Experimental methods, equipment and data reduction

EXPERIMENTAL METHODS, EQUIPMENT AND DATA REDUCTION 4.4.3.1 Vapor-liquid equilibrium (VLE) measurements... 

In this chapter the experimental ECD and NIMS procedures for studying the reactions of thermal electrons with molecules and negative ions are described. Gas phase electron affinities and rate constants for thermal electron attachment, electron detachment, anion dissociation, and bond dissociation energies are obtained from ECD and NIMS data. Techniques to test the validity of specific equipment and to identify problems are included. Examples of the data reduction procedure and a method to include other estimates of quantities and their uncertainties in a nonlinear least-squares analysis will be given. The nonlinear least-squares procedure for a simple two-parameter two-variable case is presented in the appendix. 

Depending on technical details of the equipment, on the sensitivity of the temperature detector, on measuring temperature, solvent vapor pressure and polymer concentration in the solution drop, a steady state for AT can be obtained after some minutes. The value of AT is the basis for thermodynamic data reduction (see below). If measuring conditions do not allow a steady state, an extrapolation method to AT at zero measuring time can be employed for data reduction. Sometimes a value is used that is obtained after a predetermined time however, this may lead to some problems with knowing the exact polymer concentration in the solution. The extrapolation method is somewhat more complicated and needs experience of the experimentator but gives an exact value of polymer concentration. Both methods are used within solvent activity measurements when polymer concentrations are higher and condensation is faster than in common polymer characterization experiments. A way to avoid these problems is discussed below. 

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