RSI Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter UniPHY Group iResearch App Facebook

Review of Scientific Instruments / Volume 78 / Issue 5 / INVITED ARTICLE

Rev. Sci. Instrum. 78, 051301 (2007); http://dx.doi.org/10.1063/1.2735447 (12 pages)

Invited Article: Linearization and signal recovery in photoacoustic infrared spectroscopy

K. H. Michaelian

Natural Resources Canada, CANMET Energy Technology Centre-Devon, 1 Oil Patch Drive, Suite A202, Devon, Alberta T9G 1A8, Canada

View MapView Map

(Received 15 November 2006; accepted 4 February 2007; published online 15 May 2007)

Photoacoustic (PA) infrared spectroscopy enables the characterization of a wide variety of materials, affording the spectroscopist several advantages over more traditional infrared methods. While PA spectra are readily acquired using commercial instrumentation, the quality of the data can be improved substantially through the use of specialized numerical and experimental procedures. Two of these methods are the subject of this review. Specifically, this article describes (a) linearization of PA infrared spectra, a calculation that incorporates phase and amplitude information to extend the range of linearity for strongly absorbing samples, and (b) lock-in and digital signal-recovery procedures in step-scan phase-modulation PA infrared spectroscopy. Linearization yields significant improvement in band definition, especially in the low-wavenumber region. This numerical method succeeds in situations where the PA phase of the sample is less than that of the reference (carbon black). When this criterion is not met initially, the sample or reference interferograms can be manipulated prior to the calculation. The steps involved in linearization are illustrated in detail and approximations are discussed. Lock-in demodulation of the step-scan phase-modulation signal is compared to digital (software) demodulation in this study; the lock-in technique is found to be superior in several cases. The imaginary interferograms in these experiments sometimes lack a strong central feature, a situation that necessitates the application of less commonly used methods for phase correction and spectrum calculation. These methods, which are available in commercial software, include two-quadrant and stored-phase corrections. The PA phase spectrum resembles amplitude and absorption spectra when real and imaginary PA spectra are correctly calculated.

© 2007 American Institute of Physics

Article Outline

  1. INTRODUCTION
  2. EXPERIMENT
    1. Linearization
    2. Signal recovery
  3. SPECTRUM CALCULATION IN OPUS
  4. LINEARIZATION OF PA INFRARED SPECTRA
    1. Formatting of interferograms
      1. Rotation and zero filling
      2. Apodization
    2. Linearization of PA spectrum of thimble solids
      1. Calculations
      2. Comparison of linearization equations
      3. Effect of interferogram peak shift
    3. Linearization of PA spectra of clays
      1. Kaolin
      2. Illite
  5. SIGNAL RECOVERY IN STEP-SCAN PA INFRARED SPECTROSCOPY
    1. Step-scan PA spectra of carbon black
      1. Lock-in demodulation
      2. DSP demodulation
    2. Step-scan PA spectra of kaolin
      1. Lock-in demodulation
      2. DSP demodulation
  6. DISCUSSION

EDITORIALLY RELATED

  1. Perspective: Photoacoustic spectroscopy: “Linearization and signal recovery in photoacoustic infrared spectroscopy” [Rev. Sci. Instrum. 78, 051301 (2007)]
    John F. McClelland
    Rev. Sci. Instrum. 78, 050901 (2007)RSINAK000078000005050901000001

RELATED DATABASES

To view database links for this article, you need to log in.

KEYWORDS and PACS

Keywords

photoacoustic spectroscopy, infrared spectroscopy, photoacoustic spectra, infrared spectra, phase modulation, optical modulation, demodulation

PACS

  • 07.57.Ty

    Infrared spectrometers, auxiliary equipment, and techniques

  • 43.58.-e

    Acoustical measurements and instrumentation

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.2735447

PUBLICATION DATA

ISSN

0034-6748 (print)  
1089-7623 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics

For access to fully linked references, you need to log in.
    A. Rosencweig and A. Gersho, J. Appl. Phys. 47, 64 (1976)JAPIAU000047000001000064000001.


For access to citing articles, you need to log in.


Figures (30)

Access to article objects (figures, tables, multimedia) requires a subscription; log in to view available files.
(Access to supplementary files, where available, is free for this journal.)



Close

Google Calendar

ADVERTISEMENT

Your Recent History Recent History Help

Recently Viewed

  1. Invited Article: Linearization and signal recovery in photoacoustic infrared spectroscopy
  2. Perspective: Photoacoustic spectroscopy: “Linearization and signal recovery in photoacoustic infrared spectroscopy” [ Rev. Sci. Instrum. 78, 051301 (2007) ]
  3. Easily fabricated magnetic traps for single-cell applications
  4. A distributed algorithm for multi-tau autocorrelation
  5. Artificial submicron or nanometer speckle fabricating technique and electron microscope speckle photography
Go to AIP Home
Copyright © American Institute of Physics
close