Two-Photon Spectroscopy of the NaLi Triplet Ground State

We employ two-photon spectroscopy to study the vibrational states of the triplet ground state potential ($a^3\Sigma^+$) of the $^{23}$Na$^{6}$Li molecule. Pairs of Na and Li atoms in an ultracold mixture are photoassociated into an excited triplet molecular state, which in turn is coupled to vibrational states of the triplet ground potential. Vibrational state binding energies, line strengths, and potential fitting parameters for the triplet ground $a^3\Sigma^+$ potential are reported. We also observe rotational splitting in the lowest vibrational state.Comment: 7 pages, 3 figure

Quantitative structure–activity relationship (QSAR) analysis of aromatic effector specificity in NtrC-like transcriptional activators from aromatic oxidizing bacteria

A quantitative structure–activity relationship (QSAR) approach was taken to provide mechanistic insights into the interaction between the chemical structure of inducing compounds and the transcriptional activation of aromatic monooxygenase operons among the XylR/DmpR subclass of bacterial NtrC-like transcriptional regulators. Compared to XylR and DmpR, a broader spectrum of effector compounds was observed for the TbuT system from Ralstonia pickettii PKO1. The results of QSAR analysis for TbuT suggested that a steric effect, rather than hydrophobic or electronic effects, may be the predominant factor in determining aromatic effector specificity, and the active site of the regulator may positively interact not only with the methyl moiety but also with the most electron-rich aryl side of an aromatic effector.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74885/1/S0378-1097_03_00400-2.pd

Collisional Cooling of Ultracold Molecules

Since the original work on Bose-Einstein condensation, quantum degenerate gases of atoms have allowed the quantum emulation of important systems from condensed matter and nuclear physics, as well as the study of novel many-body states with no analog in other fields of physics. Ultracold molecules in the micro- and nano-Kelvin regimes promise to bring powerful new capabilities to quantum emulation and quantum computing, thanks to their rich internal degrees of freedom compared to atoms. They also open new possibilities for precision measurement and the study of quantum chemistry. Quantum gases of atoms were made possible by collision-based cooling schemes, such as evaporative cooling. For ultracold molecules, thermalization and collisional cooling have not been realized. With other techniques such as supersonic jets and cryogenic buffer gases, studies have been limited to temperatures above 10 mK. Here we show cooling of NaLi molecules at micro- and nano-Kelvin temperatures through collisions with ultracold Na atoms, both prepared in their stretched hyperfine spin states. We find a lower bound on the elastic to inelastic collision ratio between molecules and atoms greater than 50 -- large enough to support sustained collisional cooling. By employing two stages of evaporation, we increase the phase-space density (PSD) of the molecules by a factor of 20, achieving temperatures as low as 220 nK. The favorable collisional properties of a Na and NaLi mixture show great promise for making deeply quantum degenerate dipolar molecules and suggest the potential for such cooling in other systems

Long-Lived Ultracold Molecules with Electric and Magnetic Dipole Moments

We create fermionic dipolar $^{23}$Na$^6$Li molecules in their triplet ground state from an ultracold mixture of $^{23}$Na and $^6$Li. Using magneto-association across a narrow Feshbach resonance followed by a two-photon STIRAP transfer to the triplet ground state, we produce $3\,{\times}\,10^4$ ground state molecules in a spin-polarized state. We observe a lifetime of $4.6\,\text{s}$ in an isolated molecular sample, approaching the $p$-wave universal rate limit. Electron spin resonance spectroscopy of the triplet state was used to determine the hyperfine structure of this previously unobserved molecular state.Comment: 5 pages, 5 figure

Photoassociation of Ultracold NaLi

We perform photoassociation spectroscopy in an ultracold $^{23}$Na-$^6$Li mixture to study the $c^3\Sigma^+$ excited triplet molecular potential. We observe 50 vibrational states and their substructure to an accuracy of 20 MHz, and provide line strength data from photoassociation loss measurements. An analysis of the vibrational line positions using near-dissociation expansions and a full potential fit is presented. This is the first observation of the $c^3\Sigma^+$ potential, as well as photoassociation in the NaLi system.Comment: 6 pages, 3 figure

Magnetic trapping of ultracold molecules at high density

Trapping ultracold molecules in conservative traps is essential for applications -- such as quantum state-controlled chemistry, quantum simulations, and quantum information processing. These applications require high densities or phase-space densities. We report magnetic trapping of NaLi molecules in the triplet ground state at high density ($\approx 10^{11} \; \rm{cm}^{-3}$) and ultralow temperature ($\approx 1\;{\rm \mu K}$). Magnetic trapping at these densities allows studies on both atom-molecule and molecule-molecule collisions in the ultracold regime in the absence of trapping light, which has often lead to undesired photo-chemistry. We measure the inelastic loss rates in a single spin sample and spin-mixtures of fermionic NaLi as well as spin-stretched NaLi$+$Na mixtures. We demonstrate sympathetic cooling of NaLi molecules in the magnetic trap by radio frequency evaporation of co-trapped Na atoms and observe an increase in the molecules' phase-space density by a factor of $\approx 16$.Comment: 8 pages, 4 figure

Ab initio calculation of the spectrum of Feshbach resonances in NaLi + Na collisions

We present a combined experimental and theoretical study of the spectrum of magnetically tunable Feshbach resonances in NaLi $(a^3\Sigma^+)$ $+$ Na collisions. In the accompanying paper, we observe experimentally 8 and 17 resonances occur between $B=0$ and $1400$~G in upper and lower spin-stretched states, respectively. Here, we perform ab initio calculations of the NaLi $+$ Na interaction potential and describe in detail the coupled-channel scattering calculations of the Feshbach resonance spectrum. The positions of the resonances cannot be predicted with realistic uncertainty in the state-of-the-art ab initio potential, but our calculations yield a typical number of resonances that is in near-quantitative agreement with experiment. We show that the main coupling mechanism results from spin-rotation and spin-spin couplings in combination with the anisotropic atom-molecule interaction. The calculations furthermore explain the qualitative difference between the numbers of resonances in either spin state

Spectrum of Feshbach resonances in NaLi ++ Na collisions

Collisional resonances of molecules can offer a deeper understanding of interaction potentials and collision complexes, and allow control of chemical reactions. Here, we experimentally map out the spectrum of Feshbach resonances in collisions between ultracold triplet ro-vibrational ground-state NaLi molecules and Na atoms over a range of 1400 G. Preparation of the spin-stretched state puts the system initially into the non-reactive quartet potential. A total of 25 resonances are observed, in agreement with quantum-chemistry calculations using a coupled-channels approach. Although the theory cannot predict the positions of resonances, it can account for several experimental findings and provide unprecedented insight into the nature and couplings of ultracold, strongly interacting complexes. Previous work has addressed only weakly bound complexes. We show that the main coupling mechanism results from spin-rotation and spin-spin couplings in combination with the anisotropic atom-molecule interaction, and that the collisional complexes which support the resonances have a size of 30-40 $a_0$. This study illustrates the potential of a combined experimental and theoretical approach

Rheological characterization for different phases of inulin extract from chicory roots, obtained through temperature reduction

Inulin is a functional food ingredient, generally employed as sugar or fat substitute in food systems. This ingredient can be found in several vegetal products, including chicory roots. As the solubility of inulin is susceptible to temperature changes, the product suffers a fractionalization resulting in two phases when cooled, originating a precipitated phase, more viscose, and a liquid phase, of lesser viscosity. The study of rheological properties of different phases of inulin extract is important for equipment designing, such as mixer and bombs. In this work, rheological behavior at three different temperatures (25; 40 and 50 ºC) was determined for liquid and precipitated phases of inulin liquid extract, extracted from chicory roots by hot water diffusion and cooled at two different temperatures (8 and -10 ºC), suffering phases separation. The precipitated phase was analyzed in two conditions: pure and with the addition of microencapsulating agents (maltodextrin and hydrolized starch). All of them presented a linear behavior, similar to that of the Plastics of Bingham. Some of them, however, were not an adequate fit to this model.A inulina é um ingrediente funcional, geralmente empregado na indústria alimentícia como substituto do açúcar ou da gordura. Esse ingrediente pode ser encontrado em diversos produtos vegetais, incluindo as raízes de chicória. Por ser um produto com solubilidade variável com a temperatura, a inulina sofre uma separação de fases ao ser resfriada, originando uma fase precipitada, mais viscosa, e uma fase sobrenadante, de menor viscosidade. O estudo das propriedades reológicas das diferentes fases do extrato de inulina é importante para o projeto de equipamentos, como misturadores e bombas. Neste trabalho, foi estudado o comportamento reológico, para três condições distintas de temperatura (25; 40 e 50 ºC), das fases sobrenadante e precipitada do extrato líquido de inulina, extraído de raízes de chicória por difusão em água quente e resfriado a duas temperaturas distintas (8 e -10 ºC), sofrendo separação de fases. A fase precipitada foi analisada em duas condições: pura e com a adição de agentes microencapsulantes. Todos apresentaram um comportamento linear, semelhante ao dos Plásticos de Bingham, porém, nem todos se ajustaram a esse modelo.202210Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES