Electron attachment time-of-flight mass spectrometry reveals geometrical shell closings in (CO2)70≤N≤350 van der Waals aggregates. Quantitative structural parameters obtained from the observed geometrical shell closing pattern are compared to theory. These parameters are consistent with bulk-like distorted face-centered-cubic (fcc) packing of CO2 aggregates in this size range. A magic number is seen in the mass spectrum at N = 116 which was previously shown to result from a nearly spherical object with bulk-like fcc packing. These results confirm that the critical value for the cluster-to-bulk packing transition lies below N ∼ 100, in qualitative aggreement with prior experimental and theoretical work.
Bibliographical noteFunding Information:
This work was partially supported by a grant from the National Institutes of Health under grant number 5R21HG02023-02 and National Science foundation grant number CHE-0135581. The authors would like to express thanks to Dr. Udo Buck for providing a manuscript of work not yet published and access to details of his data analysis.