43 research outputs found
Rydberg trimers and excited dimers bound by internal quantum reflection
Quantum reflection is a pure wave phenomena that predicts reflection of a
particle at a changing potential for cases where complete transmission occurs
classically. For a chemical bond, we find that this effect can lead to
non-classical vibrational turning points and bound states at extremely large
interatomic distances. Only recently has the existence of such ultralong-range
Rydberg molecules been demonstrated experimentally. Here, we identify a broad
range of molecular lines, most of which are shown to originate from two
different novel sources: a single-photon associated triatomic molecule formed
by a Rydberg atom and two ground state atoms and a series of excited dimer
states that are bound by a so far unexplored mechanism based on internal
quantum reflection at a steep potential drop. The properties of the Rydberg
molecules identified in this work qualify them as prototypes for a new type of
chemistry at ultracold temperatures.Comment: 6 pages, 3 figures, 1 tabl
Formation and interactions of cold and ultracold molecules: new challenges for interdisciplinary physics
Progress on researches in the field of molecules at cold and ultracold
temperatures is reported in this review. It covers extensively the experimental
methods to produce, detect and characterize cold and ultracold molecules
including association of ultracold atoms, deceleration by external fields and
kinematic cooling. Confinement of molecules in different kinds of traps is also
discussed. The basic theoretical issues related to the knowledge of the
molecular structure, the atom-molecule and molecule-molecule mutual
interactions, and to their possible manipulation and control with external
fields, are reviewed. A short discussion on the broad area of applications
completes the review.Comment: to appear in Reports on Progress in Physic
Enhancement of Rydberg-mediated single-photon nonlinearities by electrically tuned Förster resonances
We demonstrate experimentally that Stark-tuned Förster resonances can be used to substantially increase the interaction between individual photons mediated by Rydberg interaction inside an optical medium. This technique is employed to boost the gain of a Rydberg-mediated single-photon transistor and to enhance the non-destructive detection of single Rydberg atoms. Furthermore, our all-optical detection scheme enables high-resolution spectroscopy of two-state Förster resonances, revealing the fine structure splitting of high-n Rydberg states and the non-degeneracy of Rydberg Zeeman substates in finite fields. We show that the âŁ50S1/2,48S1/2â©ââŁ49P1/2,48P1/2â© pair state resonance in 87Rb enables simultaneously a transistor gain G>100 and all-optical detection fidelity of single Rydberg atoms F>0.8. We demonstrate for the first time the coherent operation of the Rydberg transistor with G>2 by reading out the gate photon after scattering source photons. Comparison of the observed readout efficiency to a theoretical model for the projection of the stored spin wave yields excellent agreement and thus successfully identifies the main decoherence mechanism of the Rydberg transistor
Inscuteable Regulates the Pins-Mud Spindle Orientation Pathway
During asymmetric cell division, alignment of the mitotic spindle with the cell polarity axis ensures that the cleavage furrow separates fate determinants into distinct daughter cells. The protein Inscuteable (Insc) is thought to link cell polarity and spindle positioning in diverse systems by binding the polarity protein Bazooka (Baz; aka Par-3) and the spindle orienting protein Partner of Inscuteable (Pins; mPins or LGN in mammals). Here we investigate the mechanism of spindle orientation by the Insc-Pins complex. Previously, we defined two Pins spindle orientation pathways: a complex with Mushroom body defect (Mud; NuMA in mammals) is required for full activity, whereas binding to Discs large (Dlg) is sufficient for partial activity. In the current study, we have examined the role of Inscuteable in mediating downstream Pins-mediated spindle orientation pathways. We find that the Insc-Pins complex requires Gαi for partial activity and that the complex specifically recruits Dlg but not Mud. In vitro competition experiments revealed that Insc and Mud compete for binding to the Pins TPR motifs, while Dlg can form a ternary complex with Insc-Pins. Our results suggest that Insc does not passively couple polarity and spindle orientation but preferentially inhibits the Mud pathway, while allowing the Dlg pathway to remain active. Insc-regulated complex assembly may ensure that the spindle is attached to the cortex (via Dlg) before activation of spindle pulling forces by Dynein/Dynactin (via Mud)
Ecotoxicological assessment of sediments from the Santos and SĂŁo Vicente estuarine system- Brazil
Lifetimes of ultralong-range Rydberg molecules in vibrational ground and excited states
Since their first experimental observation, ultralong-range Rydberg molecules consisting of a highly excited Rydberg atom and a ground state atom [1, 2] have attracted the interest in the field of ultracold chemistry [3, 4]. Especially the intriguing properties such as size, polarizability and type of binding they inherit from the Rydberg atom are of interest. An open question in the field is the reduced lifetime of the molecules compared to the corresponding atomic Rydberg states [2]. In this paper we present an experimental study on the lifetimes of the (3)Sigma (5s - 35s) molecule in its vibrational ground state and in an excited state. We show that the lifetimes depend on the density of ground state atoms and that this can be described in the frame of a classical scattering between the molecules and ground state atoms. We also find that the excited molecular state has an even more reduced lifetime compared to the ground state which can be attributed to an inward penetration of the bound atomic pair due to imperfect quantum reflection that takes place in the special shape of the molecular potential [5]
A Homonuclear Molecule with a Permanent Electric Dipole Moment
Permanent electric dipole moments in molecules require a breaking of parity symmetry. Conventionally, this symmetry breaking relies on the presence of heteronuclear constituents. We report the observation of a permanent electric dipole moment in a homonuclear molecule in which the binding is based on asymmetric electronic excitation between the atoms. These exotic molecules consist of a ground-state rubidium (Rb) atom bound inside a second Rb atom electronically excited to a high-lying Rydberg state. Detailed calculations predict appreciable dipole moments on the order of 1 Debye, in excellent agreement with the observations
Gαi generates multiple Pins activation states to link cortical polarity and spindle orientation in Drosophila neuroblasts
Drosophila neuroblasts divide asymmetrically by aligning their mitotic spindle with cortical cell polarity to generate distinct sibling cell types. Neuroblasts asymmetrically localize Gαi, Pins, and Mud proteins; Pins/Gαi direct cortical polarity, whereas Mud is required for spindle orientation. It is currently unknown how GαiâPinsâMud binding is regulated to link cortical polarity with spindle orientation. Here, we show that Pins forms a âclosedâ state via intramolecular GoLocoâtetratricopeptide repeat (TPR) interactions, which regulate Mud binding. Biochemical, genetic, and live imaging experiments show that Gαi binds to the first of three Pins GoLoco motifs to recruit Pins to the apical cortex without âopeningâ Pins or recruiting Mud. However, Gαi and Mud bind cooperatively to the Pins GoLocos 2/3 and tetratricopeptide repeat domains, respectively, thereby restricting PinsâMud interaction to the apical cortex and fixing spindle orientation. We conclude that Pins has multiple activity states that generate cortical polarity and link it with mitotic spindle orientation