Bridging the gap between small clusters and nanodroplets: spectroscopic study and computer simulation of carbon dioxide solvated with helium atoms.

High resolution infrared spectra of HeN–CO2 clusters with N up to about 20 have been studied in the region of the CO2 v3 fundamental band. The B rotational constant initially drops as expected for a normal molecule, reaching a minimum for N = 5. Its subsequent rise for N = 6 to 11 can be interpreted as the transition from a normal (though floppy) molecule to a quantum solvation regime. For N > 13, the B value becomes approximately constant with a value about 17% larger than that measured in much larger helium nanodroplets. Quantum Monte Carlo calculations of pure rotational spectra are in excellent agreement with the measured B in this size range, and complement the experimental study with detailed structural information. For larger cluster size (N = 30-50) the simulations show a clear sign of convergence towards the nanodroplet B value.

Digital Object Identifer:10.1103/PhysRevLett.92.145503
Published with permission from the copyright holder. This is the author's copy of the work, as published in Physical Review Letters, 9 April 2004, Volume 92, Issue 14, Pages 145503-1.
Publisher URL: http://dx.doi.org/10.1103/PhysRevLett.92.145503
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