title: A threshold-based approach to calorimetry in helium droplets: measurement of binding energies of water clusters.
abstract: Helium droplet beam methods have emerged as a versatile technique that can be used to assemble a wide variety of atomic and molecular clusters. We have developed a method to measure the binding energies of clusters assembled in helium droplets by determining the minimum droplet sizes required to assemble and detect selected clusters in the spectrum of the doped droplet beam. The differences in the droplet sizes required between the various multimers are then used to estimate the incremental binding energies. We have applied this method to measure the binding energies of cyclic water clusters from the dimer to the tetramer. We obtain measured values of D(0) that are in agreement with theoretical estimates to within ∼20%. Our results suggest that this threshold-based approach should be generally applicable using either mass spectrometry or optical spectroscopy techniques for detection, provided that the clusters selected for study are at least as strongly bound as those of water, and that a peak in the overall spectrum of the beam corresponding only to the cluster chosen (at least in the vicinity of the threshold) can be located.
authors.affiliation: University of Dayton Research Institute, Dayton, Ohio 45469, USA. wlewis2@udayton.edu
authors.forename: William K
authors.initials: WK
authors.lastname: Lewis
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Harruff-Miller
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gord
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Gord
authors.forename: Elena A
authors.initials: EA
authors.lastname: Guliants
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Bunker