Nuclear Quadrupole Hyperfine Structure of the Direct /-Type Transitions of the Fulminic Acid Isotopomers H12C14N16O and H13C14N16O

Abstract

The direct I- type transitions of H133C14N16O in the vibrational states (υ4,υ5) = (01) and (03) were measured in the frequency range from 18 to 40 GHz. These transitions show a nuclear quadrupole hyperfine structure caused by the 14N nucleus, which could partially be resolved at Doppler-limited resolution. The analogous transitions of the parent species. H12C14N16O, were remeasured. They displayed a very similar hyperfine structure, also partially resolved. The hyperfine patterns of both H12C14N16O and H13C14N16O were analysed by means of contour fitting s to the absorption profiles. The parameter ηseQq, which is responsible for the splittings, is determined to be 645(20) kHz for the vibrational state (01) and 890(44) kHz for the vibrational state (03) for H12C14N16O and 642(32) kHz for (01) and 898(22) kHz for (03) for H13C14N16O. This unexpectedly large splitting parameter for states involving the large amplitude motion υ5 (HCN bending) is discussed as another consequence of the quasilinearity of fulminic acid, in view of the fact that the analogous transitions for the vibrational state (10) (NCO bending) do not split or even show a significant line broadening at the resolution used for the present measurements