Total Rate Coefficients Research Articles

Studies of electron-ion resonant recombination of li-like Si11+ions

Abstract Theoretical investigations of L-shell △n = 0, 1, and 2 (2s → 2p, 3 l ′ , and 4 l ′ ) dielectronic recombination (DR), as well as K-shell △n = 1, 2, and 3 (1s → 2 l ′ , 3 l ′ , and 4 l ′ ) DR of Li-like Si 11+ ions are performed, using the relativistic distorted-wave approach. Detailed resonance energies, resonance strengths, and recombination rate coefficients are calculated including complex configuration mixing, Breit interaction, and QED corrections. Good agreement is achieved between the theoretical rate coefficients and the experimental results. The plasma rate coefficients are also calculated for electron temperatures ranging from 10−1 to 106 eV, and an analytical formula is presented to fit the total plasma rate coefficients for convenient modeling of astrophysical and fusion plasmas.

N 2 + Meinel band quenching coefficients for vibrational levels 0 and 1.

Experimental rate coefficients for the quenching of vibrational levels 0 and 1 of the N2+A2Πu state by N2 are presented. The experiments were performed using near-infrared observations of the N2+ Meinel bands excited by electron impact at several pressures of the N2 target/quenching gas. The total removal rate coefficients were derived from a Stern-Volmer analysis of the Meinel band intensities as a function of N2 density and yielded rate coefficients of (2.5 ± 0.5 × 10-10) and (5.6 ± 0.6 × 10-10) cm3⋅molecule-1⋅s-1 for vibrational levels 0 and 1, respectively. It is shown that rate coefficients increase with increasing vibrational level and decreasing energy gap. Our results impact modeling studies of the disturbed atmosphere and ionosphere as the reduced quenching rate coefficients for the preferentially excited A-state vibrational levels <2 lower the quenching altitude in the atmosphere by one scale height, or about 6 km.

Forward and reverse uncertainty analyses for RRKM/master equation based kinetic predictions: A case study of ethyl with oxygen

AbstractIn the realm of combustion kinetic modeling, the norm involves employing thousands of reactions to delineate the chemical conversion of hundreds of species. Notably, theoretically predicted rate coefficients and branching ratios, derived through the RRKM/master equation (ME) model, play an increasing role in kinetic modeling. Thus minimizing the uncertainty of theoretical prediction across wide working conditions is crucial to refine a kinetic model. The present study takes ethyl (C2H5) + oxygen (O2) reaction system to show that combined forward and reverse uncertainty analysis can be used to further constrain calculated rate coefficients and branching ratios, which were already calculated by high‐level quantum chemistry methods. Forward global uncertainty analysis with the artificial neural network‐high dimensional model representation (ANN‐HDMR) method is employed to select key parameters affecting total rate coefficients of C2H5 + O2 and branching ratios of C2H5 + O2 = C2H4 + HO2 (C1). Reverse uncertainty analysis with Bayesian method was then applied to refine the key input parameters based on experimental data at working conditions selected by sensitivity entropy. Although the target RRKM/ME model system was built on high level theoretical calculations, the combined forward and reverse uncertainty analyses are still able to reduce uncertainties of predicted total rate coefficients of C2H5 + O2 and branching ratios for C1 across a wide range of working conditions. Specifically, the uncertainties of total rate coefficient and C1 branching ratio have been reduced from 1.46 and 1.52 to 1.30 and 1.36 at 298 K and 1 Torr. The analysis process proposed in the present work effectively extrapolates the constraint ability of accurate measured data at one condition to wide working conditions based on the RRKM/ME model.

Cross-calibration of quantum atomic sensors for pressure metrology

Quantum atomic sensors have shown great promise for vacuum metrology. Specifically, the density of gas particles in vacuum can be determined by measuring the collision rate between the particles and an ensemble of sensor atoms. This requires preparing the sensor atoms in a particular quantum state, observing the rate of changes of that state, and using the total collision rate coefficient for state-changing collisions to convert the rate into a corresponding density. The total collision rate coefficient can be known by various methods, including quantum scattering calculations using a computed interaction potential for the collision pair, measurements of the post-collision sensor-atom momentum recoil distribution, or empirical measurements of the collision rate at a known density. Observed discrepancies between the results of these methods call into question their accuracy. To investigate this, we study the ratio of collision rate measurements of co-located sensor atoms, 87Rb and 6Li, exposed to natural abundance versions of H2, He, N2, Ne, Ar, Kr, and Xe gases. This method does not require knowledge of the test gas density and is, therefore, free of the systematic errors inherent in efforts to introduce the test gas at a known density. Our results are systematically different at the level of 3% to 4% from recent theoretical and experiment measurements. This work demonstrates a model-free method for transferring the primacy of one atomic standard to another sensor atom and highlights the utility of sensor-atom cross-calibration experiments to check the validity of direct measurements and theoretical predictions.

Experimental study of rotational relaxation for D2(1,12) in collisions with N2.

The rotational relaxation behavior of D2(1,12) in a D2-N2 mixture was investigated using coherent anti-Stokes Raman scattering (CARS) technique. The rovibrational level v = 1 and J = 12 of D2 was selectively excited through stimulated Raman pumping while monitoring the temporal evolution of population for D2(1, J ≤ 12) molecules using time-resolved CARS spectroscopy. The results demonstrate that the rotational relaxation processes of D2(1,12) encompass both multi-quantum relaxation and continuous single-quantum relaxation. When α, the molar ratio of N2, is less than 0.5, D2(1,12) predominantly undergoes a single quantum relaxation process transition. However, when α ≥ 0.5, the multi-quantum relaxation mechanism gradually predominates. The total rotational relaxation rate coefficients of D2(1,12) collisions with N2 and D2 at 295K were determined to be 3.974 × 10-14 and 1.179 × 10-14cm3s-1, respectively. The temperature dependence of rotational relaxation rate of D2(1,12) was investigated within the temperature range of 295-453K. With increasing temperature, the dominant relaxation process exhibited an accelerated behavior, while the minor relaxation process remained largely unaffected. The rotational temperature of the D2molecule at various N2 molar ratios was determined through the utilization of Boltzmann plots. The rotational temperature undergoes a rapid decline within 2 μs, corresponding to the near-resonant rotation-vibration relaxation process of D2(1,12) collisions with N2. The system reaches a quasi-equilibrium state when the delay time is 3 μs. The findings of this study can serve as a valuable empirical basis for further validation of the kinetic theory and simulation.

Safety assessment of transgenic maize CC-2 by 90-day feeding study in Sprague-Dawley rats.

The purpose of this study was to assess the safety of transgenic maize CC-2 through a 90-day feeding study in Sprague-Dawley rats. Transgenic maize CC-2 and its parental counterpart maize Zhengdan 958 were respectively incorporated into diets at levels of 70%, 35% or 17.5% (w/w) and were administrated to rats (n=10/sex/group) for 90days. An additional control group of rats (n=10/sex/group) were fed with the AIN93 breeding diet. All formulated diets were nutritionally balanced. There was no death and obvious toxic symptom in all rats. Food consumption, body weight, total food consumption rate, hematology, urinalysis, organ weight and organ coefficient were comparable between transgenic groups and the corresponding dose parental groups. There were significant differences of food consumption rate on some timepoint between high dose transgenic group and high dose parental group; male rats in high dose transgenic group showed significantly higher ALT/AST than high dose parental group on the middle or end of the experiment; but the differences showed no biological significance. There were no significant differences of other serum biochemistry parameters and pathological changes. The results in this study demonstrated that the transgenic maize CC-2 didn't cause any related toxicity in rats.

Unraveling the atmospheric oxidation mechanism and kinetics of naphthalene: Insights from theoretical exploration

Naphthalene, the most abundant polycyclic aromatic hydrocarbon in the atmosphere, significantly influences OH consumption and secondary organic aerosol (SOA) formation. Naphthoquinone (NQ) is a significant contributor to ring-retaining SOA from naphthalene degradation, impacting the redox properties and toxicity of ambient particles. However, inconsistencies persist regarding concentrations of its isomers, 1,2-NQ and 1,4-NQ. In present work, our theoretical investigation into naphthalene's reaction with OH and subsequent oxygenation unveils their role in SOA formation. The reaction kinetics of initial OH and subsequent O2 oxidation was extensively studied using high-level quantum chemical methods (DLPNO-CCSD(T)/aug-ccpVQZ//M052x-D3/6–311++G(d,p)) combined with RRKM/master equation simulations. The reactions mainly proceed through electrophilic addition and abstraction from the aromatic ring. The total rate coefficient of naphthalene + OH at 300 K and 1 atm from our calculation (7.2 × 10−12 cm3 molecule−1 s−1) agrees well with previous measurements (∼1 × 10−11 cm3 molecule−1 s−1). The computed branching ratios facilitate accurate product yield determination. The largest yield of 1-hydroxynaphthalen-1-yl radical (add1) producing the major precursor of RO2 is computed to be 93.8 % in the ambient environment. Our calculated total rate coefficient (5.2 × 10−16 cm3 molecule−1 s−1) for add1 + O2 closely matches that of limited experimental data (8.0 × 10−16 cm3 molecule−1 s−1). Peroxy radicals (RO2) generated from add1 + O2 include 4-cis/trans-(1-hydroxynaphthalen-1-yl)-peroxy radical (add1-4OOadd-cis/trans, 66.0 %/17.5 %), 2-cis/trans-(1-hydroxynaphthalen-1-yl)-peroxy radical (add1-2OOadd-cis/trans, 10.3 %/6.3 %). Regarding the debated predominance of 1,4-NQ (corresponding to the parent RO2, i.e., add1-4OOadd-cis/trans) and 1,2-NQ (corresponding to the parent RO2, i.e., add1-2OOadd-cis/trans) in the atmosphere, our findings substantiate the dominance of 1,4-NQ. This study also indicates potential weakening of 1,4-NQ's dominance due to competition from decomposition reactions of add1-4OOadd-cis/trans and add1-2OOadd-cis/trans. Precise reaction kinetics data are essential for characterizing SOA transformation derived from naphthalene and assessing their climatic impacts within modeling frameworks.

Stimulated radiative association of sodium and chlorine atoms and their ions in a coupled channel treatment.

In an extension of previous work (Šimsová et al., Phys. Chem. Chem. Phys., 2022, 24, 25250), we study stimulated radiative association of sodium chloride (NaCl) in an environment with a black body radiation. Colliding neutral (Na and Cl) and ionic (Na+ and Cl-) fragments are considered. The coupling between the diabatic ionic and neutral channels is accounted for. The cross sections are computed and resolved on the vibrational states of the formed NaCl molecule for detailed analysis. The thermal rate coefficients for neutral colliding fragments at kinetic temperatures, T, from 1 K to 5300 K are computed for use in astrochemical modelling. The total rate coefficient is affected by more than one order of magnitude by stimulated emission from a blackbody radiator of temperature Tb = 50 000 K. The effect from stimulated emission is largest for the lowest kinetic temperatures, where Tb of a few thousand kelvins has a significant effect. The rate coefficient for the colliding ionic fragments is calculated from 80 K to 3615 K. The blackbody radiation has little effect on this process.

Performance of lagoon and constructed wetland systems for tertiary wastewater treatment and potential of reclaimed water in agricultural irrigation

Climate change poses challenges to agricultural water resources, both in terms of quantity and quality. As an adaptation measure, the new European Regulation (EU) 2020/741 establishes different water quality classes for the use of reclaimed water in agricultural irrigation. Italy is also working on the definition of a new regulation on reclaimed water reuse for agricultural irrigation (in substitution of the current one) that will also include the specific requirements imposed by the European one. Nature-based Solutions (NBS) can be a cost-effective and environmentally friendly way to facilitate water reclamation and reuse. The present study reports the outcomes of a long-term monitoring campaign of two NBS (e.g., a constructed wetland (CW) and a lagoon system (LS)) comparing influent and effluent concentrations of different contaminants (e.g., E. coli, BOD5, TSS, TN and TP) with the threshold values imposed by the new regulations. The results showed that in both the case studies, E. coli (about 100 CFU 100 mL−1) and BOD5 (lower than 25 mg L−1) mean effluent concentration need to be further reduced in reclaimed water to be suitable for unlimited reuse. As a negative aspect, in both the monitored NBS, an increase in TSS mean concentration in the effluent was observed, up to 40 mg L−1 in the case of the LS, making reclaimed water unsuitable for agricultural reuse. The CW has proven to be more effective in nitrogen removal (the effluent mean concentration was 3.4 mg L−1), whereas the LS was better at phosphorus removal (with an effluent mean concentration of 0.4 mg L−1). Based on the results, recommendations were made to further improve the performance of both systems in order to have adequate water quality, even for class A. Furthermore, the capacity of reclaimed water to meet crop water and nutrient needs was analyzed, and total nitrogen removal rate coefficients were calculated for the design of future LSs.

A new approach for evaluating photosynthetic bio-hydrogen production: The dissipation rate method

A dissipative rate model is established by using the non-equilibrium thermodynamics method to evaluate photosynthetic bio-hydrogen production process. The mass transfer dissipation rate, chemical reaction dissipation rate and total dissipation rate for the bio-hydrogen production processes with glucose and acetic acid are calculated and analyzed respectively by using the proposed dissipation rate model. When substrate concentration is taken as variable (15 g/L,20 g/L and25 g/L), the total dissipation rate and mass transfer phenomenological coefficient of hydrogen production process with 20 g/L are the lowest, and the maximum dissipation rate is 7.7288J/h. The phenomenological coefficient of chemical reaction is larger at high concentration. When the temperature is variable (298.15 K,303.15Kand308.15 K), the dissipation rate is lowest at 303.15 K and the chemical reaction coefficient is largest and the maximum dissipation rate is 6.0596J/h. In addition, the mass transfer phenomenological coefficient is larger at high temperature. With the initial pH as variable (6.5,7.0,7.5), the maximum dissipation rate of 11.2271J/h is obtained at pH 7.5. At high pH, the mass transfer phenomenological coefficient is large and the chemical reaction coefficient is exactly the opposite. This model can predict the energy dissipation law in the process of photosynthetic biohydrogen production, and provide a theoretical basis for the subsequent process optimization.

Radiative association of P+(3P) and O(3P) for the PO+ formation

ABSTRACT Phosphorus (P) is essential for the development of life since it is a fundamental element in many important biological molecules. Due to its biogenic importance, many astrochemists have begun to investigate the possibility of the phosphorus-bearing species formed in interstellar environments. Radiative association (RA) is a possible way for the formation of the phosphorus monoxide ion (PO+) in interstellar and related environments. Laboratory measurements are almost impossible to carry out, so theoretical calculations are essential for investigating such formation mechanism of PO+. The quantum mechanical method is used to obtain its cross sections and rate coefficients. Thirty contributing processes for the computation of the total rate coefficient are considered, including 22 transition dipole processes and eight permanent dipole processes. The total rate coefficient varies little over the entire temperature range of 1–10 000 K and its magnitude is of the order of (4–8) × 10−17 cm3 s−1. The 2 1Σ+ → X 1Σ+ transition process dominates the formation of PO+ by RA over the entire temperature range considered here. The C 1Π → X 1Σ+ and 2 3Σ+ → a 3Σ+ are also relatively important, but their rate coefficients are about an order of magnitude smaller than that of the 2 1Σ+ → X 1Σ+ channel. The obtained cross sections and rate coefficient can be used to model the P astrochemistry in the interstellar medium.

Theoretical Investigation of Electron–Ion Recombination Process of Mg-like Gold

The L-shell dielectronic and trielectronic recombinations of highly charged Mg-like gold ions (Au67+) in the ground state 2s22p63s2 1S0 have been studied systematically. The recombination cross-sections and rate coefficients are carefully calculated for ∆n = 1 (2s/2p → 3l) transitions using a flexible atomic code based on the relativistic configuration interaction method and considering the Breit and QED corrections. Detailed resonance energies and resonance strengths are presented for the stronger resonances of the LMn (n = 3–12) series. It is found that the contributions of the trielectronic recombination to the total cross-section is about 13.75%, which cannot be neglected. For convenience of application, the plasma rate coefficients are also calculated and fitted to a semiempirical formula, and in the calculations, the contributions from the higher excited resonance groups n ≥ 13 are evaluated by an extrapolation method, which is about 2.93% of the total rate coefficient.

Formation of SiO+ through radiative association of Si+(3s23p 2Pu) and O(2s22p4 3Pg)

We investigate the radiative association of SiO+ in the collision of a Si+(3s23p 2Pu) cation and an O(2s22p4 3Pg) atom using the quantum mechanical method, including the cross sections and rate coefficients. We consider 18 dipole-allowed radiative association processes of SiO+. The results show that the 2 2Π → A 2Π transition contributes most for the SiO+ radiative association at temperatures from 10 to 10 000 K. The 2 2Π → X 2Σ+ and 2 2Σ− → A 2Π transitions are also relatively significant at high temperatures. The total rate coefficient is found to vary from 7.72 × 10−18 to 4.92 × 10−17 cm3 s−1. Finally, an analytical function is fitted to the total rate coefficient for the convenience of astrochemical modelling. The obtained cross sections and rate coefficients are expected to be useful for modelling the Si chemistry in the diffuse interstellar medium.

Radiative Recombination Plasma Rate Coefficients for Multiply Charged Ions

Radiative recombination (RR) plasma rate coefficients are often applied to estimate electron densities and temperatures under quite different plasma conditions. Despite their frequent use, however, these rate coefficients are available only for selected (few-electron) ions and isoelectronic sequences, mainly because of the computational efforts required. To overcome this limitation, we report here a (relativistic) cascade model which helps compute fine-structure and shell-resolved as well as total RR plasma rate coefficients for many, if not most, elements of the periodic table. This model is based on Jac, the Jena Atomic Calculator, and supports studies on how the electron is captured in selected levels of the recombined ion, a relativistic (Maxwellian) electron distribution, or how the multipoles beyond the electric-dipole field in the electron-photon interaction affect the RR rate coefficients and, hence, the ionization and recombination dynamics of hot plasma. As a demonstration of this model, we compute, compare, and discuss different RR plasma rate coefficients for initially helium-like ions, with an emphasis especially on Fe24+ ions.

Exploring the Effect of Different Reactivity Promoters on the Oxidation of Ammonia in a Jet-Stirred Reactor

The low reactivity of ammonia (NH3) is the main barrier to applying neat NH3 as fuel in technical applications, such as internal combustion engines and gas turbines. Introducing combustion promoters as additives in NH3-based fuel can be a feasible solution. In this work, the oxidation of ammonia by adding different reactivity promoters, i.e., hydrogen (H2), methane (CH4), and methanol (CH3OH), was investigated in a jet-stirred reactor (JSR) at temperatures between 700 and 1200 K and at a pressure of 1 bar. The effect of ozone (O3) was also studied, starting from an extremely low temperature (450 K). Species mole fraction profiles as a function of the temperature were measured by molecular-beam mass spectrometry (MBMS). With the help of the promoters, NH3 consumption can be triggered at lower temperatures than in the neat NH3 case. CH3OH has the most prominent effect on enhancing the reactivity, followed by H2 and CH4. Furthermore, two-stage NH3 consumption was observed in NH3/CH3OH blends, whereas no such phenomenon was found by adding H2 or CH4. The mechanism constructed in this work can reasonably reproduce the promoting effect of the additives on NH3 oxidation. The cyanide chemistry is validated by the measurement of HCN and HNCO. The reaction CH2O + NH2 ⇄ HCO + NH3 is responsible for the underestimation of CH2O in NH3/CH4 fuel blends. The discrepancies observed in the modeling of NH3 fuel blends are mainly due to the deviations in the neat NH3 case. The total rate coefficient and the branching ratio of NH2 + HO2 are still controversial. The high branching fraction of the chain-propagating channel NH2 + HO2 ⇄ H2NO + OH improves the model performance under low-pressure JSR conditions for neat NH3 but overestimates the reactivity for NH3 fuel blends. Based on this mechanism, the reaction pathway and rate of production analyses were conducted. The HONO-related reaction routine was found to be activated uniquely by adding CH3OH, which enhances the reactivity most significantly. It was observed from the experiment that adding ozone to the oxidant can effectively initiate NH3 consumption at temperatures below 450 K but unexpectedly inhibit the NH3 consumption at temperatures higher than 900 K. The preliminary mechanism reveals that adding the elementary reactions between NH3-related species and O3 is effective for improving the model performance, but their rate coefficients have to be refined.

Kinetics of the reaction CH2CO + O (3P): Are the CH2 and CO2 the most favorable products?

Overall thermal rate coefficients for the CH2CO + O (3P) ⟶ CH2 + CO2 reaction were estimated by combining the canonical variational theory with multidimensional small-curvature tunneling corrections (CVT/SCT) and multifaceted variable-reaction-coordinate transition state theory (VRC-TST) results. The energies, equilibrium geometries, and harmonic vibrational frequencies were calculated at M06-2X/aug-cc-pVTZ level of theory. Our thermal rate constants show excellent agreement with experimental data confirming the CH2 + CO2 as the most favorable channel. Fitted total thermal rate coefficients into a modified Arrhenius equation shows a temperature-dependent activation energy.

Elastic and glancing-angle rate coefficients for heating of ultracold Li and Rb atoms by collisions with room-temperature noble gases, H2, and N2.

Trapped ultracold alkali-metal atoms can be used to measure pressure in the ultra-high-vacuum and XHV pressure regimes, those with p < 10-6 Pa. This application for ultracold atoms relies on precise knowledge of collision rate coefficients of alkali-metal atoms with residual room-temperature atoms and molecules in the ambient vacuum or with deliberately introduced gasses. Here, we determine combined elastic and inelastic rate coefficients as well as glancing-angle rate coefficients for ultracold 7Li and 87Rb with room-temperature noble gas atoms as well as H2 and 14N2 molecules. Glancing collisions are those processes where only little momentum is transferred to the alkali-metal atom and this atom is not ejected from its trap. Rate coefficients are found by performing quantum close-coupling scattering calculations using ab initio ground-state electronic Born-Oppenheimer potential energy surfaces. The potentials for Li and Rb with noble gas atoms and also for Rb(2S)-H2(XΣg +) and Rb(2S)-N2(X1Σg +) systems are based on the non-relativistic spin-restricted coupled-cluster method with single, double, and noniterative triple excitations [RCCSD(T)]. For Li(2S)-N2(X1Σg +), the potential is computed at the explicitly correlated spin-restricted RCCSD(T)-F12 level. For Rb, Kr, and Xe atoms, scalar relativistic corrections to the core electrons have been included, while second-order spin-orbit corrections from the valence electrons have been estimated. Data for Li-H2 and Li-He were taken from the existing literature. We estimate standard uncertainties of the rate coefficients by comparing rate coefficients calculated using potentials found with electronic basis sets of increasing size, including estimates of relativistic spin-orbit corrections and the uncertainty of the van der Waals coefficients. The relative uncertainties of rate coefficients are 1%-2% with the exception of 7Li or 87Rb colliding with 20Ne. Those have relative uncertainties of 9% and 8%, respectively. We also show that a commonly used semiclassical approximation for the total elastic rate coefficient agrees with the quantum calculations to 10% with the exception of 7Li and 87Rb collisions with H2, where the semiclassical value underestimates the quantum value by 20%.

Ab initio kinetics of OH-initiated reactions of 2-furfuryl alcohol

Oxidation of furan-based biofuels in the atmosphere and combustion are mainly initiated by reactions with small radicals (e.g. OH radical), the kinetics of which are crucial to obtain a comprehensive understanding of combustion processes, especially in engine operation. However, the structure- and site-dependent chemistry for OH-initiated reactions of furans with oxygenated substituents is unknown. In the present study, 2-furfuryl alcohol (2FFOH) was selected as a model fuel, and a full schematic energy diagram for 2FFOH with OH was calculated by a high-level quantum chemical method (CCSD(T)/CBS//M06-2X/def2-TZVP). The temperature- and pressure-dependent behavior of the rate coefficients k (T, P) for 2FFOH with OH was calculated at 298–2500 K and 0.01–10 atm by using the Rice–Ramsperger–Kassel–Marcus/Master equation method. Our calculations reveal that the rate coefficients of H-abstraction from the side chain are faster than those from the ring at T ≤ 2300 K. The observed temperature dependence behaviors of the total rate coefficients are consistent with prior experimental studies of other furans (e.g., furan, 25DMF and 2MF) with OH. The total rate coefficients of 2FFOH with OH exhibit a slightly positive pressure dependence only in the temperature range of 500–1000 K. We also found that the OH-addition pathways for 2FFOH with OH system dominate at T ≤ 1300 K. Moreover, the thermodynamic and kinetic data determined in the present work would be valuable for the future development of the fundamental chemical reaction mechanism of furan-based fuels in the atmosphere and combustion.

Dielectronic recombination data for dynamic finite-density plasmas

Dielectronic (DR) and radiative (RR) recombination rate coefficients for 19 phosphorous-like ions, between S+ and W59+, forming sulphur-like ions, have been calculated as part of the assembly of a level-resolved database necessary for modelling dynamic finite-density plasmas, within the generalized collisional-radiative framework. Calculations have been performed within the multi-configuration Breit-Pauli approximation using the code AUTOSTRUCTURE, from both ground and metastable initial states, in both LS coupling and intermediate coupling (IC), allowing for ∆n = 0 and ∆n = 1 core-excitations from the ground and metastable levels involved in the DR processes. Partial and total DR coefficients have been calculated for S+ to Zn15+, as well as Kr21+, Mo27+, Xe39+, and W59+. Results for a selection of ions from the sequence are discussed in this paper, and are compared with the existing theoretical and experimental results. Dielectronic recombination results for the Fe11+ resonance spectrum associated with ∆n = 0 core excitations are compared with those from merged-beam measurements. Fits to the total (IC) DR and RR rate coefficients are presented in tabular form. Partial LS and IC DR and RR rate coefficients are archived in the open access database OPEN-ADAS in standard ADAS adf09 and adf48 file formats, respectively.

Measurement of Rb-Rb van der Waals coefficient via quantum diffractive universality

Collisions between trapped atoms or trapped molecules with room temperature particles in the surrounding vacuum induce loss of the trapped population at a rate proportional to the density of the background gas particles. The total velocity-averaged loss rate coefficient $\langle \sigma_\mathrm{tot} v \rangle$ for such collisions and the variation of the loss rate with trap depth has been shown to depend only on the long range interaction potential between the collision partners. This collision universality was previously used to realize a self-calibrating, atom-based, primary pressure standard and was validated by indirect comparison with an orifice flow standard. Here, we use collision universality to measure $\langle \sigma_\mathrm{tot} v \rangle = 6.44(11)(5) \times 10^{-15}~\rm{m^3/s}$ for Rb-Rb collisions and deduce the corresponding $C_6 = 4688(198)(95)~E_ha_0^6$, in excellent agreement with predictions based upon $\textit{ab initio}$ calculated and previously measured $C_6$ values.