Sputtering of Indium under polyatomic ion bombardment

The main goal of the present study is the investigation of the sputtering of neutral particles from a metal surface under atomic and polyatomic ion bombardment using secondary neutral time-of-flight mass spectrometry (ToF SNMS). For postionization of neutral species, UV laser irradiation with wavelength 193 nm was utilized. For generation of polyatomic projectiles, a negative sputter cesium ion source suitable for ToF SNMS setup was developed and built. The ion source delivers negatively charged (m=1÷5) and polyatomic ions produced from a gold sputter target bombarded by positive Cs−mAu2AuCs+ ions. Mass separation of primary projectiles in the ion source is performed by a built-in compact Wien filter allowing to separate heavy ions in the energy range of several keV. In the experiment, an indium surface was bombarded by (m=1÷5) projectiles with total impact energy of 5 and 10 keV. The obtained mass distributions of sputtered indium species reveal that the partial yields of sputtered clusters increase under polyatomic ion bombardment. It is shown that the enhancement in total sputtering yield per constituent atom of the projectile ion is non-additively enhanced in the case of diatomic ion bombardment in comparison with monoatomic projectile ions impinging at the same velocity. The enhancement of partial yields observed for sputtered clusters is found to increase with increasing cluster size, reaching a factor of several ten for the largest detected cluster. −mAu Apart from sputtering yields, kinetic energy distributions (KED) of sputtered neutral indium atoms ejected under mono- and polyatomic projectile ion bombardment were measured. It is shown that In monomers sputtered by monoatomic projectiles with an impact energy of 5 keV are emitted mostly from linear collision cascades. At higher kinetic energy, or polyatomic projectile impact, it is revealed that in addition to the atoms sputtered from the linear cascade, a low energetic contribution of atoms sputtered from a collisional spike appears. This contribution in the KED increases with increasing impact energy and nuclearity of projectile. In the case of 10-keV projectiles, the sputtering process is shown to be dominated by the spike contribution. By subtracting the linear cascade contribution from the measured KED, the pure emission energy spectrum produced by the collisional spike is identified. It is found that the most probable emission energy of atoms emitted from the spike is more than one order of magnitude lower in comparison with the surface binding energy of indium. The obtained KED of indium monomers emitted from the spike were interpreted in terms of published theoretical models of the sputtering process from a spike. It is shown that the obtained data cannot be explained in terms of a thermal spike model. The obtained results are shown to agree more favorably with a thermodynamic gas flow model describing the particle emission process as a quasi-free expansion of a superheated near-surface volume. −1Au−3Au By comparing the partial sputtering yields of emitted secondary ions and their neutral counterparts, the ionization probabilities of indium atoms sputtered by atomic and polyatomic projectiles were measured. It is revealed that ionization probabilities of sputtered In monomers decrease when polyatomic projectiles are utilized. Data of this kind are of great interest both from a fundamental perspective and for practical applications of Secondary Ion Mass Spectrometry (SIMS) in surface analysis. The measured data are interpreted in terms of published theories of secondary ion formation. Our results indicate that the electronic excitation of the solid induced by the projectile impact decrease with increasing projectile nuclearity, a finding which reveals an opposite trend to that observed for the sputter yields. This surprising result cannot be understood in terms of published theory and has therefore motivated an ongoing study in our group to model excitation and ionization processes in the frame of a molecular dynamics computer simulation of sputtering process

Effects of manifestations of the initial quantum correlations in the coherent scattering of the atom in the standing wave

Some effects of the initial quantum correlations between the atom and the quantum mode of the standing wave of electromagnetic field in the condition of coherent scattering are considered

Nonlinear properties of high-Q optical microresonators in normal dispersion range

We demonstrate the generation of Kerr frequency combs and platicons in whispering gallery mode crystalline microresonators in normal group velocity regime at 780 nm and 1064 nm wavelengths

Towards spontaneous parametric down-conversion at low temperatures

The possibility of observing spontaneous parametric down-conversion in doped nonlinear crystals at low temperatures, which would be useful for combining heralded single-photon sources and quantum memories, is studied theoretically. The ordinary refractive index of a lithium niobate crystal doped with magnesium oxide LiNbO3:MgO is measured at liquid nitrogen and helium temperatures. On the basis of the experimental data, the coefficients of the Sellmeier equation are determined for the temperatures from 5 to 300 K. In addition, a poling period of the nonlinear crystal has been calculated for observing type-0 spontaneous parametric down-conversion (ooo-synchronism) at the liquid helium temperature under pumping at the wavelength of λp = 532 nm and emission of the signal field at the wavelength of λs = 794 nm, which corresponds to the resonant absorption line of Tm3+ doped ions

Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL

Femtosecond transient soft X-ray Absorption Spectroscopy (XAS) is a very promising technique that can be employed at X-ray Free Electron Lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here we present a dedicated setup for soft X-rays available at the Spectroscopy & Coherent Scattering (SCS) instrument at the European X-ray Free Electron Laser (EuXFEL). It consists of a beam-splitting off-axis zone plate (BOZ) used in transmission to create three copies of the incoming beam, which are used to measure the transmitted intensity through the excited and unexcited sample, as well as to monitor the incoming intensity. Since these three intensity signals are detected shot-by-shot and simultaneously, this setup allows normalized shot-by-shot analysis of the transmission. For photon detection, the DSSC imaging detector, which is capable of recording up to 800 images at 4.5 MHz frame rate during the FEL burst, is employed and allows approaching the photon shot-noise limit. We review the setup and its capabilities, as well as the online and offline analysis tools provided to users.Comment: 11 figure

Symmetry-dependent ultrafast manipulation of nanoscale magnetic domains

Femtosecond optical pumping of magnetic materials has been used to achieve ultrafast switching and recently to nucleate symmetry-broken magnetic states. However, when the magnetic order parameter already presents a broken-symmetry state, such as a domain pattern, the dynamics are poorly understood and consensus remains elusive. Here, we resolve the controversies in the literature by studying the ultrafast response of magnetic domain patterns with varying degrees of translation symmetry with ultrafast x-ray resonant scattering. A data analysis technique is introduced to disentangle the isotropic and anisotropic components of the x-ray scattering. We find that the scattered intensity exhibits a radial shift restricted to the isotropic component, indicating that the far-from-equilibrium magnetization dynamics are intrinsically related to the spatial features of the domain pattern. Our results suggest alternative pathways for the spatiotemporal manipulation of magnetism via far-from-equilibrium dynamics and by carefully tuning the ground-state magnetic textures

Storage Potential of the Predatory Ladybird <i>Cheilomenes propinqua</i> in Relation to Temperature, Humidity, and Factitious Food

The ability of the females of the predatory ladybird Cheilomenes propinqua to survive and to retain reproductive potential in the absence of natural food (aphids) was estimated under various hydrothermal (temperatures of 7, 12, 17, 22, and 27 °C; air humidities of 50% and 80–90%) and trophic (starved vs. fed on the frozen eggs of the grain moth Sitotroga cerealella) conditions. The post-storage reproductive potential was estimated using the mean number of eggs laid over 20 days. The experiments showed that fed females can be stored at temperatures of 15–17 °C for 20 days with a rather low (about 20%) and for up to 80 days with an acceptable (not more than 50%) loss of the reproductive potential. The successful short-term (up to 3 days) storage or transportation of fed and starved females can occur at temperatures from 12 to 27 °C. However, storage for more than 10 days at temperatures of 7 °C and lower results in the 100% mortality of both the starved and fed beetles. These data suggest that (1) in greenhouses, C. propinqua can be used for the biological control of aphids by preventing colonization, although this would require the regular supplementation of factitious food, and (2) escaped individuals would not survive the winter even in the south of the temperate zone