Recommended for you They will make you ♥ Physics. Lectures by Walter Lewin. Rigid-Rotor model of diatomic molecule Usefulness of rotational spectra 11 2. Dec 21, 2020 - Rotational and Vibrational Spectra of Diatomic Molecules - Molecular Spectroscopy, CSIR-NET Government Jobs Notes | EduRev is made by best teachers of Government Jobs. (CC BY-NC-SA; anonymous by request) IR spectroscopy which has become so useful in identification, estimation, and structure determination of compounds draws its strength from being able to identify the various vibrational modes of a molecule. Vibrational and Rotational Spectroscopy of Diatomic Molecules Spectroscopy is an important tool in the study of atoms and molecules, giving us an understanding of their quantized energy levels. This document is highly rated by Government Jobs students and has been viewed 3260 times. Rotational and vibrational-rotational spectra. Example: CO B = 1.92118 cm-1 → r CO = 1.128227 Å 10-6 Å = 10-16 m Ic h 8 2 2 r e Rigid-Rotor model of diatomic molecule Measured spectra Physical characteristics of molecule Line spacing =2B B I r e Accurately! The separation between the components is of the order of 10 cm-1 – the structure is due rotational transitions Example: CO B = 1.92118 cm-1 → r CO = 1.128227 Å 10-6 Å = 10-16 m Ic h 8 2 2 re Intensities of spectral lines 14 2. Heteronuclear molecules can emit a purely rotational, or a vibrational-rotational spectrum. The right panel shows the ground and first excited vibrational states, labeled and , respectively, with thei Different ways of visualizing the 6 degrees of freedom of a diatomic molecule. Vibration-rotation (rovibrational) spectra Each line of the high-resolution vibrational spectrum of a gas-phase heteronuclear diatomic molecule is found to consist of a large number of closely spaced components (band spectra). Usefulness of rotational spectra 13 2. Quantum Vibration. From the dependence of the energy of the eigenstates on , as , we immediately see that that spectral lines due to rotational transitions satisfying will have frequencies (for ) Rigid-Rotor model of diatomic molecule Measured spectra Physical characteristics of molecule Line spacing =2B B I r e Accurately! The fundamental vibration frequency and rotational constant of carbon monoxide molecule are 6.5 x 10 13 s-1 and 1.743 x 10 11 s-1 respectively. electronic, vibrational, rotational and center of mass contributions to the energy of a diatomic molecule. The key result is simple expressions for the electronic, vibrational and rotational The vibrational energy level, which is the energy level associated with the vibrational energy of a molecule, is more difficult to estimate than the rotational energy level.However, we can estimate these levels by assuming that the two atoms in the diatomic molecule are connected by an ideal spring of spring constant k.The potential energy of this spring system is Within the harmonic and rigid rotor approximations, the rotational-vibrational energy levels (in wavenumbers) of a diatomic molecule are given by , where , are the vibrational and rotational quantum numbers, respectively, is the harmonic vibrational constant, and is the rotational constant. For the Love of Physics - Walter Lewin - May 16, 2011 - Duration: 1:01:26. Application of the laws of quantum mechanics to the rotational motion of the diatomic molecule shows that the rotational energy is quantized and is given by E J = J(J + 1)(h 2 /8π 2 I), where h is Planck’s constant and J = 0, 1, 2,… is the rotational quantum number.