Intensity of Raman scattering in gases

Abstract

Using the apparatus described in earlier notes in NATUURE, it has been found possible to estimate by photographic photometry the intensities of the Raman lines given by various simple gases and to make a quantitative test of the theory put forward by Manne-back. The results, on the whole, seem to be favourable to the theory. The intensities of the rotational Raman lines representing the 0→1, 1→3, 2→4, and 3→5 quantum transitions in hydrogen gas are respectively in the ratio 1: 3: 0.4: 0.2, Manneback's values being 1: 2.8: 0.35: 0.19. His theory further enables us to express the absolute intensities of these lines as fractions of the undisplaced Rayleigh lines if the optical anisotropy of the molecule is known. This may be computed from the observed depolarisation of the Rayleigh scattering. In the case of hydrogen, the calculated intensity of the 0→2 rotational line, the first of the above series, comes out as 3.5 × 10 ^-3, the observed value being 2 × 10 ^-3.