UV-Visible Spectra

Task: Generate and Display the UV-Visible spectrum of nitrocyclopentadiene (). 

Time: 7 minutes

We built this molecule in the Fragment Library tutorial. The geometry must be optimized before starting.

1. Open the optimized file: File|Open "nitrocyclo-PM5".
2. Generate and tabulate the UV-Visible Spectrum.
   1. Select
   2. Experiment|New
   3. Select:
   
   1. Property of: Chemical Sample
   2. Property: Chemical Sample
   3. Property: UV-Visible transitions
   4. Using: ZINDO CI at current geometry
   4. Click Start.
   5. The calculation window opens.  Information about the progress of the experiment scrolls in the window.  The Tabulator may take 3 to 4 minutes, depending on your computer processor. When the calculation is done, it will say "Tabulation complete".
   6. Save the file: File|Save
3. Visualize the spectrum. 
   1. Open the file if necessary (File|Open cyclonitro-PM5)
   2. Select Analyze|UV-visible Transitions. 
   3. A screen with the visible transitions appears.
4. Select Tile from the Window menu to view the spectrum and the molecule (with the MOs involved in the transition).
5. Chose the the Select tool, , and click on a transition indicated by a triangle in the spectrum window.
   1. The transition will be highlighted in red to show that it is selected. The MO surfaces will be displayed in the other window.  
   2. The surface of the lower energy orbital is shown in green and blue. 
   3. The higher energy orbital surface is shaded in red and yellow (click in the workspace window to select both surfaces).
   4. Select the structure window. Use the rotate button,, to visualize all sides of the orbital surface.
6. Repeat the process to view the orbitals involves in the other transitions.

   Generate and display the IR spectrum of nitrocyclopentadiene in the next lesson.