In this regard, the Morse potential model provides an accurate description of the observed vibrational energy spectra of diatomic molecules, and has great popularity with chemists. Reading: Vibrational Spectroscopy Revised: 2/24/15 In Raman spectroscopy, electromagnetic radiation is not absorbed (as in IR spectroscopy), but scattered. In particular, the well-known Morse potential function is a more reasonable and realistic model [10] for these systems. RAMAN SPECTROSCOPY PURE ROTATIONAL, VIBRATIONAL, VIBRATIONAL-ROTATIONAL, RAMAN SPECTRA. Description of vibrational modes, rotational modes, transition rules and raman spectroscopy In spectroscopy, one studies the transitions between the energy levels associated with the internal motion of atoms and molecules and concentrates on a problem of reduced dimen- sionality3 k− 3: called vibrational motion, and clearly at low energies a good model for the nuclear motion is a Harmonic oscillator. Historically, the vibrational and rotational spectra of dia-tomic molecules have played a central role in testing the con-sistency of quantum mechanics. Simple Example: Vibrational Spectroscopy of a Diatomic If we just have a diatomic molecule, there is only one degree of freedom (the bond length), and so it is reasonable to model diatomic vibrations using a 1D harmonic oscillator: A nonlinear molecule possesses 3n - 6 vibrational modes (3 translations, 3 rotations) Like the diatomic case, each normal mode of vibration has a characteristic frequency and can assume a series of quantized energies. In IR spectroscopy a specific Consider a diatomic molecule AB. 2. These tables represent the first part of a series of critical reviews on the microwave spectra of molecules. Homonuclear diatomic molecules (such as H 2, O 2, N 2, Cl 2) – have zero dipole (non polar) - have zero change of dipole during the rotation, hence NO interaction with radiation - hence homonuclear diatomic molecules are microwave inactive Heteronuclear diatomic molecules (such as HCl, HF, CO) – have Molecular Spectroscopy PPT - Free download as Powerpoint Presentation (.ppt / .pptx), PDF File (.pdf), Text File (.txt) or view presentation slides online. (From Eisbergand Resnick, Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles (1985)) 10x10-21) Estimated rotational energies vs. quantum number j, for O 2 8 All of the rotational spectral lines observed and reported in the open literature for 121 diatomic molecules have been tabulated. In the case of diatomic molecules, it is clear that vibrational spectra can only be recorded for heteronuclear compounds such as CO and HCl, but not for homonuclear species such as H 2 and N 2. 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