Quantitative Millimetre Wavelength Spectrometry

by Alder, John F.; Baker, John G.; Royal Society of Chemistry (Great Britain)

• ISBN13: 9780854045754
• ISBN10: 0854045759
• Format: Hardcover
• Copyright: 2002-03-01
• Publisher: Royal Society of Chemistry

Summary

This unique book demonstrates the current status, and future potential, of millimetre wavelength (MMW) spectrometry as a means of quantitative analysis of gaseous mixtures. After outlining the spectroscopic theory required, the authors then go on to discuss the components of an MMW cavity spectrometer, concentrating on compact, automatic, low-cost instruments. Other topics covered include solid state MMW sources with both cryogenically cooled and room temperature detectors, Post-detector signal processing, smoothing, filtering and spectral profile fitting are also discussed. The book concludes with a look at the future of the technique, in areas such as millimetre wave-over-fibre technology. Quantitative Millimetre Wavelength Spectroscopy will be welcomed by practitioners in both industry and academia.

Author Biography

Professor John Alder's distinguished career began at Imperial College. He moved to UMIST in 1980, where he is now Professor of Analytical Science Dr John Baker left Cambridge to become a Fulbright Scholar in the USA, and subsequently worked at Bristol University before joining the Schuster Physics Laboratory at the University of Manchester. He is currently Visiting Reader in the Department of Instrumentation and Analytical Science at UMIST

Table of Contents

Glossary of Terms and Symbols	xi
Interaction of Millimetre Wavelength Electromagnetic Radiation with Gases	1	(20)
Basic Spectroscopic Theory	3	(7)
Effect of Spectral Line Broadening on Absorption Intensity	10	(6)
Doppler Broadening	10	(2)
Natural Linewidth and Pressure Broadening	12	(2)
Power Saturation and Broadening	14	(1)
Effect of the Cavity Q on Power Broadening	15	(1)
Line Intensities for Diatomic and Linear Polyatomic Molecules	16	(1)
Line Intensities for Symmetric-Top and Asymmetric-Top Molecules	17	(2)
Line Spectra	17	(1)
Band Spectra	18	(1)
Significance of the Peak Absorption Coefficient Functions for Quantitative Millimetre Wavelength Spectrometry	19	(2)
References	20	(1)
The Components of a MMW Cavity Spectrometer for Quantitative Measurements	21	(17)
Cavity Absorption Cells	21	(6)
Analytical Absorption Signals in a Fabry-Perot Cavity	27	(1)
Coupling Radiation into and out of Absorption Cells	27	(8)
The Reflection Cavity	29	(4)
The Transmission Cavity	33	(2)
A Practical Coupler	35	(1)
Scanning the Cavity	35	(3)
References	37	(1)
Practical Spectral Sources and Detectors for Analytical Spectrometry	38	(27)
Negative Resistance Oscillators, Multipliers and BWOs	38	(8)
Gunn Devices	39	(2)
Impatt Diodes	41	(2)
Schottky Barrier Devices	43	(1)
Backward Wave Oscillators, BWOs	44	(1)
Marginal Oscillators	44	(2)
The Use of Isolators in MMW Circuits	46	(1)
Source Frequency Control	47	(8)
Synchronised YIG Oscillators as Intermediate Frequency Sources	48	(4)
Signal Modulation and Detection Processes	52	(3)
Detectors for Quantitative MMW Spectrometry	55	(5)
Bolometer Mixers	57	(1)
Schottky Diode Mixers	58	(2)
Noise and Signal Processing in MMW Spectrometers	60	(5)
Johnson Noise	60	(1)
Shot Noise	61	(1)
Inverse Frequency or 1 /f Noise	61	(1)
Signal Rectification Noise	61	(2)
References	63	(2)
The Quantitative Analysis of Gas Mixtures	65	(15)
Measuring the Spectral Line Profile and Area Using Frequency Modulation	65	(3)
Digital Modulation Techniques	68	(2)
Computerised Enhancement of Spectral Signals	70	(6)
Measurements at Pressures up to Atmospheric	76	(1)
Cavity Spacing Glitch Spectrometry	76	(4)
References	79	(1)
Cavity Spectrometer Designs and Applications	80	(9)
Previous Commercial Microwave Spectrometers	80	(1)
Fabry-Perot and Waveguide Cavity Spectrometers	80	(2)
Double Resonance Spectrometers	82	(1)
Recent Developments in MMW and Higher Frequency Spectrometers	83	(2)
Atmospheric Pressure MMW Spectrometers	85	(4)
References	87	(2)
A Practical Frequency Modulated Spectrometer and Its Application to Quantitative Analysis	89	(26)
To Set the Scene	89	(1)
Signal Sources and Operating Frequency Band	90	(1)
The Sample Cell and Sample Handling Techniques	91	(9)
Sample Modulation and Signal Detection	100	(1)
Computer Control, Signal Detection and Amplification	101	(2)
Post-Detection Signal Enhancement	103	(1)
Quantitative Interpretation of Data	104	(2)
Determination of Spectral Absorption Coefficients and Calibration Curves	106	(4)
Pressure Scanning	110	(3)
The Practical Spectrometer	113	(2)
References	113	(2)
The Future for Quantitative Millimetre Wavelength Spectrometry	115	(4)
References	118	(1)
Subject Index	119