Knowledge Bank

Rotational spectra are being observed for an ($H2O-HCN$)-Ar trimer with a Balle/Flygare Fourier transform microwave spectrometer. Thus far, two sets of closely related transitions have been assigned to the parent isotopic species, each with both $a-$ and $b-$dipole transitions and with $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N$ hfs corresponding to = 0.647 MHz and $\chi bb=-2.900$ MHz. There is no hfs attributable to H---H interactions in the $H2O$. A fit of the line centers, including centrifugal distortion, gives rotational constants (A, B, and C) for species 1 of 3535.64, 1845.07, and 1219.30 MHz, and for species II of 3508.55, 1897.09, and 1228.82 MHz. The structure is roughly T-shaped consisting of the linear, pseudoplanar $H2O-HCN$ $dimer1$ with an argon alongside. The a-dipole transitions are stronger than the $b$-dipole in species II but the reverse is found in species I. This suggests that the effective orientation of the $H2O$ differs in the two species. Further work is underway and will be reported.