BENZENE-WATER DIMERS; ROTATIONAL SPECTRA, DYNAMICS, AND STRUCTURE
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Date
1993
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Publisher
Ohio State University
Abstract
The $m = 0$, ground internal rotation state of the $C_{6}H_{6}-H_{2}O,-D_{2}O$, and --HDO dimers has been characterized by $Blake^{1}$ at high J (4 to 10). We report extension of the studies to low J (0 to 4), to the first excited $(m = 1)$ internal rotation state, to the hfs exhibited by some of the transitions, and to several other isotopic species $(H_{2}^{18}O, C_{6}H_{5}D, C_{5}^{13}CH_{6})$. The $m = 0$ and 1 rotational spectra of the dimers with $C_{6}H_{6}$ are fitted by the $expression^{2}$ $v = 2(J+1)[B-D_{JK}K^{2} -D_{Jm}m^{2}-D_{JKm}Km-H_{JKm}M^{2}K^{2}] - 4(J+1)^{3}D_{J}$ which for $m = 0$ is the standard description of a symmetric top. The fit indicates that the dimers with $C_{6}H_{6}$ are coaxial rotors of six- and two-fold symmetry with a near-zero effective barrier to internal $rotation.^{3}$ The dimers with $C_{6}H_{5}D$ or $C_{5}{^{13}}CH_{6}$ have $m = 0$ transitions fitted as semi-rigid, slightly asymmetric tops while the $m = 1$ transitions exhibit features implying that the D and $^{13}C$ substitution affect the barrier. The geometrical and dynamic structures of the dimers will be discussed.
Description
$^{1}$. S. Suzuki, P. G. Green, R. E. Bumgarner, S. Dasgupta, W. A. Goddard III, and G. A. Blake, Science 257, 942 (1992). $^{2}$. G. T. Fraser, F.J. Lovas, and R. D. Suenram, J. Chem. Phys. 84, 5983 (1986). $^{3}$. A. P. Cox, J. Mol. Struct. 97, 61(1983).
Author Institution: Noyes Chemical Laboratory, University of Illinois
Author Institution: Noyes Chemical Laboratory, University of Illinois