DETERMINATION SCHEMES.

$^{1}$J.K.G. Watson, J. Chem. Phys., 46, 1935 (1967). $^{2}$J.M. Brown and T.J. Sears, J. Mol. Spectrosc., 75, 111, (1979).""Author Institution: Area de Qu{\'i}mica Cu{\'a}ntica, Universidad Aut{\'o}noma Metropolitana Iztapalapa. Av. Michoac{\'a}n y La Pur{\'i}sima, Iztapalapa, Apartado Postal 55-532, C. P. 09340The model Hamiltonian propossed by Watson and Brown et $al^{2} \\ H=\sum{h_{i} o_{i}}+\sum{ h_{i}^{s}o_{i}^{s}}\\$ is widely used for fitting the rotational spectra of molecules with an unpaired electron and $D_{2h}$ symmetry. The linear dependence ammong the molecular constants has been eliminated with a reduction $scheme^{2}$. The model Hamiltonian and the number of molecular constants which participate in a reduction scheme can be divided in terms of order of magnitude. The value of zero ( reduction scheme ) is not the only one that can give a set of linearly independent molecular constants ( determination scheme ). In order to have a good fit to the spectrum the order of magnitud must he preserved, which constrains the range of possible values assigned to each molecular constant involved in the determination scheme. The fourth and eight order of magnitude constants behaivor during a fitting have been studied according to the asymmetry parameter (K) of the molecule. It has been stablish a set of equations relating two possible sets of constants in terms of transformation parameters. The transformation parameters between two possible schemes of determination have been evaluated