Molecular beam electric resonance spectroscopy of water dimer and ammonia-hydrogen sulfide complex.

摘要

The rotational spectra of hydrogen bonded complexes, such as (H{dollar}sb2{dollar}O){dollar}sb2{dollar}, NH{dollar}sb3{dollar}-H{dollar}sb2{dollar}S and NH{dollar}sb3{dollar}-H{dollar}sb2{dollar}O have been studied by the high resolution molecular beam electric resonance technique. This method is a versatile one which achieves a resolution as small as 3 kHz and ranges from 0-40 GHz.; In the NH{dollar}sb3{dollar}-H{dollar}sb2{dollar}S project, the microwave and radio frequency transitions for the K=0 states were measured for several isotopic species. Rotational constants, centrifugal distortion constants, quadrupole coupling constants and dipole moments were obtained. All these spectroscopic constants can be interpreted in terms of a vibrationally averaged structure and gives the structural parameters of R{dollar}sb{lcub}rm NS{rcub}{dollar} = 3.6389 A, {dollar}thetasb{lcub}rm N{rcub}{dollar} = 23.95{dollar}spcirc{dollar}(6) and {dollar}thetasb{lcub}rm S{rcub}{dollar} = 40.49{dollar}spcirc{dollar}. This N {dollar}cdots{dollar} H -- S arrangement is a typical linear hydrogen bonded structure and is very similar to the structure of NH{dollar}sb3{dollar}-H{dollar}sb2{dollar}O complex.; A vast amount of rigorous linear Stark effect data was observed for the slightly asymmetric rotors NH{dollar}sb3{dollar}-H{dollar}sb2{dollar}S and NH{dollar}sb3{dollar}-H{dollar}sb2{dollar}O, and their fully deuterated species as well. In order to explain the anomalous Stark effects, the internal rotation motion of the NH{dollar}sb3{dollar} monomer was investigated through a dynamics calculation using a three-fold potential function.; Each rotational energy level of water dimer is split into six sublevels which complicates the spectra. Two rigid rotor-like tunneling states of E{dollar}sppm{dollar} symmetry with K = 1 were found and extended measurements were made for the A{dollar}sb2sppm{dollar}/B{dollar}sb2sppm{dollar} states with K = 1 and E{dollar}sppm{dollar}, A{dollar}sb1sppm{dollar}, A{dollar}sb2sppm{dollar}/B{dollar}sb2sppm{dollar} species with K = 0. A four line hyperfine structure was resolved for A{dollar}sb2sppm{dollar}/B{dollar}sb2sppm{dollar} species with K = 0 and confirmed its symmetry assignment. In addition, an important Coriolis perturbation was found in the tunneling-rotational spectra by comparing rotational constants of the newly observed E{dollar}sppm{dollar} K = 1 states to that of the K = 0 states; a similar perturbed pattern also occurred in A{dollar}sb2sppm{dollar}/B{dollar}sb2sppm{dollar} symmetry. The Coriolis coupling model was used to analyze the observed perturbed spectra.