Stress-Alteration Enhancement of the Reactivity of Aluminum Nanoparticles in the Catalytic Decomposition of -Tetrahydrodicyclopentadiene (JP-10).

High-energy-density aluminum nanoparticles (AlNPs) upon thermal annealing followed by superquenching result in elevated stress levels in the metallic core and reduced surface energy at the core-shell interface. Isomer-selective vacuum ultraviolet-based photoionization mass spectrometry coupled to a high-temperature chemical microreactor reveals that these stress-altered AlNPs (SA-AlNPs) exhibit distinctive temperature-dependent reactivities toward catalytic decomposition of the hydrocarbon jet fuel -tetrahydrodicyclopentadiene (JP-10, CH) compared to untreated AlNPs (UN-AlNPs). SA-AlNPs show a delayed initiation of the decomposition for JP-10 by 200 K relative to the UN-AlNPs; however, the full decomposition is achieved at a 100 K lower temperature.

Efficient Oxidative Decomposition of Jet-Fuel -Tetrahydrodicyclopentadiene (JP-10) by Aluminum Nanoparticles in a Catalytic Microreactor: An Online Vacuum Ultraviolet Photoionization Study.

The oxidation of gas-phase -tetrahydrodicyclopentadiene (JP-10, CH) over aluminum nanoparticles (AlNP) has been explored between a temperature range of 300 and 1250 K with a novel chemical microreactor. The results are compared with those obtained from chemical microreactor studies of helium-seeded JP-10 and of helium-oxygen-seeded JP-10 without AlNP to gauge the effects of molecular oxygen and AlNP, respectively. Vacuum ultraviolet (VUV) photoionization mass spectrometry reveals that oxidative decomposition of JP-10 in the presence of AlNP is lowered by 350 and 200 K with and without AlNP, respectively, in comparison with pyrolysis of the fuel.

Counterintuitive Catalytic Reactivity of the Aluminum Oxide "Passivation" Shell of Aluminum Nanoparticles Facilitating the Thermal Decomposition of -Tetrahydrodicyclopentadiene (JP-10).

High energy density aluminum nanoparticles (AlNPs) have been at the center of attention as additives to hydrocarbon jet fuels like -tetrahydrodicyclopentadiene (JP-10, CH) aiming at the superior performance of volume-limited air-breathing propulsion systems. However, a fundamental understanding of the ignition and combustion chemistry of JP-10 in the presence of AlNPs has been elusive. Exploiting an isomer-selective comprehensive identification of the decomposition products in a newly designed high-temperature chemical microreactor coupled to vacuum ultraviolet photoionization, we reveal an active low-temperature heterogeneous surface chemistry commencing at 650 K involving the alumina (AlO) shell.

Gas-phase formation of the resonantly stabilized 1-indenyl (CH) radical in the interstellar medium.

The 1-indenyl (CH) radical, a prototype aromatic and resonantly stabilized free radical carrying a six- and a five-membered ring, has emerged as a fundamental molecular building block of nonplanar polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanostructures in deep space and combustion systems. However, the underlying formation mechanisms have remained elusive. Here, we reveal an unconventional low-temperature gas-phase formation of 1-indenyl via barrierless ring annulation involving reactions of atomic carbon [C(P)] with styrene (CHCH) and propargyl (CH) with phenyl (CH).

Exploring the Chemical Dynamics of Phenylethynyl Radical (CHCC; XA) Reactions with Allene (HCCCH; XA) and Methylacetylene (CHCCH; XA).

The bimolecular gas-phase reactions of the phenylethynyl radical (CHCC, XA) with allene (HCCCH), allene- (DCCCD), and methylacetylene (CHCCH) were studied under single-collision conditions utilizing the crossed molecular beams technique and merged with electronic structure and statistical calculations. The phenylethynyl radical was found to add without an entrance barrier to the C1 carbon of the allene and methylacetylene reactants, resulting in doublet CH collision complexes with lifetimes longer than their rotational periods. These intermediates underwent unimolecular decomposition via atomic hydrogen loss through tight exit transition states in facile radical addition─hydrogen atom elimination mechanisms forming predominantly 3,4-pentadien-1-yn-1-ylbenzene (CHCCCHCCH) and 1-phenyl-1,3-pentadiyne (CHCCCCCH) in overall exoergic reactions (-110 kJ mol and -130 kJ mol) for the phenylethynyl-allene and phenylethynyl-methylacetylene systems, respectively.

Competing SiCH-H and SiCH-SiH Channels in the Bimolecular Reaction of Ground-State Atomic Carbon (C(P)) with Disilane (SiH, XA) under Single Collision Conditions.

The bimolecular gas-phase reaction of ground-state atomic carbon (C(P)) with disilane (SiH, XA) was explored under single-collision conditions in a crossed molecular beam machine at a collision energy of 36.6 ± 4.5 kJ mol.

Photodissociation Dynamics of Astrophysically Relevant Propyl Derivatives (CHX; X = CN, OH, HCO) at 157 nm Exploiting an Ultracompact Velocity Map Imaging Spectrometer: The (Iso)Propyl Channel.

The photodissociation dynamics of astrophysically relevant propyl derivatives (CHX; X = CN, OH, HCO) at 157 nm exploiting an ultracompact velocity map imaging (UVMIS) setup has been reported. The successful operation of UVMIS allowed the exploration of the 157 nm photodissociation of six (iso)propyl systems─-propyl cyanide (CHCN), -propyl alcohol (CHOH), and (iso)butanal (CHCHO)─to explore the CH loss channel. The distinct center-of-mass translational energy distributions for the -CHX (X= CN, OH, HCO) could be explained through preferential excitation of the low frequency C-H bending modes of the formyl moiety compared to the higher frequency stretching of the cyano and hydroxy moieties.

Gas-Phase Preparation of Silyl Cyanide (SiHCN) via a Radical Substitution Mechanism.

The silyl cyanide (SiHCN) molecule, the simplest representative of a fully saturated silacyanide, was prepared in the gas phase under single-collision conditions via a radical substitution mechanism. The chemical dynamics were direct and revealed a pronounced backward scattering as a consequence of a transition state with a pentacoordinated silicon atom and almost colinear geometry of the attacking cyano radical and leaving hydrogen. Compared to the isovalent cyano (CN)-methane (CH) system, the CN-SiH system dramatically reduces the energy of the transition state to silyl cyanide by nearly 100 kJ mol, which reveals a profound effect on the chemical bonding and reaction mechanism.

Gas-Phase Study of the Elementary Reaction of the D1-Ethynyl Radical (CD; XΣ) with Propylene (CH; XA') under Single-Collision Conditions.

The bimolecular gas-phase reactions of the D1-ethynyl radical (CD; XΣ) with propylene (CH; XA') and partially substituted D3-3,3,3-propylene (CHCD; XA') were studied under single collision conditions utilizing the crossed molecular beams technique. Combining our laboratory data with electronic structure and statistical calculations, the D1-ethynyl radical is found to add without barrier to the C1 and C2 carbons of the propylene reactant, resulting in doublet CHD intermediate(s) with lifetime(s) longer than their rotational period(s). These intermediates undergo isomerization and unimolecular decomposition via atomic hydrogen loss through tight exit transition states forming predominantly /-3-penten-1-yne ((HCC)CH═CH(CH)) and, to a minor amount, 3-methyl-3-buten-1-yne ((HCC)C(CH)═CH) via overall exoergic reactions.

Probing ligand and cation binding sites in G-quadruplex nucleic acids by mass spectrometry and electron photodetachment dissociation sequencing.

Mass spectrometry provides exquisite details on ligand and cation binding stoichiometries with a DNA target. The next important step is to develop reliable methods to determine the cation and ligand binding sites in each complex separated by using a mass spectrometer. To circumvent the caveat of ligand derivatization for cross-linking, which may alter the ligand binding mode, we explored a tandem mass spectrometry (MS/MS) method that does not require ligand derivatization, and is therefore also applicable to localize metal cations.