Experimental and Computation Vibration-Rotation Spectroscopy for Carbon Monoxide Through the Use of High-Resolution Infrared (IR) Spectra
The goal of this experiment is to study the most precise way of measuring molecular bond lengths and introduction to computational software used for studying molecular properties. This is of interest in that the instrument to being used, a Fourier-transform infrared (FT-IR) spectrometer, can measure the vibrational and rotational transitions of the fundamental and first overtone of CO. Through this experiment the objective is to collect data from the aforementioned instrument in order to determine vibrational and rotational spectroscopic constants and CO’s bond length, then to compare them with quantum chemical calculation.
Experimental and Computational Methods:
- A Nicolet Nexus 670 IR Spectrometer was used.
- OMNIC software was used.
- Gaussian 98 software was used
- OMNIC software was open on the computer connected to the spectrometer.
- For data collection the following parameters were set up; in Smart Accessory Change window click OK and make sure setting is on Transition E.S.P., under Collect and Experimental Setup set scan number to 20 and resolution to 0.5 on the Collect tab, on the Bench tab selected a window material and wavelength number range (1950-2250 cm-1 for (v’=1 v’’=0) and 4100-4350 cm-1 for (v’=2 v’’=0)), on the Quality/Parameter tab made sure box was unchecked next to “special range…” and selected the maximum resolution, and clicked ok.
- A saved background sample was selected for each of the two overtones from the files under the Browse option located under the Collect section of Experimental Setup under Collect.
- A cell filled with CO was taken from storage and placed into the spectrometer Col Smpl was selected.
- When the sample was collected text orientation was selected to be Perpendicular to x-axis under the Options section of Edit, Find peaks was selected from under Analyze, the baseline was clicked to include all peaks, and the file was printed.
- The wavenumber was changed to that for the second overtone and the previous two steps were completed for that wave range.
- All devices and equipment were cleaned and returned to their rightful places and the lab area used was also tidied up.
- For computation a computer in the CP computer lab was utilized.
- The GaussView program was selected and a new molecule was built.
- Once in the program Element and C was selected under the Builder Window, then center of the View1: New window was clicked to make a CH4 molecule appear.
- Again under the Element section O was selected and the same window as previously was clicked to create a water molecule.
- A triple bond is made selecting Bond under Builder, highlighting C and O, and clicking Triple Bond.
- Delete was clicked to get rid of excess atoms and the bond length was optimized by selecting Clean.
- Next, by highlighting...