Ultracold Temperatures Research Articles

Deep cooling scheme of quantum degenerate gas and ground experimental verification for chinese space station

The Cold Atom Physics Rack (CAPR) of Chinese space station will be launched at the end of 2022. The important goal of CAPR is to achieve BEC at 100 pk. In order to obtain ultracold atoms in microgravity of space station, we propose a two-stage cooling scheme using all-optical trap with different waist beams. The cold atom cloud obtained by this scheme is composed of condensate and thermal atoms around condensate. The design of our two-stage cooling scheme will effectively reduce the temperature of the thermal atom cloud and the effective temperature generated by the interaction energy of the condensate. The atomic temperature of 5 nk is obtained from the ground test experiment, and the corresponding temperature under the microgravity condition of the space station is theoretically predicted to be less than 100 pk. Taking the advantages of ultracold temperature and long-time detection, many scientific experiments will be arranged. In this paper, the ground test experiments based on ground principle prototype and pre-prototype for CAPR are also introduced.

Capture theory models: An overview of their development, experimental verification, and applications to ion-molecule reactions.

Since Arrhenius first proposed an equation to account for the behavior of thermally activated reactions in 1889, significant progress has been made in our understanding of chemical reactivity. A number of capture theory models have been developed over the past several decades to predict the rate coefficients for reactions between ions and molecules-ranging from the Langevin equation (for reactions between ions and non-polar molecules) to more recent fully quantum theories (for reactions at ultracold temperatures). A number of different capture theory methods are discussed, with the key assumptions underpinning each approach clearly set out. The strengths and limitations of these capture theory methods are examined through detailed comparisons between low-temperature experimental measurements and capture theory predictions. Guidance is provided on the selection of an appropriate capture theory method for a given class of ion-molecule reaction and set of experimental conditions-identifying when a capture-based model is likely to provide an accurate prediction. Finally, the impact of capture theories on fields such as astrochemical modeling is noted, with some potential future directions of capture-based approaches outlined.

Three-Body Recombination of Cold 3He–3He–T− System

The atom-atom-anion three-body recombination (TBR) and collision induced dissociation (CID) processes of the 3He–3He–T− system at ultracold temperatures are investigated by solving the Schrödinger equation in the adiabatic hyperspherical representation. The variations of the TBR and CID rates with the collision energies in the ultracold temperatures are obtained. It is found that the JΠ = 1− symmetry dominates the TBR and CID processes in most of the considered collision energy range. The rate of TBR (CID) into (from) the l = 1 anion is larger than those for the l = 0 and l = 2 anions, with the l representing the rotational quantum number of 3HeT−. This can be understood via the nonadiabatic couplings among the different channels.

Warm Covid Vaccine

Over the past couple of years, Sars-CoV-2, also known as Covid-19, has gone rampant around the globe. Millions of people have gotten infected from it so far, and hundreds of thousands of people have succumbed to this virus. For this, scientists have created vaccines to solve this issue and to make sure that people who take the vaccine can build up the antibodies to protect themselves from Covid-19. The problem with this vaccine is that it is not very accessible. This is because of the storage requirements that must be met for this vaccine to remain effective. The demanding ultra-cold temperature makes it extremely hard to disperse the vaccine throughout the community. This makes it almost impossible in areas that are less fortunate and do not have the money to support the storage needed for this vaccine. So, that is why a warm vaccine is necessary to make sure that people who are in rural and less fortunate areas, still can protect themselves from the virus. Researchers and scientists all over the world are currently working to solve this issue and make sure an effective warm Covid-19 vaccine can be created.

Rotational quenching of C2 with 3He and 4He collisions at ultracold temperatures

Quantum mechanical closed coupling scattering calculations are carried out at temperatures ranging from 10-8 K to 100 K for studying rotational transitions of C2 due to collisions with 3He and 4He employing our new C2-He potential energy surface computed at the CCSD(T)- F12b/aug-cc-pVQZ level of theory. Among the isotopes of He, the heavier 4He isotope has larger value of rotational quenching cross section than 3He isotope. Wigner’s threshold law holds below 10-1 cm−1. Quenching rate coefficients suggest that C2 can be cooled with 4He buffer gas. The dominance of 4He on C2 molecule is further addressed by calculating the predissociation lifetime of C2.

Inner-shell excitation in the YbF molecule and its impact on laser cooling

The YbF molecule is a sensitive system for measuring the electron’s electric dipole moment. The precision of this measurement can be improved by direct laser cooling of the molecules to ultracold temperature. However, low-lying electronic states arising from excitation of a 4f electron may hinder laser cooling. One set of these “4f hole” states lies below the A2Π1/2 excited state used for laser cooling, and radiative decay to these intermediate levels, even with branching ratios as small as 10−5, can be a hindrance. Other 4f hole states lie very close to the A2Π1/2 state, and a perturbation results in states of mixed character that are involved in the laser cooling cycle. This perturbation may enhance the loss of molecules to states outside of the laser cooling cycle. We model the perturbation of the A2Π1/2 state to determine the strength of the coupling between the states, the de-perturbed potential energy curves, and the radiative branching ratios to various vibrational levels of the ground state, X2Σ+. We use electronic structure calculations to characterize the 4f hole states and the strengths of transitions between these states and the A2Π1/2 and X2Σ+ states. We identify a leak out of the cooling cycle with a branching ratio of roughly 5×10−4, dominated by the contribution of the ground state configuration in a 4f hole state. Finally, we assess the impact of these results for laser cooling of YbF and molecules with similar structure.

Zeeman slowing of a group-III atom

We realize the first Zeeman slower of an atom in the Main Group III of the periodic table, otherwise known as the "triel elements". Despite that our atom of choice (namely indium) does not have a ground state cycling transition suitable for laser cooling, slowing is achieved by driving the transition $\lvert 5P_{3/2},F=6 \rangle \rightarrow \lvert 5D_{5/2},F=7 \rangle$, where the lower-energy state is metastable. Using a slower based on permanent magnets in a transverse-field configuration, we observe a bright slowed atomic beam at our design goal velocity of 70 m/s. The techniques presented here can straightforwardly extend to other triel atoms such as thallium, aluminum, and gallium. Furthermore, this work opens the possibility of cooling Group III atoms to ultracold temperatures.

Strong Dynamic Interfacial Adhesion by Polymeric Ionic Liquids under Extreme Conditions.

Interfacial adhesion under extreme conditions has attracted increasing attention owing to its potential application of stopping leakages of oil or natural gas. However, interfacial adhesion is rarely stable at ultralow temperatures and in organic solvents, necessitating the elucidation of the molecular-level processes. Herein, we used the intermolecular force-control strategy to prepare four linear polymers by tuning the proportion of hydrogen bonding and the number of electrostatic sites. The obtained polymeric ion liquids displayed strong dynamic adhesion at various interfaces. They also efficiently tolerated organic solvents and ultracold temperatures. Highly reversible rheological behaviors are observed within a thermal cycle between high and ultracold temperatures. Temperature-dependent infrared spectra and theoretical calculation reveal thermal reversibility and interfacial adhesion/debonding processes at the molecular level, respectively. This intermolecular force-control strategy may be applied to produce environmentally adaptive functional materials for real applications.

Buffer gas cooling of ions in radio-frequency traps using ultracold atoms

Reaching ultracold temperatures within hybrid atom–ion systems is a major limiting factor for control and exploration of the atom–ion interaction in the quantum regime. In this work, we present results on numerical simulations of trapped ion buffer gas cooling using an ultracold atomic gas in a large number of experimentally realistic scenarios. We explore the suppression of micromotion-induced heating effects through optimization of trap parameters for various radio-frequency (rf) traps and rf driving schemes including linear and octupole traps, digital Paul traps, rotating traps and hybrid optical/rf traps. We find that very similar ion energies can be reached in all of them even when considering experimental imperfections that cause so-called excess micromotion. Moreover we look into a quantum description of the system and show that quantum mechanics cannot save the ion from micromotion-induced heating in an atom–ion collision. The results suggest that buffer gas cooling can be used to reach close to the ion’s groundstate of motion and is even competitive when compared to some sub-Doppler cooling techniques such as Sisyphus cooling. Thus, buffer gas cooling is a viable alternative for ions that are not amenable to laser cooling, a result that may be of interest for studies into cold controlled quantum chemistry and charged impurity physics.

Losses, Many‐Body Correlations, and Universality in Ultracold Molecules

AbstractRecent experimental developments have allowed physicists to freeze molecules' motion down to an ultracold temperature regime where quantum effects become profound. Furthermore, each molecule can be precisely prepared at chosen internal states and the mutual interactions between molecules are also highly tunable. As such, ultracold molecules have emerged as a powerful platform in multiple disciplines across physics and chemistry. Meanwhile, a grand challenge exists as to how losses of molecules depend on a quantum many‐body environment. In this article, the recent experimental and theoretical progress of exploring losses of ultracold molecules is reviewed. Since the conventional theoretical scheme of treating isolated pairs of molecules is no longer applicable to the quantum degenerate regime that has been reached in recent experiments, an alternative framework of universal relations between two‐body losses and many‐body correlations has been established. Regardless of microscopic parameters ranging from the temperature and the particle number to the interaction strength, these universal relations always hold. This approach unfolds a simple universality behind complex loss processes of many‐body systems and provides physicists and chemists with a new tool to explore ultracold molecules.

Engineering long-range interactions between ultracold atoms with light

Ultracold temperatures in dilute quantum gases opened the way to an exquisite control of matter at the quantum level. Here we focus on the control of ultracold atomic collisions using a laser to engineer their interactions at large interatomic distances. We show that the entrance channel of two colliding ultracold atoms can be coupled to a repulsive collisional channel by the laser light so that the overall interaction between the two atoms becomes repulsive: this prevents them to come close together and to undergo inelastic processes, thus protecting the atomic gases from unwanted losses. We illustrate such an optical shielding (OS) mechanism with 39K and 133Cs atoms colliding at ultracold temperature (<1 μK). The process is described in the framework of the dressed-state picture and we then solve the resulting stationary coupled Schrödinger equations. The role of spontaneous emission and photoinduced inelastic scattering is also investigated as possible limitations of the shielding efficiency. We predict an almost complete suppression of inelastic collisions over a broad range of Rabi frequencies and detunings from the 39K D2 line of the OS laser, both within the [0, 200 MHz] interval. We found that the polarization of the shielding laser has a minor influence on this efficiency. This proposal could easily be formulated for other bialkali-metal pairs as their long-range interaction are all very similar to each other.

Prospects for assembling ultracold radioactive molecules from laser-cooled atoms

Molecules with unstable isotopes often contain heavy and deformed nuclei and thus possess a high sensitivity to parity-violating effects, such as the Schiff moments. Currently the best limits on Schiff moments are set with diamagnetic atoms. Polar molecules with quantum-enhanced sensing capabilities, however, can offer better sensitivity. In this work, we consider the prototypical 223Fr107Ag molecule, as the octupole deformation of the unstable 223Fr francium nucleus amplifies the nuclear Schiff moment of the molecule by two orders of magnitude relative to that of spherical nuclei and as the silver atom has a large electron affinity. To develop a competitive experimental platform based on molecular quantum systems, 223Fr atoms and 107Ag atoms have to be brought together at ultracold temperatures. That is, we explore the prospects of forming 223Fr107Ag from laser-cooled Fr and Ag atoms. We have performed fully relativistic electronic-structure calculations of ground and excited states of FrAg that account for the strong spin-dependent relativistic effects of Fr and the strong ionic bond to Ag. In addition, we predict the nearest-neighbor densities of magnetic-field Feshbach resonances in ultracold 223Fr + 107Ag collisions with coupled-channel calculations. These resonances can be used for magneto-association into ultracold, weakly-bound FrAg. We also determine the conditions for creating 223Fr107Ag molecules in their absolute ground state from these weakly-bound dimers via stimulated Raman adiabatic passage using our calculations of the relativistic transition electric dipole moments.

Influence of Flagellin Polymorphisms, Gene Regulation, and Responsive Memory on the Motility of Xanthomonas Species That Cause Bacterial Spot Disease ofSolanaceous Plants.

Increasingly, new evidence has demonstrated variability in the epitope regions of bacterial flagellin, including in regions harboring the microbe-associated molecular patterns flg22 and flgII-28 that are recognized by the pattern recognition receptors FLS2 and FLS3, respectively. Additionally, because bacterial motility is known to contribute to pathogen virulence and chemotaxis, reductions in or loss of motility can significantly reduce bacterial fitness. In this study, we determined that variations in flg22 and flgII-28 epitopes allow some but not all Xanthomonas spp. to evade both FLS2- and FLS3-mediated oxidative burst responses. We observed variation in the motility for many isolates, regardless of their flagellin sequence. Instead, we determined that past growth conditions may have a significant impact on the motility status of isolates, because we could minimize this variability by inducing motility using chemoattractant assays. Additionally, motility could be significantly suppressed under nutrient-limited conditions, and bacteria could "remember" its prior motility status after storage at ultracold temperatures. Finally, we observed larger bacterial populations of strains with flagellin variants predicted not to be recognized by either FLS2 or FLS3, suggesting that these bacteria can evade flagellin recognition in tomato plants. Although some flagellin variants may impart altered motility and differential recognition by the host immune system, external growth parameters and gene expression regulation appear to have more significant impacts on the motility phenotypes for these Xanthomonas spp.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Full-dimensional quantum mechanical study of He3+He3+X− → He3+He3X−(X=HorD)

The atom-atom-anion three-body recombination (TBR) of $^{3}\mathrm{He}+^{3}\mathrm{He}+{X}^{\ensuremath{-}}$($X=\mathrm{H}\phantom{\rule{4pt}{0ex}}\text{or}\phantom{\rule{4pt}{0ex}}\mathrm{D}$) systems at ultracold temperatures ($T=0.01\ensuremath{\sim}100$ mK) are studied by solving the Schr\"odinger equation in the adiabatic hyperspherical representation. It is found that for each system, $^{3}\mathrm{He}+^{3}\mathrm{He}+{\mathrm{H}}^{\ensuremath{-}}$ or $^{3}\mathrm{He}+^{3}\mathrm{He}+{\mathrm{D}}^{\ensuremath{-}}$, the ${J}^{\mathrm{\ensuremath{\Pi}}}={1}^{\ensuremath{-}}$ symmetry dominates the TBR process, and the rates of TBR into $l=1\phantom{\rule{4pt}{0ex}}^{3}\mathrm{He}{X}^{\ensuremath{-}}$ molecular anions are roughly three times as large as than that into $l=0\phantom{\rule{4pt}{0ex}}^{3}\mathrm{He}{X}^{\ensuremath{-}}$ molecular anions for $T\ensuremath{\in}[0.01,10]$ mK, where $l$ denotes the two-body rotational quantum number. In addition, for a given product state, the TBR rates of the $^{3}\mathrm{He}{+}^{3}\mathrm{He}+{\mathrm{H}}^{\ensuremath{-}}$ system are larger than that of the $^{3}\mathrm{He}+^{3}\mathrm{He}+{\mathrm{D}}^{\ensuremath{-}}$ system by roughly two orders of magnitude which could be ascribed to the major nonadiabatic couplings between the entrance and recombination channels.

Battery Separator Characterization Strategy via Electron Microscopes

Lithium Ion (Li-ion) batteries store energy and power billions of devices globally, so manufacturers face pressure to ensure high energy density while maintaining safety. Among a battery’s components, a thin separator material prevents physical contact between electrodes while directing ion transport within a cell. Both processes impact cell rate performance, cycle life, and safety [1]. Therefore, an in-depth understanding of separator structure is essential to improving batteries [2-4]. 2D and 3D electron microscopy (EM) effectively characterize separator structure; however, due to intrinsic beam sensitivity to most separators, care is needed to accurately characterize separator structure in its native state. Our work tested 2D scanning EM (SEM) and 3D DualBeamTM (Focused Ion Beam-Scanning Electron Microscope, FIB-SEM) imaging conditions to understand their effect on recovered separator structure.We investigated battery separator structure using a Thermo Scientific ApreoTM SEM and Thermo Scientific DualBeam systems equipped with CryoMAT. The SEM assisted with understanding surface-level electron beam damage in 2D and the DualBeam uncovered 3D structure using FIB milling. In the 2D case, we found the accelerating voltage could warp the separator. Low kV imaging is thus recommended to minimize structure damage.Additionally, in 2D SEM cross-section studies, sample preparation could affect separator structure. We tested an Al2O3-coated composite separator by FIB milling at three different temperatures (Figure 1). We found that cryogenic temperatures (-80° C; i.e., cryo-FIB) achieved the highest quality cross-section (Figure 1). FIB milling at either room temperature (25° C) or ultracold temperature (-180° C) both introduced defects on the microstructure.Finally, given the previous result, we collected 3D separator structure via cryo-FIB. With the 3D image stack, we used Thermo Scientific Avizo™ Software to recover structural parameters: open pore volume fraction, closed pore count and volume fraction, pore connectivity, tortuosity, and permeability. Such information should be useful for understanding battery separator performance. It is expected the strategies discussed in this talk will facilitate separator technology development.

A Global Thermal Conductivity Model for Lunar Regolith at Low Temperatures

AbstractAlthough some of the coldest surface temperatures in the entire Solar System are found near the poles of our own Moon, the thermophysical properties of lunar regolith at these ultracold temperatures (i.e., below ∼150 K) are not well understood. Standard lunar thermal models generally match the surface temperatures observed by global orbital remote sensing data but are inconsistent with infrared data collected from ultracold polar terrain. We build upon previous theoretical work on the low‐temperature physics of lunar regolith to introduce a global thermal conductivity model consistent with the temperature trends observed by the Diviner Lunar Radiometer Experiment (Diviner). This updated thermophysical model primarily affects nighttime surface temperatures, subsurface temperatures at high latitudes, and permanently shadowed regions (PSRs). An additional outcome of this thermophysical model is the ability to accommodate the surface temperature trends observed by Diviner both in warm low latitudes and cold high latitudes. Subsurface temperatures in near‐polar craters are ∼5–10 K warmer than previous thermal models, and cooler nighttime surface temperatures are observed globally. Model results of PSRs reveal larger surface temperature amplitudes (as observed by Diviner) and steeper geothermal gradients. A comprehensive understanding of lunar regolith's low‐temperature thermal behavior is an essential step in modeling the potential location and quantity of cold trapped volatiles in the lunar south pole. Here, we hope to provide theoretical support and motivation for more complete low‐temperature thermal conductivity laboratory measurements.

Electronic Spectroscopy and Photoionization of LiBe.

LiBe has been the subject of several theoretical investigations and one spectroscopic study. Initially, these efforts were motivated by interest in the intermetallic bond. More recent work has explored the potential for producing LiBe and LiBe+ at ultracold temperatures. In the present study, we have advanced the spectroscopic characterization of several electronic states of LiBe and the ground state of LiBe+. For the neutral molecule, the 12Π, 22Σ+, 32Σ+, and 42Π(3d) states were observed for the first time. Data for the 22Σ+-X2Σ+ transition support a theoretical prediction that this band system is suitable for direct laser cooling. Photoelectron spectroscopy has been used to determine the ionization energy of LiBe and map the low-energy vibrational levels of LiBe+ X1Σ+. Overall, the results validate the predictions of high-level quantum chemistry calculations for both LiBe and LiBe+.

Generation of maximal three-state field-free molecular orientation with terahertz pulses

We present a combined analytical and numerical investigation to show how an optimal control field can be designed to generate maximum field-free orientation of molecules for three populated rotational states. Based on a model involving pure rotational ladder-climbing excitation between rotational states, a set of optimal amplitude and phase conditions are analytically derived for the applied control fields. The maximum degree of orientation can be achieved when the field satisfies amplitude and phase conditions at the two transition frequencies. Multiple optimal solutions exist and to examine these conditions, we devise a quantum coherent control scheme using two terahertz pulses and successfully apply it to the linear polar molecule HCN at ultracold temperature. The sensitivity of both populations and phases of rotational states to control field parameters, i.e., the detuning, bandwidth, and time delay, is analyzed for understanding the optimal orientation mechanism. This work thus examines the frequency domain landscape belonging to optimal pulses.

Protecting COVID-19 Vaccine Transportation and Storage from Analog Cybersecurity Threats

Protecting COVID-19 Vaccine Transportation and Storage from Analog Cybersecurity Threats

COVID-19 Vaccination in Developing Nations: Challenges and Opportunities for Innovation.

Vaccines offer a hope toward ending the global pandemic caused by SARS-CoV2. Mass vaccination of the global population offers hope to curb the spread. Developing nations, however, face monumental challenges in procurement, allocation, distribution and uptake of vaccines. Inequities in vaccine supply are already evident with resource-rich nations having secured a large chunk of the available vaccine doses for 2021. Once supplies are made available, vaccines will have to be distributed and administered to entire populations—with considerations for individual risk level, remote geography, cultural and socio-economic factors. This would require logistical and trained personnel support that can be hard to come by for resource-poor nations. Several vaccines also require ultra-cold temperatures for storage and transport and therefore the need for specialized equipment and reliable power supply which may also not be readily available. Lastly, attention will need to be paid to ensuring adequate uptake of vaccines since vaccine hesitancy has already been reported for COVID vaccines. However, existing strengths of local and regional communities can be leveraged to provide innovative solutions and mitigate some of the challenges. Regional and international cooperation can also play a big role in ensuring equity in vaccine access and vaccination.