We present high resolution UV-photoelectron spectra of cold mass selected ${\mathrm{C}\mathrm{u}}_{n}^{\ensuremath{-}}$, ${\mathrm{A}\mathrm{g}}_{n}^{\ensuremath{-}}$, and ${\mathrm{A}\mathrm{u}}_{n}^{\ensuremath{-}}$ with $n=53--58$. The observed electron density states is not the expected simple shell structure, but strongly influenced by electron-lattice interactions. Only ${\mathrm{C}\mathrm{u}}_{55}^{\ensuremath{-}}$ ${\mathrm{A}\mathrm{g}}_{55}^{\ensuremath{-}}$ exhibit highly...

Ground-state structures and other experimentally relevant isomers of Au(15) (-) to Au(24) clusters are determined through joint first-principles density functional theory photoelectron spectroscopy measurements. Subsequent calculations molecular O(2) adsorption the optimal cluster reveal a size-dependent reactivity pattern that agrees well with earlier experiments. A detailed analysis underlying electronic structure shows chemical gold anions can be elucidated in terms partial-jellium...

Melting temperatures of Na clusters show size-dependent fluctuations that have resisted interpretation so far. Here we discuss these temperatures, in fact, cannot be expected to exhibit an easily understandable behavior. The energy and entropy differences between the liquid solid turn out much more relevant parameters. They pronounced maxima correlate well with geometrical shell closings, demonstrating importance geometric structure for melting process. Icosahedral symmetry dominates, a...

In this article, we first explored the chemical dynamics of simple diatomic radicals (dicarbon, methylidyne) utilizing crossed molecular beams method. This versatile experimental technique can be applied to study reactions relevant atmospheres planets and their moons as long intense stable supersonic beam sources reactant species exist. By focusing on dicarbon with hydrogen cyanide, untangled contribution in its singlet ground excited triplet states. These results were understand re-analyze...

Gold prospecting: Trapped-ion electron diffraction, photoelectron spectroscopy, and density functional theory are used to establish the structure of free gold cluster ion Au34−. The results suggest a chiral with an internal trigonal pyramid C3 point symmetry.

We report high-level ab initio calculations and single-photon ionization mass spectrometry study of adenine (A), thymine (T), cytosine (C), guanine (G). For adenine, only the lowest-energy tautomers were considered, whereas for we characterized five tautomeric forms. The first adiabatic several vertical energies computed using equation-of-motion coupled-cluster method potentials with single double substitutions. Equilibrium structures cationic ground states by DFT ωB97X-D functional....

A combined theoretical and experimental study of the ionized dimers thymine adenine, TT, AA, AT, is presented. Experimentally observed computed adiabatic vertical ionization energies (IEs) for monomers as well thresholds appearance protonated species are reported analyzed. Non-covalent interactions strongly affect IEs. The magnitude nature effect different isomers dimers. computations reveal that largest changes in IEs (0.4 eV) relative to monomer occur asymmetric H-bonded symmetric...

The hydrogen abstraction/acetylene addition (HACA) mechanism has long been viewed as a key route to aromatic ring growth of polycyclic hydrocarbons (PAHs) in combustion systems. However, doubt drawn on the ubiquity by recent electronic structure calculations which predict that HACA starting from naphthyl radical preferentially forms acenaphthylene, thereby blocking cyclization third six-membered ring. Here, probing products formed reaction 1- and 2-naphthyl radicals excess acetylene under...

Tunable vacuum ultraviolet (VUV) radiation coupled to mass spectrometry is applied the study of complex chemical systems. The identification novel reactive intermediates and radicals revealed in flame, pulsed photolysis, pyrolysis reactors, leading elucidation spectroscopy, reaction mechanisms, kinetics. Mass-resolved threshold photoelectron photoion coincidence measurements provide unprecedented access vibrationally resolved spectra free present high-temperature reactors. Photoionization...

Knowledge of the acid dissociation constant an amino has very important ramifications in biochemistry proteins and lipid bilayers aqueous environments because charge proton transfer depend on its value. The for guanidinium group arginine historically been posited as 12.5, but there is substantial variation published values over years. Recent experiments suggest that much higher than which explains why retains positive under all physiological conditions. In this work, we use X-ray...

Sodium cluster anions Na(n)(-) with n = 39-350 have been studied by low temperature photoelectron spectroscopy and density functional theory (DFT). The highly structured experimental spectra are in excellent agreement the electronic of states (DOS) DFT lowest energy structures. Even for largest sizes, a pronounced sensitivity DOS on fine geometric details could be observed, allowing reliable identification specific icosahedral growth motif. intermediate sizes between closed-shell Mackay...

Using full-dimensional EOM-IP-CCSD/aug-cc-pVTZ potential energy surfaces, the photoelectron spectrum, vibrational structure, and ionization dynamics of water dimer radical cation, (H2O)2+, were computed. We also report an experimental spectrum which is derived from photoionization efficiency measurements compares favorably with theoretical spectrum. The structure compared to recent work Gardenier et al. [J. Phys. Chem. A 113, 4772 (2009)] calculations by Cheng 13779 (2009)]....

We report a combined theoretical and experimental study of ionization cytosine monomers dimers. Gas-phase molecules are generated by thermal vaporization followed expansion the vapor in continuous supersonic jet seeded Ar. The resulting species investigated single photon with tunable vacuum-ultraviolet (VUV) synchrotron radiation mass analyzed using reflectron spectrometry. Energy onsets for measured photoionization efficiency (PIE) spectra 8.60 ± 0.05 eV 7.6 0.1 monomer dimer, respectively,...

In order to better understand the volatilization process for ionic liquids, vapor evolved from heating liquid 1-ethyl-3-methylimidazolium bromide (EMIM(+)Br(-)) was analyzed via tunable vacuum ultraviolet photoionization time-of-flight mass spectrometry (VUV-PI-TOFMS) and thermogravimetric analysis (TGA-MS). For this liquid, experimental results indicate that vaporization takes place evolution of alkyl bromides alkylimidazoles, presumably through abstraction an S(N)2 type mechanism, intact...

The hydrogen-abstraction/acetylene-addition (HACA) mechanism has been central for the last decades in attempting to rationalize formation of polycyclic aromatic hydrocarbons (PAHs) as detected carbonaceous meteorites such Murchison. Nevertheless, basic reaction mechanisms leading even simplest tricyclic PAHs like anthracene and phenanthrene are still elusive. Here, by exploring previously unknown chemistry ortho-biphenylyl radical with acetylene, we deliver compelling evidence on efficient...

Abstract Polycyclic aromatic hydrocarbons (PAHs) are omnipresent in the interstellar medium (ISM) and also carbonaceous meteorites (CM) such as Murchison. However, basic reaction routes leading to formation of even simplest PAH—naphthalene (C 10 H 8 )—via hydrogen‐abstraction/acetylene‐addition (HACA) mechanism still remain ambiguous. Here, by revealing uncharted fundamental chemistry styrenyl 7 ) ortho ‐vinylphenyl radicals )—key transient species HACA mechanism—with acetylene 2 ), we...

Tunable synchrotron radiation provides a universal yet selective scalpel to decipher molecular information in complex chemical systems when coupled mass spectrometry and X-ray spectroscopy. At the Chemical Dynamics Beamline, emanating from Advanced Light Source at Berkeley has been utilized by physical chemists physicists probe reactivity, energetics spectroscopy for over two decades. Emerging themes are study of growth mechanisms, solvation, electronic structure reactivity clusters,...

A heated SiC microtubular reactor has been used to decompose acetaldehyde and its isotopomers (CH3CDO, CD3CHO, CD3CDO). The pyrolysis experiments are carried out by passing a dilute mixture of (roughly 0.1%–1%) entrained in stream buffer gas (either He or Ar) through that is 2–3 cm long 1 mm diameter. Typical pressures the 50–200 Torr with tube wall temperature range 1200–1900 K. Characteristic residence times μs after which emerges as skimmed molecular beam at pressure approximately 10...

The reaction of the phenyl radical (C6H5) with molecular oxygen (O2) plays a central role in degradation poly- and monocyclic aromatic radicals combustion systems which would otherwise react fuel components to form polycyclic hydrocarbons (PAHs) eventually soot. Despite intense theoretical experimental scrutiny over half century, overall channels have not all been experimentally identified. Tunable vacuum ultraviolet photoionization conjunction simulating chemical reactor uniquely provides...

The pyrolysis of the benzyl radical has been studied in a set heated micro-reactors. A combination photoionization mass spectrometry (PIMS) and matrix isolation infrared (IR) spectroscopy used to identify decomposition products. Both bromide ethyl benzene have as precursors parent species, C6H5CH2, well isotopically labeled radicals: C6H5CD2, C6D5CH2, C6H513CH2. PIMS IR earliest products from as: C5H4=C=CH2, H atom, C5H4—C ≡ CH, C5H5, HCCCH2, HC CH. Pyrolysis C6H513CH2 radicals produces...

We have used a heated 2 cm × 1 mm SiC microtubular (μtubular) reactor to decompose acetaldehyde: CH3CHO + Δ → products. Thermal decomposition is followed at pressures of 75–150 Torr and temperatures up 1675 K, conditions that correspond residence times roughly 50–100 μs in the μtubular reactor. The acetaldehyde products are identified by two independent techniques: vacuum ultraviolet photoionization mass spectroscopy (PIMS) infrared (IR) absorption after isolation cryogenic matrix. Besides...

The combustion of fossil fuels forms polycyclic aromatic hydrocarbons (PAHs) composed five- and six- membered rings, such as indene (C9 H8 ), which are carcinogenic, mutagenic, deleterious to the environment. Indene, simplest PAH with single six-membered has been predicted theoretically be formed through reaction benzyl radicals acetylene. Benzyl found in significant concentrations flames, owing their highly stable resonantly stabilized free-radical character. We provide compelling...

The nitrogen bearing aromatic molecule pyridine (C₅H₅N) is revealed to form in high temperature environments simulating conditions carbon-rich circumstellar envelopes <italic>via</italic> the reaction of cyano vinyl radical with cyanide.

Nitrogen-substituted polycyclic aromatic hydrocarbons (NPAHs) have been proposed to play a key role in the astrochemical evolution of interstellar medium, yet formation mechanisms even their simplest prototypes—quinoline and isoquinoline—remain elusive. Here, we reveal novel concept that under high temperature conditions representing circumstellar envelopes carbon stars, (iso)quinoline can be synthesized via reaction pyridyl radicals with two acetylene molecules. The facile gas phase defines...