Photoionization cross sections measurements of the excited states of lutetium and ytterbium in the near threshold region.

In this work, the threshold photoionization cross sections from the excited states of lutetium and ytterbium atoms were investigated by the laser pump-probe scheme under the condition of saturated resonant excitation. We obtained the resonance enhanced multiphoton ionization spectra of the lutetium and ytterbium atoms of the lanthanide metals in the range of 307.50-312.50 nm and 265.00-269.00 nm, respectively; the photoionization cross sections of the 5d6s(1D)6p(2D05/2) and 5d6s(3D)6p(2P01/2) states of lutetium and the 4f13(2F0)5d6s2(J = 1) states of ytterbium above threshold regions (0.4-1.6 eV) were measured, and measured values ranged from 2.3 ± 0.2 to 17.7 ± 1.5 Mb.

Spreading a water droplet through filter paper on the metal substrate for surface-enhanced laser-induced breakdown spectroscopy.

To improve the quantitative analysis accuracy of an aqueous solution using surface-enhanced laser-induced breakdown spectroscopy (SENLIBS), the filter paper was used as a transmission medium by placing it onto the surface of a metallic substrate to make the microdroplet spreading more uniform in a fixed region of the substrate surface. The trace elements (Cu, Pb, Cd, and Cr) in an aqueous solution were detected successfully using this method. The results showed that the sample preparation repeatability of SENLIBS was noticeably improved with the aid of filter paper. Moreover, the limit of detection (LoD) values was similar to those without filter paper. Furthermore, the R2 values were improved from 0.6192~0.9321 to 0.9481~0.9766, the RMSECV values were decreased from 0.53~1.95 µg/mL to 0.33~1.06 µg/mL, and the average relative error (ARE) values were decreased from 8.96~22.31% to 4.28~14.37% with the aid of filter paper. This demonstrated that the use of filter paper could improve the quantitative analysis accuracy of SENLIBS by increasing the sample preparation repeatability.

Analytical-performance improvement of aqueous solution by chemical replacement combined with surface-enhanced laser-induced breakdown spectroscopy.

In this study, chemical replacement combined with surface-enhanced laser-induced breakdown spectroscopy (CR-SENLIBS) was introduced for detecting the trace chromium (Cr) element in an aqueous solution, which could use chemical replacement to change the sample from liquid to solid. In order to illustrate the analytical-performance of the CR-SENLIBS, the direct analysis of the liquid surface by LIBS (LSLIBS) was investigated for comparison. The results show that the spectral intensity of Cr I 357.86 nm, plasma lifetime, and spectral stability were improved. Moreover, the limit of detection of Cr I 357.86 nm was 0.018 µg/mL, which was lower than 1.814 µg/mL for LSLIBS. Furthermore, the accuracy and precision were improved more than 60% and 80%, respectively; for example, the root-mean-square error of cross-validation was improved from 1.09 to 0.75 µg/mL, and the average relative standard deviation of the predicted concentration of Cr was reduced from 22.89% to 4.53% by using CR-SENLIBS. These results suggest that CR-SENLIBS has good analytical-performance, which exhibits great potential in water quality monitoring.

Fresh keeping decision and coordination of fresh agricultural products supply chain under carbon cap-and-trade.

Considering the carbon emissions caused by the fresh-keeping of fresh agricultural products, this paper studied the rules of fresh-keeping decision-making in the two-echelon fresh agricultural product supply chain led by suppliers under the carbon cap-and-trade policy. In addition, we designed two contracts, cost-sharing contract and two-part pricing contract, to coordinate the supplier's fresh-keeping decision and the supply chain's revenue. The results show that: whether the carbon cap-and-trade policy is implemented or not, the higher the consumer's preference for freshness and the lower the price sensitivity coefficient of consumers, the more favorable it is for suppliers to improve their fresh-keeping efforts. Under the implementation of carbon cap-and-trade policy, suppliers' fresh-keeping efforts are only related to the carbon transaction price, not the carbon cap; the higher the carbon transaction price, the less the supplier's fresh-keeping efforts, but the more the supplier's income; the smaller the cost coefficient of carbon emission reduction and the larger the coefficient of carbon emission reduction, the more favorable it is for suppliers to increase their fresh-keeping efforts; both cost-sharing contract and two-part pricing contract can coordinate the supply chain of fresh agricultural products, but they have different application scope and coordination effect. These conclusions are of great significance to the operation and management of fresh agricultural products suppliers, the improvement of consumers' quality of life and the protection of ecological environment under carbon cap-and-trade.

State-dependent photoionization cross-sections of 3d transition metal atoms.

Using the saturation method, we measured the absolute photoionization cross-sections of several excited states of titanium, vanadium, chromium, iron, and cobalt. These results are reported for the first time in this paper. The measured values range from 0.4 ± 0.1 Mb to 6.9 ± 2.0 Mb. The results show that the photoionization cross-section depends on the atomic state and not just on the electronic configuration.

Strategy Optimization of Quality Improvement and Price Subsidy of Agri-Foods Supply Chain.

Based on the realistic concerns about the improvement of the quality of agricultural foods (agri-foods), the optimal supply quality and price subsidy strategies of producers and sellers for the two-level agricultural supply chain, composed of a producer and a seller, are studied. The differences in the quality safety, price, and market demand of agri-foods in the supply chain are compared and analyzed. The study found that the maximum profit of supply chain participants decreases with the increase of price elasticity of demand. When the quality of agri-foods is upgraded in a producer-led manner, the quality of agri-foods in the supply chain does not undergo substantial improvement, and the maximum profit of agri-foods operators is insensitive to the price elasticity of demand at this time. When the seller-led quality upgrading is launched, the maximum profit of the producer decreases with the increase of the quality elasticity of demand, the maximum profit of the seller increases with the increase of the quality elasticity of demand, and the total profit of the supply chain also increases with the increase of the quality elasticity of demand under the centralized decision situation. The quality and safety of agri-foods as well as the overall profit of the supply chain can be improved most effectively under the centralized control decision with the goal of maximizing the supply chain benefits. In terms of quality and price, quality improvement actions of agri-foods driven by supply-side producers are less effective than those driven by demand-side consumption. In addition, cost-sharing contracts can significantly improve the quality of agri-foods in the supply chain and make them more "high-quality and low-price" than before the adoption of cost-sharing contracts.

Social and natural risk factor correlation in China's fresh agricultural product supply.

The perishable nature of fresh agricultural products and their vulnerability to environmental impacts make fresh agricultural product supplies susceptible to more complex social risks and unpredictable natural risks. This study identifies 13 social and natural risk factors that could adversely affect the fresh agricultural product supply and uses ISM and MICMAC to develop a hierarchical structure of the risks to analyze the correlation of these risk factors. The results showed that these risk factors have a strong positive correlation, a reasonable risk-sharing mechanism should be established for the fresh agricultural product supply and the improvement in the supervision error correction system should be strengthened.

Aqua-(2-hydr-oxy-5-sulfonatobenzoato-κO)bis-(2-phenyl-1H-1,3,7,8-tetra-aza-cyclo-penta-[l]phenanthrene-κN,N)zinc(II).

In the title compound, [Zn(C(7)H(4)O(6)S)(C(19)H(12)N(4))(2)(H(2)O)], the Zn(II) ion is coordinated by two N,N'-bidentate 2-phenyl-1H-1,3,7,8-tetra-azacyclo-penta-[l]phenanthrene ligands, one O-monodentate 5-sulfosalicylate dianion and a water mol-ecule. This results in a distorted cis-ZnO(2)N(4) octa-hedral coordination geometry for the metal ion. In the crystal, mol-ecules are expanded into a three-dimensional supra-molecular motif via O-H⋯O, O-H⋯N and N-H⋯(O,S) hydrogen bonds. In addition, π-π stacking inter-actions between the aromatic rings of the polycyclic ligands consolidate the sturcture [shortest centroid-centroid distance = 3.501 (2) Å].

Slow-electron velocity-map imaging study of aniline via resonance-enhanced two-photon ionization method.

Slow electron velocity-map imaging (SEVI) of aniline has been investigated via two-color resonant-enhanced two-photo (1+1') ionization (2C-R2PI) method. A number of vibrational frequencies in the first excited state of neutral (S1) and 2B1 ground electronic state of cation (D0) have been accurately determined. In addition, photoelectron angular distributions (PADs) in the two-step transitions are presented and reveal a near threshold shape resonance in the ionization of aniline. The SEVI spectra taken via various S1 intermediate states provide the detailed vibrational structures of D0 state and directly deduce the accurate adiabatic ionization potential (IP) of 62,271±6cm-1. Ab initio calculations excellently reproduce the experimental IP value (Theo. 62,242cm-1). For most vibrational modes, good agreement between theoretical and experimental frequencies in the S0 and D0 states of aniline is obtained to aid us to clearly assign vibrational modes. Especially, the vibrational frequencies calculated at the CASSCF level are much better consistent with experimental data than that obtained using the TDDFT and CIS methods.

The design of double electrostatic-lens optics for resonance enhanced multiphoton ionization and photoelectron imaging experiments.

Compared to single ion/electron-optics for velocity-map imaging, a double-focusing lens assembly designed not only allows for mapping velocity imaging of photoelectrons but also allows for investigating the vibrational structure of the intermediate states of neutral species in resonance enhanced multiphoton ionization (REMPI) spectra. In this presentation, in order to record REMPI and photoelectron spectra separately, we have constructed a compact photoelectron velocity-map imaging (VMI) apparatus combined with an opposite linear Wiley-Mclaren time-of-flight mass spectrometer (TOFMS). A mass resolution (m/Δm) of ∼1300 for TOFMS and electron energy resolution (ΔE/E) of 2.4% for VMI have been achieved upon three-photon ionization of Xe atom at 258.00 nm laser wavelength. As a benchmark, in combination of one-color (1 + 1) REMPI and photoelectron imaging of benzene via 6(1) and 6(1)1(1) vibronic levels in the S1 state, the vibrational structures of the cation and photoelectron angular anisotropy are unraveled. In addition, two-color (1 + 1') REMPI and photoelectron imaging of aniline was used to complete the accurate measurement of ionization potential (62,271 ± 3 cm(-1)). The results suggest that the apparatus is a powerful tool for studying photoionization dynamics in the photoelectron imaging using vibrational-state selected excitation to the intermediate states of neutrals based on REMPI technique.