FTIR Vibration-Rotation Spectrum and Analysis of the 13CO2 Asymmetric Stretch Fundamental Band

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 20 (2015) pp 53-59

FTIR Vibration-Rotation Spectrum and Analysis of the ¹³CO₂Asymmetric Stretch Fundamental Band

David A. Dolson*^,† and Catherine B. Anders^†,‡

^†Department of Chemistry, Wright State University, Dayton, OH 45435, USA, david.dolson@wright.edu; ^‡Department of Biomolecular Sciences, Boise State University, Boise, ID 83725
Received January 7, 2014. Accepted February 17, 2014.

Published: 24 March 2015

Abstract. A physical chemistry experiment involving the acquisition and analysis of the FTIR vibration-rotation spectrum of the asymmetric stretch fundamental band of ¹³CO₂ is presented. Due to the large band strength and 1.1% natural abundance of carbon-13, this band is readily observable in a typical air background spectrum and is shifted sufficiently from the stronger ¹²CO₂ fundamental such that the ¹³CO₂ P-branch lines from P(2) to P(50) are almost completely free of interferences and easily assigned. All of the ¹³CO₂ R-branch lines appear within the lower frequency region of the ¹²CO₂ P-branch, which creates assignment challenges. While preserving all of the pedagogical benefits of the similar ¹²CO₂ experiment, this experiment offers students the realistic opportunity of engaging in the more common spectroscopic practice of predicting additional line positions from analysis of a partial data set and then finding and adding as many of the predicted lines as may be identified to obtain a refined fit of the larger data set. This experiment may best be conducted with a spectral resolution of 0.5 wavenumber or better.

Key Words: Laboratories and Demonstrations; physical chemistry; FTIR vibration-rotation spectrum bond length determination; carbon dioxide asymmetric stretch; isotopic carbon dioxide rigid rotor; nonrigid rotor; nuclear spin statistical weights

(*) Corresponding author. (E-mail: david.dolson@wright.edu )

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Supporting Materials:

There are 5 supporting files available (s00897152601asm.zip). CO₂ 001 band (x,y) data columns at 0.125 cm^–1 and 0.5 cm^–1 resolution (co2_001band.xlsx), Laboratory handout (13co2_001band.docx), Figure 1 (figure-1.tif), Peak-labeled spectrum at 0.5 cm^–1 resolution (peak-labeled 0500 res spectrum.tif), and Peak-labeled spectrum at 0.125 cm^–1 resolution (peak-labeled 0125 res spectrum.tif). (1.53 MB)