2. Use an approximate 20-fold dilution of the available stock solutions. Knowing the exact concentration is not important in this lab--what is important is having solutions with peak absorbances between 0.5 and 1.0.
3. Since the peak absorbances are located well into the visible region, you may use the plastic cells for this experiment.
4. Each dye will have two peaks--the lower wavelength peak should correspond to the dimer. At the recommended maximum absorbances, the dimer should have a lower peak absorbance than the monomer.
4. To find the actual peak location, take the three points at each peak and do a 2nd order regression. You can print the spectra into a file and upload the file into a spreadsheet. Note: Here is a 2nd order model: Absorbance = a* w^2 + b*w + c, where w is the wavelength. Set up spreadsheet columns of w^2 and w for the independent variables and of Absorbance for the dependent variable. You will need to use at least three points, but you may use more.
5. Compare your maxima with the literature values and with your predicted maxima using the particle in the box model.
6. In determining the length of the "box," the number of bonds
used is Nb=p+3, where p is the number of carbon atoms.
For each of the dyes, take the experimental maxima and determine the "effective"
length of the box. You may do this by calculating a value for a,
where Nb=p+3+a.