Scanning Spectrophotometer Determination Of The Quantum Numbers (Initial And Final States), Wavelength, And Length Of The Box Using Particle In A One Dimensional Box Model For Experimental And Computation Vibration-Rotation Spectroscopy For Carbon Monoxid

Experimental and Computation Vibration-Rotation Spectroscopy for Carbon Monoxide Through the Use of High-Resolution Infrared (IR) Spectra

Sarah Keeling

Partner: Ishan Mehta

Experiment #6

CHE 441G вЂ" 002

Date of Experiment: February 22, 2006

Date Due: March 1, 2006

Introduction:

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:

Materials:

- A Nicolet Nexus 670 IR Spectrometer was used.

- OMNIC software was used.

- Gaussian 98 software was used

Procedure

- 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 пÑ"ÑŸvвЂ™Ð²Ð‚™=0) and 4100-4350 cm-1 for (v’=2 пÑ"ÑŸ vвЂ™Ð²Ð‚™=0)), on the Quality/Parameter tab made sure box was unchecked next to “special rangeвЂ¦Ð²Ð‚Ñœ 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 Calculate and going to Gaussian under the GaussView 2.1 window another screen appeared.

- On the new screen job type was selected as opt+freq, charge as 0, spin as 1, method as HF, basis set as 6-311G(d,p), and the input was saved to the computer for further reference.

Results:

Data from the machines was collected to make the needed calculations in finding the variables пЃ¶e, vo (1  0), vo (2  0), пЃ¶exe, Be, Bo, B1, B2, Ie, Io, I1, I2, re, ro, r1, r2, пЃЎe, and De to compare with the literature values. To further define the above variables; пЃ¶e is the fundamental vibrational or harmonic frequency in cmвЂ"1, v is the vibrational quantum number, пЃ¶exe is the anharmonicity correction, B is the rotational constant in cmпЂ­1, I is the moment of inertia, r is the internuclear distance, пЃЎe is the rotation-vibration interaction parameter, and De is the dissociation energy. In the following equations other variables can be taken as follows; Ev is the vibrational energy level, J is the rotational quantum number, h is Planck's constant, c is the speed of light, пЃ¶v is the vibrational frequency, Dv is the centrifugal distortion term (correction of rigid rotor) , EJ is the rotational energy level, Bv is the rotational constant of the molecule in the vibrational level v, пЂ¤e is a correction term with is very small in size compared with De and therefore is not considered, пЃ­ is the reduced mass of the molecule, and Ev,J is the total energy at v and J. The tables shown below include wavelength, J, and M values for the R and P branches for both sets of the collected data. Information from these tables will be used throughout the calculations to obtain the desired quantities. The R branch, located on the left side begins with a value of J=0 as the wave number increase, the value of J increases as well with each transition adding a factor of +1, and m=J+1. The P branch, located on the right side begins with a value of J=1 as the wave number increase, the value of J decreases with each transition adding a factor of -1, and m=-J. At the wavenumber where О"J=0 the division between these two branches occurs.

The next step in the calculation process was to establish the values of vo, (Bv+Bo), (Bv-Bo), and De where the value of v is either 1 or 2. Tablecurve program