THE ROTATIONAL SPECTRUM OF THE $H_{2}-OCS$ VAN DER WAALS COMPLEX
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Date
2001
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The microwave spectrum of the $H_{2}-OCS$ complex has been studied using molecular beam electric resonance optothermal spectrometer with 20% 40:1 $H_{2}/OCS$ gas mixture in 5 atm He. This investigation is stimulated by the recent He droplet study of this $species^{a}$. The $H_{2}/OCS$ complex has T-shaped global minimum according to a high-level ab initio potential surface calculation. We have performed bound state calculations with bound $program^{b}$ to obtain the rotational transitions of the ground state for $para-H_{2}/OCS$ complex. Several spectral transitions of $^{32}S$ and $^{34}S$ isomers have been measured at frequencies close to the prediction in the frequency region of 9-31 GHz. For example, two observed peaks at 10218.3 and 20385.7 MHz from $H_{2}-OC^{32}S$ complex have been compared with the predicted $1_{01}\leftarrow 0_{00}$ and $2_{02}\leftarrow 1_{01}$ transitions at 10594.7 and 21110.2 MHz, respectively. However a number of transitions predicted were not observed although the analogous transitions in the He-OCS complex have been readily $seen^{c}$. In addition, small doublet splitting of near 50 KHz is observed. Since ortho-$H_{2}$ contributes to about 75 percent abundance of normal $H_{2}$ at room temperature and might bind stronger with OCS molecule than para-$H_{2}$, we believe that what we observed in this study may belongs to ortho-$H_{2}-OCS$ complex. Our current experimental measurement with pure para-$H_{2}$ would provide detailed results for rotational transitions of the ground state for $H_{2}-OCS$ complex in the near future.
Description
$^{a}$S. Grebenev, B. G. Sartakov, J. P. Toennies and A. F. Vilesov, J. Chem. Phys. 114(2), 617, 2001. $^{b}$J. M. Hutson, Bound Computer Program, Version5, 1993. $^{c}$Kelly Higgins and William Klemperer, J. Chem. Phys. 110(3), 1383, 1999.
Author Institution: Harvard University; Department of Chemistry and Chemical Biology, Harvard University; Department of Chemistry and Chemical Biology, University of Minnesota
Author Institution: Harvard University; Department of Chemistry and Chemical Biology, Harvard University; Department of Chemistry and Chemical Biology, University of Minnesota