MILLIMETER WAVE SPECTROSCOPY OF THE VAN DER WAALS BENDING BAND OF He-HCN WITH A MULTI-REFLECTION JET CELL
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Date
2000
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Publisher
Ohio State University
Abstract
The He-HCN cluster is a weakly bound cluster with a binding energy of only $9 cm^{-1}, ^{a,b}$ Previously, two van der waals transitions were reported by electric resonance $spectroscopy.^{a}$ In the present study, a number of new j=1-0 van der waals bending transitions predicted below the dissociation $limit^{b}$ have been observed in 95-125 GHz region with a high sensitivity multi-reflection millimeter wave jet cell. 10 round trip optical paths were used in the measurement. We used a pulsed jet nozzle and the jet cell was evacuated by a diffusion pump. We have measured 13 Q-branch lines up to 1=4 with j=1-0 where l and j are the rotational quantum number of the cluster and the HCN subunit. The lines were fitted to a Hamiltonian expanded using a anisotropic intermolecular potential. The potential function was determined to be $V = - 2.2530(43) P_{1}(\cos\theta) -0.665(62) P_{2}(cos \theta) -0.45(17) P_{3}(\cos\theta)$ (in $cm^{-1}$ units)and shows a large anisotropy with respect to the angle $\theta$ between the HCN and the intermolecular cluster axis.
Description
$^{a}$S. Drucker, Fu-Ming Tao, W. Klemperer, J. Phys. Chem. 99, 2646 (1995). $^{b}$ K. M. Atkins, J. M. Hutson, J. Chem. Phys. 105, 440 (1996).
Author Institution: Institute for Molecular Science
Author Institution: Institute for Molecular Science