Electron attachment time-of-flight mass spectrometry reveals fcc bulk-like packing in CO2 aggregates

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 agreement with prior experimental and theoretical work.