Title | THE MICROWAVE-SPECTRUM, STRUCTURE, AND HARMONIC FORCE-FIELD OF THE VANDERWAALS TRIMER AR2-OCS |
Publication Type | Journal Article |
Year of Publication | 1993 |
Authors | Xu, YJ, Gerry, MCL, Connelly, JP, Howard, BJ |
Journal | Journal of Chemical Physics |
Volume | 98 |
Pagination | 2735-2741 |
Date Published | Feb |
Type of Article | Article |
ISBN Number | 0021-9606 |
Keywords | AR-HCN, AR2HCL, ARHCL, CLUSTER, CONSTANTS, laser spectroscopy, ROTATIONAL SPECTRA |
Abstract | The microwave rotational spectra of the van der Waals trimers Ar2-OCS, (Ar2-OCS)-S-34, and (Ar2-OCS)-18 have been observed between 7.0 and 18.0 GHz using pulsed molecular beam microwave Fourier transform (MWFT) spectroscopy. Sixty-five transitions, both a and c type, have been assigned for Ar2-OCS, as well as 37 transitions and 19 transitions for (Ar2-OCS)-S-34 and (Ar2-COS)-O-18 respectively. The rotational constants and quartic centrifugal distortion constants have been determined. The trimer has been found to be a distorted tetrahedrally shaped highly asymmetric top (K= approximately 0.377) with the OCS subunit lying in the C(s) symmetry plane. An effective ground state structure has been determined. The Ar-Ar distance and the two ’’Ar-center of mass of OCS’’ distances are slightly longer than those in the corresponding dimers Ar2 and Ar-OCS, respectively. A harmonic force field analysis has been performed on the basis of the centrifugal distortion constants, to predict the van der Waals force constants and the corresponding vibrational frequencies. The Ar-Ar stretch force constant of the trimer is 0.008 42 mdyn angstrom-1 which compares favorably with 0.0078 mdyn angstrom-1 reported for the free dimer Ar2. A comparison of the geometry and spectroscopic properties of Ar2-OCS with those of Ar2 and of the Ar2-HX (X = F, Cl, CN) trimers is given. |
URL | <Go to ISI>://A1993KP93800024 |
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