Effect of the Oscillating Electric Field Due to the Oscillating Electric Dipole on Raman Lines

Abstract

Raman Effect is the measurement of the intensity and wavelength of the inelastically scattered radiation that falls on a molecule. The electric field of the incident radiation polarizes the molecule on which it falls and this leads to the creation of an oscillating dipole. The incident polarized laser light is inelastically scattered by the molecular sample. The scattered light contains modified wavelengths called the Stokes and anti-Stokes lines or wavelengths. The oscillating electric dipole, created by the incident radiation, creates an oscillating electric field around it. Since the oscillating electric field of the incident radiation creates an oscillating electric dipole that create an oscillating electric field around it, it was surmised that this oscillating electric field can affect the frequency of vibration or oscillation of the oscillating electric dipole that produces it. This novel effect will change the frequency (frequencies) of the scattered radiation resulting in Stokes and anti-Stokes lines with modified frequencies. This theoretical research and its importance can be understood like this. For instance, if there are two cells or molecules, side by side, in which one is a healthy cell and the other is cancerous, or two different types of molecules are sitting side by side, this types of scattering should be able to distinguish one from the other since the Stokes and anti-Stokes lines from the two molecules will not be identical. Thus, the incident radiation of angular frequency ω1 polarizes the charges of the molecule on which it falls and this leads to the creation of an oscillating dipole of frequency ω2. The oscillating dipole creates an oscillating electric field that can create additional frequency of the oscillating dipole that created it, and let this be ωD. Then the Raman lines can have frequencies (ω1+ω2+ωD), (ω1+ω2-ωD), (ω1-ω2+ωD), and (ω1-ω2-ωD). Depending on the relative magnitudes of ω2 and ωD, Raman lines will be designated as Stokes and Anti-Stokes lines. Due to the law of conservation of energy, ωD will be less than ω2 since an oscillating dipole cannot create field of frequency more than its own frequency. Hence the frequencies (ω1-ω2+ωD) and (ω1-ω2-ωD) correspond to Stokes lines, and frequencies. (ω1+ω2+ωD) and (ω1+ω2‑ωD) will correspond to Anti-Stokes lines. Calculations for Stokes and Anti-stokes lines have been done for some molecules, namely Ammonia compound (NH3), Nitrousoxide compound (N2O), Water (H2O), Sulphur dioxide compound (SO2), Ozone compound (O3). Calculations have also been done for compounds containing carbon, such as Dichloromethane compound (CH4Cl2), Formic acid compound (CH2O2), Methanol compound (CH4O), Benzene compound (C6H6), Propane compound (C3H8), and Carbonyl chloride compound (Cl2CO). The theory developed predicts new phenomena of getting Stokes and anti-Stokes lines with modified wavelengths which have not been observed experimentally as of to-day.

Keywords

• electric dipole
• raman lines
• stokes lines
• anti-stokes lines
• oscillating