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Rotational spectra of mono-substituted asymmetric $C_{6}H_{6}-H_{2}O$ dimers

Prasad, Ram B and Krishnan, Mangala Sunder and Arunan, E (2005) Rotational spectra of mono-substituted asymmetric $C_{6}H_{6}-H_{2}O$ dimers. In: Journal of Molecular Spectroscopy, 232 (2). pp. 308-314.

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Abstract

This paper reports the assignment of the rotational spectra of the m = 0 and 1 states of $^{13}CC_{5}H_{6}-H_{2}0$ and $C_{6}H_{5}D-H_{2}O$ dimers. The m = 1 progression was not identified or assigned for both $^{13}CC_{5}H_{6}-H_{2}0$ and $C_{6}H_{5}D-H_{2}O$ in the earlier work, though for the symmetric isotopomers$(C_{6}H_{6}-H_{2}O/D_{2}O/H_{2}^{18}O)$, they were identified [H.S. Gutowsky, T.Emilsson, E. Arunan, J. Chem. Phys. 99 (1993) 4883]. The m = 1 transitions for $^{13}CC_{5}H_{6}-H_{2}0$ and $C_{6}H_{5}D-H_{2}O$ were split into two,unlike that of the parent $C_{6}H_{6}-H_{2}O$ isotopomer. The splitting varied,somewhat randomly, with quantum numbers J and K. The m = 0 lines of$C_{6}H_{5}D-H_{2}O$ had significant overlap with the m = 1 lines of the parent isotopomer, clouding proper assignment, and leading to an rms deviation of about 200 kHz in the earlier work. The general semi-rigid molecular Hamiltonian coupled to an internal rotor, described recently by Duan et al. [Y.B. Duan, H.M. Zhang, K. Takagi, J. Chem. Phys. 104(1996) 3914], is used in this work to assign both m = 0 and 1 states of $^{13}CC_{5}H_{6}-H_{2}0$ and $C_{6}H_{5}D-H_{2}O$ dimers. Consequently, the m = 0 fits for $^{13}CC_{5}H_{6}-H_{2}0/D_{2}O$ have an rms deviation of only 4/7 kHz, comparable to experimental uncertainties. The fits for m = 1 transitions for $^{13}CC_{5}H_{6}-H_{2}0$ and $C_{6}H_{5}D-H_{2}O$ dimers have an rms deviation of about 200 kHz. However, it is of the same order of magnitude as that of the m = 1 state of the parent $C_{6}H_{5}D-H_{2}O$ dimer. The A rotational constants determined from the m = 0 fits for both $^{13}CC_{5}H_{6}-H_{2}0$ and $^{13}CC_{5}H_{6}-D_{2}0$ isotopomers are identical and very close to the Crotational constant for $^{13}CC_{5}H_{6}$. This provides a direct experimental determination for the C rotational constant of $^{13}CC_{5}H_{6}$, which has a negligible dipole moment.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to Elsevier.
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 08 Sep 2005
Last Modified: 19 Sep 2010 04:20
URI: http://eprints.iisc.ernet.in/id/eprint/3619

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