Experimental Investigation of Long-Lived ZEKE Rydberg States in Ultracold Argon

There is considerable interest in the dynamics of ultracold plasmas and ultracold Rydberg gases. Ultracold plasmas are typically formed by photo-excitation of ultracold atoms to an energy region near (both above and below) an ionization threshold. Excitation to bound, highly-excited Rydberg states can lead to formation of a plasma via several processes, including collisions between Rydberg atoms. Three-body recombination in an ultracold plasma can also result in the production of ultracold Rydberg atoms. Understanding the dynamics of ultracold Rydberg gases is therefore important for understanding the dynamics of ultracold plasmas. In this dissertation, we have investigated the formation and survival of a particular class of Rydberg atoms. These atoms are known as ZEKE state Rydberg atoms, where the term ZEKE is derived from Zero Kinetic Energy. ZEKE Rydberg states are high angular momentum and high angular momentum projection excited states which can be formed by laser excitation in the presence of electric fields. Without the electric fields, these states would be optically dark. We have investigated ZEKE Rydberg states in ultracold argon in an energy region just below the second ionization threshold of the atoms in our magneto-optical trap. Here, low angular momentum states decay very quickly (\u3c 1 ns) by auto-ionization through a core spin flip due to the Rydberg electron-core interaction. This interaction has been significantly reduced due to the dilution of low l and m states as a result of l and m mixing during excitation. Hence, ZEKE Rydberg states live orders of magnitude longer than low angular momentum states. We are reporting on our experimental investigation of these states in the ultracold regime and prospects for future studies in which external control of these states may be used to control ultracold plasma dynamics

Zeptonewton force sensing with nanospheres in an optical lattice

Optically trapped nanospheres in high-vaccum experience little friction and hence are promising for ultra-sensitive force detection. Here we demonstrate measurement times exceeding $10^5$ seconds and zeptonewton force sensitivity with laser-cooled silica nanospheres trapped in an optical lattice. The sensitivity achieved exceeds that of conventional room-temperature solid-state force sensors, and enables a variety of applications including electric field sensing, inertial sensing, and gravimetry. The optical potential allows the particle to be confined in a number of possible trapping sites, with precise localization at the anti-nodes of the optical standing wave. By studying the motion of a particle which has been moved to an adjacent trapping site, the known spacing of the lattice anti-nodes can be used to calibrate the displacement spectrum of the particle. Finally, we study the dependence of the trap stability and lifetime on the laser intensity and gas pressure, and examine the heating rate of the particle in high vacuum in the absence of optical feedback cooling.Comment: 5 pages, 4 figures, minor changes, typos corrected, references adde

Analysis of International Policies In The Solar Electricity Sector: Lessons for India

Although solar costs are dropping rapidly, solar power is still more expensive than conventional and other renewable energy options. The solar sector still needs continuing government policy support. These policies are driven by objectives that go beyond the goal of achieving grid parity. The need to achieve multiple objectives and ensure sufficient political support for solar power makes it diffi cult for policy makers to design the optimal solar power policy. The dynamic and uncertain nature of the solar industry, combined with the constraints offered by broader economic, political and social conditions further complicates the task of policy making. This report presents an analysis of solar promotion policies in seven countries - Germany, Spain, the United States, Japan, China, Taiwan, and India - in terms of their outlook, objectives, policy mechanisms and outcomes. The report presents key insights, primarily in qualitative terms, and recommendations for two distinct audiences. The first audience consists of global policy makers who are exploring various mechanisms to increase the penetration of solar power in markets to mitigate climate change. The second audience consists of key Indian policy makers who are developing a long-term implementation plan under the Jawaharlal Nehru National Solar Mission and various state initiatives

Quantum optics; (120.3180) Interferometry; (000.1600) Classical and quantum physics

A recent neutron interferometry experiment claims to demonstrate a paradoxical phenomenon dubbed the "quantum Cheshire cat" [Nat. Commun. 5, 4492 (2014)]. We have reproduced and extended these results with an equivalent optical interferometer. The results suggest that the photon travels through one arm of the interferometer, while its polarization travels through the other. However, we show that these experimental results belong to the domain where quantum and classical wave theories coincide; there is nothing uniquely quantum about the illusion of this Cheshire cat