Neutral Parent Research Articles

Electronic structure and spectroscopic properties of some low-lying electronic states of neutral and ionic species CN and CN−

ABSTRACT The present work provides Potential Energy Curves (PECs) of both cyano radical CN and cyanide anion CN − up to the third asymptote of dissociation out of ab initio calculations. The [MRCI+Q] method is the level of theory used here and we have associated it with the Dunning basis set AV6Z (Augmented correlation-consistent polarised Valence sextet Zeta) for geometry optimisation of our systems. Electronic configurations of the states of the two species were explored and based on these configurations and the relative positions of the PECs of CN − against those of the neutral radical CN, stable and metastable states have been found and exhibited. The calculated electron affinity here that proves itself to be positive and the position of the X 1 Σ + state against its corresponding neutral parent state ( X 2 Σ + ) from which it derives led to confirm that this state is a long-lived and stable ground state of the cyanide anion CN − . Spectroscopic constants of both ground and low-lying excited states are calculated and exhibited in this work.

On the thermodynamic stability of polycations.

We present a simple approximation to estimate the largest charge that a given molecule can hold until fragmentation into smaller charged species becomes more energetically favorable. This approximation solely relies on the ionization potentials, electron affinities of the parent and fragment species, and also on the neutral parent's dissociation energy. By parameterizing these quantities, it is possible to obtain analytical phase diagrams of polycationic stability. We demonstrate the applicability of this approach by discussing the maximal charge dependence on the size of the molecular system. A numerical demonstration for linear polyenes, monocyclic annulenes, and helium clusters is provided.

Unveiling the Multielectron Acceptor Properties of π-Expanded Pyracylene: Reversible Boat to Chair Conversion.

In this work, the chemical reduction of a hybrid pyracylene-hexa-peri-hexabenzocoronene (HPH) nanographene was investigated with different alkali metals (Na, K, Rb) to reveal its remarkable multielectron acceptor abilities. The UV-vis and 1H NMR spectroscopy monitoring of the stepwise reduction reactions supports the existence of all intermediate reduction states up to the hexaanion for HPH. Tuning the experimental conditions enabled the synthesis of the HPH anions with gradually increasing reduction states (up to -5) isolated with different alkali metal ions as crystalline materials. The single-crystal X-ray diffraction structure analysis demonstrates that the highly negatively charged HPH anions (-4 and -5) exhibit a drastic geometry change from boat-shaped (observed in the neutral parent, mono- and dianions) to a chair conformation, which was proved to be fully reversible by NMR spectroscopy. DFT calculations show that this geometry change is induced by an enhanced interaction between the coordinated metal ions and negatively charged HPH core in the chair conformation.

Gauging the Aromatic, Antiaromatic, and Nonaromatic Character of the Dications and Dianions Derived from Fused Carbocyclic and Heterocyclic Compoundsǂ

AbstractDications and dianions derived from fused PAHs and hetero‐PAHs were investigated by means of DFT calculations. The electronic, energetic, and structural features of the singlet and triplet electronic states of these doubly charged species were computationally determined and compared with those of the corresponding neutral parent aromatic and heteroaromatic compounds. The aromatic, nonaromatic or antiaromatic character of the studied diions was evaluated via magnetic criteria, namely NICS and 1H NMR chemical shifts, and by the HOMA structural index. Linear correlations were revealed between the computed HOMO‐LUMO gaps and the magnetic parameters which could serve as a guiding tool in the modulation of molecular properties, and for designing new materials derived from this type of compounds.

Taming the parent oxoborane.

Despite recent advancements in the chemistry of multiply bound boron compounds, the laboratory isolation of the parent oxoborane moiety, HBO has long remained an unsolved and well-recognized challenge. The reaction of 6-SIDipp·BH3 [6-SIDipp = 1,3-di(2,6-diisopropylphenyl)tetrahydropyrimidine-2-ylidene] with GaCl3 afforded an unusual boron-gallium 3c-2e compound (1). The addition of water to 1 resulted in the release of H2 and the formation of a rare acid stabilized neutral parent oxoborane, LB(H)[double bond, length as m-dash]O (2). Crystallographic and density functional theory (DFT) analyses support the presence of a terminal B[double bond, length as m-dash]O double bond. Subsequent addition of another equivalent of water molecule led to hydrolysis of the B-H bond to the B-OH bond, but the 'B[double bond, length as m-dash]O' moiety remained intact, resulting in the formation of the hydroxy oxoborane compound (3), which can be classified as a monomeric form of metaboric acid.

Ab initio calculation of the potential energy curves and spectroscopic properties of low-lying electronic states of CH+ molecular cation

The combined use of the MRCI-SD(T) method with the cc-pV6Z basis set has enabled us to determine the potential energy curves of the molecular cation whose fundamental state lies above the corresponding state of its neutral parent at the dissociation limit. With the accurate potential energy curves thus obtained, we have calculated spectroscopic constants which show good agreement with the experimental and other theoretical values available in the literature. To account for perturbations where necessary, spin-orbit coupling effects have been introduced. An understanding of the polarity of studied in the various electronic states is made possible by calculating the dipole moments. In addition, transition dipole moments were computed prior to the obtention of molecular parameters such as oscillator strength, Einstein coefficients, radiative probabilities and Franck–Condon factors. Overall good accuracy is observed.

Collision integrals and viscosity coefficients of argon–carbon thermal plasmas: Comparison using different interaction potentials

The calculated values of collision integrals of the majority of binary interactions that can be involved in argon/carbon (Ar/C) plasmas are presented in this work. The studied plasmas are considered to be in local thermodynamic equilibrium, and calculations are performed from 1000 to 30 000 K. Computations have been carried out first for standard potentials and second for the Improved Lennard-Jones (ILJ) potential. In this paper, a clear and well detailed report is given for each methodology adopted to calculate the omega integrals, together with the main data needed to perform these computations. The obtained values of collision integrals have been compared with some data reported in the literature, and then, they are used to estimate the viscosity of two plasma systems, namely, pure argon and a mixture of argon and carbon (Ar/C). The calculation of viscosity coefficients is made on the basis of the Chapman–Enskog method and developed to the first approximation. The important contribution of the charge exchange process and its influence on the accuracy of the diffusion-type collision integrals of neutral–parent ion systems are emphasized. Although some discrepancies are observed, comparisons of our results with those of previously published studies show an overall satisfactory agreement in most of the cases. Our investigation of the data uncertainty further confirms the suggestion that the ILJ approach is an excellent candidate to provide collision integrals with acceptable accuracy when reliable experimental data or accurate theoretical calculations are unavailable. For that, all the necessary collision integrals needed to calculate reliable transport properties of the Ar/C plasma mixtures are reported in this work.

Examination of Neutral Intervals and Parent Scales in Persian Art Music: A Step toward the Standardization of the Musical System

Neutral intervals between minor and major intervals have been used in Persian/Iranian art music for centuries or even millennia. During the medieval era in the Muslim world, several scholars proposed ratios for the various intervals used in their recognized musical species and presented systematized parent scales. However, this did not result in unanimously accepted or standardized neutral interval sizes or fretting systems in practice, either in the past or in modern times. This article examines neutral intervals and parent scales in Persian art music in four sections. First, the neutral intervals according to the main medieval theorists of the Muslim world (specifically, from the eighth through the fifteenth centuries) are reviewed. Second, the opinions of several twentieth-century mu sicologists and their measured/proposed neutral intervals are critically examined. Third, several ratios for neutral seconds are considered based on different theoretical approach es, and a unique ratio, close to the current practice, is proposed. Finally, the arithmetic mean calculation method is directly applied to an 18-tone scale (for the fretting of a Persian tār/sitār) as an example of a standardized parent scale.

Hydrogen migration in triply charged acetylene.

We report on the direct experimental evidence of hydrogen migration in triply charged acetylene. The roaming hydrogen atom in a triply charged molecular ion is counter intuitive. The three body breakup channel C2H2 3+→H++C++CH+ is studied using the technique of recoil ion momentum spectroscopy. The triply charged ion was generated in collisions of the neutral parent with a slow highly charged Xe9+ ion. Three different dissociation pathways have been identified and separated, namely, concerted breakup in an acetylene configuration, concerted breakup in a vinylidene configuration, and sequential breakup via a [C2H]2+ intermediate, and the branching ratio for all three pathways are determined.

Synthesis and spectroscopic characterization of 3-(3,4-dimethoxyphenylethylamino)-methylidene-1,2,3,9-tetrahydropyrrolo[2,1-b]-quinazolin-9-one and crystal structure of its hydrochloride

The structure of 3-(3,4-dimethoxyphenylethylamino)-methylidene-1,2,3,9-tetrahydropyrrolo[2,1-b]-quinazolin-9-one hydrochloride was determined by single-crystal X-ray diffraction at 100 K. The compound crystallizes in the monoclinic space group Cc, with a = 4.7149(18), b = 30.075(12), c = 14.199(6) Å, β = 91.852(8)°, Z = 4, V = 2012.4(14) Å3. The crystallographic study revealed E configuration of the C11 = N9′ bond. Electrostatic interactions between the organic cation and the chloride anion and classical N-H…Cl hydrogen bonds stabilize this salt. A Hirshfeld surface analysis revealed that H···H, H···C/C···H, and H···O/O···H represent the most prominent Van-der-Waals contacts. For the neutral parent molecule, nuclear magnetic resonance spectroscopy in deuterated chloroform solution showed that two tautomeric forms coexist in 3:1 ratio.

Reactions of Photoionization-Induced CO-H2O Cluster: Direct Ab Initio Molecular Dynamics Study.

The hydrocarboxyl radical (HOCO) is an important species in combustion and astrochemistry because it is easily converted to CO2 after hydrogen reduction. In this study, the formation mechanism of the HOCO radical in a CO–H2O system was investigated by direct ab initio molecular dynamics calculations. Two reactions were examined for HOCO formation. First, the reaction dynamics of the CO–H2O cluster cation, following the ionization of the neutral parent cluster CO(H2O)n (n = 1–4), were investigated. Second, the bimolecular collision reaction between CO and (H2O)n+ was studied. In the ionization of the CO(H2O)n clusters (n = 3 and 4), proton transfer, expressed as CO(H2O)n+ → CO–(OH)H3O+(H2O)n–2, occurred within the (H2O)n+ cluster cation, and the HOCO radical was yielded as a product upon addition of CO and OH. This reaction proceeds under zero-point energy. Also, this radical was effectively formed from the collision reaction of CO with water cluster cation (H2O)n+, expressed as CO + OH(H3O+)(H2O)n–2 → HOCO–H3O+ + (H2O)n–2. If the intermolecular vibrational stretching mode is excited in the CO(H2O)n cluster (vibrational stretching between CO and the water cluster), the HOCO radical was detected after ionization when n = 2. The reaction mechanism was discussed based on the theoretical results.

“The parent trap”: gender stereotypes and parenting roles in an Australian parenting website

ABSTRACT Objective Gender role stereotypes play an important role in all areas of human development, and parents play a vital role in the formation and development of these stereotypes in children. Parents’ attitudes and beliefs about gender roles may be influenced by the parenting information and messages they receive. We aimed to determine the extent to which gender stereotypes and traditional parenting roles were portrayed in an officially endorsed online resource for parents of infants and toddlers. Method A quantitative content analysis of an Australian government supported parenting website was conducted. We explored the ways in which child and adult gender roles are represented. Specifically, we examined the frequency of stereotypical pronoun use, stereotypical content and implicit and explicit presentation. Method The website contains little evidence of child gender stereotypical portrayals, with approximately 6% of content gender-stereotypical and 3% counter-stereotypical. However, traditional parenting roles were more commonly referenced. Conclusions The direct addressal of fathers in specific “for dad” pages and use of neutral parent references (mostly “you”) throughout the website suggests an underlying assumption that mothers were accessing the website and therefore, information was tailored to mothers. By implicitly encouraging traditional parenting roles, traditional gender roles may be reinforced. KEY POINTS What is already known about this topic: (1) Gender role stereotypes are pervasive and influence child development. (2) Parents commonly seek guidance and information about raising children online and the information and messages they find serve as a potential source of influence on parents’ attitudes, beliefs and gender role stereotypes. (3) Little is known about how information about gender is communicated to parents online. What this topic adds: (1) Information presented to parents in a government supported website contains little evidence of child gender stereotypical portrayals. (2) Traditional parenting roles were more commonly referenced on the website. (3) Sections specifically addressed to fathers suggests website information was implicitlytargeted to mothers.

Hierarchical three-dimensionally ordered mesoporous carbon (3DOm) zeolite composites for the adsorption of Contaminants of emerging concern

Effective removal of contaminants of emerging concern (CECs) from water via adsorption requires adsorbent materials that showcase a synergistic combination of textural properties, hydrophobicity, and specific surface interactions. In this work, we present a hierarchical composite prepared on the basis of in-situ or confined growth of a faujasite zeolite (FAU) within the voids of a 3D mesoporous ordered carbon (3DOm). This adsorbent was tested for the removal of several CECs (i.e., caffeine, carbamazepine, naproxen and metabolites clofibric acid, 10,11-epoxy-carbamazepine, o-desmethyl naproxen, paraxanthine, and salicylic acid) from water at ambient conditions. Upon inclusion of copper(II) extra-framework cations, the hierarchical composite (Cu-3DOm-FAU) excelled at adsorbing ionic CECs and offered similar uptake capacity toward neutral parent compounds in both single- and multi-component fashion and while covering a μg L−1 - mg L−1 concentration range. Compared to other adsorbents reported so far in the literature, the Cu-3DOm-FAU composite adsorption capacities were larger, in many cases by at least one order of magnitude. Given the substantial thermal stability of the composite, regeneration could be accomplished via thermal cycling also depending on the type of CEC involved.

Estimating the maximal solubility advantage of drug salts

Salt formation can enable the development of poorly water-soluble drugs containing at least one ionizable moiety. Not only can salts offer a solubility enhancement that can sometimes far exceed that of other commonly used solubilization strategies applied across the pharmaceutical industry, they can simultaneously bestow additional benefits such as providing low-cost formulation options. The goal of this work is to put forth a simple methodology to enable one to accurately predict the maximal solubility advantage of acidic and basic drugs whose unionized conjugate (neutral parent molecule) is poorly soluble. While published equations leveraging the Henderson-Hasselbalch/H-H relationship reasonably estimate the thermodynamic solubility limit (in systems where there is no supersaturation), under physiologically relevant conditions the maximal/kinetic solubility can play an important role in determining oral bioavailability, as in the case of amorphous drugs. Under these circumstances, a higher solubility can be maintained for short durations through drug supersaturation provided that the precipitation is slow, thereby causing deviations from H-H predictions. It is possible also that, in some instances, supersaturation could coincide with behavior previously attributed to drug aggregation in solution. The proposed methodology utilizes speciation across the pH range to allow one to determine the maximal amount of ionized and unionized drug in solution at each pH. The calculation is easily extended to cases where the counterion serves as a competing weak acid, weak base, or as a common ion. Additionally, a more thorough assessment of the Gibbs free energy change associated with the solubilization of salts is also presented, as this energy describes the key driving force for the recrystallization of the neutral parent by triggering its nucleation. Lastly, to demonstrate applicability to real-world compounds containing multiple ionizable moieties, the complex pH-solubility profile of a drug maleate salt taken from the literature is simulated.

Proton Transfer Reaction Rates in Phenol-Ammonia Cluster Cation.

Proton transfer (PT) in an interaction system of a hydroxyl-amino group (OH-NH) plays a crucial role in photoinduced DNA and enzyme damage. A phenol-ammonia cluster is a prototype of an OH-NH interaction and is sometimes used as a DNA model. In the present study, the reaction dynamics of phenol-ammonia cluster cations, [PhOH-(NH3)n]+ (n = 1-5), following ionization of the neutral parent clusters, were investigated using a direct ab initio molecular dynamics (AIMD) method. In all clusters, PTs from PhOH+ to (NH3)n were found postionization, the reaction of which is expressed as PhOH+-(NH3)n → PhO-H+(NH3)n. The time of the PT was calculated as 43 (n = 1), 26 (n = 2), and 13 fs (n = 3-5), suggesting that the rate of PT increases with an increase in n and is saturated at n = 3-5. The difference in the PT rate originates strongly from the proton affinity of the (NH3)n cluster. In the case of n = 3-5, a second PT was found, the reaction of which is expressed as PhO-H+(NH3)n → PhO-NH3-H+(NH3)n-1, and a third PT occurred at n = 4 and 5. The time of the PT was calculated as 10-13 (first PT), 80-100 (second PT), and 150-200 fs (third PT) in the case of larger clusters (n = 4 and 5). The reaction mechanism based on the theoretical results is discussed herein.

Probing dark matter freeze-in with long-lived particle signatures: MATHUSLA, HL-LHC and FCC-hh

Collider searches for long-lived particles yield a promising avenue to probe the freeze-in production of Dark Matter via the decay of a parent particle. We analyze the prospects of probing the parameter space of Dark Matter freeze-in from the decay of neutral parent particles at the LHC and beyond, taking as a case study a freeze-in Dark Matter scenario via the Standard Model Higgs. We obtain the projected sensitivity of the proposed MATHUSLA surface detector (for MATHUSLA100 and MATHUSLA200 configurations) for long-lived particle searches to the freeze-in Dark Matter parameter space, and study its complementarity to searches by ATLAS and CMS at HL-LHC, as well as the interplay with constraints from Cosmology: Big-Bang Nucleosynthesis and Lyman-α forest observations. We then analyze the improvement in sensitivity that would come from a forward detector within a future 100 TeV pp-collider. In addition, we discuss several technical aspects of the present Dark Matter freeze-in scenario: the role of the electroweak phase transition; the inclusion of thermal masses, which have been previously disregarded in freeze-in from decay studies; the impact of 2 → 2 scattering processes on the Dark Matter relic abundance; and the interplay between freeze-in and super-WIMP Dark Matter production mechanisms.

Angular distribution in two-body dissociation of

SynopsisThe two-body dissociation of multiply charged SO2 molecules is studied using a recoil ion momentum spectrometer. These molecular ions were generated in collision of the neutral parent with an energetic highly charged ion. From the measured momenta of the recoil ions, angular distributions are generated with respect to the incoming beam direction and are found to vary strongly with kinetic energy release.

Ammonium Salts as a Source of Small Molecules Observed with High-Resolution Electron-Impact Ionization Mass Spectrometry.

Recent high-resolution in situ mass spectrometry at comet 67P/Churyumov-Gerasimenko visited by European Space Agency's Rosetta spacecraft raised the question, if sublimating ammonium salts can unequivocally be detected in the cometary coma. In laboratory experiments with the twin model of the space instrument, two prototypic ammonium salts NH4B, namely, ammonium chloride (B = Cl-) and ammonium formate (B = HCOO-) (as well as methodologically relevant isotopologues), were allowed to sublimate in vacuum while mass spectra were collected. High-resolution electron-impact ionization mass spectrometry provides an outstanding experimental tool to investigate the complex physicochemical processes occurring during the sublimation of ammonium salts. Sublimation of ammonium chloride led to the observation of the ammonium cation NH4+ and the chloramide molecule NH2Cl in the neutral gas mode of the instrument. These observations could be jointly interpreted as indirect evidence for the existence of a neutral gaseous parent species (either as the molecular complex NH3···HB or the double-ionic species NH4+···B-). However, the qualitative fragmentation pattern we present for 13C15N-ammonium formate suggests an alternative route of NH4+ production within the ionization region of the instrument, namely, by protonation/hydrogenation. Besides NH4+, other species were observed that were formed in protonation/hydrogenation reactions. Moreover, together with the two major species from the decomposition of the salt, ammonia and formic acid, three minor species also contributed to the fragmentation pattern: HCN/HNC, HOCN/HNCO, and CH3NO. Like chloramide, formamide (CH3NO) also is a secondary species probably formed in a pseudo-intramolecular chemical reaction while ammonia and the respective acid are in a state of association. HCN/HNC and HOCN/HNCO are ternary products coming out of formamide decomposition reactions. We discuss our experimental findings, summarized in a tentative chemical reaction network, in light of the available theoretical literature and highlight their relevance for the interpretation of in situ measurements in space research.

Reactions of aliphatic amines with ozone: Kinetics and mechanisms

Aliphatic amines are common constituents in micropollutants and dissolved organic matter and present in elevated concentrations in wastewater-impacted source waters. Due to high reactivity, reactions of aliphatic amines with ozone are likely to occur during ozonation in water and wastewater treatment. We investigated the kinetics and mechanisms of the reactions of ozone with ethylamine, diethylamine, and triethylamine as model nitrogenous compounds. Species-specific second-order rate constants for the neutral parent amines ranged from 9.3 × 104 to 2.2 × 106 M−1s−1 and the apparent second-order rate constants at pH 7 for potential or identified transformation products were 6.8 × 105 M−1s−1 for N,N-diethylhydroxylamine, ∼105 M−1s−1 for N-ethylhydroxylamine, 1.9 × 103 M−1s−1 for N-ethylethanimine oxide, and 3.4 M−1s−1 for nitroethane. Product analyses revealed that all amines were transformed to products containing a nitrogen-oxygen bond (e.g., triethylamine N-oxide and nitroethane) with high yields, i.e., 64–100% with regard to the abated target amines. These findings could be confirmed by measurements of singlet oxygen and hydroxyl radical which are formed during the amine-ozone reactions. Based on the high yields of nitroethane from ethylamine and diethylamine, a significant formation of nitroalkanes can be expected during ozonation of waters containing high levels of dissolved organic nitrogen, as expected in wastewaters or wastewater-impaired source waters. This may pose adverse effects on the aquatic environment and human health.

Electron-Induced Formation of Ethyl Methyl Ether in Condensed Mixtures of Methanol and Ethylene.

Electron-induced reactions in condensed mixtures of ethylene (C2H4) and methanol (CH3OH) lead to the formation of ethyl methyl ether (EME, C2H5OCH3), as shown by post-irradiation thermal desorption spectrometry (TDS). In contrast to the electron-induced reaction between water (H2O) and C2H4, product formation as a consequence of proton transfer following electron attachment (EA) to C2H4 is not observed in the analogous reaction between CH3OH and C2H4. However, a resonant process centered around 5.5 eV and a threshold-type increase of product yield starting at 9 eV is observed. On the basis of the presence and absence of particular side products after irradiation of the mixture as well as of the pure parent compounds, reaction mechanisms related to the two energy regimes are proposed. Below the ionization threshold of the reactants, dissociative electron attachment (DEA) to CH3OH triggers the reaction sequence by producing reactive methoxy radicals, which attack neighboring C2H4 molecules. The resulting adduct then abstracts a hydrogen atom to yield EME. Above but near the ionization threshold, electron impact ionization (EI) produces primarily intact molecular cations, which drive the reaction by converting the repulsive Coulomb force between the high electron densities at the reactive sites of the two neutral parent species into an attractive force. This again induces the formation of an adduct between the two reactants that rearranges to the product EME. Fragmentation of the molecular CH3OH+• cation into CH3O+, however, may provide an additional reaction pathway toward EME. In this scenario, CH3O+ attacks a neighboring C2H4 molecule. The resulting adduct is then neutralized by a thermalized electron and abstracts a hydrogen atom from a nearby CH3OH molecule to yield EME.