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Raman Spectra of Pinene

1930 
IN a series of researches to be published in full shortly on the Raman spectra of d- and l-pinene in the liquid condition, we have observed near the line σ = 23257 (corresponding to the Raman ½ = 1454 excited by the line λ = 404.6 of mercury) a series of eight lines, very weak, sensibly at the same distance, and the distances of which from the Raman line above mentioned can be represented to a good approximation by the relation Δ½ = B(4m + 4),1 which, as is well known, corresponds to the series of Raman frequencies of rotation relative to the rotator with fixed axis. By putting B = 6.15, the mean differences between calculated and observed values amount to ±0.017 per cent. The value of m should correspond to the even series, namely, 2, 4, 6, 8, etc. Supposing the rotator composed by two atoms of H of one CH2 rotating round the carbon atom (considering that the Raman frequency σ = 1454 is attributed2 to the transverse oscillations of the two H atoms in the group CH2), we calculate, from the value of B, that the distance between the atoms of hydrogen and carbon in the CH2 group is 1.16 × 10−8 cm., in good accordance with the values published by Mecke,3 namely, 1.13 × 10−8 cm. In view, however, of the difficulty of obtaining good vibration and rotation spectra in liquids with complex molecules, we merely direct attention to the coincidence observed (working with a spectrograph with small dispersion); we intend to repeat the work with higher dispersion, before giving a definite interpretation to the results.
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