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首页> 美国政府科技报告 >Raman Spectroscopic Studies of Isotopic Diatomic Molecules and a Technique for Measuring Stable Isotope Ratios Using Raman Scattering.
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Raman Spectroscopic Studies of Isotopic Diatomic Molecules and a Technique for Measuring Stable Isotope Ratios Using Raman Scattering.

机译：同位素双原子分子的拉曼光谱研究和利用拉曼散射测量稳定同位素比的技术。

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A method for measuring stable isotope ratios using Raman scattering has been developed. This method consists of simultaneously counting photons scattered out of a high-intensity laser beam by different isotopically-substituted molecules. A number of studies of isotopic diatomic molecules have been made. The Q-branches of the Raman spectra of the isotopic molecules exp 14 N exp 15 N and exp 16 O exp 18 O were observed at natural abundance in nitrogen and oxygen samples. Comparison of the ratios of the intensities of the Q-branches of the major nitrogen and oxygen isotopic molecules with mass spectrometric determinations of the isotopic compositions yielded scattering cross sections of exp 14 N exp 15 N relative to exp 14 N exp 14 N and exp 16 O exp 18 O relative to exp 16 O exp 16 O. These cross section ratios differ from unity, a difference which can be explained by considering nuclear mass effects on the Franck-Condon factors of the molecular transitions. The measured intensities of the exp 14 N exp 15 N and exp 16 O exp 18 O Q-branches provided the baseline data needed to make the previously-mentioned extrapolation. High-resolution (approximately 0.15cm exp -1 ) spectra of the Q-branches of exp 14 N exp 14 N and exp 16 O exp 16 O yielded a direct determination of alpha /sub e/ (the difference between the rotational constant in the ground and first excited vibrational states) for these molecules. The measured values are in excellent agreement with those obtained by other means. Complete Raman spectra (pure rotation,rotation-vibration,and high-resolution Q-branch) were obtained on a sample of pure exp 18 O exp 18 O. Analysis of this data yielded the molecular parameters:the equilibrium internuclear separation r/sub e/,the moment of inertia I/sub e/,and the energy parameters alpha /sub e/, B/sub e/,and delta G/sub exp 1 /sub 2 /. These are in good agreement with data obtained by microwave spectroscopy. (ERA citation 01:026695)

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