Infrared

Moustafa Abdaly Laborantuddannelsen Metropol 20-09-2013

Introduction

The infrared (IR) spectrum of CO has been analyzed to determine the fundamental constants of the molecule. The results can be expressed in terms of the rotation constant , the rotationvibrational frequency and the vibrational frequency. BY IR spectroscopy on ground state molecules, it is not possible to determine the zeroth-order vibrational frequency, so we report the vibrational frequency . The results are consistent with data in the literature, wthin experimental error.

Experimental

The experiment was carried out with a Nicolet Fourier transform infrared (FTIR) spectrometer. The resolution of the spectrometer was set at for all spectra. The experiment involved the accumulation of background spectra which were subtracted from the spectra of the sample to provide the response of the sample. The detector was a nitrogen-cooled cadmium-telluride detector. Each experiment resulted from the average 64 transient responses coaded, with the background spectrum being the accumulation of 64 spectra without the sample present. The data were analyzed by Fourier transformation using the software of the instrument. The data were saved to disk, and were subsequently analyzed with a spreadsheet program, in this case, Microsoft EXCEL.

Results and Discussion

One difficulty in resolving the data in the vibration-rotation spectroscopy experiment is determining the F J J transition is forbidden and will be absent from the spectrum. This makes the separation of the first transition of the R branch from the first transition of the P branch approximately twice the spacing of the other transitions (which are otherwise roughly equally spaced). Examination of the difference between the line positions