Efficient Formation of Size-Selected Clusters upon Pickup of Dopants into Multiply Charged Helium Droplets

Abstract

Properties of clusters often depend critically on the exact number of atomic or molecular building blocks, however, most methods of cluster formation lead to a broad, size distribution and cluster intensity anomalies that are often designated as magic numbers. Here we present a novel approach of breeding size-selected clusters via pickup of dopants into multiply charged helium nanodroplets. The size and charge state of the initially undoped droplets and the vapor pressure of the dopant in the pickup region, determines the size of the dopant cluster ions that are extracted from the host droplets, via evaporation of the helium matrix in a collision cell filled with room temperature helium or via surface collisions. Size distributions of the selected dopant cluster ions are determined utilizing a high-resolution time of flight mass spectrometer. The comparison of the experimental data, with simulations taking into consideration the pickup probability into a shrinking He droplet due to evaporation during the pickup process, provides a simple explanation for the emergence of size distributions that are narrower than Poisson.

Conical Shape Fluctuations Determine the Rate of Ion Evaporation and the Emitted Cluster Size Distribution from Multicharged Droplets

“…A significant complication in the atomistic modeling of these systems arises from their large size that makes the use of a polarizable model challenging. The ion emission mechanism and the ion dopant distributions from multicharged supercooled helium droplets add even more interesting questions to be examined related to the role of a low dielectric constant solvent in the released cluster ion distributions. , …”

“…The ion emission mechanism and the ion dopant distributions from multicharged supercooled helium droplets add even more interesting questions to be examined related to the role of a low dielectric constant solvent in the released cluster ion distributions. 32,69 ■ ASSOCIATED CONTENT * sı Supporting Information…”

“…Since IEM is considered to take place in nanodroplets with a radius of approximately 10 nm, its direct experimental detection has been challenging and as a result there are continuous efforts for its verification. ,− In a recent article, Williams et al observed ion emission from electrosprayed droplets with mass ranging from 1 to 10 MDa (which corresponds to 55,000–550,000 water molecules) at the charge state of ≈+50–300 e (where e denotes the positive elementary charge). The mean charge loss at an emission event is 1.1 e , which implies that the majority of the emission events correspond to the loss of a single charge, with rare occurrence of a loss of double or triple charge.…”

Conical shape fluctuations determine the rate of ion-evaporation and the emitted cluster-size distribution from multiple-charged droplets

“…The ion-emission mechanism and the ion-dopant distributions from multi-charged supercooled helium droplets add even more interesting questions to be examined related to the role of a low dielectric constant solvent in the released cluster-ion distributions. 32,69 Supporting Information…”

“…8,9,26,27 The process can be written as Since IEM is considered to take place in nanodroplets with a radius of approximately 10 nm its direct experimental detection has been challenging and as a result there are continuous efforts for its verification. 8,[30][31][32] In a recent article, 31 Williams et al observed ion-emission from electrosprayed droplets with mass ranging from 1-10 MDa (which corresponds to 55000 to 550000 water molecules) at charge state of ≈ +50-300e (where e denotes the positive elementary charge). The mean charge loss at an emission event is 1.1e, which implies that the majority of the emission events corresponds to the loss of a single charge, with rare occurrence of a loss of double or triple charge.…”