Dynamical studies of the reaction H~++He+He→HHe~++He

The classical trajectory method is employed to calculate the rate coefficient kr for the reaction H++He+He-HHe++He at the temperatures ranging 200-350 K, based on an ab initio potential energy surface. The results show that kr is strongly dependent on the temperature, which can be well fitted by the function kr=ATDr-3 with A=4.192x10-31 cm6/s and the reaction dimension Dr=2.706. The product molecules HHe+ are found in high vibrational states.     

Break-down of the born-oppenheimer approximation in the He(23S)-H2 and He(21S)-H2 autoionizing systems?

The possibility of non-adiabatic behaviour of the He(2¹S)-H₂ and He(2³S)-H₂ collision systems is reexamined by means of extended diatomics-in-molecules calculations. In the triplet case, the calculations support the idea that at collision energies above ≈ 1 eV the system could behave non-adiabatically. In the singlet He*-H₂ system, a break-down of the Born-Oppenheimer approximation is predicted to take place at higher energies.     

Low energy collisions of CN(X2Σ+) with He in magnetic fields

A theoretical investigation of the He-CN((2)Σ(+)) complex is presented. We perform ab initio calculations of the interaction potential energy surface and carry out accurate calculations of bound energy levels of the complex including the molecular fine structure. We find the potential has a shallow minimum and supports seven and nine bound levels in complex with (3)He and (4)He, respectively. Based on the potential the quantum scattering calculation is then implemented for elastic and inelastic cross sections of the magnetically trappable low-field-seeking state of CN((2)Σ(+)) in collision with (3)He atom. The cold collision properties and the influence of the external magnetic field as well as the effect of the uncertainty of interaction potential on the collisionally induced Zeeman relaxation are explored and discussed in detail. The ratios of elastic to inelastic cross sections are large over a wide range of collision energy, magnetic field, and scaling factor of the potential, suggesting helium buffer gas loading and cooling of CN in a magnetic trap is a good prospect.     

He2+和He2++分子离子基态和激发态的特性研究

采用SAC/SAC-CI方法在CC-PV5Z基组下, 计算研究了He2+、He2++的基态及低激发态的分子特性, 给出了其基态和一些激发态的势能函数和光谱数据(Be、αe、ωe和ωeχe). 从群论出发推导了相应状态的离解极限；与已有实验结果的He2+(X2Σu+)相比, 计算结果令人满意. 还计算了激发态2Πu、4Σu+和4Πg的结构与光谱数据. 对于He2++, 计算的九个电子态中只有三个态(X1Σg+、1Σg+和1Σu+)属束缚态, 并得到了其光谱常数. 用价键理论模型的不相交规则对He2++基态的势能曲线极大点产生的原因做了较好的分析.     

He 2++ molecular ion in a strong time-dependent magnetic field: a current-density functional study

The He molecular ion exposed to a strong ultrashort time‐dependent (TD) magnetic field of the order of 10⁹ G is investigated through a quantum fluid dynamics (QFD) and current‐density functional theory (CDFT) based approach using vector exchange‐correlation (XC) potential and energy density functional that depend not only on the electronic charge‐density but also on the current density. The TD‐QFD‐CDFT computations are performed in a parallel internuclear‐axis and magnetic field‐axis configuration at the field‐free equilibrium internuclear separation R = 1.3 au with the field‐strength varying between 0 and 10¹¹ G. The TD behavior of the exchange‐ and correlation energy of the He is analyzed and compared with that obtained using a [B‐TD‐QFD‐density functional theory (DFT)] approach based on the conventional TD‐DFT under similar computational constraints but using only scalar XC potential and energy density functional dependent on the electronic charge‐density alone. The CDFT based approach yields TD exchange‐ and correlation energy and TD electronic charge‐density significantly different from that obtained using the conventional TD‐DFT based approach, particularly, at typical magnetic field strengths and during a typical time period of the TD field. This peculiar behavior of the CDFT‐based approach is traced to the TD current‐density dependent vector XC potential, which can induce nonadiabatic effects causing retardation of the oscillating electronic charge density. Such dissipative electron dynamics of the He molecular ion is elucidated by treating electronic charge density as an electron‐“fluid” in the terminology of QFD. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

OH Dynamics in a Nanosecond Pulsed Plasma Filament in Atmospheric Pressure He–H2O upon the Addition of O2

The influence of the addition of O₂ on the OH production in a He + 0.1 % H₂O discharge is investigated using laser induced fluorescence. The plasma properties $(T_{\rm g},\;n_{\rm e})$ are reported and used to explain the observed time and spatially resolved OH density, which is absolutely calibrated using Rayleigh scattering. Compared to the case when only H₂O is added, an increase in the measured OH density is observed in the far afterglow. A zero-dimensional chemical kinetic model is constructed, which allows to determine the reactions responsible for the OH production in the far afterglow. When O₂ is admixed, the key reaction $\hbox{O} + \hbox{OH} \longrightarrow \hbox{O}_{2} + \hbox{H}$ causes quenching of OH and production of increased densities of H, HO₂ and H₂O₂, which subsequently leads to additional OH production in the late afterglow.     

Electronic structure of He2−

The electronic structure of the He₂⁻ anion has been studied using optimized CI wavefunctions. We find that the ⁴Π_g state of He₂⁻ is bound relative to the a³Σ⁺_u state of He₂, with a calculated electron affinity of 0.182 eV. Only the lowest vibrational level of this anion is stable relative to the He₂(a³Σ⁺_u)+e continuum.     

Laser-induced fluorescence detection of N+2(X 2Σ+g) resulting from the He(23S) + N2 and He+, He+2 + N2 reactions in a flowing afterglow

The formation processes of N⁺₂ (X ²Σ⁺_g) resulting from the He(2 ³S) + N₂ Penning ionization and the thermal energy He⁺, He⁺₂ + N₂ charge transfer reaction are studied by observing the N⁺₂ (B ²Σ⁺_u ← X ²Σ⁺_g) laser-induced fluorescence (LIF) in a flowing afterglow. In both reactions, the vibrational population) decrease monotonically with increasing vibrational quantum number from υ″ = 0 to 3, and a population inversion with a peak at υ″ = 4 is seen. In the He(2 ³S) + N₂ Penning ionization, the vibrational populations of N⁺₂ (X, υ″ = 0–2) are explained by a direct channel and the B —X radiative cascade, while those of N⁺₂ (X, υ″ = 4–6) are ascribed to the collision-induced electronic energy transfer between the A ²Π_u and X ²Σ⁺_g states. In the He⁺, He⁺₂ + N₂ reaction, the N⁺₂ (X, υ″ = 0–3) is interpreted as the B−X radiative cascade and the collisional quenching of the unidentified states produced from the He⁺ + N₂ reaction, while the collision-induced electronic energy transfer from the N⁺₂ (A) state produced through the He⁺₂ + N₂ reaction is probably important for the formation of N⁺₂ (X, υ″ = 4–6).     

Density inversions between fluid and solid phases in the system HeH2 at high pressures

One of the well-known interesting features of the helium—hydrogen system is the occurence of the barotropic phenomenon: the density inversion between the gaseous and the liquid phase. However, density inversions between the liquid and the solid phases of mixtures (if the pure solids are more dense than the pure liquids) have not been observed experimentally. Such inversions may be of importance in modelling the atmosphere of the planets. In this paper results are presented concerning the measurements of the relative density of gaseous, liquid and solid phases in several types of phase equilibria in the system helium—hydrogen.     

He原子基态波函数的实验检验

以作者所在实验室最近完成的He原子基态的电子动全港学实验结果为基础，对三类He原子基态波函数进行了分析与检验．结果表明，电子动量话学是获取电子波西数信息的有用手段．且实验结果与理论计算的联系文＊已报导了本实验室最近完成的He原子基态的电子动量话学实验结果．此实验的条件满足准自由碰撞的要求问，平面波冲量近似是适用的，因而实验测定的（e，Ze）反应的符合计数N可表为问本文自始至终采用原子单位（an），除非另有说明．在（1）中，C是比例常数，只与实验条件有关；PO，PI和马分别是人射电子和两个出射电子的动量，Th是…     

Extraterrestrial ~3He in marine polymetallic nodules: a potential method for measuring growth rate of nodules

The comparative measurements of helium isotope compositions between marine poly-metallic nodules and their surrounding sediments, their magnetic fractions and bulk from C-C Zoneof the East Pacific Basin are reported. The ~4He content and ~3He/~4He ratio of polymetallic nodulesand their surrounding sediments are extremely high; the ~3He, ~4He concentrations and most~3He/~4He ratios of magnetic fractions in nodules and sediments are apparently higher than those inbulk. The helium isotope data points of nodules and sediments are all distributed along or closelyto the mixing curve of the interplanetary dust particles (IDPs) and the terrigenous sediments in thechart of ~3He-~3He/~4He. In the same sampling site, the ~3He/~4He ratios of nodules and their surround-ing sediments are very similar, and the changes of both ratios are synchronous. It shows that thehigh ~3He/~4He ratios in nodules and sediments may all result from IDPs. So, if the flux of extrater-restrial ~3He into the nodules and sediments is constant, the growth rate of polymetallic nodules andthe sedimentation rate of sediments can be independently calculated according to the concentra-tion of extraterrestrial ~3He in nodules and sediments.     

Zur physikalischen Interpretation der in Mehrelektronensystemen (He,H2 +, H2) auftretenden Kräfte

Zusammenfassung Die bei Mehrelektronenproblemen auftretenden Kräfte und Energien sind nicht nur z. B. für die Mehrelektronenspektren der Atome und Moleküle und für die Bewegung der Elektronen im Innern eines Metalls, sondern auch für das Zustandekommen derhomöopolaren chemischen Bindung wichtig. Es wird an einigen einfachen Beispielen klargestellt, was hieran schon vom Standpunkt der klassischen Physik aus zumindest qualitativ verständlich ist und wo man zu ihrer Erklärung die Quantenmechanik heranziehen muß. In diesem Sinne wird aufgezeigt, daß die Austauschkräfte rein elektrischer Natur sind, daß dagegen die Ladungsverteilung, die zu diesen Kräften führt, klassisch nicht vollständig verstanden werden kann.Mit 3 Abbildungen.     

Quantum and quasi-classical studies of the He + HeD+ → HeD+ + He exchange reaction and its isotopic variant

The interaction of hydrogen sulfide (H₂S) with F, Cl, Br, and OH is investigated using ab initio methods to identify the two-center three-electron hemibond responsible for their complexation. The binding energies are found to be stronger than those in the analogous water complexes, but follow the same trend of increasing strength: F > Cl > Br > OH. The radicals are located nearly perpendicular to the H₂S plane forming an angle of about 90°. Analysis of molecular orbitals and natural bond orbitals are carried out to understand the energetics, structures, and bonding characteristics of these hemibonded complexes.     

Determination of tritium in Li–Pb alloy irradiated by thermal neutrons with quantitatively analyzing the byproduct 4He

The mass of the tritium produced in ⁶Li(n,α)T reaction was obtained by quantitatively analyzing the byproduct ⁴He with mass spectrometer. The self-expending seal method was employed to quantitatively prepare the Li–Pb alloy targets in room temperature. They were irradiated for 2 h in two rabbit irradiation channels in Xi’an pulsed reactor and measured after cooling 15 days. A sample purifying unit was set up to get rid of the hydrogen isotopes to remarkably reduce the interference to helium isotopes when measuring. And the sample disposal platform including purifying unit was testified with simulative gas and nature atmosphere. The targets were melted at 700 °C to release most of the ⁴He atoms which were measured by adding dilution gas ³He. And it was testified that ⁴He had released completely by repetitiously melting the targets. This approach had solved the problem that the tritium couldn’t be accurately determined by directly analyzing it because of non-complete releasing from lithium alloy.     

Spatially Dependent Kinetics of Electrons and Excited Atoms in the Column Plasma of a He–Xe dc Discharge

The radially varying kinetics of electrons and excited atoms in the cylindrical axially homogeneous positive column of a dc glow discharge in a gas mixture of helium and 2% xenon was studied. The experimental investigations comprise the radially resolved measurements of the isotropic part of the electron velocity distribution function (EVDF) using a single-probe technique and of the densities of atoms in the lower excited states by using a laser diode absorption method. The theoretical investigations are based on the solution of the space-dependent kinetic equation for the EVDF and the balance equations of excited gas atoms. Besides a strict solution, various simplified treatments of the electron kinetics as the conventional homogeneous approach and the nonlocal approach have been applied. The electron kinetic behavior in the helium–xenon column plasma changes remarkably with increasing helium gas pressure from a distinctly nonlocal behavior at a low pressure of 100 Pa to a nearly local behavior at a medium pressure of 600 Pa.     

Ground-state path integral Monte Carlo simulations of positive ions in (4)He clusters: bubbles or snowballs?

The local order around alkali (Li(+) and Na(+)) and alkaline-earth (Be(+), Mg(+), and Ca(+)) ions in (4)He clusters has been studied using ground-state path integral Monte Carlo calculations. The authors apply a criterion based on multipole dynamical correlations to discriminate between solidlike and liquidlike behaviors of the (4)He shells coating the ions. As it was earlier suggested by experimental measurements in bulk (4)He, their findings indicate that Be(+) produces a solidlike ("snowball") structure, similar to alkali ions and in contrast to the more liquidlike (4)He structure embedding heavier alkaline-earth ions.     

Congratulationsto Professor He Binglin on the Occasion of His 80th Birthday——Biographic Sketch of Professor He Binglin

He Binglin was born on August 24, 1918 in Fanyu County, Guangdong Province.He graduated from the Chemistry Department of Southwest Associated Universityin 1942. After graduation he worked in Chongqing Central Institute of Industry forone year as an assistant engineer and then returned to his Alma Mater University     

热扩散法浓缩~3He工艺研究简介

惰性气体氦由~3He和~4He两种稳定同位素组成。大气中氦的含量为 7×10~(-7)(重量),其中~3He与~4He之比为1.2×10~(-6)。因此想从自然界获得有实用价值的~3He十分困难。现在各国都不再从大气氦中波集~3He,而是从生产氚的副产物中获得~3He。近年来,~3He在各个研究领域里的应用日益重要,如~He中子计数管,以~3He作工作物质的氦-氖激光器,以及~3He在低温物理中的应用需要大量的高纯,高浓度的~3He。热扩散法是分离气体同位素的基本方法之一。由于~He、~He分子量的相对差较大,有比较大的热扩散