Chem 120 / Dr. Rusay

Energy Absorbance


Lab & Webshop: Greenhouse Gases II
Energy Absorbance, Infrared Spectroscopy, Molecular Motion, Vibrational Energies

Image above: Visible light being absorbed by the earth's atmosphere

Energy / Sunlight / EM Spectrum / Infrared / Ultraviolet / Greenhouse Gases

Refer to the course Lab Manual:

1) Complete the table with a list of the respective frequencies (wavenumber, cm-1) of the infrared (IR) absorbances and their corresponding percent transmission in the spectrum for your assigned greenhouse gas. (Check in lab for individual gas assignment) Consult the ChemConnections, MC2/Chemlinks and NIST WebBook pages:

2) Using IR Tutor (downloadable from:, view the IR spectrum of your assigned greenhouse gas. For each of the absorbances (peaks) that you listed in question #1, list the type of molecular vibration that corresponds to each of the absorbances in the spectrum. Eg. anti-symmetrical stretching vibration.

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