Bp. Nuccio et al., MILLIMETER-WAVE ROTATIONAL SPECTROSCOPY OF MGOD AND CAOD (X(2)SIGMA(+)), The Journal of chemical physics, 103(21), 1995, pp. 9193-9199
Pure rotational spectra of CaOD and MgOD have been recorded in the ran
ge 200-390 GHz using millimeter/sub-mm direct absorption spectroscopy.
Transitions arising from the (000), (010), (020), and (100) modes hav
e been measured for the (2) Sigma(+) ground electronic states of these
free radicals. The data were analyzed successfully using a linear (2)
Sigma(+) model for CaOD; for MgOD, only the (000) and (010) states co
uld be fit with this Hamiltonian. Moreover, the (010) data required th
e addition of a substantial p(Pi) term to account for contamination of
excited (2) Pi electronic states. For both species, the alpha(2) vibr
ation-rotation term was found to be negative, in contrast to MgOH and
CaOH, suggesting a less anharmonic contribution to the bending potenti
al in CaOD and MgOD. These measurements also indicate a shorter O-H bo
nd in MgOH than the other alkaline earth hydroxide radicals, which lik
ely results because this species is quasilinear. (C) 1995 American Ins
titute of Physics.