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We present a combined experimental and theoretical study of state-to-state inelastic collisions between NO (X

We present a combined experimental and theoretical study of state-to-state inelastic collisions between NO (X 2Π1/2, j = 1/2, f) radicals and D2 (j = 0, 1, 2, 3) molecules at collision energies of 100 cm−1 and 750 cm−1. Using the combination of Stark deceleration and velocity map imaging, we fully resolve pair-correlated excitations in the scattered molecules. Both spin–orbit conserving and spin–orbit changing transitions in the NO radical are measured, while the coincident rotational excitation (j = 0 → j = 2) and rotational de-excitation (j = 2 → j = 0 and j = 3 → j = 1) in D2 are observed. De-excitation of D2 shows a strong dependence on the spin–orbit excitation of NO. We observe translation-to-rotation energy transfer as well as direct rotation-to-rotation energy transfer at the lowest collision energy probed. The experimental results are in good agreement with cross sections obtained from quantum coupled-channels calculations based on recent NO–D2 potential energy surfaces. The observed trends in the correlated scattering cross sections are understood in terms of the NO–D2 quadrupole–quadrupole interaction.

One of the most important parameters in a collision is the 'miss distance' or impact parameter, which in quantum mechanics is described by quantized partial waves. Usually, the collision outcome is the result of unavoidable averaging over many partial waves. Here we present a study of low-energy NO\textendash He collisions, that enables us to probe how individual partial waves evolve during the collision. By tuning the collision energies to scattering resonances between 0.4 and 6 cm$^{-1}$, the initial conditions are characterized by a limited set of partial waves. By preparing NO in a rotationally excited state before the collision and by studying rotational de-excitation collisions, we were able to add one quantum of angular momentum to the system and trace how it evolves. Distinct fingerprints in the differential cross sections yield a comprehensive picture of the partial wave dynamics during the scattering process. Exploiting the principle of detailed balance, we show that rotational de-excitation collisions probe time-reversed excitation processes with superior energy and angular resolution., Comment: 18 pages, 4 figures

The experimental characterization of scattering resonances in low energy collisions has proven to be a stringent test for quantum chemistry calculations. Previous measurements on the NO-H

At low energies, the quantum wave-like nature of molecular interactions result in unique scattering behavior, ranging from the universal Wigner laws near zero Kelvin to the occurrence of scattering resonances at higher energies. It has proven challenging to experimentally probe the individual waves underlying these phenomena. We report measurements of state-to-state integral and differential cross sections for inelastic NO-He collisions in the 0.2 - 8.5 cm$^{-1}$ range with 0.02 cm$^{-1}$ resolution. We study the onset of the resonance regime by probing the lowest-lying resonance dominated by s and p waves only. The highly structured differential cross sections directly reflect the increasing number of contributing waves as the energy is increased. A new NO-He potential calculated at the CCSDT(Q) level was required to reproduce our measurements., 14 pages, 4 figures

The experimental characterization of scattering resonances in low energy collisions has proven to be a stringent test for quantum chemistry calculations. Previous measurements on the NO-H$_2$ system at energies down to $10$ cm$^{-1}$ challenged the most sophisticated calculations of potential energy surfaces available. In this report, we continue these investigations by measuring the scattering behavior of the NO-H$_2$ system in the previously unexplored $0.4 - 10$ cm$^{-1}$ region for the parity changing de-excitation channel of NO. We study state-specific inelastic collisions with both \textit{para}- and \textit{ortho}-H$_2$ in a crossed molecular beam experiment involving Stark deceleration and velocity map imaging. We are able to resolve resonance features in the measured integral and differential cross sections. Results are compared to predictions from two previously available potential energy surfaces and we are able to clearly discriminate between the two potentials. We furthermore identify the partial wave contributions to these resonances, and investigate the nature of the differences between collisions with \textit{para}- and \textit{ortho}-H$_2$. Additionally, we tune the energy spreads in the experiment to our advantage to probe scattering behavior at energies beyond our mean experimental limit., Comment: The following article has been submitted to the Journal of Chemical Physics. 8 pages, 8 figures

The dissociative adsorption reaction of hydrogen on noble metals is believed to be well-described within the Born–Oppenheimer approximation. In this work, we have experimentally derived translational energy distributions for selected quantum states of H2 and D2 formed in associative desorption reactions at a Au(111) surface. Using the principle of detailed balance, we compare our results to theory carried out at the same level of sophistication as was done for the reaction on copper. The theory predicts translational excitation that is much higher than is seen in experiment and fails to reproduce the experimentally observed isotope effect. The large deviations between experiment and theory are surprising because, for the same reactions occurring on Cu(111), a similar theoretical strategy agreed with experiment, yielding “chemical accuracy”. We argue that electron–hole pair excitation is more important for the reaction on gold, an effect that may be related to the reaction’s later transition state.

The dissociative adsorption reaction of hydrogen on noble metals is believed to be well-described within the Born-Oppenheimer approximation. In this work, we have experimentally derived translational energy distributions for selected quantum states of H

Following our previous study on the H + CD4 → HD + CD3 reaction [ Proc. Natl. Acad. Sci. U.S.A. 2010 , 107 , 12782 ], the reaction of H + CH4 → H2 + CH3 at collision energies ranging from 0.72 to 1.99 eV is studied using crossed-beam and time-sliced velocity map ion imaging techniques. The product angular and translational energy distributions at four different collision energies were derived from the measured images. The excitation function was also measured from these images together with a careful calibration of the H atom beam intensities at different collision energies. All of these results are compared with those of the H + CD4 reaction to investigate the isotope effects. The isotope effects are all observed in the product angular distributions, the translational energy distributions, and the excitation function and further confirm the reaction mechanism proposed in the previous study on the H + CD4 reaction.

The O((1)D) + CD4 → OD + CD3 reaction was investigated using the crossed molecular beam technique with sliced velocity map imaging at four different collision energies: 1.6, 2.8, 4.6, and 6.8 kcal/mol. The vibrational ground state product CD3 was detected using a (2 + 1) resonance-enhanced multiphoton ionization (REMPI). Remarkably different features were found in the forward and backward scatterings, and gradually changed with the collision energy. These features were attributed to two distinctive reaction mechanisms-insertion and abstraction-that occur on the ground and excited state surfaces, respectively. Contributions from the two mechanisms were extracted from the experiment results, and a positive correlation was found between the abstraction proportion and the collision energy. The threshold for the abstraction pathway was determined and compared with results from calculations.

According to the phenomena of regular grooves on the face of seal gasket which causes the hundreds of gaskets irrational failure in the valves of pressure-swing absorption (PSA) for CO refinement in a cathay coal chemical CO.LTD, the method of computational fluid dynamics (CFD) has been used to analyze the fluid dynamical performances of the mixed gas flowing in the pipe system of the PSA to study the reasons of the irrational failure of the seal gasket. Conclusions have been obtained as following: the main reason of Teflon seal local inactivation is the irrational seal system structure which causes the local high-velocity over the face; a rational modified scheme has been offered; the method which can be used to analyze similar problem has been explored in this paper.

PurposeThe purpose of this paper is to develop feasible composite electrodes with a long cycle life and large specific capacitance and to investigate optimal ratio between aniline and activated carbon materials.Design/methodology/approachPANI/AC composite electrode materials were synthesised by in situ polymerisation of aniline on activated carbon with ammonium persulphate as oxidant. Hybrid supercapacitors are assembled by putting Ni‐MH battery separator between positive and negative electrodes. The electrochemical performances of PANI/AC composite electrode materials and supercapacitors are studied.FindingsThe results show that the optimal ratio between aniline and activated carbon is 1:1.08. The specific capacitance of polyaniline electrode materials is 956 F g−1. The specific capacitance of supercapacitors is 159.37 F g−1. This result could be attributed to the pseudocapacitive effect of Ni(OH)2. What's more, the activated carbon addition reduced the resistance of polymer electrode materials thus improving the cyclic life.Research limitations/implicationsThe supercapacitors can be used in the field of automobiles and can solve the problems of energy shortage and environmental pollutions.Originality/valueA hybrid supercapacitor, which was immersed in alkaline solution, was assembled by putting Ni‐MH battery separator between two electrodes Ni(OH)2 as positive electrode and polyaniline composites as negative electrode. In the case of alkaline solution, the capacitive performance of hybrid supercapacitor was improved and excellent.

Crossed molecular beam experiments and accurate quantum scattering calculations have been carried out for the polyatomic H + CD 4 → HD + CD 3 reaction. Unprecedented agreement has been achieved between theory and experiments on the energy dependence of the integral cross section in a wide collision energy region that first rises and then falls considerably as the collision energy increases far over the reaction barrier for this simple hydrogen abstraction reaction. Detailed theoretical analysis shows that at collision energies far above the barrier the incoming H-atom moves so quickly that the heavier D-atom on CD 4 cannot concertedly follow it to form the HD product, resulting in the decline of reactivity with the increase of collision energy. We propose that this is also the very mechanism, operating in many abstraction reactions, which causes the differential cross section in the backward direction to decrease substantially or even vanish at collision energies far above the barrier height.

Sliced velocity mapping ion imaging technique was employed to investigate the dynamics of the hydroxyl elimination channel in the photodissociaiton of nitric acid in the ultraviolet region. The OH product was detected by (2+1) resonance enhanced multiphoton ionization via the D2Σ− electronic state. The total kinetic energy spectra of the OH+NO2 channel from the photolysis of HONO2 show that both NO2(2A1) and NO2(AB2) channels are present, suggesting that both 11A″ and 21A″ excited electronic states of HONO2 are involved in the excitation. The parallel angular distributions suggest that the dissociation of the nitric acid is a fast process in comparison with the rotational period of the HNO3 molecule. The anisotropy parameter β for the hydroxyl elimination channel is found to be dependent on the OH product rotational state as well as the photolysis energy.

The dynamics of the F + SiH(4) --HF + SiH(3) reaction has been studied using the crossed molecular beam technique with slice imaging at collision energies from 1.25 to 8.17 kcal/mol. The product silyl radical, SiH(3)(v(2) = 0-5), was detected using the (2 + 1) resonance enhanced multiphoton ionization technique. The product velocity distributions and angular distributions of this reaction were obtained from the recorded images. Experimental results show that the silyl radical product is mainly forward scattered relative to the silane beam direction, and the majority of the available energy was partitioned into the vibration of the HF product. The state-to-state correlation between the two reaction products, SiH(3) and HF, was also determined. In addition, we found that the reaction cross section goes down as the collision energy increases. From these results, we conclude that the F + SiH(4) --HF + SiH(3) reaction proceeds through a direct abstraction mechanism with little or no reaction barrier.