Atomic Molecular Physics Rajkumar 37.pdf
Antonette Hespe
The goals of atomic, molecular, and optical physics (AMO physics) are to elucidate the fundamental laws of physics, to understand the structure of matter and how matter evolves at the atomic and molecular levels, to understand light in all its manifestations, and to create new techniques and devices. AMO physics provides theoretical and experimental methods and essential data to neighboring areas of science such as chemistry, astrophysics, condensed-matter physics, plasma physics, surface science, biology, and medicine. It contributes to the national security system and to the nation's programs in fusion, directed energy, and materials research. Lasers and advanced technologies such as optical processing and laser isotope separation have been made possible by discoveries in AMO physics, and the research underlies new industries such as fiber-optics communications and laser-assisted manufacturing. These developments are expected to help the nation to maintain its industrial competitiveness and its military strength in the years to come. This report describes the field, characterizes recent advances, and identifies current frontiers of research.
Elemental Dirac and Dirac-like materials are of intense research interest, as they typically do not suffer from impurities in structural phases, offering enhanced electronic mobility, in contrast to other compound two-dimensional (2D) materials. Elemental Dirac materials include graphene1, borophene2,3,4, phosphorene5, silicene6, 2D gold7 and so on (Supplementary Fig. 1). Advancements in elemental Dirac materials are destined to involve higher-atomic-number metallic elements such as molybdenum, tungsten, titanium and so on, for which the sea of electrons would be confined in two dimensions, potentially leading to exotic electronic and excitonic behaviour. In addition, these materials are structurally robust under mechanical load and at elevated temperature8. Moreover, transition metals exhibit variable oxidation states, a property essential to catalyse chemical reactions, thus their 2D confined atomic sheets could demonstrate extremely high catalytic activity. The advantage of a 2D form of transition metals could also be exploited in niche areas, such as field emitters9, scanning tunnelling microscopy tips10, nanoscale interconnects11, nanoelectromechanical systems12 and surface-enhanced Raman spectroscopy (SERS)-based molecular sensing13. Growth of these 2D materials under ambient conditions is challenging due to their tendency to form clusters as well as their affinity towards oxygen14.
Research InterestsMy research focuses on the organization of the microscopic interactions between atoms and molecules in condensed phases of materials including biomaterials. This research involves large scale dynamical simulations of systems in condensed phases, computational statistical mechanics algorithms, physics of elemental and molecular clusters, development of model potentials and molecular dynamics modeling, applications of quantum chemistry to nanoscience, and machine learning discovery in solid state and soft materials including biomaterials.
Development of ceramic nanoparticles with improved properties has been studied with much success in several areas such as synthesis and surface science. Examples of ceramic are silica, alumina, titania, zirconia, silicon nitride, silicon carbide, and so forth. Advancement in nanotechnology has led to the production of nanosized silica, SiO2, which has been widely used as filler in engineering composite. The silica particles extracted from natural resources contains metal impurities and not favorable for advanced scientific and industrial applications. Thus, focus is given to synthetic silica (colloidal silica, silica gels, pyrogenic silica, and precipitated silica), which is pure and produced mostly in amorphous powder forms compared to natural mineral silica (quartz, tridymite, cristobalite) which are in crystalline forms [6]. As shown in Figure 1, various methods that have been used to obtain silica particles can be categorized into two main approaches: top-down and bottom-up [2, 7]. Top-down is characterized by reducing the dimension of the original size by utilizing special size reduction techniques (physical approach). Bottom-up or chemical approach involves a common route used to produce silica nanoparticles from atomic or molecular scale. Some of the widely used methods to synthesize silica nanoparticles are sol-gel process, reverse microemulsion, and flame synthesis. The sol-gel process is widely used to produce pure silica particles due to its ability to control the particle size, size distribution and morphology through systematic monitoring of reaction parameters.
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