Raman spectroscopic studies of isotopic diatomic molecules and a technique for measuring stable isotope ratios using Raman scattering. [Cross sections]
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 /sup 14/N/sup 15/N and /sup 16/O/sup 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 /sup 14/N/sup 15/N relative to /sup 14/N/sup 14/N and /sup 16/O/sup 18/O relative to /sup 16/O/sup 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 /sup 14/N/sup 15/N and /sup 16/O/sup 18/O Q-branches provided the baseline data needed to make the previously-mentioned extrapolation. High-resolution (approximately 0.15 cm/sup -1/) spectra of the Q-branches of /sup 14/N/sup 14/N and /sup 16/O/sup 16/O yielded a direct determination of ..cap 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 /sup 18/O/sup 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 ..cap alpha../sub e/, B/sub e/, and ..delta..G/sub /sup 1///sub 2//. These are in good agreement with data obtained by microwave spectroscopy.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 7358154
- Report Number(s):
- UCRL-52077; TRN: 76-019040
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NITROGEN
EMISSION SPECTRA
INTERATOMIC DISTANCES
MOLECULE COLLISIONS
MOMENT OF INERTIA
OXYGEN
CROSS SECTIONS
FRANCK-CONDON PRINCIPLE
ISOTOPE EFFECTS
LASERS
MASS
MOLECULES
NITROGEN 14
NITROGEN 15
OXYGEN 16
OXYGEN 18
RAMAN EFFECT
COLLISIONS
CRYOGENIC FLUIDS
DISTANCE
ELEMENTS
EVEN-EVEN NUCLEI
FLUIDS
ISOTOPES
LIGHT NUCLEI
NITROGEN ISOTOPES
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
OXYGEN ISOTOPES
SPECTRA
STABLE ISOTOPES
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena