Techniques in the Study of Emission Spectra of Polyatomic Molecules—The Spectra of Benzaldehyde and Acetophenone

A rather simple method is presented for obtaining the electrodeless discharge emission spectra of polyatomic molecules. The spectra obtained for benzaldehyde and acetophenone were of very high intensity and without a trace of spectral impurities. It was possible in the case of benzaldehyde to detect over a hundred sharp bands in the region 3688—5433 A, and to observe some structure in the ``broad'' emission bands of acetophenone. In both these molecules there is strong evidence that the emission involves the same upper state as does the long-wave absorption. The (0,0) band of benzaldehyde is assigned at 26914 cm—1 and that of acetophenone at 27501 cm—1. The possibility of extending the techniques to other molecules is discussed.