Microwave spectrum, structure, and nuclear quadrupole coupling constant tensor of vinyl bromide and iodide

Ab initio anharmonic force field and equilibrium structure of vinyl bromide

“…We have only used the constants of [8] because mixing sets of rotational constants is a questionable practice: a small incompatibility of the sets would affect the accuracy of the structure determination whereas the error practically compensates if all lines are measured and analyzed in the same way. The equilibrium inertial defect, D e , is also given in this table.…”

“…For the ''effective'' r 0 -structure and the more recent r m -structure models which include approximate mass-dependent rovibrational contributions, the experimental ground state rotational constants of 16 isotopologues listed in [8] were used as input to a program for iterated, weighted and correlated least-squares fitting the 3 · 16 inertial moments to obtain the nine independent structural parameters of the planar molecule plus up to six optional rovibrational parameters (program Ru211a, author H.D. Rudolph, unpublished).…”

“…The relation of the errors may influence the result in a way that should be retained. Therefore, we have used for all experimental models and also for the semi-experimental equilibrium model the uncorrelated average experimental errors of [8], (in MHz) errðAÞ ¼ 0:311, errðBÞ ¼ 0:018, errðCÞ ¼ 0:018 as the basis for computing the weights. Vinyl bromide being a near-prolate rotator (j = À0.988), errðAÞ is by far the largest error.…”

“…The theoretical rotation-vibration interaction constants deduced from the ab initio force field were combined with the known experimental ground state rotational constants [8] to yield the semi-experimental equilibrium rotational constants of Table 4. We have only used the constants of [8] because mixing sets of rotational constants is a questionable practice: a small incompatibility of the sets would affect the accuracy of the structure determination whereas the error practically compensates if all lines are measured and analyzed in the same way.…”

“…In 1990, Hayashi et al [8] measured the microwave spectra of 16 isotopologues and determined for each species two diagonal quartic centrifugal distortion and bromine quadrupole coupling constants. They also derived the substitution (r s ) structure.…”