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Rotational spectra, structures, and dynamics of small Arm–(H2O)n clusters: The Ar–(H2O)2 trimer

Arunan, E and Emilsson, T and Gutowsky, HS (2002) Rotational spectra, structures, and dynamics of small Arm–(H2O)n clusters: The Ar–(H2O)2 trimer. In: Journal of Chemical Physics, 116 (12). pp. 4886-95.


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Rotational-tunneling spectra for Ar–(H2O)2 and Ar–(D2O)2 have been observed with the Balle–Flygare Fourier transform microwave spectrometer. The tunneling levels of the trimer appear to correlate with those of the water dimer. The "a" dipole transitions from the A and E+ states of Ar–(H2O)2 and A, B, and E+ states of Ar–(D2O)2 could be fit to a semirigid rotor Watson Hamiltonian. However, only the E+ states give "b" dipole transitions near rigid rotor predictions. The "b" dipole transitions for A and B are rotational-tunneling spectra. For Ar–(D2O)2, these transitions were observed and the donor–acceptor interchange tunneling splitting is determined as 106.3 MHz, compared to about 1100 MHz in the free (D2O)2. From this splitting, the barrier for interchange tunneling is calculated to be 642 cm–1. This splitting for Ar–(H2O)2 is estimated as 4–5 GHz. This and the spin statistical weight of 0 for the B state have made it difficult to observe the "b" dipole rotational tunneling spectra for Ar–(H2O)2. From the rotational constants for (H2 18O) containing trimers, the O–O distance in the trimer is estimated as 2.945 Å. This is significantly (0.035 Å) shorter than the O–O distance reported for water dimer. The Ar is located on the "b" axis of the water dimer. Assuming the water to be a structureless sphere in the trimer, leads to Ar-c.m.(H2O) distance of 3.637 Å, very close to the same value in the Ar–H2O dimer.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to American Institute of Physics (AIP)
Keywords: microwave spectrometer;Rotational spectra;Arm–(H2O)n clusters;Ar–(H2O)2 trimer
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 09 Jun 2004
Last Modified: 19 Sep 2010 04:12
URI: http://eprints.iisc.ernet.in/id/eprint/61

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