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Spectroscopic Simulator

(see description below the applet)


This applet covers an aspect of the Physical Chemistry II course that students often find confusing. Although it is based on relatively simple mathematics, a complete understanding of the phenomenon requires assimilating the following concepts:

  • The energy levels of a diatomic molecule are given by the formula:
    • E(v,J) = hv (v + ) + BJ (J + 1); v = 0..infinity, J=0..infinity
  • A molecule absorbs light at frequencies that correspond to difference between energy levels. In this case, we are interested in the following differences, frequency of light:
    • E (v = 1, J') - E (v = 0, J); with J' = J + 1 or J -1
  • The intensity of the transition is proportional to the population of the lower state, intensity is proportional to:
    • (2J + 1) exp[-E (v = 0, J) / kT]

Many students are comfortable with these separate concepts, but find it difficult to combine them together to produce an understanding of rovibrational spectroscopy. This applet simulates an infra-red spectrometer, allowing students to adjust the experimental and molecular parameters and observe the effects on the infra-red spectrum. Students may use the applet to first focus on each of the individual concepts, within the context of the actual experiment, and then to integrate these concepts into a coherent whole.

For your convenience, you can additionally [download] and run this applet offline as a standalone application.


   Page Last Updated: 02.23.2010