Three-body Recombination Coefficient Research Articles

High efficient Raman sideband cooling and strong three-body recombination of atoms

We report a highly efficient three-dimensional degenerated Raman sideband cooling (3D dRSC) that enhances the loading of a magnetically levitated optical dipole trap, and observe the strong atom loss due to the three-body recombination. The 3D dRSC is implemented to obtain 5 × 107 Cs atoms with the temperature of ∼ 480 nK. The cold temperature enables 1.8 × 107 atoms loaded into a crossed dipole trap with an optimized excessive levitation magnetic gradient. Compared to the loading of atoms from a bare magneto-optical trap or the gray-molasses cooling, there is a significant increase in the number of atoms loaded into the optical dipole trap. We derive for the three-body recombination coefficient of L 3 = 7.73 × 10−25 cm6/s by analyzing the strong atom loss at a large scattering length of 1418 Bohr radius, and discover the transition from the strong three-body loss to the dominant one-body loss. Our result indicates that the lifetime of atoms in the optical dipole trap is finally decided by the one-body loss after the initial strong three-body loss.

Effect of dielectronic recombination on charge-state distribution in laser-produced plasma based on steady-state collisional-radiative models

Armed with four different steady-state collisional-radiative (CR) models, we investigated the effect of dielectronic recombination (DR) on the charge-state distribution in laser-produced silicon plasma. To assess this effect, we performed a series of temporally resolved spectra of highly charged Si ions in the extreme ultraviolet region. Ab initio calculations of the DR rate coefficients were done for Si6+–Si4+ ions. We also analyzed the evolution of the collisional ionization, radiative recombination, three-body recombination, photo-ionization, and DR rate coefficients as a function of electron temperature. The electron temperature and electron density for different delay times were obtained by comparing the normalized experimental and simulated spectra. The ion fraction and average charge state from the four different CR models were also obtained. The results indicate that the DR process has a greater influence in the stage of plasma evolution that cannot be neglected in plasma diagnoses.

Features of triple recombination in ultracold plasma

We show that in the ultracold plasma, when the coupling parameter characterizes the interaction of electrons and ions exceeds unity, the collisional threebody (e – e – ion) recombination coefficient (TBR) becomes inversely proportional to the plasma frequency, whereas for the small values of this parameter it ∼ T−9/2 (T is the temperature). We compare the results obtained with different theoretical models and numerical simulation data of the recombination process.

Universal Three-Body Physics in Ultracold KRb Mixtures.

Ultracold atomic gases have recently become a driving force in few-body physics due to the observation of the Efimov effect. While initially observed in equal mass systems, one expects even richer few-body physics in the heteronuclear case. In previous experiments with ultracold mixtures of potassium and rubidium, an unexpected nonuniversal behavior of Efimov resonances was observed. In contrast, we measure the scattering length dependent three-body recombination coefficient in ultracold heteronuclear mixtures of ^{39}K-^{87}Rb and ^{41}K-^{87}Rb and do not observe any signatures of Efimov resonances for accessible scattering lengths in either mixture. Our results show good agreement with our theoretical model for the scattering dependent three-body recombination coefficient and reestablish universality across isotopic mixtures.

Theoretical studies of dielectronic recombination for Au34+ ions

Dielectronic recombination (DR) rate coefficients of complex structure ions are very important for spectral simulation in some application researches, such as nuclear fusion and extreme ultraviolet lithography. Theoretical calculations are made for dielectronic recombination rate coefficients of Au34+ ions by using a flexible relativistic atomic code. Influences of excitation and radiation channels, configuration interactions, and decays to autoionizing levels possibly followed by radiative cascades (DAC) on DR rate coefficient are analyzed. The contribution of DAC is evident. The total DR rate coefficient is greater than either the radiation recombination coefficient or three-body recombination coefficient for electron temperature greater than 1 eV. In order to facilitate simple applications, the total DR rate coefficients for the ground state and the first excited state are fitted to an empirical formula. These results should be useful for further analyzing the DR process of complex structures ions.

Temporal Spectra Behavior in Femtosecond LIBS of Marine Water

Spectral dynamics of femtosecond laser plasma induced on the sea water surface is investigated. Characteristic decay time of continuum and line intensity of Mg II, Ca II and Na I are determined. Electron density that changes from 3.0·1016to 2.4·1015cm-3was provided by usage of three-body recombination coefficient. It is shown that Na detection limit will be least in comparison with Mg and Ca.

Theoretical investigation of dielectronic recombination of Sn12+ions

Theoretical calculations have been made for the dielectronic recombination (DR) rate coefficients of Sn${}^{12+}$ ion using a relativistic flexible atomic code with configuration interaction. Comparison of the rate coefficients for $4s$, $4p$, and $4d$ subshell excitation shows that while the $4p$ subshell excitation dominates over the whole temperature region, $4d$ subshell excitation at low temperature and $4s$ subshell excitation at high temperature cannot be neglected. In order to facilitate simple applications, the calculated DR rate coefficients are fitted to an empirical formula. The total DR rate coefficient is greater than either the radiative recombination or three-body recombination coefficients for electron temperatures greater than 1 eV. Therefore, DR can strongly influence the ionization balance of laser-produced tin plasmas.

Theoretical studies on dielectronic recombination of neonlike gold and its effects on plasma ionization balance and radiation energy

The dielectronic recombination (DR) of neonlike gold ions is investigated employing the flexible atomic code based on the relativistic configuration interaction method, and its influence on the ionization balance and radiation energy in high-temperature plasma is also studied. The total resonance strength for LMM configuration complex is in a good agreement with the experimental measurement and other theoretical works. The DR rate coefficients are calculated and compared with the three-body recombination and radiative recombination rate coefficients. The DR process is the dominant recombination mechanism of Ne-like gold ions for plasma with temperature Te≥6.5 keV and density ne≤2×1022 cm-3, which is close to the condition of X-ray conversion region in the inertial confinement fusion. Moreover, the DR satellite spectra of LMM, LMN and LMO resonances are simulated, and compared with the intensities of the corresponding resonance lines induced by the electron impact excitation. The intensity ratio of the satellite line 3D’ $[(2p^{5}_{3/2}3d_{3/2}3d_{5/2})_{J=5/2}$ – $(2p^{6}3d_{3/2})_{ J=3/2}]$ and the resonance line 3D $[(2p^{5}_{3/2}3d_{5/2})_{J=1}$ – $(2p^{6})_{J=0}]$ is given, which can be applied for diagnostics of plasma temperature.

Three-Body Recombination in Ultracold Systems: Prediction of Weakly-Bound Atomic Trimer Energies

The three-body recombination coefficient of a trapped ultracold atomic system, together with the corresponding two-body scattering length $a$, allow us to predict the energy $E_3$ of the shallow trimer bound state, using a universal scaling function. The production of dimers in Bose-Einstein condensates, from three-body recombination processes, in the regime of short magnetic pulses near a Feshbach resonance, is also studied in line with the experimental observation.

Feasibility study on frozen inert gas plasma MHD generator

The feasibility of a magnetohydrodynamics (MHD) generator with frozen inert gas plasma (FIP) is examined numerically. The FIP is produced by pre-ionizing helium of inert gas without alkali metal seed at the generator inlet. Because the three-body recombination coefficient of helium ions is low at the electron temperature more than 5000 K, the ionization degree of inert gas is kept almost constant in the entire region of the generator channel and the relation between the electron temperature and the electron number density deviates from the Saha equilibrium. In a small-scale disk-shaped generator, the enthalpy extraction ratio of 22.7% and the isentropic efficiency of 54.8% are obtainable for the load resistance of 3.0 /spl Omega/ and magnetic flux density of 4 T under the pre-ionization degree of 4.79/spl times/10/sup -5/. The auxiliary power to sustain the pre-ionized plasma corresponds to about 2% of the thermal input. For high-magnetic flux density, the generator performance can be improved as well as a conventional-seeded plasma MHD generator.

Reaction rates for dense nonideal alkali plasmas

The quantum statistical theory of collisional rate coefficients of nonideal plasmas, developed in some recent papers for hydrogen, is applied to calculate the impact ionization and three-body recombination coefficients for the valence electron of the atoms in Li-, Na-, K-, Rb- and Cs-plasmas. The many-body effects are included by static screening in the quasiparticle energy shifts and in the effective potentials. Because the ionization of alkali atoms represents a multielectron problem, an effective two-body electron-ion potential is derived using the method of close coupling equations of quantum scattering theory. The latter is replaced by a suited two-parametric pseudopotential taking into account the shielding effects of the inner shell atomic electrons. Finally, numerical results are given for the ionization cross sections and the rate coefficients.

Ionization and recombination coefficients for a dense nonideal hydrogen plasma: effects of screening and degeneracy

Rate equations are derived for a strongly coupled hydrogen plasma starting from a generalized kinetic equation which accounts for chemical reactions and many-particle effects. The impact ionization and three-body recombination coefficients are calculated taking into account effective interaction potentials, self-energy shifts and Pauli-blocking. The density dependence is discussed which follows for the ionization as well as for the recombination coefficients.

Electron-ion three-body recombination coefficient of argon

Spectroscopic measurements of a 15-kW flowing argon plasma, produced by an atmospheric pressure radio frequency inductively coupled plasma torch, have been made. The plasma is found to be in partial local thermodynamic equilibrium at electronic levels as low as 4p. Ionizational nonequilibrium is observed in the form of an elevated electron density due to the finite three-body electron-ion recombination rate. The flowing plasma is modeled using a two-dimensional axisymmetric flow code, incorporating partial local thermodynamic equilibrium effects, radiative transfer, and ionizational nonequilibrium through the coupled electron continuity equation

Electron-ion recombination in an ambient molecular gas

Three-body electron-ion recombination in a molecular ambient gas is investigated theoretically. The limited success attained by a classical treatment is lost when necessary account is taken of the discreteness of the negative energy levels of the recombining electron. Thus the three-body recombination coefficients calculated in carbon dioxide and in water vapour differ from those measured by Warman et al. (1979) and Sennhauser et al. (1980) being much lower and falling off far more steeply with increase in temperature. It is noted that the ions involved in the laboratory study, (CO2+)n and H3O+(H2O)n, are open to dissociative recombination and it is pointed out that this process and three-body recombination supplement one another with striking consequences. The mechanism is in two stages: firstly, collisions between the electrons and the ambient gas molecules populate the Rydberg levels; secondly, the electrons in the Rydberg levels participate in radiationless transitions leading to dissociation in the same way as free electrons. A suitably descriptive name for the mechanism is collisional dissociative recombination. Detailed calculations give gas-density-dependent recombination coefficients in quite good agreement with those measured.

Ion-ion recombination rates in the earth's atmosphere

The temperature dependence of the binary recombination coefficient, α 2, for the reaction NO ++NO 2 − → products has been obtained over the range 185–530 K. It is found that the corresponding mean cross section σ is described by the power law σ ≅ A · T −0.9 , and that α 2 ≅ B · T −0.4. Data has also been obtained for two cluster ion recombination reactions which indicate that their recombination cross sections are only about 40% larger than for the parent ions at a given temperature, the cross sections for these reactions also apparently increasing with decreasing temperature. In the light of this data and by considering the most probable positive and negative ions existing at various altitudes up to 90km in the atmosphere, the most appropriate ionic recombination coefficients in various altitude ranges are deduced. Thus, between 30 and 90 km, where the recombination process is two-body, the coefficient varies over the narrow range 5–9 × 10 −8 cm 3s −1, while below 30 km the process is predominantly three-body with an effective two-body rate increasing rapidly to a maximum value ≈3 × 10 −6 cm 3s −1 in the troposphere, these deductions being based on published laboratory determinations of three-body recombination coefficients.

Thermal dissociation and recombination of hydrogen according to the reactions H2+H⇄ H+H+H

Three-body recombination and dissociation rate coefficients (kr and kd, respectively) for the reactions H2+H⇄ H+H+H have been evaluated for temperatures ranging between 300 and 10 000°K on the basis of the modified phase-space theory of reaction rates and Monte Carlo trajectory calculations. The semiempirical Porter-Karplus surface for H3 was used in the calculations. Good agreement was obtained between the theoretical estimates of kd and the bulk of the dissociation rate measurements. However, in contradistinction to some of the recent experimental investigations, neither the extremely steep temperature decay ([inverted lazy s] T−6) of kr at high temperatures nor the existence of a pronounced maximum in kr at moderate temperatures are supported by this theoretical work. Possible reasons for these differences are suggested. A simple ratio was deduced which relates kr(H) and the corresponding rate coefficients of the isotopes of hydrogen. The result is in good agreement with available experimental measurements and enables one to predict the latter rate coefficients without additional trajectory calculations. An example is given to illustrate the capability of the present Monte Carlo method in obtaining other useful information about atomic and molecular collision processes.

Measurements of the Electronic Recombination Coefficient in a Helium Plasma Jet

The three-body recombination coefficient has been measured in a partially ionized plasma jet mainly by using a spectroscopic technique. Experimental data were treated by the consideration that the net number of particles that were deexcited across a minimum in the total rate of deexcitation of atoms was substantially equal to the number of electronic recombinations. Experimental results are in good agreement with other investigated values and show ${T}_{e}^{\ensuremath{-}4.4}$ dependence of the recombination coefficient.

Gas-Phase Recombination of Hydrogen. A Comparison between Theory and Experiment

The modified phase-space theory of reaction rates has been used to calculate the three-body recombination and dissociation rate coefficients of hydrogen in the presence of H2, He, Ar, and Xe collision partners. The theoretical predictions, which rely on semiempirically derived interatomic potential information, are shown to be in excellent agreement with the measured rate coefficients over wide temperature ranges.

The three-body recombination and dissociation of diatomic molecules: A comparison between theory and experiment

The modified phase-space theory of reaction rates has been used to predict the three-body recombination and dissociation rate coefficients of the diatomic gas molecules: H2, N2, O2, F2, Cl2, Br2, I2, HF, HCl, CO and NO, in the presence of argon as a collision partner. The ability of the theory to quantitatively predict and correlate both low-temperature recombination rate measurements and high-temperature dissociation rate measurements is substantial. The success of the theory clearly illustrates the importance of the weak attractive forces between the recombining atoms and argon atoms for recombination at low temperatures, the marked reduction in the rates at high temperatures due to nonequilibrium distributions in the vibrational state populations of the molecules, and the major contributions to reaction progress via electronically excited molecular states at all temperatures for such molecules as N2 and CO.

Application of three-body recombination and attachment coefficients to tropospheric ions

A modification ofNatanson's three-body recombination theory is used to determine empirical values of the ion-ion trapping distance. The modified theory is shown to predict accurately the altitude variation of electrical conductivity in the troposphere. The empirical trapping distance for ion-ion recombination is then used to determine the ion-aerosol trapping distance and a three-body theory for calculating the ion-aerosol attachment coefficients is developed. The theory should be valid for the small aerosols (Aitken nuclei) found naturally in the troposphere.