Heteronudear System

The experiment is used to separate chemical shifts and J-couplings for homo- and heteronudear systems. In simple cases the chemical shifts and J-couplings may be directly obtained from the 2D spectrum by inspection. For severely overlapped first-order spectra or strongly coupled spin systems the estimated parameters obtained from the spectrum may be used as starting values in a computer assisted spectral analysis as outlined in Modern Spectral Analysis (Volume 3). 

Spin-Edio Production in a Heteronudear AX Spin System... 

The series of well-defined sulfur marker peaks provides the data points on which the computer system performs a high-order polynomial fit to construct a mass axis calibration curve. The latter can then be used to convert experimentally measured intensity-time profiles to intensity-m/z plots (mass spectra). A caveat that should not be ignored is the formation of heteronudear species by gas-phase reactions of sulfur with other inorganic substances [13]. Even though none of these het-eronuclear species may exist in the solid state or in solution, their presence in the gas phase complicates mass spectra. 

The heteronudear molecule. 4B is thereforeless stable than the homonu-dear molecules and Bg. At decreasing temperature the equilibrium composition is more and more diifted in favour of A and Ba. We may say that isotopic substitution lowers the stability of the system. 

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