Rb Mixture Research Articles

Mitigation of arsenic release by calcium peroxide (CaO2) and rice straw biochar in paddy soil

Biochar has a great potential in the stabilization of soil heavy metals; however, the application can actually enhance the mobility of Arsenic (As) in soil. Here, a biochar-coupled calcium peroxide system was proposed to control the increase in As mobility caused by biochar amendment in paddy soil environment. The capability of rice straw biochar pyrolyzed at 500 °C (RB) and CaO2 to control As mobility was evaluated by incubation for 91 days. CaO2 encapsulation was performed for pH control of CaO2, and As mobility was evaluated using a mixture of RB + CaO2 powder (CaO2-p), and RB + CaO2 bead (CaO2-b), respectively. The control soil solely and RB alone were included for comparison. The combination of RB with CaO2 exhibited remarkable performance in controlling As mobility in soil, and As mobility decreased by 40.2% (RB + CaO2-p) and 58.9% (RB + CaO2-b) compared to RB alone. The result was due to high dissolved oxygen (6 mg L-1 in RB + CaO2-p and RB + CaO2-b) and calcium concentrations (296.3 mg L-1 in RB + CaO2-b); oxygen (O2) and Ca2+ derived from CaO2 is able to prevent the reductive dissolution and chelate-promoted dissolution of As bound to iron (Fe) oxide by biochar. This study revealed that the simultaneous application of CaO2 and biochar could be a promising way to mitigate the environmental risk of As.

Spectral profiles of strongly saturated resonance transitions in high-density rb vapor

We study a nonlinear selective reflection from an interface YAG/high density vapor of the natural mixture of Rb isotopes at the components of 5S1/2−5P3/2 transition. The Doppler width is small by compare with the dipole-dipole interactions induced width of 6.1 GHz. In the experiment a cw laser beam with a variable intensity is used. There are two main contributions to the effective spectral linewidth: the excitation dependent dipole broadening, and the field broadening which defined by the Rabi frequency. At moderate laser beam intensities, when the Rabi frequency is less than the excitation-reduced dipole broadening, a remarkable narrowing of the spectral profiles is observed. At high intensities, when the Rabi frequency exceeds the reduced dipole broadening, the spectral profiles are practically independent of the laser intensity. This effect can be attributed to intensity induced saturation of the dipole broadening and the strong reduction of the field broadening.

Observation of magnetization transfer in spin-exchange collisions of cesium and rubidium atoms

Spin exchange is one of the effective processes for obtaining spin-polarized atoms. Such mechanism of spin polarization is usually used to transmit and observe the longitudinal (along magnetic field) component magnetization of atoms. However, spin-exchange collisions can also lead to the transfer of the transverse component of magnetization, which occurs when the atoms involved in the collisions are exposed to an alternating resonant magnetic field. This article describes experiments to observe the transmission of transverse magnetization between alkali metal atoms 133Cs and 85Rb in spin-exchange collisions. The calculation of the spin exchange in a mixture of Cs and Rb under magnetic resonance conditions gave a qualitative agreement with the experimental results.

Magnetic Resonance Frequency Shifts of Spin-Polarized Cesium Atoms in a Cs–Rb Mixture

The interaction of spin-polarized cesium atoms with cesium and rubidium atoms under conditions of optical orientation of atoms is considered. On the basis of data on spin-exchange complex cross sections in the Cs–Cs and Cs–Rb systems, a calculation of a magnetic resonance frequency shift of cesium atoms in a Cs–Rb mixture, as well as comparison of the calculated values of the frequency shift with experimental data, is performed.

EFFECT OF RICE STRAW BIOCHAR AND COMPOST APPLICATION AT DIFFERENT RATIOS ON HEAVY METALS IMMOBILIZATION IN THE CANOLA PLANTS GROWN IN CONTAMINATED SOIL

Industrial activities can contribute to the heavy metal accumulation in soils, which could potentially threaten human health, agricultural crop productivity and the environment. This research was conducted to use metal uptake and spectroscopic analysis (X-Ray Diffraction (XRD), Energy Dispersive spectroscopy by X-rays (EDX) and Fourier Transmission Infrared Spectroscopy (FTIR) to evaluate the effect of application of both rice straw biochar and compost with different ratios on heavy metal immobilization in the canola plants grown in the contaminated soil. The results showed that the Cd, Pb, Ni and Zn uptake in the root and shoot of canola plants significantly decreased with the addition of rice straw compost (RC) and biochar (RB) to contaminated soil. The addition of 1% mixture of RC and RB gives the most effective immobilizing metals as 100% and 74.2%, reduction in Cd and Pb accumulation by canola shoots, respectively. The biochar and compost obtained from rice straw showed high carbon content, silica and a high absorption character. The use of spectroscopic analysis observed the precipitation, inner-sphere complex reaction and electrostatic attraction are the dominating mechanism for heavy metal immobilization with organic amendments. Our results indicate that the metal uptake is considered to be the effective tool to assess the efficiency of immobilizing agents on metal phyto-availability.

Ion-Exchange Interaction of Glass-Forming Silicate Melts with Mixed Chloride Melts

The ion-exchange interaction of the sodium aluminosilicate and sodium galliumsilicate melts with a mixture of molten Li, Na, K, Rb, Cs, and Ba chlorides is studied. It is established that two alkaline silicate melts are characterized by negative deviations from the ideal behavior, and silicate melts containing alkaline and alkaline-earth cations are characterized by noticeable positive deviations from the ideal behavior.

The RbSr 2Σ+ ground state investigated via spectroscopy of hot and ultracold molecules.

We report on spectroscopic studies of hot and ultracold RbSr molecules, and combine the results in an analysis that allows us to fit a potential energy curve (PEC) for the X(1)2Σ+ ground state bridging the short-to-long-range domains. The ultracold RbSr molecules are created in a μK sample of Rb and Sr atoms and probed by two-colour photoassociation spectroscopy. The data yield the long-range dispersion coefficients C6 and C8, along with the total number of supported bound levels. The hot RbSr molecules are created in a 1000 K gas mixture of Rb and Sr in a heat-pipe oven and probed by thermoluminescence and laser-induced fluorescence spectroscopy. We compare the hot molecule data with spectra we simulated using previously published PECs determined by three different ab initio theoretical methods. We identify several band heads corresponding to radiative decay from the B(2)2Σ+ state to the deepest bound levels of X(1)2Σ+. We determine a mass-scaled high-precision model for X(1)2Σ+ by fitting all data using a single fit procedure. The corresponding PEC is consistent with all data, thus spanning short-to-long internuclear distances and bridging an energy gap of about 75% of the potential well depth, still uncharted by any experiment. We benchmark previous ab initio PECs against our results, and give the PEC fit parameters for both X(1)2Σ+ and B(2)2Σ+ states. As first outcomes of our analysis, we calculate the s-wave scattering properties for all stable isotopic combinations and corroborate the locations of Fano-Feshbach resonances between alkali Rb and closed-shell Sr atoms recently observed [V. Barbéet al., Nat. Phys., 2018, 14, 881]. These results and more generally our strategy should greatly contribute to the generation of ultracold alkali-alkaline-earth dimers, whose applications range from quantum simulation to state-controlled quantum chemistry.

Observation of polarized atoms of rubidium isotopes in experiments on optical orientation in a He–Rb mixture under conditions of a pulsed gas discharge

We are the first to have observed magnetic resonance signals from atoms of 85Rb and 87Rb isotopes when using the indirect optical orientation in conditions of helium–rubidium gas discharge plasma. An anomalously small ratio of magnetic resonance signals from isotopes of rubidium and metastable helium upon optical orientation of 4Не atoms has been detected. The experimental results have been considered theoretically, and an explanation of the observed anomaly in the signals is presented.Z

Satellite bands of the RbCs molecule in the range of highly excited states

We report on the observation of three RbCs satellite bands in the blue and green ranges of the visible spectrum. Absorption measurements are performed using all-sapphire cell filled with a mixture of Rb and Cs. We compare high resolution absorption spectrum of Rb-Cs vapor mixture with pure Rb and Cs vapor spectra from the literature. After detailed analysis, the new satellite bands of RbCs molecule at 418.3 nm, 468.3, and 527.5 nm are identified. The origin of these bands is discussed by direct comparison with difference potentials derived from quantum chemistry calculations of RbCs potential energy curves. These bands originate from the lower Rydberg states of the RbCs molecule. This study thus provides further insight into photoassociation of lower Rydberg molecular states, approximately between Cs(7s) + Rb(5s) and Cs(6s) + Rb(6p) asymptotes, in ultracold gases.

DIELECTRIC SPECTROSCOPY ON MIXTURE OF RICE HUSK, RICE HUSK ASH AND RICE BRAN FROM 4 Hz TO 1 MHz

In this study, mixtures of rice husk/rice husk ashes (RHA) with RB on different ratios were prepared. Dielectric permittivity ( ' e ), loss factor ( e ) and AC conductivity ( ' σ ) were measured in the frequency range of 4 Hz to 1 MHz in ambient temperature. Results for mixture of RHA and RB indicate that a dipolar relaxation occurring between 10 3 - 10 5 Hz and the peak is depressed and shifted to lower frequency as the RB content increases in the mixture. Moreover, AC conductivity decreases as the RB content increase. This may attributed to production of natural oil content from RB. In contrast, a dielectric characteristic for RH is generally not affected by the RB contents. This study explore dielectric characteristic of mixture between RH/RHA and RB in low frequency range because lack of literature is reported on low frequency response. Additionally, the potential application of RH/RHA and RB could be explored in effort to diminish waste disposal and enhance environmental protection.

Efimov Resonance and Three-Body Parameter in a Lithium-Rubidium Mixture.

We study collisional heating in a cold ^{7}Li-^{87}Rb mixture near a broad Feshbach resonance at 661 G. At the high field slope of the resonance, we find an enhanced three-body recombination rate that we interpret as a heteronuclear Efimov resonance. With improved Feshbach spectroscopy of two further resonances, a model for the molecular potentials has been developed that now consistently explains all known Feshbach resonances of the various Li-Rb isotope mixtures. The model is used to determine the scattering length of the observed Efimov state. Its value of -1870a_{0} Bohr radii supports the currently discussed assumption of universality of the three-body parameter also in heteronuclear mixtures.

Extended Fourier-transform spectroscopy studies and deperturbation analysis of the spin-orbit coupled A1Σ+ and b3Π states in RbCs.

The article presents a study of the strongly spin-orbit coupled singlet A(1)Σ(+) and triplet b(3)Π states of the RbCs molecule, which provide an efficient optical path to transfer ultracold molecules to their rovibrational ground state. Fourier-transform A(1)Σ(+) - b(3)Π → X(1)Σ(+) and (4)(1)Σ(+) → A(1)Σ(+) - b(3)Π laser-induced fluorescence (LIF) spectra were recorded for the natural mixture of the (85)Rb(133)Cs and (87)Rb(133)Cs isotopologues produced in a heat pipe oven. Overall 8730 rovibronic term values of A(1)Σ(+) and b(3)Π states were determined with an uncertainty of 0.01 cm(-1) in the energy range [9012, 14087] cm(-1), covering rotational quantum numbers J ∈ [6, 324]. An energy-based deperturbation analysis performed in the framework of the four A(1)Σ(+) - b(3)Π(Ω = 0, 1, 2) coupled-channels approach reproduces 97% of the experimental term values of both isotopologues with a standard deviation of 0.0036 cm(-1). The reliability of the deperturbed mass-invariant potentials and spin-orbit coupling functions of the interacting A(1)Σ(+) and b(3)Π states is additionally proved by a good reproduction of the A - b → X and (4)(1)Σ(+) → A - b relative intensity distributions. The achieved accuracy of the A - b complex description allowed us to use the latter to assign the observed (5)(1)Σ(+) → A - b and (3)(1)Π → A - b transitions. As is demonstrated, LIF to the A - b complex becomes as informative as to the ground X(1)Σ(+) state, which is confirmed by comparing the results of (4)(1)Σ(+) state analysis based on (4)(1)Σ(+) → A - b LIF with the data from V. Zuters et al. [Phys. Rev. A 87, 022504 (2013)] based on (4)(1)Σ(+) → X LIF.

Ultracold mixtures of metastable He and Rb: Scattering lengths fromab initiocalculations and thermalization measurements

We have investigated the ultracold interspecies scattering properties of metastable triplet He and Rb. We performed state-of-the-art ab initio calculations of the relevant interaction potential, and measured the interspecies elastic cross section for an ultracold mixture of metastable triplet $^4$He and $^{87}$Rb in a quadrupole magnetic trap at a temperature of 0.5 mK. Our combined theoretical and experimental study gives an interspecies scattering length $a_{4+87}=+17^{+1}_{-4}$ $a_0$, which prior to this work was unknown. More general, our work shows the possibility of obtaining accurate scattering lengths using ab initio calculations for a system containing a heavy, many-electron atom, such as Rb.

Tests of universal three-body physics in an ultracold bose-fermi mixture.

Recent measurements of Efimov resonances for a number of ultracold atom species have revealed an unexpected universality, in which three-body scattering properties are determined by the van der Waals length of the two-body interaction potential. To investigate whether this universality extends to heteronuclear mixtures, we measure loss rate coefficients in an ultracold trapped gas of 40K and 87Rb atoms. We find an Efimov-like resonance in the rate of inelastic collisions between 40K87Rb Feshbach molecules and 87Rb atoms. However, we do not observe any Efimov-related resonances in the rates of inelastic collisions between three atoms. These observations are compared to previous measurements by the LENS group of Efimov resonances in a 41K and 87Rb mixture as well as to recent predictions.

Photoionization loss in simultaneous magneto-optical trapping of Rb and Sr

We demonstrate the simultaneous magneto-optical trapping (MOT) of Rb and Sr and examine the characteristic loss of Rb in the MOT due to photoionization by the cooling laser for Sr. The photoionization cross section of Rb in the $5P_{3/2}$ state at 461 nm is determined to be $1.4(1)\times10^{-17}$ cm$^2$. It is important to consider this loss rate to realize a sufficiently large number of trapped Rb atoms to achieve a quantum degenerate mixture of Rb and Sr.

ChemInform Abstract: Two New Cluster Ions, Ga[GaH3]5‐4 with a Neopentane Structure in Rb8Ga5H15 and [GaH2]n‐n with a Polyethylene Structure in Rbn(GaH2)n, Represent a New Class of Compounds with Direct Ga—Ga Bonds Mimicking Common Hydrocarbons.

AbstractThe title compounds are prepared from mixtures of Ga and Rb under 5 MPa H2 at 573 K and characterized by powder XRD and neutron powder diffraction.

ESI-QIMS Investigation of Sr, Rb, and Crown Ether Mixture Solutions

The isotope distribution of Sr, alternatively 87Sr/86Sr ratio frequently reported in geologic investigations, is obtained by direct electrospray ionization of aqueous samples containing Sr(II), Rb(I) with added 18-crown-6 (18c6) [1,4,7,10,13,16-Hexaoxacyclooctadecane C12H24O6 m/z 264.3]. At relatively high concentrations of Sr and Rb, we observed favorable formation of Sr2+(18c6)2 and Rb+(18c6) rather than Sr2+(18c6) complexes. Significant Sr2+(18c6)2 suppression observed in post column addition of samples into water solvent disappeared when formic acid was present in the carrier solvent. Electrospray ionization-quadrupole-ion trap mass spectrometry (ESI-QITMS) successfully obtained the expected isotope distribution of Sr showing no interference from Rb without chromatographic separation of 87Sr and 87Rb necessary in ICP-MS studies.

Magnetic merging of ultracold atomic gases ofRb85andRb87

We report on the magnetic merging of ultracold atomic gases of $^{85}$Rb and $^{87}$Rb by the controlled overlap of two initially spatially-separated magnetic traps. We present a detailed analysis of the combined magnetic field potential as the two traps are brought together which predicts a clear optimum trajectory for the merging. We verify this prediction experimentally using $^{85}$Rb and find that the final atom number in the merged trap is maximised with minimal heating by following the predicted optimum trajectory. Using the magnetic merging approach allows us to create variable ratio isotopic Rb mixtures with a single laser cooling setup by simply storing one isotope in a magnetic trap before jumping the laser frequencies to the transitions necessary to laser cool the second isotope. This offers a simple and cost effective way to achieve suitable starting conditions for sympathetic cooling of $^{85}$Rb by $^{87}$Rb towards quantum degeneracy.

Two-photon photoassociation spectroscopy of heteronuclear YbRb

We report on the spectroscopic investigation of vibrational levels in the electronic ground state of the heteronuclear molecule (176)Yb(87)Rb. Using two-photon photoassociation spectroscopy in a laser-cooled mixture of (176)Yb and (87)Rb we are able to determine the binding energies of weakly-bound vibrational levels. By applying the LeRoy-Bernstein method we assign the vibrational quantum numbers and deduce a C(6) coefficient for the long-range part of the molecular potential of ∼2500 a.u.

Investigation of ammonium substitution in the perovskite-like structure Rb 0.79(NH 4) 0.21CdCl 3

A novel rubidium–ammonium cadmium trichloride has been prepared and characterized by X-ray single crystal analysis at room temperature. Rb 0.79(NH 4) 0.21CdCl 3 crystallizes in the orthorhombic space group Pnma with Z = 4 and unit cell dimensions a = 8.9654(2) Å, b = 4.0200(1) Å, c = 14.9489(6) Å. Several cycles of least-squares refinement reduced the disagreement R (F) factor for 733 reflections to a final value of 0.0207. The compound structure consists of Rb + (or NH 4 + ) ions and double chains of CdCl 6 octahedra sharing one edge extending along “ b” axis. The mixture of Rb +/ NH 4 + cations are located between the double chains ensuring the stability of the structure by ionic and hydrogen bonding contacts N–H ⋯ Cl. By comparison with RbCdCl 3 the ammonium-substituting does not affect the structural arrangement, but it leads to decrease of the “ b” and “ c” orthorhombic lattice cell dimensions and the Cd–Cl distances and gives more disorder of NH 4 + groups.