Computed Rotational Collision Rate Coefficients for Recently Detected Anionic Cyanopolyynes

We report new results from quantum calculations of energy-transfer processes taking place in interstellar environments and involving two newly observed molecular species: C$_5$N$^-$ and C$_7$N$^-$ in collision with He atoms and the p-H$_2$ molecules. These species are part of the anionic molecular chains labeled as cyanopolyynes which have been observed over the years in molecule-rich Circumstellar Envelopes and in molecular clouds. In the present work, we first carry out new $ab$ $initio$ calculations for the C$_7$N$^-$ interaction potential with He atom and then obtain state-to-state rotationally inelastic cross sections and rate coefficients involving the same transitions which have been observed experimentally by emission in the interstellar medium (ISM) from both of these linear species. For the C$_5$N$^-$/He system we extend the calculations already published in our earlier work (see reference below) to compare more directly the two molecular anions. We extend further the quantum calculations by also computing in this work collision rate coefficients for the hydrogen molecule interacting with C5N$^-$, using our previously computed interaction potential. Additionally, we obtain the same rate coefficients for the C$_7$N$^-$/H$_2$ system by using a scaling procedure that makes use of the new C$_7$N$^-$/He rate coefficients, as discussed in detail in the present paper. Their significance in affecting internal state populations in ISM environments where the title anions have been found is analyzed by using the concept of critical density indicators. Finally, similarities and differences between such species and the comparative efficiency of their collision rate coefficients are discussed. These new calculations suggest that, at least for the case of these longer chains, the rotational populations could reach local thermal equilibrium conditions within their observational environments

Brand champion behaviour: Its role in corporate branding

yesBrand champions are responsible for encouraging employee commitment to the corporate brand strategy. They strongly believe in and identify with the brand concept—the company’s selected brand meaning, which underpins corporate brand strategy implementation. We conducted research to explore why and how brand champion behaviour operates within companies implementing a new corporate brand strategy. Against a backdrop of growing interest in brand champion behaviour in corporate branding research, we grounded our study in social identity theory and rhetorical theory from change management literature. Our findings show that articulating a compelling brand vision, taking responsibility, and getting the right people involved are the most widely used strategies by brand champions. We uncover how rhetorical strategies within brand champion behaviour generate employee commitment to a new corporate brand strategy. The dimension of brand champion behaviour that is effective depends on the type of brand evolution, involving shifts in the brand concept. We make suggestions for further studies underpinned by social identity theory and rhetorical theory to investigate brand champion behaviour processes within companies introducing a new corporate brand strategy

Dynamical effects on the O(3P) + D2 reaction and its impact on the Λ-doublet population

11 pags., 9 figs. -- This article is part of the themed collection: Molecular Dynamics in the Gas PhaseThe O(P) + D → OD(Π) + D reaction presents the peculiarity of taking place on two different potential energy surfaces (PESs) of different symmetry, A′ and A′′, which become degenerate for collinear configurations where the saddle-point of the reaction is located. The degeneracy is broken for non-collinear approaches with the energy on the A′ PES rising more abruptly with the bending angle, making the frequency of this mode higher on the A′ state. Consequently, the A′ PES should be less reactive than the A′′ one. Nevertheless, quantum scattering calculations show that the cross section is higher on the A′ PES for energies close to the classical reaction threshold and rotationless reactant. It is found that the differences between the reactivity on the two PESs are greater for low values of total angular momentum, where the centrifugal barrier is lower and contribute to the higher population of the Π(A′) Λ-doublet states of OD at low collision energies. At high collision energies, the Π(A′) Λ-doublet state is also preferentially populated. Analysis of the differential cross sections reveals that the preponderance for the Π(A′) Λ-doublet at low energies comes from backward scattering, originating from the reaction on the A′ PES, while at high energies, it proceeds from a different mechanism that leads to sideways scattering on the A′′ PES and that populates the Π(A′) manifold.The authors gratefully acknowledge grant PID2020-113147GA-I00, PID2021-122839NB-I00, PID2019-107115GB-C21 and PID2021-122549NB-C21 funded by Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/MCIN/AEI/10.13039/501100011033)

Quantum study of reaction O (

The reaction between atomic oxygen and molecular hydrogen is an important one in astrochemistry as it regulates the abundance of the hydroxyl radical and serves to open the chemistry of oxygen in diverse astronomical environments. However, the existence of a high activation barrier in the reaction with ground-state oxygen atoms limits its efficiency in cold gas. In this study we calculated the dependence of the reaction rate coefficient on the rotational and vibrational state of H2, and evaluated the impact on the abundance of OH in interstellar regions strongly irradiated by far-UV photons where H2 can be efficiently pumped to excited vibrational states. We used a recently calculated potential energy surface and carried out time-independent quantum mechanical scattering calculations to compute rate coefficients for the reaction O (3P) + H2 (v, j) → OH + H, with H2 in vibrational states v = 0–7 and rotational states j = 0–10. We find that the reaction becomes significantly faster with increasing vibrational quantum number of H2. However, even for high vibrational states of H2 (v = 4–5), for which the reaction is barrierless, the rate coefficient does not strictly attain the collision limit and still maintains a positive dependence with temperature. We implemented the calculated state-specific rate coefficients in the Meudon PDR code to model the Orion Bar PDR and to evaluate the impact on the abundance of the OH radical. We find the fractional abundance of OH is enhanced by up to one order of magnitude in regions of the cloud corresponding to AV = 1.3–2.3 mag, compared to the use of a thermal rate coefficient for O + H2, although the impact on the column density of OH is modest, about 60%. The calculated rate coefficients will be useful to model and interpret JWST observations of OH in strongly UV-illuminated environments

Multi- and single-reference methods for the analysis of multi-state peroxidation of enolates

9 pags., 6 figs., 2 tabs.In spite of being spin-forbidden, some enzymes are capable of catalyzing the incorporation of O2(ςg-3) to organic substrates without needing any cofactor. It has been established that the process followed by these enzymes starts with the deprotonation of the substrate forming an enolate. In a second stage, the peroxidation of the enolate formation occurs, a process in which the system changes its spin multiplicity from a triplet state to a singlet state. In this article, we study the addition of O2 to enolates using state-of-the-art multi-reference and single-reference methods. Our results confirm that intersystem crossing is promoted by stabilization of the singlet state along the reaction path. When multi-reference methods are used, large active spaces are required, and in this situation, semistochastic heat-bath configuration interaction emerges as a powerful method to study these multi-configurational systems and is in good agreement with PNO-LCCSD(T) when the system is well-represented by a single-configuration.Funding by the Spanish Ministry of Science and Innovation (Grant Nos. FIS2017-83473-C2-P, PID2019-107115GB-C21, and PGC2018-096444-B-I00) is acknowledged. P.O. acknowledges Grant No. EDU/601/2020 (Junta de Castilla y León and European Social Fund) and thank James E. T. Smith for his practical hints and helpful comments on the PySCF code. The authors acknowledge funding by the Fundación Salamanca City of Culture and Knowledge (program for attracting scientific talent to Salamanca). The authors thank Dr. M. Mandado from the University of Vigo for kindly providing the NDELOC code used to calculate the electron density descriptor

Quantum study of reaction O (3P) + H2(v,j) → OH + H: OH formation in strongly UV-irradiated gas

13 pags., 3 figs., 1 tab.The reaction between atomic oxygen and molecular hydrogen is an important one in astrochemistry as it regulates the abundance of the hydroxyl radical and serves to open the chemistry of oxygen in diverse astronomical environments. However, the existence of a high activation barrier in the reaction with ground-state oxygen atoms limits its efficiency in cold gas. In this study we calculated the dependence of the reaction rate coefficient on the rotational and vibrational state of H2, and evaluated the impact on the abundance of OH in interstellar regions strongly irradiated by far-UV photons where H2 can be efficiently pumped to excited vibrational states. We used a recently calculated potential energy surface and carried out time-independent quantum mechanical scattering calculations to compute rate coefficients for the reaction O (3P) + H2 (v, j) → OH + H, with H2 in vibrational states v = 0-7 and rotational states j = 0-10. We find that the reaction becomes significantly faster with increasing vibrational quantum number of H2. However, even for high vibrational states of H2 (v = 4-5), for which the reaction is barrierless, the rate coefficient does not strictly attain the collision limit and still maintains a positive dependence with temperature. We implemented the calculated state-specific rate coefficients in the Meudon PDR code to model the Orion Bar PDR and to evaluate the impact on the abundance of the OH radical. We find the fractional abundance of OH is enhanced by up to one order of magnitude in regions of the cloud corresponding to AV = 1.3-2.3 mag, compared to the use of a thermal rate coefficient for O + H2, although the impact on the column density of OH is modest, about 60%. The calculated rate coefficients will be useful to model and interpret JWST observations of OH in strongly UV-illuminated environments.We acknowledge the Spanish Ministerio de Ciencia e Innovación for funding support through the projects AYA2016-75066-C2-1-P, FIS2017-83473-C2, PGC2018-096444-B-I00, PID2019-106110GB-I00, and PID2019-107115GB-C21. A.V. and P.G.J. acknowledge funding by Fundación Salamanca City of Culture and Knowledge (programme for attracting scientific talent to Salamanca). M.A. also acknowledges funding support from the Ramón y Cajal programme of Spanish Ministerio de Ciencia e Innovación (grant RyC-2014-16277)

Multi- and single-reference methods for the analysis of multi-state peroxidation of enolates

[EN]In spite of being spin-forbidden, some enzymes are capable of catalyzing the incorporation of O2(Σg−3Σg−3) to organic substrates without needing any cofactor. It has been established that the process followed by these enzymes starts with the deprotonation of the substrate forming an enolate. In a second stage, the peroxidation of the enolate formation occurs, a process in which the system changes its spin multiplicity from a triplet state to a singlet state. In this article, we study the addition of O2 to enolates using state-of-the-art multi-reference and single-reference methods. Our results confirm that intersystem crossing is promoted by stabilization of the singlet state along the reaction path. When multi-reference methods are used, large active spaces are required, and in this situation, semistochastic heat-bath configuration interaction emerges as a powerful method to study these multi-configurational systems and is in good agreement with PNO-LCCSD(T) when the system is well-represented by a single-configuration

Computed Rotational Collision Rate Coefficients for Recently Detected Anionic Cyanopolyynes

We report new results from quantum calculations of energy-transfer processes taking place in interstellar environments and involving two newly observed molecular species: C _5 N ^− and C _7 N ^− in collision with He atoms and p–H _2 molecules. These species are part of the anionic molecular chains labeled as cyanopolyynes, which have been observed over the years in molecule-rich circumstellar envelopes and in molecular clouds. In the present work, we first carry out new ab initio calculations for the C _7 N ^− interaction potential with He atoms and then obtain state-to-state rotationally inelastic cross sections and rate coefficients involving the same transitions, which have been observed experimentally by emission in the interstellar medium (ISM) from both of these linear species. For the C _5 N ^− /He system, we extend the calculations already published in Biwas et al. to compare more directly the two molecular anions. We extend further the quantum calculations by also computing in this work collision rate coefficients for the hydrogen molecule interacting with C _5 N ^− , using our previously computed interaction potential. Additionally, we obtain the same rate coefficients for the C _7 N ^− /H _2 system by using a scaling procedure that makes use of the new C _7 N ^− /He rate coefficients, as discussed in detail in the present paper. Their significance in affecting internal state populations in ISM environments where the anionic cyanopolyynes have been found is analyzed by using the concept of critical density indicators. Finally, similarities and differences between such species and the comparative efficiency of their collision rate coefficients are discussed. These new calculations suggest that, at least for the case of these longer chains, the rotational populations could reach local thermal equilibrium conditions within their observational environments