9.6: Emission Spectrum of Iodine Vapor
- Page ID
- 370546
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This semester, you use a laser spectrometer to investigate the Molecular Spectroscopy of Iodine Vapor. In this assignment you will plot the electronic potential energy curves (Morse potentials) for the iodine molecule. A discussion of the terms used in this assignment can be found in your textbook (D. A. McQuarrie, and J. D. Simon "Physical Chemistry: A Molecular Approach", University Science Books, CA, 1997, Chapter 13, Section 13.1-13.7.
The functional form of the ground and excited state Morse potential wells for iodine molecule I2 are given by the expression
\(V(R)= {T}_{e}+ {D}_{e} {\left[ 1- {e}^{-a(R- {R}_{e}) } \right]}^{2}\)
where V(R) is the potential energy of the system (y-axis), R is the interatomic separation (x-axis) between the iodine atoms, and Te, and De, a and Re are constants. Literature values for these constants are given below.
| Constant | Ground State | Excited State |
| Te | 0 \(( {cm}^{1})\) (arbitrarily set) | 15730 \(( {cm}^{1})\) |
| De | 12244 \(( {cm}^{1})\) | 4112 \(( {cm}^{1})\) |
| a | 1.87 \({ \left(\overset{\circ}{ A}\right) }^{-1}\) | 2.00 \({ \left(\overset{\circ}{ A}\right) }^{-1}\) |
| Re | 2.67 \(( \overset{\circ}{ A})\) | 2.97 \(( \overset{\circ}{ A})\) |
- Generate a vector R that varies between 2 and 6 Å, in increments of 0.01 Å.
- For both ground and excited states, calculate V(R) for each value of R using the above expression and the constants from the table. NOTE: These constants should be used in the units given above. No conversions are necessary.
- On the same graph, plot V(R) (y-axis) versus R (x-axis), for both ground and excited states. Rescale the axes using the following axis scales:
- V(R): 0 – 22500 cm–1
- R: 2 – 6 Å
- Assemble a pdf document that contains both this assignment and the FTIR assignment into one pdf document and submit your work on Gradescope.