Study Of Fermi Resonance By The Method Of Solvent Variation

Fermi resonance is a very common phenomenon in molecularvibration spectra, especially in polyatomic molecule with complexstructure. The second harmonic intensity only corresponds to from1/10 to 1/100 of fundamental frequency intensity, to say nothing of thethird harmonic or overtone. But because of Fermi resonance, theintensity of doubling-frequency or combination frequency is greatlystrengthened. Solvent variation is still a chief method to the study ofFermi resonance. In our opinion, concentration variation is alsoconsidered, besides the different solvents. A major object of our workis to try finding a method, which can reflect not only the change ofsolvent sorts, but also the concentration. Obviously, this paper is veryhelpful to establish the related theory.Ultraviolet spectrum, Infrared spectrum, Raman spectrum,nuclear magnetic resonance spectrum and mass spectrum in molecularspectrum have abroad applications in studying the properties of thecomplexes. Ultraviolet spectrum mainly reveals the nature ofunsaturated group, the interaction of electrons and spatial effects;theinfrared spectrum can reflect the existence of the functional group;Raman spectrum is tightly related to the molecular structure, whichintensity, frequency shift, line width and depolarization ratio arecontacting with the molecular structure closely, including vibrationlevel, rotational level, symmetry, and so on. With the development ofchemistry, biology and single molecular study, it becomes imperativeto study solvent effect deeply. Most of chemical reactions andphysiological mechanism perform in solution. Furthermore, manyreactions were effected by solvent environment. Whether solventpolarity or solution concentration changes, some vibration peaks willhave frequency shift. Then solvent effect becomes important, and it issignificant to study it. In order to have deep considerations of therelationship between solvent and solute towards the study of Fermiresonance, this paper contains the detailed contents to discuss thesolvent effect.In the paper, intramolecular Fermi resonance of p-Benzoquinonewas mainly discussed by the method of solvent variation and itsinfrared spectra were collected in thirteen solvents. The frequency ofC=O stretching motion of p-Benzoquinone in carbon tetrachloride is1669cm-1 and there is obvious Fermi resonance of p-Benzoquinone inorganic solvents. Generally, the result must involve Fermi resonance ofthe C=O stretching fundamental at 1666cm-1 with two combinationsbetween ring bend at 600cm-1 and C-H bend at 1066cm-1. In ourexperiment, the p-Benzoquinone solutions were 0.1M and its Fermidoublet in thirteen solvents were collected using Nicolet 360 FT-IR.From the spectrum of p-Benzoquinone, the positions of every peakwere observed, then the frequency separations Δ between the twopeaks were calculated, the integrated intensity ratio R were calculatedwith the software of OriginPro7.5. Thus, the Fermi couplingcoefficients W in different solvents were easily obtained by putting thevalues of R and Δ into equations, which is a necessary preparationfor estimating the values of each vibration frequency before coupling.According to the theory of J.Fernandez Bertran and others, the plot ofΔ0 versus R, which is used to judge the coupling extent, has indicatedthat experimental data are in good agreement with theoretical analysis.After the deep discussion, we find that if we consider therelationship between the relative change of Δ0 versus R, it can moreclearly explain the experimental results, moreover, a concretemathematical expression of them has been derived. Their functionformula and coordinate curve are presented in this paper. From theexperiments, both of them can be the reference to the theoreticalanalysis. Thus, we believe this is an improvement of the analyticmethod and it'll be very helpful to the further study.This paper also contains a tentative work of intermolecular Fermiresonance. Raman spectra of carbon tetrachloride in carbon disulfideare collected by different concentrations and experimental phenomenaare presented. In CS2 the band at 800cm-1 shows a blue shift about2cm-1. However, because of the effect of isotope on Fermi resonance,in CCL4 the band 759cm-1 doesn't present a perfect result by curvefitting. Also, there are no enough reports and theories aboutintermolecular Fermi resonance and we only present the preliminaryexperimental phenomena. So, it is very difficult to discuss further thefrequency shift and intensity variation.It is well known that the method of spectral analysis like otherinstrumental analysis has a wide application to whether the ultrapurematerial, the environmental science, space science or the super-traceand remote control. Each analytic method has its different feature.With the enlargement of analysis task and analysis object, the samplebecomes more and more complicated and it puts forward the newchallenges to the spectral analysis method. For example, the quickdevelopment of Molecule Biology accelerates the bioscience,chemistry subject, even detecting single molecule.The advancement of science requires us to measure the wholecharacteristic of material, in addition, to explore the chemical andphysical features of the single molecular. Study of Fermi resonance byvarying the solvent provides an evidence and experimental basis on thestudy of microcosmic action mechanism. The more important thing isto contribute to the basic theoretical study, for example, quantummechanics and intermolecular interaction.