Energetic ion irradiation of N2O ices relevant for Solar system surfaces

ABSTRACT Ices are the dominant surface material of many Solar system objects, such as comets and trans-Neptunian objects. They are continuously exposed to ion bombardment by solar wind ions and cosmic rays, which trigger secondary ion emission, contributing to the exosphere formation. Laboratory studies demonstrated the effects of energetic processing of ices at low temperature, showing the production of molecules and free radicals of astrophysical interest. Nitrous oxide (N2O) is one of the molecular species observed in star-forming sites, reason why it may be present in the ices covering some minor bodies in the outer Solar system. In the current work, N2O ice at 10 K was irradiated by energetic (MeV/u) multicharged heavy ions (e.g. 105Rh and 140Ba); the sputtered species were detected and analysed by the TOF-PDMS technique (time-of-flight plasma desorption mass spectrometry). Small positive and negative secondary ions were identified: N+, N2+, NO+, O+, and O−. The bombardment also induces production of ion cluster series: (N2)nR$_{m}^+$, (NO)nR$_{m}^+$, (N2O)nR$_{m}^+$, where R = N+, N2+, NO+, N2O+, Om+ (n up to ∼ 10, m = 1−3). Their yield distributions follow the sum of two decreasing exponentials, one fast -F and another slow -S, suggesting a two-regime formation. Most of the yield distributions have the same pair of exponential decay constants, around kF ∼ 1.4 and kS ∼ 0.15 u−1. Based on this behavior, an emission description for aggregates is proposed, useful to understand the processes by which neutral and ionized molecular species are delivery to the gas phase in space.

Insights into the structural evolution and electronic properties of deficient-electron sodium chloride clusters

We have explored the structural evolution and electronic properties of cationic sodium chloride (NaCl)+n (n = 1–8) clusters. The global minimum of cationic (NaCl)+n clusters have been extensively searched using CALYPSO method combined with DFT calculations. The structural evolution of (NaCl)+n clusters can be divided into three stages: linear structure, planar ring-like structure and three-dimensional structure. It is worth to note that cuboid structure is more common in the cluster series as the cluster size increases. (NaCl)+4 clusters is identified as "magic number" clusters by means of the relative stabilities analyses. The following chemical bonding analysis indicate that the stability of (NaCl)+ 4cluster mainly comes from the interaction between Na 3s and Cl 3p atomic orbitals.

Stress-induced trend: the clustering feature of coal mine disasters and earthquakes in China

Nearly half of coal mine disasters in China have been found to occur in clusters or to be accompanied by earthquakes nearby, in which all the disaster types are involved. Stress disturbances seem to exist among mining areas and to be responsible for the observed clustering. The earthquakes accompanied by coal mine disasters may be the vital geophysical evidence for tectonic stress disturbances around mining areas. This paper analyzes all the possible causative factors to demonstrate the authenticity and reliability of the observed phenomena. A quantitative study was performed on the degree of clustering, and space–time distribution curves are obtained. Under the threshold of 100 km, 47% of disasters are involved in cluster series and 372 coal mine disasters accompanied by earthquakes. The majority cluster series lasting for 1–2 days correspond well earthquakes nearby, which are speculated to be related to local stress disturbance. While the minority lasting longer than 4 days correspond well with fatal earthquakes, which are speculated to be related to regional stress disturbance. The cluster series possess multiple properties, such as the area, the distance, the related disasters, etc., and compared with the energy and the magnitude of earthquakes, good correspondences are acquired. It indicates that the cluster series of coal mine disasters and earthquakes are linked with fatal earthquakes and may serve as footprints of regional stress disturbance. Speculations relating to the geological model are made, and five disaster-causing models are examined. To earthquake research and disaster prevention, widely scientific significance is suggested.

Categorization of Boranes Into Clan Series

Boranes, despite their instability in nature, can be regarded as hydrocarbon relatives since a [BH] fragment corresponds to a carbon [C] skeletal element in terms of the number of valence electrons. The borane formula which can be expressed as BnHm usually appears in such a way that when (n) is even, then (m) is even and when (n) is odd, (m) is odd as well. Through the study of cluster series, it appears that the cluster number K which represents skeletal linkages is usually a whole number. This inherent characteristic confers unique order within borane clusters with nodal connectivity of 5 and the polyhedral nature of the borane clusters. The orderliness of the borane clusters is reflected by the ease of their categorization into clan series and their readily constructed geometrical isomeric structures. The cluster valence electrons can easily be calculated using one of the six recently discovered fundamental equations.

Inside out Capping Clusters: Matryoshka Series

Matryoshka clusters have been analyzed and categorized using skeletal numbers for the first time. They have been found to portray a unique way of capping by having the nuclear elements occupying the outer layer and what were supposed to be the capping elements on the outside taking the place of the nucleus. Hence they belong to a new type of cluster series. The different types of capping clusters have been identified. Isomeric graphical structures of the clusters can be constructed in accordance with the connectivity rule of the series. It appears that the elements with large skeletal numbers have a tendency of going inside and forming an icosahedral shape. The 4N series method is a useful hypothetical model for analyzing and categorizing clusters of the main group and transition metals.

{Np38} clusters: the missing link in the largest poly-oxo cluster series of tetravalent actinides

The poly-oxo clusters of neptunium, {Np38}, fill the gap in the largest poly-oxo cluster series of tetravalent actinides.