Trapping effects on the vibration-inversion-rotation motions of an ammonia molecule encapsulated in C60_{60} fullerene molecule

The infrared bar-spectrum of a single ammonia molecule encapsulated in nano-cage C$_{60}$ fullerene molecule is modelled using the site inclusion model successfully applied to analyze spectra of CO$_2$ isotopologues isolated in rare gas matrix. Calculations show that NH$_3$ can rotate freely on a sphere of radius 0.184 $\text{\AA}$ around the site centre of the nano-cage and spin freely about its C$_3$ symmetry axis. In the static field inside the cage degenerate $\nu_3$ and $\nu_4$ vibrational modes are blue shifted and split. When dynamic coupling with translational motion is considered, the spectral signature of the $\nu_2$ mode is modified with a higher hindering barrier (2451 cm$^{-1}$), an effective reduced mass (6.569 g.mol$^{-1}$) and a longer tunneling time (55594 ps) for the fundamental level compared to gas-phase values (2047 cm$^{-1}$), (2.563 g.mol$^{-1}$) and (20.85 ps). As a result this mode is red shifted. Moreover, simulation shows that the changes in the bar-spectrum of the latter mode can be used to probe the temperature of the surrounding media in which fullerene is observed

Van't Hoff law for temperature dependent Langmuir constants in clathrate hydrate nanocavities

This work gives a van't Hoff law expression of Langmuir constants of different species for determining their occupancy in the nanocavities of clathrate hydrates. The van't Hoff law's parameters are derived from a fit with Langmuir constants calculated using a pairwise site-site interaction potential to model the anisotropic potential environment in the cavities, as a function of temperature. The parameters can be used for calculating clathrates compositions. Results are given for nineteen gas species trapped in the small and large cavities of structure types I and II [1]. The accuracy of this approach is based on a comparison with available experimental data for ethane and cyclo- propane clathrate hydrates. The numerical method applied in this work, was recently validated from a comparison with the spherical cell method based on analytical considerations [1]Comment: 2 figure

Investigation of the interaction of some astrobiological molecules with the surface of a graphite (0001) substrate. Application to the CO, HCN, H2O and H2CO molecules

Detailed semi-empirical interaction potential calculations are performed to determine the potential energy surface experienced by the molecules CO, HCN, H2O and H2CO, when adsorbed on the basal plane (0001) of graphite at low temperature. The potential energy surface is used to find the equilibrium site and configuration of a molecule on the surface and its corresponding adsorption energy. The diffusion constant associated with molecular surface diffusion is calculated for each molecule.Comment: 15 pages, 3 figure

Etude théorique de la molécule d'ammoniac piégée en matrice : Interactions, mouvements et phénomènes relaxationnels

A theorical study of the dynamics and the relaxation of a symmetric top molecule (ammonia) trapped in a rare gas of nitrogen matrix is performed to interpret experimental results recorded from high-resolution infrared spectrocopy and double-resonance spectroscopyCe travail est une étude théorique de la dynamique d'une molécule toupie symétrique piégée dans une matrice de gaz rare ou d'azote à basse température. Il s'agit d'interpréter les résultats expérimentaux récents obtenus, en spectroscopie infrarouge haute résolution et en double résonance, sur la bande v2 de vibration-inversion de l'ammoniac isolée dans le cristal

Preface

International audienceThis book is dedicated to the application of the different theoretical models described in Volume 1 to identify the near-, mid- and far-infrared spectra of linear and nonlinear triatomic molecules in gaseous phase or subjected to environmental constraints, useful for the study of environmental sciences, planetology and astrophysics.The Van Vleck contact transformation method, described in Volume 1, is applied in the calculation and analysis of IR transitions between vibration–rotation energy levels. The extended Lakhlifi–Dahoo substitution model is used in the framework of Liouville’s formalism and the line profiles of triatomic molecules and their isotopologues subjected to environmental constraints are calculated by applying the cumulant expansion.The applications presented in this book show how interactions at the molecular level modify the infrared spectra of triatomics trapped in a nano-cage (substitution site of a rare gas matrix, clathrate, fullerene, zeolite) or adsorbed on a surface, and how these interactions may be used to identify the characteristics of the perturbing environment

Spectroscopie infrarouge de molécules triatomiques pour l’observation spatiale, Volume 2

International audienceCet ouvrage est dédié à l’application des différents modèles théoriques pour identifier les spectres IR proche, moyen et lointain de molécules triatomiques, linéaires ou non linéaires, en phase gazeuse ou soumises à des contraintes environnementales, utiles aux sciences de l’environnement, la planétologie et l’astrophysique.La méthode de transformation de contact de Van Vleck est appliquée dans le calcul et l’analyse des transitions IR entre les niveaux d’énergie de vibration-rotation. Le modèle de substitution étendu de Lakhlifi-Dahoo est utilisé dans le cadre du formalisme de Liouville et les profils de raies de molécules triatomiques et leurs isotopologues soumis à des contraintes environnementales sont calculés en appliquant le théorème des cumulants.Les applications montrent comment les interactions à l’échelle moléculaire modifient les spectres IR d’une triatomique piégée dans une nano-cage (site de substitution d’une matrice de gaz rare, clathrate, fullerène, zéolithe) ou adsorbée sur une surface et permettent d’identifier les caractéristiques de l’environnement perturbateur

Volume 3: Infrared Spectroscopy of Symmetric and Spherical Top Molecules for Space Observation 1

International audienceThis book is dedicated to the description and application of various different theoretical models to identify the near and mid-infrared spectra of symmetric and spherical top molecules in their gaseous form.Theoretical models based on the use of group theory are applied to rigid and non-rigid molecules, characterized by the phenomenon of tunneling and large amplitude motions. The calculation of vibration-rotation energy levels and the analysis of infrared transitions are applied to molecules of ammonia (NH3) and methane (CH4). The applications show how interactions at the molecular scale modify the near and mid-infrared spectra of isolated molecules, under the influence of the pressure of a nano-cage (the substitution site of a rare gas matrix, clathrate, fullerene or zeolite) or a surface, and allow us to identify the characteristics of the perturbing environment.This book provides valuable support for teachers and researchers but is also intended for engineering students, working research engineers and Masters and doctorate students

Spectroscopie infrarouge de molécules diatomiques pour l’observation spatiale, Volume 1

International audienceCet ouvrage décrit les méthodes théoriques qui sont mises en oeuvre dans le cadre de recherches fondamentales pour interpréter les spectres de molécules diatomiques observées dans le domaine infrarouge lorsque ces molécules sont soumises à un environnement où la température et la pression modifient leurs spectres infrarouges en phase gazeuse ou dans des nanocages.Il présente les modèles théoriques qui ont été développés pour étudier la modification des spectres infrarouges des diatomiques sous l’effet de la pression, l’élargissement du profil de raie, le déplacement des centres de bandes et la modification du spectre rovibrationnel dans les nanocages ou sur des surfaces.Cet ouvrage s’adresse aux étudiants de master ou de doctorat, aux enseignants, chercheurs, astronomes et astrophysiciens qui analysent les données correspondant à l’interaction du rayonnement électromagnétique avec la matière dans le domaine de l’infrarouge afin d’identifier les espèces chimiques et leurs environnements

Preface

International audienceThis book is dedicated to the application of the different theoretical models described in Volume 1 to identify the near-, mid- and far-infrared spectra of linear and nonlinear triatomic molecules in gaseous phase or subjected to environmental constraints, useful for the study of environmental sciences, planetology and astrophysics.The Van Vleck contact transformation method, described in Volume 1, is applied in the calculation and analysis of IR transitions between vibration–rotation energy levels. The extended Lakhlifi–Dahoo substitution model is used in the framework of Liouville’s formalism and the line profiles of triatomic molecules and their isotopologues subjected to environmental constraints are calculated by applying the cumulant expansion.The applications presented in this book show how interactions at the molecular level modify the infrared spectra of triatomics trapped in a nano-cage (substitution site of a rare gas matrix, clathrate, fullerene, zeolite) or adsorbed on a surface, and how these interactions may be used to identify the characteristics of the perturbing environment