Electron attachment time-of-flight mass spectrometry reveals geometrical shell closings in van der Waals aggregates

Abstract

Articles you may be interested inPhotodissociation of (SO2XH) Van der Waals complexes and clusters (XH = C2H2, C2H4, C2H6) excited at 32 040-32090 cm−1 with formation of HSO2 and X J. Chem. Phys. 140, 054304 (2014); 10.1063/1.4863445Infrared absorption of methanethiol clusters (CH3SH) n , n = 2-5, recorded with a time-of-flight mass spectrometer using IR depletion and VUV ionization A new method to study metastable fragmentation of clusters using a reflectron time-of-flight mass spectrometer Rev.Using electron attachment time-of-flight mass spectrometry, we show how high-precision structural constants of van der Waals aggregates may be obtained for two kinds of homogeneous clusters, (SF 6 ) N and (CO 2 ) N . Furthermore, we obtain size-specific structural information over a wide range of aggregate sizes. Mass spectrometric data are presented regarding the size needed to facilitate the transition from ''cluster packing,'' dominated by nearest-neighbor interactions, to bulk-like packing.For both examples, it appears that the cluster-to-bulk packing transition may occur even for aggregates where the majority of the molecules resides at the surface. The critical size for the cluster-to-bulk transition may be related to the size at which molecules packed as bulk crystals can begin forming nearly spherical shapes. A discussion of the mechanism by which geometrical shell closings are visualized in electron attachment time-of-flight mass spectrometry is also presented. We postulate that these observations reflect the dynamics of electron localization in ordered crystallites with and without defects.

Van der Waals Clusters

“…Since the size ranges covered by the electron diffraction and the EA-TOF experiments overlap strongly, this immediately suggests that the geometrical shell closing pattern detected by the EA-TOF experiments corresponds to the monoclinic crystal structure, and that this structure persists to very small clusters. The overall geometrical characteristics of the clusters, derived from the analysis of the oscillations in mass spectra are consistent with the monoclinic structure [44]. Two pronounced intensity maxima close to the transition region, namely (SF 6 ) 59 and (SF 6 ) 52 apparently correspond to nearly spherical clusters cut from the crystal, and this suggests that the transition for these clusters may be related to the size where nearly spherical clusters may be built out of the bulk crystal.…”

“…This is the case for (SF 6 ) N and (CO 2 ) N . The experiments that have revealed this transition use Electron Attachment Time-of-Flight (EA-TOF) mass spectrometry [44] and electron diffraction [45,46]. Negative cluster ions are formed in the molecular beam by directing a continuous electron beam along the TOF axis of the mass spectrometer.…”

Electron Attachment to CO2 Embedded in Superfluid He Droplets

“…Both cluster size distributions exhibit pronounced intensity anomalies (magic numbers) that are also known from cluster size distributions obtained via electron attachment to pristine CO 2 clusters. 43,44 To compare the present mass spectrum of the (CO 2 ) n – anions with cluster size distributions published in the literature, 43,44 we plotted the difference of the measured anion yields and a strongly smoothed curve for the same data for all three series. Thereby intensity anomalies are more easily visible and can be compared for the three different experiments.…”

“…The lower diagram shows the relative ion intensities for (CO 2 ) n – , i.e., a difference of measured anion yields (upper panel) and a strongly smoothed fit to this curve in comparison to equally treated data published in the literature. 43,44 …”

Evaporative attachment of slow electrons to alkali-metal nanoclusters

“…Experimental work on electron attachment to clusters has focused on molecular clusters and fullerenes (see, e.g., [1,2,[5][6][7][8][9] and references therein).…”