Rotational Raman spectrum of benzene

To detennine the interatomic distances in the benzene molecule from the rotational Raman spectrum. 

The pure rotational Raman spectra of gaseous C H, and CjD, were photographed by Stoicheff (Canadian J. Phj. 1954, 32, 339) in the second order of a 21 ft grating. Both spectra were resolved and analysed yielding for the rotational constants the values in the lowest vibrational state 

The relevant atomic weights on the physical scale are (Birge, Phjre. Soc. Rep. Prog. Phys. 1941, 8,127) 

It is assumed that the benzene molecule has the symmetry of a plane hexagon, and that the differences between the atomic distances in C H, and CgD, are negligible. The moments of inertia Ib are then just half the moments of inertia Ic about the sixfold axis of sjonmetiy. 

The technique of precise measurement of the pure rotational Raman spectrum has been developed only recently. As appHed in this instance it leads to values of the interatomic distances between five and twenty times as accurate as the values obtained from electron diffraction. 

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