Chapter 11, Problem 11B.5ST

Interpretation Introduction

Interpretation:

Rotational Raman spectrum of the molecule ${\text{NH}}_3$ has to be determined.

Concept Introduction:

In Raman, spectroscopy, scattering of radiation by molecules are studied.

• If the scattering of radiation is at lower frequency comparing to the incident radiation, then it is Stokes lines.
• If the scattering of radiation is at higher frequency comparing to the incident radiation, then it is Anti-Stokes lines.

Gross selection rule for rotational Raman spectra:

The polarizability of the molecule should not be the same in every directions (anisotropic).

The shift in frequency of the radiation during a transition from the level J to $J+2$ is given by,

  $\Delta {\nu }_J\text{ = 2B}\left(2J+3\right)$

Wavenumber is the total number of wavelengths observed at a unit distance. Equation for wavenumber can be given as,

  $\begin{array}{c}\text{Wavenumber, }\overline{\text{ν}}\text{ =}\frac{\text{1}}{\text{λ}}\text{ = }\frac{\text{ν}}{\text{c}}\\ \\ \text{where, }\\ \text{λ}\text{=}\text{wavelength}\\ \text{ν}=\text{frequency}\\ \text{c = speed of light}\end{array}$