Table Of ContentTHE SPECTROSCOPY OF FLAMES
The Spectroscopy
of Flames
A.G.GAYDON
D.Se., F.R.S.
Warren Research Fellow
of the Royal Society
and
Emeritus Professor of Molecular Spectroscopy
Imperial College, London
SECOND EDITION
LONDON
CHAPMAN AND HALL
First published 1957
by Chapman and Hall Ltd
11 New Fetter Lane, London EC4 P 4EE
Second edition 1974
© 1957, 1974 A. G. Gaydon
Softcover reprint ofthe hardcover 1st edition 1957
Typeset by Preface Ltd, Salisbury, Wilts
and printed in Great Britain by
T & A Constable Ltd,
Edinburgh
ISBN-13: 978-94-009-5722-0 e-ISBN- 13: 978-94-009-5720-6
DOl: 10.1007/978-94-009-5720-6
All rights reserved. No part of
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Distributed in the U.S.A.
by Halsted Press, a Division
of John Wiley & Sons, Inc., New York
Preface to Second Edition
The spectrum of a candle flame was first mapped by Swan in 1857
and early observations on spectra of metals in flames were made by
Bunsen and Kirchhoff around 1860. Since then investigations have
continued at an increasing pace and knowledge obtained from these
spectroscopic studies is accepted as making an important contribu
tion to the understanding of flame processes. I have myself been
working in this field for some 40 years now and have been associated
with some of the recent advances in techniques.
My small monograph on Spectroscopy and Combustion Theory
first appeared in 1942, and the revised edition in 1948. This
summarized not only direct observations on the visible and ultra
violet emission spectra of flames, but also covered the infra-red
region and absorption spectroscopy. Indirect applications, such as
the use of spectroscopic data for determining dissociation equilibria
and flame temperatures were also included. The spectroscopic
observations were interpreted in relation to chemical processes of
combustion, to the initial energy distribution resulting from the
reactions, and to the state of equilibrium in the flame gases. This
earlier monograph served to summarize work up to about 1947 and,
I hope, to stimulate further research.
These research developments, and also the coverage of parts of the
field in my other books, Flames, their Structure, Radiation and
Temperature, jointly with H. G. Wolfhard, and my Dissociation
Energies, led to a complete revision of the older monograph under
the new title Spectroscopy of Flames in 1957. That edition covered
many exciting new developments - the work on low-pressure flames,
burners for flat diffusion and flat premixed flames, flames supported
by free atoms, flash photolysis, early investigations in shock tubes,
and the use of isotope tracer methods. The 1957 edition did indeed
stand the test of time rather better than the older monograph,
because the information about flame spectra and flame processes was
by then much more definite.
vi PREFACE TO SECOND EDITION
During the 17 years since the previous edition was prepared there
have been many refinements in techniques and some important
related advances, such as the discovery of the laser and the use of
atomic absorption and atomic fluorescence for analytical work. For
this thorough revision the whole book has been completely re
worked, but the same plan has been retained so that it appears,
deceptively, similar to the previous edition. It is hoped that the new
book is now in a sufficiently definitive form to be of continuing
value, because although further advances are to be expected and
hoped for, the main facts, such as the identity of emitting and
absorbing species and the reactions forming them in flames, are now
established. Many of the older publications tend to get forgotten, but
my long continuity of work in this field has enabled me to make use
of old data where still relevant.
The book deals primarily with the use of spectroscopic observa
tions to interpret combustion processes in flames and flame
structure, including explosion flames and engines. This is not a book
on flame photometry, but the understanding of flame equilibria, and
departures therefrom, is relevant to this subject and in the final
chapter I have commented on the use of flames for spectrochemical
analysis including the recently developed atomic absorption and
atomic fluorescence methods.
I have endeavoured to present the ,subject in such a way that the
book may be of service to those engaged in research, but so that it
may be read easily by the beginner and the non-specialist. The
treatment is not mathematical, and where an understanding of the
theory of molecular spectra is necessary I have endeavoured to give
this theory in simple terms. I have included a fairly extensive
Bibliography and an Appendix, giving tables of wavelengths, and in
this edition wavenumbers as well, of all the main band spectra
frequently found in flames and combustion systems; these should
make the book valuable for reference purposes.
My early work owes much to the initial stimulation of the late
Professors Alfred Fowler and Sir Alfred Egerton, and also I have
benefited from collaboration, at Imperial College, with my former
colleagues Drs H. P. Broida, R. A. Durie, P. F. Jessen, N. P. W.
Moore, W. M. Vaidya and H. G. Wolfhard, to whom I express my
PREFACE TO SECOND EDITION vii
thanks. I am grateful to my wife and Miss D. Waller for some help
with indexing and proof reading. I would also like to acknowledge
support over many years from the Warren Research Fund of the
Royal Society.
Department of Chemical
Engineering and Chemical Technology, A.G.G.
Imperial College,
London, S. W. 7.
April 1974.
ix
Contents
Preface page v
I. FLAME SPECTRA 1
The purpose of studying flame spectra - Types of
spectra - The structure of flames - The spectrum of
the Bunsen flame - Equilibria, radiation and collision
processes.
II. EXPERIMENTAL METHODS 14
The recording of spectra - Spectrographic equipment -
Optical systems - The study of absorption spectra -
Wavelength determination - Intensity measurements -
Effects of flame shape.
III. SPECIAL TECHNIQUES 41
Flat flames - Low-pressure flames - Temperature
effects on flames - Atomic flames - Flash photolysis -
Shock tube studies - Fluorescence and laser-Raman
scattering - Use of isotope shifts
IV. INTRODUCTION TO THE THEORY OF SPECTRA 65
Line or atomic spectra - Bohr theory - The spectra of
diatomic molecules: vibrational structure - Rotational
structure of the spectra of diatomic molecules -
Electronic states of diatomic molecules - Vibrational
intensity distribution: the Franck-Condon principle -
Predissociation - Infra-red spectra - Raman spectra -
Electronic spectra of polyatomic molecules - Con
tinuous spectra - Ionization continua - Dissociation
continua - Association continua - The width and shape
of spectrum lines
x CONTENTS
V. HYDROGEN FLAMES 99
The OH bands - Hydrogen/air flames - Hydrogen!
oxygen flames - Pressure effects - Absorption spectra
- Excitation of metal spectra in H /0 /N flames -
2 2 2
Candoluminescence - Applications to combustion
mechanism - The hydrogen/nitrous oxide flame -
Flames with NO and N0
2
VI. THE CARBON MONOXIDE FLAME 127
The spectrum - The carbon monoxide flame bands -
The excitation of the flame bands - The continuous
spectrum: pressure and temperature effects - Com
bustion processes for carbon monoxide - Flames of
carbon and carbon suboxide
VII. THE SPECTRA OF ORGANIC FLAMES 144
The CH bands - Bands of C Vaidya's hydrocarbon
2 -
flame bands (HCO) - The 4050 A "comet head" group
(C EmelaIs's cool flame bands (CH 0) - Band
3) - 2
systems of CO - Other band systems in flames - The
carbon line, X2478 - Premixed flames - Diffusion
flames - Cool flames and preignition glows - Absorp-
tion spectra
VIII. MEASUREMENTS OF EFFECTIVE TEMPERATURE 182
AND STUDIES WITH SPECIAL SOURCES
Electronic excitation temperatures - Translational
temperatures from Doppler broadening - Measurement
of rotational temperatures: OH - Rotational tempera
tures for CH, C NH etc. - Effective vibrational
2,
temperatures - Predissociation - Flash photolysis -
Atomic flames - Spectra excited by shock waves -
Occurrence of C and CH in some special flames -
2
Isotope tracer experiments
IX. THE INFRA-RED REGION 221
The amount of radiation from flames - Infra-red
spectra of organic flames - Relative band intensities and
temperature measurements - Radiation from explosion
flames - Cool flames - Flames with nitrous oxide -
Flames with halogens
CONTENTS xi
X. FLAME STRUCTURE AND REACTION PROCESSES 244
Reactions in cool flames - The formaldehyde excitation
process - Reactions in diffusion flames - Reactions in
premixed flames - Carbon formation in premixed
flames - Concentrations of free radicals - Reactions
forming excited species - Ionization and electron
temperatures - The high electronic excitation in the
flame front - Effects on flame structure of lags in
equipartition of energy.
XI. EXPLOSIONS, ENGINES AND INDUSTRIAL FLAMES 282
Explosions in closed vessels - Detonations - The
internal combustion engine: flame fronts and afterburn-
ing - Knock - Compression-ignition (diesel) engines -
Engines with continuous combustion - Exhaust flames
- Furnace flames - Solid propellants.
XII. FLAMES CONTAINING NITROGEN, HALOGENS, 296
SULPHUR AND INORGANIC SUBSTANCES
Flames of ammonia, hydrazine etc. - Flames of organic
nitrogen compounds - Flames supported by oxides of
nitrogen - Formation of oxides of J.litrogen - Ozone
Halogens in oxidizing flames - Flames supported by
halogens - Flames of sulphur, hydrogen sulphide and
carbon disulphide - Flames with added SO SO or
2, 3
H S - Phosphorus in flames - Flames containing boron
2
- Metals in flames.
XIII. FLAME SPECTROPHOTOMETRY 320
The choice of flame type - The burner and spray
system - Recording methods - The relation between
line intensity and concentration - Interference by one
element with the estimation of another - Atomic
absorption - Atomic fluorescence - Effects of flame
disequilibria
APPENDIX
I Band spectra emitted by flames 338
II Absorption spectra 369
III Some atomic and molecular energy levels and constants 376
xli CONTENTS
REFERENCES 381
AUTHOR INDEX 397
SUBJECT INDEX (Including symbols used and values
of physical constants) 405
PLA TES
Plates 1 to 8 appear between pages 212-213
