# Diatomic Vibrating Indicator Lab Report

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Diatomic vibrating rotator: The near infra-red spectra of molecules consist of bands not lines, each band being composed of close lines arranged in a particular manner. In the series of lines which are not equidistant, a line is missing at the centre of the band. The missing line is known as the null line or zero gap. The lines show a rather poor tendency of convergence toward the high-wave number side and the band is said to be degraded toward the low-wave number side, that is, towards the red. The observed fine structure in infra-red band suggests that in a vibrational transition the molecule also changes its rotational energy state that is it must be treated as a vibrating rotator. The energies of two motions are so different; we consider…show more content…
For a given vibrational transition, the rotational transitions ΔJ=+1 give one set of lines called the R-branch, while the rotational transitions ΔJ=-1 give the other set of lines called the P-branch. All the lines of both branches form a vibration-rotation band. For ΔJ=+1 J’=J’’+1 J’-J’’=+1 ΔεJ, v= ϖ0 + 2B (J’’+1) cm-1 J’’=0, 1, 2…….. For ΔJ=-1 J’’=J’+1 J’-J’’=-1 ΔεJ, v= ϖ0 + 2B(J’’+1) cm-1 J’’=0,1,2………. ΔεJ, v= ϖ0 + 2Bm m=-2,-1, +1, +2……. This equation represents the combined vibrational-rotational spectrum. It will consists of equally spaced lines (spacing=2B) on each side of band origin ϖ0 ϖ0 will not appear as m is not equal to…show more content…
Since then many types of lasers have been constructed at different wavelengths at which laser light may interact with matter. Light assigned to the middle infrared (MIR) range (2.5µm-25µm) can excite fundamental bonding vibrations of molecules. Thereby, the absorbed photon energy matching the natural vibrational energy of the molecules to increase the amplitude of the vibration motion of bonds in molecules. However, only those bonds that have a dipole moment which changes as a function of time are capable of absorbing infrared radiation (infra-red active molecules). Overtone vibrations of molecules can be excited by photon absorption processes in the near-infrared (NIR) region