Low-energy collisions of NH3 and ND3 with ultracold Rb atoms

We carry out quantum inelastic scattering calculations of collisions of Rb atoms with inverting NH3 and ND3 molecules in the energy range between 0 and 100 cm−1, which are important for experiments using velocity-controlled molecular beams to probe scattering resonances. We focus on molecules initially in the upper level of the ammonia inversion doublet for j=1, k=1, which is low-field seeking and can be controlled in a Stark decelerator. We calculate the integral elastic and state-to-state inelastic cross sections in the coupled-states approximation. We demonstrate the presence of both shape and Feshbach resonances in the elastic and inelastic cross sections at low collision energies and discuss their origin in terms of the bound states of the Rb-ND3 complex. We also consider elastic and inelastic cross sections in the ultracold regime, using close-coupling calculations, in order to assess the viability of sympathetic cooling of ND3 by Rb. The inelastic cross section for relaxation to the lower level of the inversion doublet is smaller than expected for such a strongly coupled system but is still likely to be too large to allow sympathetic cooling for ND3 in low-field-seeking states. However, there is a good prospect that sympathetic cooling will be possible for molecules in high-field-seeking states even when the collision partner is a magnetically trapped atom in a low-field-seeking state

Reactions of ultracold alkali-metal dimers

We investigate the energetics of reactions involving pairs of alkali-metal dimers. Atom exchange reactions to form homonuclear dimers are energetically allowed for some but not all of the heteronuclear dimers. We carry out high-level electronic structure calculations on the potential energy surfaces of all the heteronuclear alkali-metal trimers and show that trimer formation reactions are always energetically forbidden for low-lying singlet states of the dimers. The results have important implications for the stability of quantum gases of alkali-metal dimers

Organic food attributes determing consumer choices

The aim of the research was to identify the factors influencing consumption of organic food. In our research an attempt was made to find a method for identifying organic food and assessing the features ascribed to it by consumers. These features were then analyzed in terms of their technical and market attributes. The paper presents results of research conducted in 2005, 2010 and 2013 on the organic food market with special emphasis placed on pricing, distribution systems and consumers in the north-eastern Poland. Respondents’ answers indicate their increasing interest, knowledge and commitment to the environment. They also indicate that the most important technological attribute of organic food is its way of production, which ensures that the food is healthy, contains no chemical additives and has good, natural taste. Market attributes include the food’s high nutritious value and naturalness, the producer’s logo and price. Consumers buying organic food believe that the production and processing of food does not destroy the natural environment. Emphasizing the health and taste attributes of organic food is not enough, however, and it has to coincide with the consumer’s behavior and pro-environmental bias, which become explicit in his choice of food.peer-reviewe

Impact of new member accession to the European Union on food trade

Purpose: The main focus is on the export and import of agricultural products in the EU in the years 2002-2017 outside the EU (extra-EU). Design/Methodology/Approach: This paper investigates the impact of EU (European Union) enlargement on food trade using descriptive statistics. First, EU-28 exports, imports, and trade balance of agricultural products outside the EU (extra-EU) are presented for 2002-2017. Findings: The trade balance between EU countries for food, beverages, and tobacco are also presented. Accession has led to the elimination of trade tariffs and accelerated improvements in trade. The most exported products by EU countries were alcoholic beverages (spirits and liquors, wine, and vermouth), bakery products, and wheat. Most of the export of agri-food products is directed to other EU countries, Russia, China, and various countries in South America, Africa, and Asia. Imports to EU countries comprised mostly of vegetables and fruits, coffee, tea, cocoa, and various fish products. Practical implications: The results will fill in the gap concerning the food trade of agricultural products in the EU. Originality/Value: The new information about extra EU trade of agricultural products and a GARCH (Generalized Autoregressive Conditionally Heteroscedastic) model was presented.peer-reviewe

Gas phase Elemental abundances in Molecular cloudS (GEMS) VIII. Unlocking the CS chemistry: the CH + S→\rightarrow CS + H and C2_2 + S→\rightarrow CS + C reactions

We revise the rates of reactions CH + S -> CS + H and C_2 + S -> CS + C, important CS formation routes in dark and diffuse warm gas. We performed ab initio calculations to characterize the main features of all the electronic states correlating to the open shell reactants. For CH+S we have calculated the full potential energy surfaces for the lowest doublet states and the reaction rate constant with a quasi-classical method. For C_2+S, the reaction can only take place through the three lower triplet states, which all present deep insertion wells. A detailed study of the long-range interactions for these triplet states allowed to apply a statistic adiabatic method to determine the rate constants. This study of the CH + S reaction shows that its rate is nearly independent on the temperature in a range of 10-500 K with an almost constant value of 5.5 10^{-11} cm^3/s at temperatures above 100~K. This is a factor \sim 2-3 lower than the value obtained with the capture model. The rate of the reaction C_2 + S depends on the temperature taking values close to 2.0 10^{-10} cm^3/s at low temperatures and increasing to 5. 10^{-10} cm^3/s for temperatures higher than 200~K. Our modeling provides a rate higher than the one currently used by factor of \sim 2. These reactions were selected for involving open-shell species with many degenerate electronic states, and the results obtained in the present detailed calculations provide values which differ a factor of \sim 2-3 from the simpler classical capture method. We have updated the sulphur network with these new rates and compare our results in the prototypical case of TMC1 (CP). We find a reasonable agreement between model predictions and observations with a sulphur depletion factor of 20 relative to the sulphur cosmic abundance, but it is not possible to fit all sulphur-bearing molecules better than a factor of 10 at the same chemical time.Comment: 13 pages, 10 figure

Potential energy surface of Li–O2 system for cold collisions

This paper explores the interactions between Li and oxygen in their van der Waals state for the study of cold collisions between these two species. The quartet surface was calculated using a basis set converged spin-restricted CCSD(T) method, while for the doublet state, we obtained energy splitting with respect to high-spin using both CASSCF and MRCI approaches. Our findings suggest that the interaction in the quartet state of Li–O2 is weak, with a shallow and nearly isotropic well depth of 37.5 cm−1. The shallow potential well and small reduced mass of the system allow us to predict the scattering length for all possible combinations of 6Li and 7Li with 16O2 and 17O2. This result could be useful for understanding the collision dynamics of Li-O2 in ultra-cold regime

Dispersion energy from the time-independent coupled-clusters polarization propagator

We present a new method of calculation of the dispersion energy in the second-order symmetry-adapted perturbation theory. Using the Longuet-Higgins integral and time-independent coupled-cluster response theory one shows that the general expression for the dispersion energy can be written in terms of cluster amplitudes and the excitation operators $\sigma$, which can be obtained by solving a linear equation. We introduced an approximate scheme dubbed CCPP2(T) for the dispersion energy accurate to the second order of intramonomer correlation, which includes certain classes to be summed to infinity. Assessment of the accuracy of the CCPP2(T) dispersion energy against the FCI dispersion for He$_2$ demonstrates its high accuracy. For more complex systems CCPP2(T) matches the accuracy of the best methods introduced for calculations of dispersion so far. The method can be extended to higher-order levels of excitations, providing a systematically improvable theory of dispersion interaction

Cold collisions of N (S-4) atoms and NH ((3)Sigma) molecules in magnetic fields

We calculate the interaction potential between N atoms and NH molecules and use it to investigate cold and ultracold collisions important for sympathetic cooling. The ratio of elastic to inelastic cross sections is large over a wide range of collision energy and magnetic field for most isotopic combinations, so that sympathetic cooling of NH molecules by N atoms is a good prospect. However, there are important effects due to a p-wave shape resonance that may inhibit cooling in some cases. We show that scaling the reduced mass used in the collision is approximately equivalent to scaling the interaction potential. We then explore the dependence of the scattering properties on the reduced mass and explain the resonant effects observed using angular-momentum-insensitive quantum defect theory

Prospects for producing ultracold NH(3) molecules by sympathetic cooling : a survey of interaction potentials

We investigate the possibility of producing ultracold NH3 molecules by sympathetic cooling in a bath of ultracold atoms. We consider the interactions of NH3 with alkali-metal and alkaline-earth-metal atoms, and with Xe, using ab initio coupled-cluster calculations. For Rb-NH3 and Xe-NH3 we develop full potential energy surfaces, while for the other systems we characterize the stationary points (global and local minima and saddle points). We also calculate isotropic and anisotropic van der Waals C6 coefficients for all the systems. The potential energy surfaces for interaction of NH3 with alkali-metal and alkaline-earth-metal atoms all show deep potential wells and strong anisotropies. The well depths vary from 887 cm−1 for Mg-NH3 to 5104 cm−1 for Li-NH3. This suggests that all these systems will exhibit strong inelasticity whenever inelastic collisions are energetically allowed and that sympathetic cooling will work only when both the atoms and the molecules are already in their lowest internal states. Xe-NH3 is more weakly bound and less anisotropic