Halogen oxides

European Commission Directorate-General For Research And Innovation

Description

Radicals, sources and reservoirs in the laboratory and in the atmosphere
Environment policy and protection of the environment

Sujets

• Air pollution
• Environmental movement
• Oxyde

Informations

• Publié par: EUROPEAN-COMMISSION-DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION
• Nombre de lectures: 10
• Langue: English
• Poids de l'ouvrage: 9 Mo

Extrait

European Commission
DG XII t
Science. Research
and Development
Halogen oxides:
radicals, sources and reservoirs
in the laboratory and in the atmosphere
Cl F
Cl
Cl F
Br I
Br
Br I
Br
Ϋ European Commission
Directorate-General Science, Research and Development
Environment research programme
Air pollution research report 55
Halogen oxides:
radicals, sources and reservoirs in the
laboratory and in the atmosphere
R. P. Wayne,1 G. Poulet,2 P. Biggs,1 J. P. Burrows,3 R. A. Cox,4
P. J. Crutzen,5 G. D. Hayman,6 M. E. Jenkin,6 G. Le Bras,2
G. K. Moortgat,5 U. Platt,7 R. N. Schindler8
1 Physical Chemistry Laboratory, South Parks Rd., Oxford 0X1 3QZ,
United Kingdom,
2 Laboratoire de Combustion et Systèmes Réactifs CNRS, 1c Avenue
de la Recherche Scientifique, F-45071 Orléans, Cedex 2,
3 Institute for Remote Sensing/FBI, Universität Bremen, Postfach 330400,
D-28334 Bremen,
4 The Chemistry Laboratories, Lensfield Rd., Cambridge, United Kingdom,
5 Max-Planck-Institut für Chemie, Air Chemistry Division, Postfach 3060,
D-55020 Mainz,
6 National Environmental Technology Centre, AEA Technology,
E5 Culham, Abingdon 0X14 3DB, United Kingdom,
7 Institut für Umweltphysik, INF 366, Universität Heidelberg, D-6900 Heidelberg,
8 Institut für Physikalische Chemie,t Kiel, Olshausenstrasse 40,
D-24098 Kiel Published by the
EUROPEAN COMMISSION
Directorate-General XII
Science, Research and Development
B-1049 Brussels
LEGAL NOTICE
Neither the European Commission nor any person acting
on behalf of the Commission is responsible for the use which might be made of
the following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1995
ISBN 92-827-4642-9
© ECSC-EC-EAEC, Brussels · Luxembourg, 1995
Reproduction is authorized, except for commercial purposes,
provided the source is acknowledged
Printed in Portugal PREFACE
R.P. WAYNE
Editor. Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, U.K.
This review is the third in a series devoted to been positively identified spectroscopically for 45
a critical assessment of the literature concerning years or more. Other oxides, such as OCIO and
certain species that play key rôles in the C120, have an even longer history that dates back
chemistry of the Earth's atmosphere. The first of to the early nineteenth century. However, a great
these reviews examined the nitrate (N03) radical deal of new experimental information has
(Wayne et al., 1991) and the second looked at emerged over the last two decades or so, and it is
peroxy (R02) radicals (Lightfoot et al., 1992). thus now an appropriate time to provide a
Another group of radicals of very great balanced view of the laboratory studies, the
importance for the atmosphere is that of the atmospheric interpretations and observations, and
monoxides of the halogens, ΧΟ (Ç10, BrO, IO, the relation between them.
and possibly FO as well). The present review Our purpose has been to lead the reader to
attempts to summarize current knowledge of the the primary literature and to provide some
physics and chemistry of these radicals, and of a comment on it, rather than to give
series of related compounds that may be their recommendations for the various parameters.
sources, reservoirs or sinks, and to put that Evaluations are provided by others, for example,
knowledge into the context of its relevance for by IUPAC in a series of publications in J. Phys.
atmospheric studies. The atmospheric chemistry Chem. Ref. Data, and by NASA. We note that
of the XO radicals, as well as the laboratory the NASA evaluation number 11 (DeMore et al,
study of them, is inextricably linked to related 1994) appeared after our work was almost
species, such as OCIO or the dimer C1202 in the complete, and most references in our review are
case of CIO. Our review thus covers a wider to the earlier version (DeMore et al., 1992).
scope than the two earlier surveys.
The authors of the review make up a
multinational team that includes representatives Free radicals participate as important
intermediates in the chemical changes that occur from many of the European groups that have
in the Earth's atmosphere. Since the early 1970s, been active on research on the various halogen
it has become increasingly evident that Man's compounds. I have been honoured to act as
release of CFCs and other halogen­containing Chairman of this group, and to coordinate its
compounds have an impact on stratospheric efforts, as well as to act as the Editor for the
ozone, the most dramatic manifestation of which document. I have been ably assisted by Dr Gilles
is the appearance of the Antarctic ozone 'holes'. Poulet, who has acted as Associate Editor and as
deputy coordinator. The team has received help The XO radicals are central to the chemistry that
and advice from many colleagues, and they occurs. There are also natural contributions to
the halogen species in the stratosphere, but Man's gratefully acknowledge this assistance. They
activities dominate. Participation of XO radicals particularly thank Dr Rolf Müller (then of
and related species in tropospheric chemistry has MPI­Mainz, now at KFA­Jülich) for wiiting parts
also become recognized. The species have a of Section VII, and Dr Michel Rossi (EPF,
potential impact on the oxidizing capacity of the Lausanne), whose own review formed the
troposphere, because there are processes that can framework for our Section VI. Dr Stan Sander
(JPL, Pasadena) kindly provided an advance copy both destroy and create ozone.
of a review; this and other help is acknowledged
Detailed knowledge of the kinetics, product
at the end of the text.
channels, and branching ratios for the possible
interactions is required in the interpretation and Much impetus for the preparation of this
modelling of chemical transformations in the review came from research collaborations
atmosphere. Laboratory studies of photochemistry stimulated by the European Commission, in
and spectroscopy are often also required to programmes such as HALOX, CHAOS and
supplement the data on thermal chemical CABRIS. The Commission also generously
processes. The information is not only essential provided funding for the meetings of the review
in incorporating photochemical processes into team, and for secretarial and editorial costs. We
models, but may also be crucial in deploying all gratefully acknowledge this support, as well as
optical techniques to examine qualitatively and the personal involvement of Drs H. Ott, J. Busing
quantitatively trace components of the and G. Amanatidis of Directorate­General XII of
atmosphere. The CIO radical has been invoked the Commission. The Commission is publishing
as an intermediate in laboratory chemistry for the review from Brussels in parallel with its
roughly three­quarters of a century, and it has appearance in Atmospheric Environment. I. INTRODUCTION 2
II. TECHNIQUES FOR THE STUDY OF HALOGEN OXIDES 5
ILA Generation and properties of XO radicals and other oxides 7
H.A. 1 Sources of XO involving halogen atoms
II.A.2 Reactions involving O atoms 10
II.A.3 Photolysis of XOX1
II.A.4 Miscellaneous methods2
II.A.5 Preparation of precursor oxides XOX and OXO 1
II.A.6n of oxides XOO, X202 and X20,4
II.A.7 Higher oxides of the halogens6
II.B. Detection and measurement of XO in the Laboratory8
II.B. 1. Direct detection of XO
II.B.2 Detection of XO after conversion to X atoms 23
II.B.3. Absolute calibrations. 2
II.C Kinetic tools
U.C. 1 General considerations
II.C.2 Flow methods
II.C.3 Flash photolysis and pulse radiolysis7
II.C.4 Modulated photolysis
III. GENERAL PROPERTIES, THEORETICAL STUDIES, SPECTROSCOPY AND STRUCTURE,
PHOTOCHEMISTRY AND THERMOCHEMISTRY OF HALOGEN OXIDES 29
III.A. General Properties of the Halogen Oxides 2
III.B. Theoretical Calculations
III.B.1. Methodology
III.B.2. Spectroscopy of Halogen Oxides 30
III.B.3. Reaction Mechanisms of Halogen Oxides3
III.C. Spectroscopy and Structure5
III.C.l. Spectroscopy of XO (X = F, CI, Br, I)6
III.C.2. Structure and Spectroscopy of F20 48
III.C.3.e andy of F02 5
III.C.4. Structure andy of F2022
III.C.5.e and Spectroscopy of F,Oy
III.C.6. Structure andy of C1203
III.C.7. Structure andy of CICIO
III.C.8.e and Spectroscopy of ClOO
III.C.9. Structure andy of OCIO
III.C. 10.e andy of C1202 6
III.C. 11. Structure and Spectroscopy of CIC1026
III.C. 12.e andy of Cl20,9
III.C. 13. Structure andy of CIO, 71
III.C. 14.e and Spectroscopy of C12042
III.C.15. Structure andy of C1206
III.C. 16e andy of C120,5
III.C. 17. Structure and Spectroscopy of Br20
III.C. 18.e andy of Br20 (BrBrO)
III.C. 19. Structure andy of Br2026
III.C.20.e and Spectroscopy of OBrO7
III.D. Photochemistry, Channels and Quantum Yields 78
III.D.l. Photolysis of XO
III.D.2.s of X20.
III.D.3. Photolysis of XOO.9
III.D.4.s of OXO (OCIO).
III.D.5. Photolysis of X202.
III.D.6.s of XO, and XO, 80 III.E. Spectroscopic and P