INVESTIGATION OF MOLECULAR FORCE FIELD WITH HELP OF PARAMETER REPRESENTATION OF FORCE CONSTANTS .2. NITROSYL FLUORIDE

The parameter method is described in the cases where the force field is over- and underdetermined by the experimental data, respectively. In the first case a least-squares method is used. Advantages of the parameter method vs. the conventional least-squares calculations are its stability and uniformity, and the easy control of the assignment. In the underdetermined case, maximum and minimum values of force constants which are compatible with the measured data and other constraints are obtained. The use of the parameter method is in this case vital. As an example, the force constants of ONF were determined by a least-squares method, using both isotopic frequencies and centrifugal distortion constants. The results are similar to those of Jones et al.11, but FON,α is much higher, FNO, NF is lower and FNO is higher. No other solution exists compatible with both the isotope and τ data. The final force field reproduces all experimental data very well. © 1969.