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An Experiment in Electronic Spectroscopy: Information Enhancement Using Second Derivative Analysis

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B. R. Ramachandran and Arthur M. Halpern

Indiana State University, Department of Chemistry, Terre Haute, IN 47809

J. Chem. Educ., 1998, 75 (2), p 234

DOI: 10.1021/ed075p234

Publication Date (Web): February 1, 1998

Section:

History, Education, and Documentation

Abstract

Second derivative (SD) analysis is extremely effective in enhancing and extracting information from experimental data where the information sought lies hidden. This paper describes an interesting experiment in molecular electronic spectroscopy in which information about the excited state vibrational levels of a molecule, contained in the absorption spectrum in latent form, is extracted by the SD analysis. The efficacy of the SD method is first demonstrated using synthetic data where the positions of hardly-noticeable gaussian features, buried obscurely in a strong, rising background, are recovered quantitatively. The method is then applied to the absorption spectrum of trimethylamine (TMA), which contains two absorption bands (arising from the n_N --> 3s_N and n_N â€”> 3p_N transitions) that show subtle undulations due to the presence of underlying vibronic features corresponding to the out-of-plane bending motion of the molecule. The positions of more than 30 vibrational features are determined using the SD analysis. The constancy of the spacing between adjacent features in each absorption band in the spectrum suggests that the excited state out-of-plane bending potential of TMA is considerably harmonic.

Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Laboratory Instruction

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Laboratory Computing / Interfacing

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This article has been cited by 1 ACS Journal articles (1 most recent appear below).

Comparison of Analytical Methods: Direct Emission versus First-Derivative Fluorometric Methods for Quinine Determination in Tonic Waters
Siddharth Pandey , Tammie L. Borders , Carmen E. Hernández , Lindsay E. Roy , Gaddum D. Reddy , Geo L. Martinez , Autumn Jackson , Guenevere Brown and William E. Acree Jr.
Journal of Chemical Education1999 76 (1), 85
- Comparison of Analytical Methods: Direct Emission versus First-Derivative Fluorometric Methods for Quinine Determination in Tonic Waters
  Siddharth Pandey , Tammie L. Borders , Carmen E. Hernández , Lindsay E. Roy , Gaddum D. Reddy , Geo L. Martinez , Autumn Jackson , Guenevere Brown and William E. Acree Jr.
  Journal of Chemical Education1999 76 (1), 85
  An undergraduate laboratory experiment is designed for the quantitative determination of quinine in tonic water samples. It is based upon direct fluorescence emission and first-derivative spectroscopic methods. Unlike other published laboratory ...
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