6-311+G (2d,p) levels are used to support and interpret the experimental results.

Protonated silanoic acid HSi(OH)2+ and its neutral counterpart: a tandem mass spectrometric and CBS-QB3 computational study

Protonated silanoic acid, HSi(OH)2+, 1a+, is cleanly generated by the dissociative electron ionization of triethoxysilane, HSi(OC2H5)3, and tetraethoxysilane, Si(OC2H5)4. This follows from tandem mass spectrometric experiments and CBS-QB3 model chemistry calculations. The calculations predict that 1a+ (ΔHf(298 K) = 205 kJ mol−1) is separated by high barriers from its isomers HOSiOH2+, 1b+ and HSi(O)OH2+, 1c+. Low-energy (metastable) ions 1a+ dissociate by loss of H2O via the pathway 1a+ → 1b+ → SiOH+ + H2O. Analysis of the metastable peak for this process confirms that the isomerization step 1a+ → 1b+ is rate determining. The calculations further predict that the incipient ions 1b+ communicate via a low barrier with the proton-bound dimer SiO···H···OH2+, 1d+. This dimer ion is much lower in energy than its counterpart OSi···H···OH2+, 1e+, which is calculated to be only marginally stable. A comparison of the potential energy diagram for the silicon-containing ions 1a+–1e+ with that of their carbon analogues reveals that the dissociation chemistries of HSi(OH)2+ and HC(OH)2+ are only superficially similar. Neutralization–reionization experiments confirm the theoretical prediction that the HSi(OH)2• radical (ΔHf(298 K) = −455 kJ mol−1) is a stable species in the rarefied gas phase. However, owing to a mismatch of Franck–Condon factors a large fraction of the neutralized ions dissociates by loss of H• yielding Si(OH)2. Copyright © 2004 John Wiley & Sons, Ltd.

Hydrogen Atom Adducts to the Amide Bond. Generation and Energetics of Amide Radicals in the Gas Phase

The 1-hydroxy-1-(N-methyl)aminoethyl radical (1) represents a simple model system for hydrogen atom adducts to the amide bond in gas-phase peptide and protein ions relevant to electron capture dissociation (ECD). Radical 1 was generated in the rarefied gas phase by femtosecond electron transfer to the stable cation prepared by selective O-protonation of N-methylacetamide. The main dissociations of 1 were loss of the hydroxyl hydrogen atom and the N-methyl group in a 1.7:1 ratio, as deduced from product analysis and deuterium labeling. The dissociations that occur on the 4.1 microsecond time scale are driven by large Franck−Condon effects on collisional electron transfer that deposit 93−103 kJ mol-1 in the nascent radicals. Detailed analysis of the potential energy surface for dissociations of 1 revealed several conformers and isomeric transition states for dissociations of the O−H and N−CH3 bonds. The experimental branching ratio is in quantitative agreement with RRKM calculations within the accuracy of t...

Hydrogen-shift isomers of ionic and neutral hydroxypyridines: a combined experimental and computational investigation

Apart from pyridine N-oxide ( 1a), the C 5H 5NO family of stable molecules comprises, 2-, 3- and 4-hydroxypyridine ( 2a, 3a and 4a) as well as their keto counterparts 2-, 3- and 4(1 H)-pyridone ( 2b, 3b and 4b). This study focuses on the characterisation of their radical cations and a number of stable H-shift isomers, which are α- or β-distonic ions. This was done by using a combination of mass spectrometric experiments and computational chemistry, at the B3LYP/CBSB7 level of theory. The ionic species were identified on the basis of both their collision-induced dissociation (CID) characteristics and specific associative ion–molecule reactions with dimethyl disulfide and tert-butyl isocyanide as substrates. The distonic ions ( 1b +, 2c +, 2d + and 3c +) were obtained by dissociative electron impact ionisation and subjected to neutralisation–reionisation mass spectrometry (NRMS). From CID spectra of the intense survivor ions, it follows that the neutral counterparts of the α-distonic ions 2c + and 3c + are viable chemical species in the rarefied gas phase. The energy-rich ylide type neutrals 1b, on the other hand, readily isomerise into pyridine N-oxide, 1a, or else dissociate. The neutral counterpart of the β-distonic ion 2d + only has a marginal stability and part of these neutrals are proposed to isomerise into energy-rich 2-pyridone molecules 2b. This is in agreement with the computational results. However, ionised 2-pyridone cannot readily be differentiated from its enol isomer 2-hydroxypyridine. In contrast, the keto isomers of ionised 3- and 4-hydroxypyridine display characteristically different CID spectra.

Pyrimidine-ylidenes produced using neutralization–reionization mass spectrometry and probed by density functional methods

The potential energy surface comprising ionized pyrimidine, 1·+, and eight of its hydrogen-shift isomers, as well as that of the corresponding neutrals was explored at a level of theory (B3LYP/TZVP) that has proven adequate for related species. The computations predicted that among the isomers there are four C4H4N2·+ distonic radical cations, 2·+– 5·+, of comparable stability to 1·+, and transition state calculations indicated that high barriers separate these stable ions. Thus, the ions 2·+– 5·+ should also be viable chemical species, and indeed mass spectrometry based experiments lead to the generation and characterization of three of the four, that is 2·+, 3·+, and 4·+, as stable ions in the gas phase. Ions 2·+– 4·+ were identified on the basis of their collision-induced dissociation characteristics in the mass spectrometer. The ions 2·+ and 3·+ obtained by dissociative electron impact ionization were subjected to neutralization–reionization mass spectrometry (NRMS). From collision-induced dissociation spectra of the intense NRMS survivor ions, it follows that the neutral ylide/carbene counterparts, i.e. pyrimidine-4-ylidene, 2, and pyrimidine-2-ylidene, 3, have lifetimes of at least microseconds in the rarefied gas phase. The interpretation of the experimental observations that 2 and 3 are viable chemical species in gaseous environs was supported computationally. According to the calculations the neutral isomers 2 – 5 each represent a minimum separated by high hydrogen-shift barriers, although situated some 50 kcal/mol higher in energy than 1, pyrimidine itself. However, molecules 4 and 5 remained elusive since ions 4· +, only obtainable by a collision-induced dissociation process, were not amenable to NR experiments and a viable strategy to produce a beam of pure ions 5·+ could not be realized.

THE PHOSPHOROTRITHIOUS ACID (HS)3P IS STABLE IN THE DILUTE GAS PHASE

Abstract Using the technique of neutralization-reionization mass spectrometry (NRMS) it could be shown that the elusive phosphorotrithious acid (HS)3P is a stable molecule in the rarefied gas phase. A triple propene elimination from the molecular ions of the dipropyl ester of propylphosphonotrithioic acid, PrP(S)(SPr)2, (70 eV EI) yields m/z 130 radical cations of composition “[H3PS3] +”. Analysis of their collisional activation (CA) mass spectrum using thermochemical data, shows that these “[H3PS3] +” ions have the structure [(HS)3P] + rather than that of the tautomer [(HS)2P(=S)H| +. Subjected to a NRMS experiment, these ions retain their structure and are cleanly reduced to (HS)3P. The results are entirely compatible with ab initio MO-calculations executed at the HF/3-21G∗ and HF/6-31G∗∗ levels of theory (GAUSSIAN 92 system of programs). The calculations predict that [(HS)3P] + and [(HS)2P(=S)H] + and their respective neutral counterparts are local minima which are separated by high potential energy ba...

DARSTELLUNG UND REAKTIONEN EINIGER LITHIUMPHOSPHINOFORMIATE R2PCOOLi UND RHPCOOLi—AB INITIO-RECHNUNGEN IM SYSTEM H2PCOOH—PH3/CO2

Abstract The preparation of lithiumphosphinoformates R2PCOOLi 1 (R = Ph, c-Hexyl, i-Pr, Et) and RHPCOOLi 2 (R = Ph, c-Hexyl) from R2PLi or RPHLi and CO2 is described. In the latter reaction RP(COOLi)2 3 and RPH2 are formed in addition to 2. In protic media 1–3 are rapidly decomposed with decarboxylation and formation of R2PH and RPH2, respectively. Reactions of 1 with McI, (MeO)2SO2, Me3SiCl and CS2 are similar to those of Ph2PCOONa and no significant influence of R was detected. With (MeO)2SO2 mixtures of 2 and 3 gave esters RHPCOOMe and RP(COOMe)2 while with Me3SiCl RHPCOOSiMe3 was obtained as the sole product. Ab initio MO calculations (GAUSSIAN 90 system of programs; HF/3-21G∗, HF/6-31G∗∗ and MP2/6-31G∗∗ basis sets) showed the phosphinoformic acid to be less stable than its decomposition products, from which it is separated by a high barrier of isomerization. Therefore the acid should be stable in the rarefied gas phase. Die Darstellung der Lithiumphosphinoformiate R2PCOOLi 1 (R = Ph, c-Hex, i-Pr, Et)...

On the generation and identification of dimethoxycarbene and 2-oxazolidinylidene in the rarefied gas phase of the mass spectrometer

Dimethoxycarbene radical cations, 1 + , are cleanly generated by the dissociative electron impact ionization of 2,2-dimethoxy-5,5-dimethyl-Δ 3-1,3,4-oxadiazoline, I. Using the technique of neutralization—reionization (NR) mass spectrometry, it is shown that reduction of 1 + yields the neutral carbene 1 as a stable species in the rarefied gas phase. The collisional activation mass spectra of the m/ z 74 C 3H 6O 2 ions generated by very low vapour pressure pyrolysis—mass spectrometry of I show that the carbene 1 can also be generated by pyrolysis but only in admixture with its isomer methyl acetate. The above techniques were also employed to study the m/ z 71 C 3H 5NO ion generated from 3,4,9-triaza-2,2,-dimethyl-1,6-dioxaspiro-[4,4]non-3-ene, II. NR experiments on this ion show that the cyclic carbene 2-oxazolidinylidene, 2, is a viable species in the gas phase. The pyrolysis experiments indicate that it rapidly isomerizes to 2-oxazoline, 2a.

Triphosphorus disulfide: The elusive P3S radical generated and identified by neutralization/reionization mass spectrometry

AbstractThe dissociative ionization by electron impact (70 eV) of terraphosphorus trisulfide, P4S3, yields P3S ions whose neutralization/reionization mass spectrum shows that the elusive P3S radical is a viable species in the rarefied gas phase. Ab initio molecular orbital calculations indicate that the structure of this radical is that of a planar five‐membered PPSPS ring of C2v symmetry.