Relaxation processes nomenclature

As mentioned in the introduction, the above discussion of the small-, large-, and intermediate-molecule limits of electronic relaxation processes can also be utilized with very minor modifications to discuss the phenomena of intramolecular vibrational relaxation in isolated polyatomic mole-cules. ° Figure 4 is still applicable to this situation. The basis functions are now taken to be either pure harmonic vibrational states, some local-mode vibrational eigenfunctions, or some alternative nonlinear mode-type wave-functions. In the following the nomenclature of vibrational modes is utilized, but its interpretation as normal or local can be chosen to suit the circumstances at hand. 

We adopt the nomenclature of molecular spectroscopy to describe the excitation and relaxation processes in PPV derivatives, since the polymer photophysics is similar to the photophysics of large organic molecules [146]. Figure 22.11 shows schematically the configuration coordinate diagram of all... 

We make one important note here regarding nomenclature. Early explanations of CIDNP invoked an Overhauser-type mechanism, implying a dynamic process similar to spin relaxation hence the word dynamic m the CIDNP acronym. This is now known to be incorrect, but the acronym has prevailed in its infant fomi. 

I In some ways the nomenclature is a little confusing. In nmr it is traditional to use Ti and to describe the relaxation times of specific nuclear processes and t the mean lifetime of a nucleus in a particular state. In chemical relaxation methods, however, t refers to the relaxation time. Chemical relaxation methods and nmr are similar in that in each, one time function is measured and its variation with concentration is followed. The difference comes in the relationships of the respective time functions to the concentrations. 

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