Use the spectrometer on the second floor. Take the spectrum first at room temperature and then after heating the iodine cell at 60 degrees in an oven and insulating it. Make sure you save a table of all the minima in the measured spectrum electronically in addition to printing out the spectrum. Bring a floppy disk or a USB memory stick to transfer the data from the computer connected to the instrument to your own computer.
Directions for operating the spectrometer: pdf file
The goal of the experiment is to obtain the harmonic and anaharmonic constant(s) characterizing the ground and one of the excited electronic states of the iodine molecule, I2. Use figure 2 in the description of the experiment in NGS to assign all the minima (band-heads) in the spectrum you obtained. A printout of the spectrum with all minima assigned to vibrational state in the lower and upper electronic state must accompany your report. Make a Deslandres table (see NGS) to spot any inconsistencies in the assignment.
Do a Birge-Spooner plot which is described well in the photocopy from the book "Physical Chemistry" by R.J. Sime (experiment 31). First of all, use all the peaks corresponding to excitations from the vibrational ground state in the electronic ground state to the various vibrational states in the excited electronic state to obtain the harmonic and two anharmonic constants for the excited state. Then, choose an excited state for which you have peaks corresponding to excitations from the ground vibrational state as well as from the first and second excited vibrational states in the electronic ground state. Use the three numbers to determine the harmonic and one anharmonic constant for the ground electronic state. Repeat this procedure for other sets of peaks and compare the results. Fit Morse potential curves to the data for the ground and excited electronic states. Make a plot of the two curves on the same graph (see NGS). Make use of the Frank-Condon principle to estimate the displacement of the minimum energy in the excited electronic state with respect to the minimum in the ground electronic state.