The existence of magic numbers for atomic microclusters has been found experimentally the first time. ${n}^{*}$ manifest themselves in mass spectra free xenon clusters, nucleated gas phase. observed ${n}^{*}=13, 55, \mathrm{and} 147$ coincide with spheres required complete-shell icosahedra. appearance further (19, 25, 71, and 87) is only partially explained by previous calculations.

Mass spectra of Pb, NaI, and Xe microclusters show that below a critical number atoms per cluster, ${n}^{**}$, doubly charged particles are not stable. These numbers 30 for ${\mathrm{Pb}}_{n}$, 20 ${(\mathrm{NaI})}_{n}$ 52 ${\mathrm{Xe}}_{n}$. The two positive charges generated at one atom by electron bombardment likely to move opposite sides the cluster which then explodes into singly fragments as long Coulomb repulsion energy is greater than binding energy.

Clusters of argon, krypton, and xenon are grown in a free jet ionized by electron impact. The size these clusters, (Rg)+n, extends up to n≂1000. Individual cluster sizes mass resolved n≂570 the case Ar+n. well known, but puzzling differences distributions Kr Xe clusters disappear beyond n≂130, while those between Ar n≂220. most pronounced ‘‘magic numbers’’ large ions occur at n=147 (148 for Ar), 309, 561, striking agreement with number atoms required build icosahedral 3, 4, 5 complete...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectron attachment to water clusters under collision-free conditionsMartin. Knapp, Olof. Echt, Dietmar. Kreisle, and Ekkehard. RecknagelCite this: J. Phys. Chem. 1987, 91, 10, 2601–2607Publication Date (Print):May 1, 1987Publication History Published online1 May 2002Published inissue 1 1987https://pubs.acs.org/doi/10.1021/j100294a031https://doi.org/10.1021/j100294a031research-articleACS PublicationsRequest reuse permissionsArticle...

Ammonia clusters, produced via supersonic expansion, are subjected to multiphoton ionization using a tunable pulsed laser. The products of and subsequent dissociation processes investigated time-of-flight mass spectrometer equipped with reflectron (reflecting electric field). Cluster ions containing more than 65 ammonia molecules were formed internal ion molecule reactions taking place within the initially ionized aggregate. proton transfer reaction which ensues leads substantial excess...

Measurements of the mass-abundance spectra sodium clusters from supersonic expansions are presented. The show evidence a regular spherical shell structure with magic numbers ${\mathit{N}}_{0}$ scaling approximately cube root number atoms N, and hence delocalized (valence) electrons in cluster. Altogether, twelve closings observed, adding to previously known closings, ${\mathit{N}}_{0}$=2, 8, 20, 40, 58, 92, 138; 8--12th ${\mathit{N}}_{0}$=196, 260, 344, 440, 558. implications such large...

Long-lived water cluster anions [(H2O)−n, n≥11, and (D2O)−n, n≥12] can be formed by electron attachment to a beam of preformed, neutral clusters; collisional stabilization is not required. Attachment occurs resonantly at or very close 0 eV incident energy; the ion yield unexpectedly large.

The transition in cluster growth from succesive monomer absorption to coalescence has been observed for C${\mathrm{O}}_{2}$ condensed a supersonic beam under high pressure. A model which considers all cluster-cluster reactions achieves good qualitative agreement with the measured size distributions of clusters. This is first attempt fit an experimental spectrum first-principles model.

We have analyzed the reaction channels for delayed, unimolecular dissociation of multiply charged clusters made from ${\mathrm{CO}}_{2}$ and ${\mathrm{C}}_{2}$${\mathrm{H}}_{4}$. The smallest observable triply quadruply feature a large probability fission into at least two fragments. size distribution heavy, doubly fragments (${\mathrm{CO}}_{2}$${)}_{\mathrm{n}}^{3+}$, 109\ensuremath{\lesssim}n\ensuremath{\lesssim}123, has been in detail shows strong peak 92% precursor size. Delayed...

We analyze the rate of delayed (thermionic) ionization photoexcited ${\mathrm{C}}_{60}$ molecules. The has a power-law dependence, indicating presence continuum constants. value exponent provides information about competition between and unimolecular fragmentation; it is equal to ratio energy activation for fragmentation. This result novel method measure controversial bond dissociation neutral ${\mathrm{C}}_{60}$. obtain $11.9\ifmmode\pm\else\textpm\fi{}1.9\mathrm{eV}$.

Size distributions of fragments from multiply charged clusters have been determined. On a time scale 0.1 ms with respect to ionization, triply C${\mathrm{O}}_{2}$ size $n\ensuremath{\approx}114$ are found fission extremely asymmetrically, their doubly carrying 92% the mass. For clusters, however, evaporation neutral monomers is only channel for delayed dissociation. A model, based on liquid-drop approximation, can quantitatively account lower limits as well distribution (C${\mathrm{O}}_{2}$)...

Abstract Mass spectra of xenon clusters show pronounced intensity maxima for cluster sizes n * = 13, 19, 25, 55, 71, 87, and 147. The occurrence these “magic numbers” is explained by shell closure growing in the icosahedral structure. Magic numbers mass 1,2‐dichlorotetra‐fluoroethane are 13 19. only maximum sulfurhexafluoride occurs at whereas a minimum observed 18. In contrast, size distributions 17 other molecular gases decrease strictly monotonically with increasing size. origin effects discussed.

The evaporation of monomers following electron-impact ionization causes a significant enhancement the intensity anomalies (``magic numbers'') in mass spectra xenon clusters. dissociation rates are measured on microsecond time scale for clusters containing between 10 and 79 atoms. highest probability, 99(1)%, is found ${\mathrm{Xe}}_{57}$${\mathrm{}}^{+}$, which two atoms larger than closed-shell icosahedral cluster. Each anomaly corresponds to an number'') spectrum. Recent Monte Carlo...

Helium adsorbed on $\mathrm{C}_{60}{}^{+}$ and $C_{70}{}^{+}$ exhibits phenomena akin to helium graphite. Mass spectra suggest that commensurate layers form when all carbon hexagons pentagons are occupied by one He each, but the solvation shell does not close until 60 atoms $\mathrm{C}_{60}{}^{+}$, or 62 $\mathrm{C}_{70}{}^{+}$. Molecular dynamics simulations of ${\mathrm{C}}_{60}\mathrm{He}_{n}{}^{+}$ at 4 K show phase is solid. added ${\mathrm{C}}_{60}\mathrm{He}_{32}{}^{+}$ will displace...

Helium droplets are doped with fullerenes (either C60 or C70) and hydrogen (H2 D2) investigated by high-resolution mass spectrometry. In addition to pure helium cluster ions, hydrogen-fullerene complexes observed upon electron ionization. The composition of the main ion series is (H2)nHCm+ where m = 60 70. Another even-numbered (H2)nCm+, slightly weaker in stark contrast ions for which (H2)n+ barely detectable. (H2)nCm+ exhibit abrupt drops abundance at n 32 37 C70, indicating formation an...

We review the solvation of atomic, molecular or cluster ions in HNDs. After briefly discussing properties snowballs bulk helium we consider experimental conditions for efficient synthesis charged, doped show that observed conventional mass spectrometers originate from fission highly charged The ionization threshold HNDs with alkalis reveals minimum size required full immersion. abundance distributions HeNX± frequently reveal local anomalies magic numbers. demonstrate is approximately...

Abstract Helium atoms bind strongly to alkali cations which, when embedded in liquid helium, form so‐called snowballs. Calculations suggest that helium the first solvation layer of these snowballs rigid structures and their number ( n ) is well defined, especially for lighter alkalis. However, experiments have so far failed accurately determine values . We present high‐resolution mass spectra Na + He , K 2 formed by electron ionization doped droplets; data allow a critical comparison with...

Abstract Clusters of ammonia, formed by adiabatic expansion, were subjected to analysis in a time‐of‐flight mass spectrometer following multiphoton ionization. All cluster ions had the composition (NH 3 ) n · H + (with ranging up approximately 65) and none corresponding detected with exception = 1. An unusually stable species 4 )(NH was produced under all expansion ionizing conditions investigated; it is attributed an especially ion structure. Well resolved rotational structure for β c̄...