Limiting case requirement large-molecule

A useful tool to be gained from this theory is the predictive power based on the large-molecule limiting case requirement that, for an intramolecular decay pathway to be available to an "isolated" molecule, the condition pfV >> 1 must be met. When pf is small (usually for small molecules or small energy gaps between initial and final states), it is most likely that no final states are in resonance with the initial state and no mixing occurs an external perturbation is required to produce the transition and the process is observed to be collision-induced. Very small values of Pf, therefore, would indicate the possibility of small-molecule behavior. 

However, TSI-LC/MS applications did not completely capture the imagination of chemists and biologists in the pharmaceutical industry. TSI- LC/MS was overshadowed by its unpredictable performance and questionable ruggedness when compared to HPLC with ultraviolet (UV) detection. This perception was the case, in part, because pharmaceutical researchers were ready for a universal LC/MS system, but with very few limits. Simple methods to handle small and large molecules, combined with a gentle technique for ionization, were needed. Researchers were not content with the unique capabilities of TSI-LC/MS. They wanted few boundaries for applicability with familiar levels of analytical performance (i.e., similar to LC/U V). This requirement was not necessarily derived from an analytical perspective, but rather an industry perspective, which ultimately forms the basis of acceptance. Whether this requirement... 

Recent work by Lim and coworkers [11,12] on small thiones of C, and Cjv excited state symmetry has clearly demonstrated the symmetry requirements of vibronicaUy induced radiationless transitions. In the low pressure gas phase, Cjv molecules such as thioformaldehyde, HjCS, exhibit both strong Sj - Sq fluorescence and strong Tj - Sq phosphorescence. These molecules therefore exhibit rates of S, - Sq internal conversion and Tj - Sq intersystem crossing that are small in comparison with the excited state radiative decay rates, despite the fact that the density of states in Sq is sufficiently large that the molecule s radiationless transitions should fall into the statistical limit case. On the other hand similar thiones of C, excited state symmetry exhibit small quantum... 

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