What is the Origin of Positional Fluctuation of Spectral Features: True Frequency Shift or Relative Intensity Changes of Two Overlapped Bands?

$29.00 plus tax (Refund Policy)

Buy Article:

Abstract:

We investigated what is really meant by so-called positional or frequency fluctuation of spectral features. To show the difference between the true frequency shift of a single band and apparent peak maximum shift caused by relative intensity changes of overlapped adjacent bands, we analyzed infrared (IR) spectra of the OH stretching band of ethylene glycol during the heating process and the C=O stretching band of acetone in a mixed solvent CHCl3/CCl4 with varying solvent compositions. These spectra are well-known examples of so-called “band shift” phenomena often interpreted as the manifestation of gradual changes in the IR frequency associated with a specific chemical bond under the influence of molecular interactions. Analyses of IR spectra showed that the apparent positional shifts of peak maxima in these systems are actually due to relative contribution changes of two overlapped bands, instead of the gradual frequency shift of a single band induced by the change in the strength of molecular interactions. To further clarify our interpretation of “peak maximum shifts”, we also analyzed simulated spectral datasets, comparing the true band frequency shift and change in the relative contributions of overlapped bands. It was found that principal component analysis (PCA) is a surprisingly sensitive tool to distinguish the two possible mechanisms of peak maximum shift. The new insight revealed by this study should help the interpretation of molecular interactions probed by vibrational spectroscopy.

Keywords: FREQUENCY SHIFTS; HYDROGEN BONDS; MOLECULAR INTERACTIONS; PCA; PRINCIPAL COMPONENT ANALYSIS; SELF-MODELING CURVE RESOLUTION; SMCR; VIBRATIONAL SPECTROSCOPY

Document Type: Research Article

DOI: http://dx.doi.org/10.1366/000370210792434396

Affiliations: 1: Department of Chemistry, and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chunchon 200-701, Korea 2: The Procter & Gamble Company, West Chester, Ohio 45069, USA 3: Department of Chemistry, and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chunchon 200-701, Korea. ymjung@kangwon.ac.kr

Publication date: September 1, 2010

More about this publication?
Related content

Tools

Favourites

Share Content

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content
Cookie Policy
X
Cookie Policy
ingentaconnect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more