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Spectroscopic Simulator

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 + ½) + 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:
  • J (J + 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.