THE QUANTUM SOLVATION OF CYANOACETYLENE WITH HELIUM ATOMS: MICROWAVE SPECTROSCOPIC STUDIES
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Date
2005
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Ohio State University
Abstract
The rotational spectra of He$_N$-cyanoacetylene clusters ($N$ = 1, 2,3, 4, 5..) have been measured in the 3-27 GHz range using a high-resolution Fourier transform microwave spectrometer. The weakly bound clusters were generated in a pulsed free jet expansion. Manipulating the sample and nozzle conditions allowed some degree of control over the successive solvation of the molecule with He-atoms. Both the HCCCN and DCCCN isotopomers have been studied, allowing information about cluster geometry and dynamics to be determined. The presence of $^{14}$N and D nuclei in the clusters causes nuclear quadrupole hyperfine splitting of the He$_N$-HCCCN and He$_N$-DCCCN rotational transitions. This hyperfine structure was resolved, assigned, and analysed for low-$J$ transitions. The value of the rotational constants decreases towards the helium nanodroplet value with increasing cluster size for small clusters. A "turn-around" in rotational constant value is expected for $N$ $>$6. Hyperfine fitting parameters and rotational constants will be interpreted in terms of the structure and dynamics of He$_N$-HCCCN clusters.
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Author Institution: Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada