Infrared Spectroscopy of Symmetric and Spherical Top Molecules for Space Observation, Volume 2 E-Book
Pierre-Richard Dahoo
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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
This book, Volume 4 in the series, is dedicated to the relationship between laboratory spectroscopy, recording ever-more-complex spectra using increasingly powerful instruments benefiting from the latest technology, and the development of observation using instruments that are embedded in mobile probes or nanosatellites. The theoretical models described in Volumes 1, 2 and 3 are used in this volume, applying the cumulant theorem in the mean-field theory framework to interpret the near and mid-infrared spectra of symmetric top molecules, such as ammonia (NH3) and spherical molecules, such as methane (CH4). These molecules can be isolated in their gaseous form or subjected to the environmental constraints of a nano-cage (a substitution site, clathrate, fullerene or zeolite) or surfaces. These methods are not only valuable in the fields of environmental sciences, planetology and astrophysics, but also fit into the framework of data processing and the concept of Big Data.
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Table of Contents
Cover
Title Page
Copyright
Foreword
Preface
1 IR Spectra in Space Observation
1.1. Introduction
1.2. Fourier transform spectroscopy
1.3. Resonant cavity laser absorption spectroscopy
1.4. Spectroscopy for space observation
1.5. Conclusion
1.6. Appendices
2 Interactions Between a Molecule and Its Solid Environment
2.1. Introduction
2.2. Active molecule – solid environment system
2.3. Two-center expansion of the term
2.4. Conclusion
2.5. Appendices
3 Nanocage of Rare Gas Matrix
3.1. Introduction
3.2. Rare gases in solid state
3.3. Molecule inclusion and deformation of the doped crystal
3.4. Motions of NH
3
trapped in an argon matrix
3.5. Infrared spectra
3.6. Appendices
4 Nanocages of Hydrate Clathrates
4.1. Introduction
4.2. The extended substitution model
4.3. Clathrate structures
4.4. Inclusion of a CH
4
or NH
3
molecule in a clathrate nanocage
4.5. System Hamiltonian and separation of movements
4.6. Translational motion
4.7. Vibrational motions
4.8. Orientational motion
4.9. Bar spectra
4.10. Appendices
5 Fullerene Nanocage
5.1. Introduction
5.2. Ammonia molecule trapped in a fullerene C
60
nanocage
5.3. Potential energy surfaces – inertial model
5.4. Quantum treatment
5.5. Bar spectra
5.6. Appendices
6 Adsorption on a Graphite Substrate
6.1. Introduction
6.2. “NH
3
molecule–substrate” system interaction energy
6.3. Equilibrium configuration and potential energy surfaces
6.4. Hamiltonian of the system
6.5. Infrared spectra of the NH
3
molecule adsorbed on the graphite substrate
6.6. Conclusion
6.7. Appendices
References
Index
End User License Agreement
Guide
Cover
Table of Contents
Title Page
Copyright
Foreword
Preface
Begin Reading
References
Index
Other titles from iSTE in Waves
End User License Agreement
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Infrared Spectroscopy Set
coordinated byPierre Richard Dahoo and Azzedine Lakhlifi
Volume 4
Infrared Spectroscopy of Symmetric and Spherical Top Molecules for Space Observation 2
Pierre Richard Dahoo
Azzedine Lakhlifi
First published 2021 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:
ISTE Ltd27-37 St George’s RoadLondon SW19 4EUUKwww.iste.co.uk
John Wiley & Sons, Inc.111 River StreetHoboken, NJ 07030USAwww.wiley.com
© ISTE Ltd 2021
The rights of Pierre Richard Dahoo and Azzedine Lakhlifi to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.
Library of Congress Control Number: 2021938325
British Library Cataloguing-in-Publication DataA CIP record for this book is available from the British LibraryISBN 978-1-78630-652-4
Foreword
Spectroscopy is the high road to physico-chemical measurements of astrophysical objects, such as the interstellar medium, stars or planets and exoplanets. In recent decades, the understanding of the increasingly finer details of the interaction between matter and radiation, as reflected in the spectral range by effects, sometimes unexpected, on the observed spectra, has led to outstanding advances in spectroscopy, from ground- or space-based observations. For this purpose, increasingly sophisticated instruments were developed for space probes, initially inspired by laboratory instruments, in order to cope with the severe constraints of space observation and exploration.
The challenge of laboratory spectroscopy presented in this book, the fourth volume in this series, resides not only in registering increasingly complex spectra, even for the simplest molecules observed at high temperature or excited to high vibrational states, but also in understanding specific molecular mechanisms, such as the spectroscopy of molecules in rare gas matrices, clathrates or physico-chemical mechanisms related to the adsorption on graphite substrates. These mechanisms can be used to extrapolate to the very specific conditions of the interstellar medium, where the very rich chemistry discovered by the observations in the millimetric range in the last 50 years is highly dependent on ion–molecule–substrate mechanisms.
Spatial instrumentation in remote spectroscopy offers the possibility of exploring planets with atmospheres, particularly by means of instruments with medium to high resolution. However, Earth observations should be treated separately, as they have other objectives, particularly operational ones, and a different approach and constraints compared to the various distant exploration missions, even though they involve similar categories of instruments. Fourier transform spectrometers have measured, in particular, the atmospheres of Mars, Venus and giant planets and their satellites, thanks to their performances in combining large spectral extent and (relatively) high resolution. The pioneering missions were Mariner, Venera and Voyager. Grating or prism spectrometers, particularly those using adjustable prisms (AOTF – Acoustic Optic Tunable Filter), have also provided remarkable results on Mars and Venus. After the first observations using variable circular filter spectrophotometry (IKS on Vega probe), comets, with their highly specific atmosphere, were observed with grating spectrometers (VIRTIS on Rosetta), which led to a better understanding of their composition and revealed surprising isotopic ratios.
Substrate spectroscopy issues are connected with planetary studies in order to understand the adsorption chemistry at play in the interstellar medium, as well as in the very high atmosphere of planets: one of the key results of the Cassini mission showed that the complex hydrocarbons observed on Titan were generated not only from the photochemistry of nitrogen or methane atmosphere at the level of high clouds, but also in the ionic chemistry of the very high atmosphere, measured directly using mass spectrometry from the instrument aboard the Cassini during its flight over Titan.
There is no doubt that there is still room for embedded spectroscopy to significantly evolve into future space missions: Raman spectroscopy methods, still fresh on planetary probes (Mars Curiosity and Perseverance missions), LIDAR observations or the CRDS technique will lead the way to new advances, which laboratory techniques and theoretical models will help to interpret. The joint progress of various disciplines of chemistry, spectroscopy and of Earth and universe sciences is a remarkable example of a coordinated multidisciplinary approach that involves the joint research efforts of laboratories of various specializations. This book, the fourth volume in the series “Infrared Spectroscopy of Molecules for Space Observation”, focuses on the context and results of this research.
Pierre DROSSARTParis Institute of Astrophysics, CNRS, Sorbonne UniversityJune 2021
Preface
The observable universe is visible thanks to the light that reaches us from the point being observed. These extreme points form the contour of a sphere, whose limit lies at the cosmological horizon, with the Earth at its center. Other observers, located elsewhere in the universe, see a different observable sphere of the same radius. It is a relative notion. Let us recall that in cosmology, the unit of measurement for distances is the light-year, which is the distance that light travels in one year, which corresponds to about 9.5 1012 km. The megaparsec, which amounts to 3.26 million (3.26 106) light-years, is another unit of distance used particularly in extragalactic astrophysics. The Standard Model of Cosmology elaborated at the beginning of this century, by 2000, is perhaps the most successful model presently that offers a description of the evolution of the universe, in terms of the major stages in the history of the observable universe, as well as its current composition resulting from astronomers’ observations. In order to explain the myriad of observable galaxies and planetary systems, suns and black holes, cosmologists proposed an inflationary model.
As mentioned in the prefaces of the previous volumes, the universe is a preferred spatial environment for astrophysicists, cosmologists, astronomers and physicists, both for observations and for testing the theory of general relativity of Albert Einstein by means of predicted and observed phenomena, elaboration of new theories and their expected confirmation by observations. This is the context in which the Nobel Prize for Physics was awarded to Sir Roger Penrose in 2020, for his work on the existence of black holes based on the theory of general relativity, and to astronomers Andrea Ghez and Reinhard Genzel, for their research on the phenomena observed at the center of the Milky Way galaxy in the Sagittarius A region, where the existence of a black hole was predicted, and who showed that, indeed, a supermassive black hole was present there.
This book, the fourth volume of this series, offers an overview of several experimental instruments used for the observation and analysis of a physico-chemical system, in order to determine relevant characteristics such as the position, intensity and width of IR absorption lines. Some instruments rely on the principle of light interferences, such as the Fourier transform infrared (FTIR) spectroscopy, or on the operating principle of a resonant laser cavity, such as the cavity ring-down spectroscopy (CRDS), or the frequency comb techniques. The species present in a given atmosphere, such as the tholins on Titan (satellite of Saturn), can be prepared in situ in the laboratory and studied by spectroscopic ellipsometry, in order to determine their optical properties. This data can be used to calculate the albedo, for example. A spectrometer employing an acoustic optic tunable filter (AOTF) was used to obtain IR data on Mars and Venus from Mars Express and Venus Express missions. Data analysis made it possible to identify the nature of certain observations in the IR spectrum and to eliminate possible ambiguities. Hence, the absorption by the 628 CO2 isotopic species could be confirmed at the expense of a possible absorption by a C–H bond in the same IR spectrum. Finally, LIDAR is the preferred instrument for observing distant objects and species present in the atmosphere of planets, in a given environment.
This volume, however, focuses on the applications of the theoretical models described for diatomic and triatomic molecules to symmetric tops such as NH3 and/or spherical tops such as CH4, when they are in an environment that may be present in the universe, i.e. when they are trapped in a nanocage of rare gas matrix, clathrate, fullerene or adsorbed on a graphite substrate. All of these models are theoretical instruments for the simulation-based observation of a molecule. The results of these theoretical models should be compared with those of experimental observations, using instruments that are specifically developed for various observation situations. The latter may be related to the observation site, such as a laboratory, an observatory or a space probe, or a telescope in space. They may also relate to the type of molecular system observed, molecules or chemical species (ions, radicals, macromolecules, nanocages, etc.) that compose, on the one hand, the atmospheres of planets, the Earth or the planets of the solar system and possibly their satellites, and on the other hand, the interstellar media, the comets or the exoplanets throughout the spatial extent of the universe, estimated by the cosmologists as 1023 km.
As underlined in Volumes 1, 2 and 3, theoretical and experimental approaches to spectroscopies led to the development of methods and instruments for the observation and analysis of the spectral characteristics of chemical species, molecules, radicals and ions in specific environments. Volumes 1 and 2 of this series [DAH 17] describe the theoretical models developed in order to determine the absorption spectra of diatomic molecules (homonuclear or heteronuclear), triatomic molecules (linear or nonlinear, symmetric or non-symmetric) in the gas phase and particularly when they are trapped in the nanocages of inert matrices of rare gases, or hydrate clathrates at a very low temperature. Volume 3 deals with the spectroscopy of symmetric and spherical tops in the gas phase.
This book (Volume 4) is a continuation of Volume 3, focusing on the application of theoretical models for the simulation of IR spectra of symmetric or spherical top species evolving in various media. The method of an extended substitution model is explained in terms of the determination of the type of symmetry of the environment in the immediate vicinity of the trapped molecule. The objective is to propose theoretical spectra that match with experimental IR data and hence identify molecules based on transitions and profiles, not only in the gas phase, but also when they are constrained to evolve in an environment, such as a nanocage or a surface.
Chapter 1 provides a brief overview of the instruments developed and used in the laboratory for the study or observation of molecules, FTIR spectroscopy or laser cavity spectroscopy. An example of embedded instruments such as SPICAM, SPICAV or SOIR aboard an orbiter or a space probe serves to illustrate the instrumental context of space observation and of the international collaboration required to develop measurement instruments, as well as the analysis methods for the identification according to the scientific norms of the molecules that may be present in the probed atmosphere, such as on Mars or Venus during Mars Express and Venus Express missions. Aerosol characterization by spectroscopic ellipsometry is also discussed as a non-standard method. The LIDAR technique, which is used for observing the terrestrial atmosphere, is also described.
Chapter 2 presents various contributions to the interaction potential energy between the studied molecule and its solid environment, considering the hypothesis of binary interactions: “studied molecule – molecule or atom of the environment”. The quantum “dispersion–repulsion” contribution is modeled by an atom–atom Lennard-Jones potential energy type, while the electrical contribution is modeled by a charge–charge potential energy in the case of clathrate nanocages or multipole–multipole in the case of nanocages of rare gas, fullerene or graphite substrate matrix.
Chapter 3 provides a description of the substitution model applied to the study of NH3 in rare gas matrices. An atom–atom potential is used to calculate the interaction between the trapped molecule and its environment. A numerical method is applied to determine the perturbed motions of the molecule. The IR spectral profiles are determined and compared to the experimental spectra. The influence of lattice phonon modes on the shift and width of spectral lines is also discussed.
Chapters 4 and 5 provide a description of the extended substitution model, based on the effect of the local symmetry around the equilibrium position of the molecule in the cage for calculating IR spectra in natural nanocages, such as clathrates and fullerene. This model relies on the substitution model used for building theoretical models in IR spectroscopy in rare gas matrices. The model is applied to CH4 and NH3 molecules included in clathrate nanocages (Chapter 4) and NH3 in a fullerene nanocage.
In Chapter 6, the theoretical models developed in Volumes 1 and 2 to deal with the adsorption of diatomic and triatomic molecules on a graphite substrate, are applied to the NH3 molecule in order to determine the IR absorption spectra at a very low temperature. This substrate is often used to model the surface of interstellar dust grains.
Pierre Richard DAHOOAzzedine LAKHLIFIJune 2021
