scholarly journals The effect of CO−H2O collisions in the rotational excitation of cometary CO

2020 ◽  
Vol 493 (1) ◽  
pp. 776-782 ◽  
Author(s):  
A Faure ◽  
F Lique ◽  
J Loreau
Keyword(s):  
Radiative Decay ◽  
Energy Surface ◽  
Population Distribution ◽  
Rate Coefficients ◽  
Intermolecular Potential ◽  
Kinetic Temperature ◽  
Rotational Excitation ◽  
Rotational Distribution ◽  
High Level ◽  
The Impact

ABSTRACT We present the first accurate rate coefficients for the rotational excitation of CO by H2O in the kinetic temperature range 5–100 K. The statistical adiabatic channel method (SACM) is combined with a high-level rigid-rotor CO−H2O intermolecular potential energy surface. Transitions among the first 11 rotational levels of CO and the first 8 rotational levels of both para-H2O and ortho-H2O are considered. Our rate coefficients are compared to previous data from the literature and they are also incorporated in a simple non-LTE model of cometary coma including collision-induced transitions, solar radiative pumping and radiative decay. We find that the uncertainties in the collision data have significant influence on the CO population distribution for H2O densities in the range 103–108 cm−3. We also show that the rotational distribution of H2O plays an important role in CO excitation (owing to correlated energy transfer in both CO and H2O), while the impact of the ortho-to-para ratio of H2O is found to be negligible.

Electron-impact rotational excitation of : relevance for thermalization and dissociation dynamics

2006 ◽  
Vol 364 (1848) ◽  
pp. 3113-3120 ◽  
Author(s):  
Alexandre Faure ◽  
Laurent Wiesenfeld ◽  
Pierre Valiron ◽  
Jonathan Tennyson
Keyword(s):  
Dissociative Recombination ◽  
Molecular Ions ◽  
Rate Coefficients ◽  
Galactic Centre ◽  
Low Density ◽  
Rotational Excitation ◽  
Astrophysical Plasmas ◽  
Electron Collisions ◽  
Dissociation Dynamics ◽  
Rotational Distribution

Electrons are known to be efficient in rotationally exciting molecular ions in low-density astrophysical plasmas. Rotational excitation of molecular ions has also been shown to affect the measured values of dissociative recombination (DR) rate coefficients. Thus, electron collisions with are expected to play a significant role in thermalization and dissociation dynamics of this ion, both in the laboratory and in space. Using the molecular R -matrix method combined with the adiabatic-nuclei-rotation approximation, we have computed new rate coefficients for the rotational excitation of by electrons at temperatures from 10 to 10 000 K. De-excitation rates are found to amount to a few 10 −7  cm 3  s −1 below 1000 K, i.e. comparable in magnitude to that of DR. In astrophysical environments where the electron fraction exceeds 10 −4 , electron collisions are thus expected to contribute to the non-thermal rotational distribution of . The competition between electron and neutral collisions is discussed in the context of recent observations of towards Galactic centre sources.

Rotational excitation of HNCO by He: potential energy surface, collisional cross-sections and rate coefficients

2017 ◽  
Vol 471 (1) ◽  
pp. 80-88 ◽  
Author(s):  
E. Sahnoun ◽  
Y. Ajili ◽  
K. Hammami ◽  
N.-E. Jaidane ◽  
M. Mogren Al Mogren ◽  
...  
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Cross Sections ◽  
Energy Surface ◽  
Rate Coefficients ◽  
Rotational Excitation

scholarly journals Probing the rate-determining region of the potential energy surface for a prototypical ion–molecule reaction

2018 ◽  
Vol 376 (2115) ◽  
pp. 20170146 ◽  
Author(s):  
Changjian Xie ◽  
Xinguo Liu ◽  
Brendan C. Sweeny ◽  
Thomas M. Miller ◽  
Shaun G. Ard ◽  
...  
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Classical Trajectory ◽  
Rate Coefficients ◽  
Molecule Reaction ◽  
Induced Dipole ◽  
Phase Space Theory ◽  
Selected Ion Flow Tube ◽  
High Level

We report a joint experimental–theoretical study of the F –  + HCl → HF + Cl − reaction kinetics. The experimental measurement of the rate coefficient at several temperatures was made using the selected ion flow tube method. Theoretical rate coefficients are calculated using the quasi-classical trajectory method on a newly developed global potential energy surface, obtained by fitting a large number of high-level ab initio points with augmentation of long-range electrostatic terms. In addition to good agreement between experiment and theory, analyses suggest that the ion–molecule reaction rate is significantly affected by shorter-range interactions, in addition to the traditionally recognized ion–dipole and ion–induced dipole terms. Furthermore, the statistical nature of the reaction is assessed by comparing the measured and calculated HF product vibrational state distributions to that predicted by the phase space theory. This article is part of the theme issue ‘Modern theoretical chemistry’.

Comparison of approximate intermolecular potentials for ab initio fragment calculations on medium sized N-heterocycles

2021 ◽  
Author(s):  
Bónis Barcza ◽  
Ádám B. Szirmai ◽  
Katalin J. Szántó ◽  
Attila Tajti ◽  
Péter G. Szalay
Keyword(s):  
Ab Initio ◽  
Ground State ◽  
Energy Surface ◽  
Intermolecular Potential ◽  
Intermolecular Potentials ◽  
Long Distance ◽  
Pauli Repulsion ◽  
Dispersion Terms ◽  
The Impact ◽  
Good Agreement

The ground state intermolecular potential of bimolecular complexes of N-heterocycles is analysed for the impact of different terms of the interaction energy as provided by various, conceptually different theories. Novel combinations with several formulations of the electrostatic, Pauli repulsion, dispersion and other contributions are tested for a good performance at both short- and long-distance sides of the potential energy surface for various alignments of the pyrrole dimer as well as the cytosine-uracil complex. The integration of a DFT/CC density embedding scheme and dispersion terms from the effective fragment potential (EFP) method is found to provide very good agreement with the reference CCSD(T) potential overall, but a QM/MM approach using CHELPG atomic point charges for the electrostatic interaction augmented by EFP dispersion and Pauli repulsion contributions comes also close. Both of these schemes has the advantage of not relying on predefined force fields, rather the interaction parameters can be obtained for the system under study, therefore excellent candidates for ab initio modeling.

scholarly journals Chemical loss processes of isocyanic acid, HNCO, in the atmosphere

2020 ◽  
Author(s):  
Simon Rosanka ◽  
Giang H. T. Vu ◽  
Hue M. T. Nguyen ◽  
Tien V. Pham ◽  
Umar Javed ◽  
...  
Keyword(s):  
Potential Energy Surfaces ◽  
Deep Convection ◽  
Rate Coefficients ◽  
Isocyanic Acid ◽  
Free Troposphere ◽  
Atmospheric Conditions ◽  
Kinetic Predictions ◽  
High Level ◽  
Energy Surfaces ◽  
The Impact

Abstract. The impact of chemical loss processes of isocyanic acid was studied by a combined theoretical and modeling study. The potential energy surfaces of the reactions of HNCO with OH and NO3 radicals, Cl atoms, and ozone, were studied using high-level CCSD(T)/CBS(DTQ)//M06-2X/aug-cc-pVTZ quantum chemical methodologies, followed by TST theoretical kinetic predictions of the rate coefficients at temperatures of 200–3000 K. It was found that the reactions are all slow in atmospheric conditions, with k(300 K) ≤ 7 × 10−16 cm3 molecule−1 s−1; the predictions are in good agreement with earlier experimental work, where available. The reverse reactions of NCO radicals, of importance mostly in combustion, were also examined briefly. The global model confirms that gas phase chemical loss of HNCO is a negligible process, contributing less than 1 %. Removal of HNCO by clouds and precipitation is a larger sink, contributing for about 10 % of the total loss, while globally dry deposition is the main sink, accounting for ~ 90 %. The global simulation also shows that due to its long chemical lifetime in the free troposphere, HNCO can be efficiently transported into the UTLS by deep convection events. Average daily concentrations of HNCO are found to rarely exceed levels considered potentially toxic, though locally instantaneous toxic levels are expected.the free troposphere, HNCO can be efficiently transported into the UTLS by deep convection events. Average daily concentrations of HNCO are found to rarely exceed levels considered potentially toxic, though locally instantaneous toxic levels are expected.

scholarly journals Comparison of approximate intermolecular potentials for ab initio fragment calculations on medium sized N-heterocycles

2021 ◽  
Author(s):  
Bónis Barcza ◽  
Ádám B. Szirmai ◽  
Katalin J. Szántó ◽  
Attila Tajti ◽  
Péter G. Szalay
Keyword(s):  
Ab Initio ◽  
Ground State ◽  
Energy Surface ◽  
Intermolecular Potential ◽  
Intermolecular Potentials ◽  
Long Distance ◽  
Pauli Repulsion ◽  
Dispersion Terms ◽  
The Impact ◽  
Good Agreement

The ground state intermolecular potential of bimolecular complexes of N-heterocycles is analysed for the impact of different terms of the interaction energy as provided by various, conceptually different theories. Novel combinations with several formulations of the electrostatic, Pauli repulsion, dispersion and other contributions are tested for a good performance at both short- and long-distance sides of the potential energy surface for various alignments of the pyrrole dimer as well as the cytosine-uracil complex. The integration of a DFT/CC density embedding scheme and dispersion terms from the effective fragment potential (EFP) method is found to provide very good agreement with the reference CCSD(T) potential overall, but a QM/MM approach using CHELPG atomic point charges for the electrostatic interaction augmented by EFP dispersion and Pauli repulsion contributions comes also close. Both of these schemes has the advantage of not relying on predefined force fields, rather the interaction parameters can be obtained for the system under study, therefore excellent candidates for ab initio modeling.

ПРАГМАТИЧНИЙ ПОТЕНЦІАЛ НАТИВНОЇ РЕКЛАМИ: ФОРМИ, ТРЕНДИ (НА ПРИКЛАДІ НАТИВНОГО КОНТЕНТУ В СОЦІАЛЬНІЙ МЕРЕЖІ FACEBOOK ЩОДО БРЕНДА ФАКУЛЬТЕТУ ЖУРНАЛІСТИКИ ЗНУ)

2020 ◽  
pp. 113
Author(s):  
V. Kovpak ◽  
N. Trotsenko
Keyword(s):  
Social Network ◽  
Professional Training ◽  
Educational Process ◽  
Communication Strategy ◽  
Student Centered ◽  
Teacher Student ◽  
The Social ◽  
National University ◽  
High Level ◽  
The Impact

<div><p><em>The article analyzes the peculiarities of the format of native advertising in the media space, its pragmatic potential (in particular, on the example of native content in the social network Facebook by the brand of the journalism department of ZNU), highlights the types and trends of native advertising. The following research methods were used to achieve the purpose of intelligence: descriptive (content content, including various examples), comparative (content presentation options) and typological (types, trends of native advertising, in particular, cross-media as an opportunity to submit content in different formats (video, audio, photos, text, infographics, etc.)), content analysis method using Internet services (using Popsters service). And the native code for analytics was the page of the journalism department of Zaporizhzhya National University on the social network Facebook. After all, the brand of the journalism department of Zaporozhye National University in 2019 celebrates its 15th anniversary. The brand vector is its value component and professional training with balanced distribution of theoretical and practical blocks (seven practices), student-centered (democratic interaction and high-level teacher-student dialogue) and integration into Ukrainian and world educational process (participation in grant programs).</em></p></div><p><em>And advertising on social networks is also a kind of native content, which does not appear in special blocks, and is organically inscribed on one page or another and unobtrusively offers, just remembering the product as if «to the word». Popsters service functionality, which evaluates an account (or linked accounts of one person) for 35 parameters, but the main three areas: reach or influence, or how many users evaluate, comment on the recording; true reach – the number of people affected; network score – an assessment of the audience’s response to the impact, or how far the network information diverges (how many share information on this page).</em></p><p><strong><em>Key words:</em></strong><em> nativeness, native advertising, branded content, special project, communication strategy.</em></p>

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