Extension of two-dimensional global phase difference correlation analysis to step-scan FT-IR photoacoustic spectral depth profiling of layered systems

2006 ◽  
Vol 799 (1-3) ◽  
pp. 188-195 ◽  
Author(s):  
Eric Y. Jiang ◽  
Alexander Grenov
Keyword(s):  
Correlation Analysis ◽  
Phase Difference ◽  
Depth Profiling ◽  
Two Dimensional ◽  
Layered Systems ◽  
Ft Ir

Generalized Two-Dimensional Fourier Transform Infrared Photoacoustic Spectral Depth-Profiling Analysis

1997 ◽  
Vol 51 (11) ◽  
pp. 1736-1740 ◽  
Author(s):  
Eric Y. Jiang ◽  
William J. McCarthy ◽  
David L. Drapcho ◽  
Richard A. Crocombe
Keyword(s):  
Correlation Analysis ◽  
Depth Profiling ◽  
Correlation Method ◽  
Digital Signal ◽  
Two Dimensional ◽  
Negative Band ◽  
Ft Ir ◽  
Correlated Signals ◽  
Profiling Analysis ◽  
2D Correlation Analysis

This paper reports the first application of a generalized two-dimensional (G2D) correlation method in photoacoustic spectral depth-profiling analysis of laminate/heterogeneous samples. In this method, photoacoustic magnitude spectra at different modulation frequencies are used to generate two-dimensional (2D) correlation spectra. The relative spatial origins of correlated signals are then determined from the signs of the corresponding contours. The unique features and advantages of this technique over previously reported depth-profiling methods are demonstrated and discussed. These include simplification of step-scan photoacoustic phase-modulation experiments as well as 2D correlation-analysis rules, avoidance of phase-related negative-band ambiguities, and enhancement of both spectral and depth resolutions, etc. The recently developed software-based digital signal-processing (DSP) technique for step-scan photoacoustic measurements offers an efficient means (sampling-depth multiplexing advantage) to collect within a single scan all necessary data for this type of 2D correlation analysis. Index Headings: Photoacoustic; PAS; Two-dimensional; Step-scan; FT-IR; Depth profiling; Polymer films; DSP.

Variable-Temperature Fourier Transform Infrared Spectroscopic Investigations of Poly(3-Hydroxyalkanoates) and Perturbation-Correlation Moving-Window Two-Dimensional Correlation Analysis. Part I: Study of Non-Annealed and Annealed Poly(3-Hydroxybutyrate) Homopolymer

2009 ◽  
Vol 63 (9) ◽  
pp. 1027-1033 ◽  
Author(s):  
Miriam Unger ◽  
Shigeaki Morita ◽  
Harumi Sato ◽  
Yukihiro Ozaki ◽  
Heinz W. Siesler
Keyword(s):  
Fourier Transform ◽  
Correlation Analysis ◽  
Crystalline State ◽  
Variable Temperature ◽  
Fourier Transform Infrared ◽  
Melting Behavior ◽  
Correlation Spectroscopy ◽  
Moving Window ◽  
Two Dimensional ◽  
Ft Ir

Generalized two-dimensional correlation spectroscopy (2DCOS) and perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy were applied to explore the melting behavior of non-annealed and annealed poly(3-hydroxybutyrate) (PHB) homopolymer as studied by variable-temperature Fourier transform infrared (FT-IR) spectroscopy. The absorption band of the C=O stretching vibration was employed to investigate the structural changes during the heating process (30–200 °C). Non-annealed PHB showed a recrystallization process in the temperature range 30–120 °C. In the asynchronous 2D correlation spectrum we clearly captured the existence of two components in the crystallinity-sensitive wing of the C=O stretching mode: a well-ordered crystalline state at lower wavenumbers (1718 cm−1) and a less ordered crystalline state at higher wavenumbers (1724 cm−1). These crystallinity-sensitive bands at 1718 and 1724 cm−1, which are not readily detectable in the one-dimensional (1D) FT-IR spectra, share asynchronous cross-peaks with bands at around 1737 and 1747 cm−1 assignable to the C=O stretching absorptions due to the amorphous components. In the case of the melting process of non-annealed PHB in the temperature range 120–200 °C, it is helpful to use the PCMW2D correlation analysis, which indicates the recrystallization between 40 and 110 °C by the shift of the C=O stretching band from 1726 cm−1 to 1722 cm−1 and the sharp change to the broad amorphous C=O stretching absorption at 1747 cm−1 at the melting temperature of PHB around 190 °C. For an annealed sample of PHB only the melting behavior was observed in the PCMW2D correlation analysis by the sharp transition from the crystalline to the amorphous C=O stretching band.

Two-Dimensional Correlation Analysis of Temperature-Dependent FT-IR Spectra of Oleic Acid

2013 ◽  
Vol 46 (1) ◽  
pp. 21-27 ◽  
Author(s):  
Miriam Unger ◽  
Deepika Chaturvedi ◽  
Soni Mishra ◽  
Poonam Tandon ◽  
Heinz W. Siesler
Keyword(s):  
Oleic Acid ◽  
Correlation Analysis ◽  
Ir Spectra ◽  
Two Dimensional ◽  
Temperature Dependent ◽  
Ft Ir

Two-Dimensional Correlation Analysis of Time-Resolved Step-Scan FT-IR Spectra of a Liquid Crystalline Guest—Host System in an Electric Field

1997 ◽  
Vol 51 (11) ◽  
pp. 1698-1702 ◽  
Author(s):  
Miroslaw A. Czarnecki ◽  
Bojidar Jordanov ◽  
Stefano Okretic ◽  
Heinz W. Siesler
Keyword(s):  
Correlation Analysis ◽  
Electric Field ◽  
Ir Spectra ◽  
Relaxation Times ◽  
Hydrocarbon Chain ◽  
Aliphatic Chain ◽  
Two Dimensional ◽  
Time Resolved ◽  
Ft Ir ◽  
Nematic Solvent

The time-resolved step-scan FT-IR spectra of a solution of 2-naphthaldehyde in a nematic solvent were recorded during switching of an electric field. The mesogen of the nematic solvent consisted of a nitrile-substituted bicyclohexyl unit and had a flexible aliphatic chain attached to it. Two-dimensional (2D) correlation analysis of the dynamic spectra was undertaken in order to investigate the details of the molecular orientation and relaxation of the sample under the influence of this electric field. In addition, from the time-resolved spectra the relaxation times of selected functionalities were estimated. The results yield strong evidence that both the nematic solvent and the solute reorient in phase at similar rates. However, the movement of the hydrocarbon chain of the nematic solvent seems to be slightly delayed with respect to the mesogen and the solute. It has been shown that the rigidity of the mesogen plays an important role in the mechanism of the electric-field-induced reorientation of the aliphatic chain.

Two-Dimensional FT-IR Correlation Analysis of the Chemisorption of Nitric Oxide on Pt(100)

1999 ◽  
Vol 53 (2) ◽  
pp. 178-183 ◽  
Author(s):  
Noel P. Magtoto ◽  
Nelson L. Sefara ◽  
Hugh H. Richardson
Keyword(s):  
Nitric Oxide ◽  
Correlation Analysis ◽  
Two Dimensional ◽  
Ft Ir
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