Factors determining feasibility experiments

Utilizing ionization efficiency curves to determine relative populations of vibrationally excited states (as in the photoionization experiments) is a quite valid procedure in view of the long radiative lifetime that characterizes vibrational transitions within an electronic state (several milliseconds). However, use of any ionization efficiency curve (electron impact, photon impact, or photoelectron spectroscopic) to obtain relative populations of electronically excited states requires great care. A more direct experimental determination using a procedure such as the attenuation method is to be preferred. If the latter is not feasible, accurate knowledge of the lifetimes of the states is necessary for calculation of the fraction that has decayed within the time scale of the experiment. Accurate Franck -Condon factors for the transitions from these radiating states to the various lower vibronic states are also required for calculation of the modified distribution of internal states relevant to the experiment.991 102... 

As we have seen, there are many 2D methods and variants that can provide data critical to structure determination. There is no general way to decide which ones are best for solving a particular problem, as various kinds of information may be needed. Also, some experiments may be less feasible than others because of instrumental capabilities, amount of sample available, and time requirements. We summarize here only a few of the major factors involved in selecting such 2D methods. 

The experiment design involves selecting multiple levels of each factor to define the conditions for each experimental run, and some subject matter expert/end-user knowledge is required to select the range of the factor levels to cover. As the optimum level of the response is not known in advance, at least five factor levels should be used, and the range of these levels should be as wide as possible with the low and high levels determined by the end user s input of feasibility and safety considerations. 

The tests on porous polymer formation described in this section are quite rudimentary. Certainly more need to be performed before such factors as pore size and size distribution can be controlled or predicted. Examination of swelling, plasticization, and melting phenomena in a view cell determination of molecular weight distributions of the extract and substrate (and of the parent polymer) and investigations of other thermoplastic polymers are just a few areas for study. In spite of the rudimentary nature of the experiments, the feasibility tests have established that the concept is reduced to practice, at least... 

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