Ground state rotational and K=3 splitting parameters determined from high resolution infrared spectra: (HSiD3)-Si-28, (HGeD3)-Ge-70 and (HSnD3)-Sn-120

High-resolution (ca. 0.003 cm(-1)) FTIR spectra in the nu(5) range of HSiD3 and monoisotopic (HSnD3)-Sn-120 were recorded and analyzed to yield ground state parameters by means of combination differences. The splitting of the ground state K = 3 level into A(+) and A(-) sublevels was detected and could be equivalently accounted for by two different models. Model I involves Delta k = +/- 3 interactions which affect all K levels. The value of the interaction constant epsilon strongly depends on those of C-0 and D-K,D-0, and J-dependent distortion parameters different to those from model II are obtained. This involves Delta k = +/- 6 interactions which account almost exclusively for the K = 3 splitting in the HMD(3) molecules, M = Si, Ge and Sn. Also including data for (HGeD3)-Ge-70, obtained from a re-analysis of previous nu(4) and nu(5) spectra for the K = 3 transitions, the following values of the model II splitting parameter h(3) were obtained (all in 10(-11) cm(-1)): (HSiD3)-Si-28 3.996(14), (HGeD3)-Ge-70 4.058(49), (HSnD3)-Sn-120 3.637(33).