Molecular state calculations of charge transfer in H+ + Li and He2+ + Li collisions

Charge-transfer cross sections for H⁺ + Li and He²⁺+Licollisions were calculated at low to intermediate impact energies. A multistate perturbed-stationary-state method was employed that includes electron translation factors.     

Radiative lifetimes and collisional quenching cross sections of selectively excited vibrational states of the B 2p1Σu+ state of H2

Radiative lifetimes between 0.54 ns and 0.69 ns have been measured for the vibrational levels υ′ = 0...4 of the B 2p¹Σ_u⁺ state of H₂ after selective excitation by synchroton radiation. Quenching by collisions with H₂ ground state molecules has been observed with cross sections of 5 × 10^-15 cm².     

He+离子和Ar原子碰撞过程中激发态的研究

在He⁺离子和Ar原子碰撞过程中,同样存在着电子俘获激发和直接激发两种过程。本文把实验结果同He⁺离子和Ne原子碰撞体系进行了比较,发现:在入射离子速度较小时,实验所得到的Hel三重态发射截面要大得多;当入射离子He⁺的速度大于一个原子单位(2.2×10⁸cm/s)时,情况则相反。因此,在俘获电子过程中,势能亏损同He⁺离子的入射速度是两个非常重要的因素,而且它们之间存在一个竞争过程。入射离子He 关键词：     

On the neutralization in low energy ion scattering spectroscopy (leiss): He+ ions on clean and oxygen covered Ni(001) surfaces

A formula for the He⁺ ion survival probability against neutralization is presented, which was derived from the fit of the azimuthal angular dependence of the Ni peak heights on clean and O covered Ni(001) surfaces observed in LEISS experiments and computer simulations. The formula contains a collision- and two Auger-type neutralization terms for the ion trajectories prolonged by multiple collisions above the “neutralization surface plane”, which was assumed to be corrugated and shaped like muffin-tins.     

X-ray photoelectron spectroscopic studies of PbO surfaces bombarded with He+, Ne+, Ar+, Xe+ and Kr+

The surface composition of PbO has been studied with X-ray photoelectron spectroscopy after bombardment with several inert gas ions of 400 eV. The results show reduction of PbO to metallic Pb with the degree of damage following the order He⁺ > Ne⁺ >Ar⁺. Both Kr⁺ and Xe⁺ did not reduce the oxide. The depth of damage varied from ≈9 Å for He⁺ to ≈1 Å for Ar⁺ bombardment. The results were compared to a collisional and a thermal model of the sputtering process.     

Ar+, He+，S+离子轰击n-InP单晶表面的机理研究

通过X射线光电子能谱和低能电子衍射实验研究了10～180 eV的Ar⁺、 He⁺、S⁺离子轰击n-InP(100)表面, 发现S⁺离子轰击可以产生In-S组分,减轻离子轰击对表面的物理损伤.对于Ar⁺离子轰击后的表面,经过S⁺离子处理和加热过程以后,表面损伤得到了修复,最终得到了2×2的InP表面,进一步验证了S⁺离子对InP表面的修复作用.     

Cross sections for slow ion production and charge transfer in H+3(D+3)−H2(D2) collisions

Slow ion production cross sections for collisions of H⁺₃ and D⁺₃ ions with H₂ and D₂ have been measured at collision energies between 100 eV and 500 eV. The values vary from 2 × 10^-17 cm² to 6 × 10^-17 cm². The smaller cross sections for D₃ projectiles may be explained as an internal energy effect.     

Quenching cross sections of the B3Π+(Ou+) v′ = 14 level of I2 by H2, CO,and CH4

In this work the deexcitation of the B³Π⁺(O_u⁺), v′ = 14 level of I₂ after pulsed laser excitation has been studied. The quenching cross sections by collisions with I₂, H₂, CO, and CH₄ have been measured. The experimental results are 190 ± 14, 2.5 ± 0.3, 15.1 ± 0.4, and 18.0 ± 0.6 Ų, respectively. These values are compatible (within 30%) with the semiempirical scaling law of proportionality with the product of polarizability and the square root of reduced mass.     

Neutrino production of M+ and E+ heavy leptons (II)

A theoretical analysis is made of possible experimental searches for the production of M⁺ heavy leptons in inclusive neutrino reactions by detection of their decay into μ⁺. Distributions of observable energy E_obs (sum of hadron and muon energies) and of the apparent y variable y_obs(y_obs=E_had/E_obs) are presented. These distributions are used to discuss the problem of distinguishing M⁺ production from effects of antineutrino admixtures in a neutrino beam.     

H1+,H2+,H3+和He,Ne,Ar碰撞过程中的巴耳末系Hα,Hβ,Hγ发射

实验利用TN-1710光学多道分析系统(OMA),对H₁⁺,H₂⁺,H₃⁺和He,Ne,Ar碰撞过程中产生的巴耳末系H_α,H_β,H_γ发射进行了测量,入射离子H₁⁺,H₂⁺,H₃⁺的 关键词：     

He+和He2+离子与碱金属原子Na碰撞中靶激发过程的实验研究

本文通过光学方法,在q×(20—140)keV能量范围内,研究了He⁺和He²⁺离子与碱金属原子Na碰撞中的靶激发过程。通过光学多道分析系统(OMA),对He⁺与Na碰撞过程,观察到NaI589.0+589.6nm(3p→3s),NaI818.3nm(3d→3p)和NaI568.8nm(4d→3p)等谱线。对He²⁺与Na碰撞过程,只观察到NaI589.0+589.6nm谱线。计算了所有观察到的谱线的发射截面和Na(3 关键词：     

Scattering of low energy Na+ ions from a clean polycrystalline Ag surface

The energy distributions of low energy (E₀ = 0.4–3.2 keV) Na⁺ ions scattered from a clean polycrystalline Ag surface were measured. The angle between the incident beam and the surface was fixed at ψ = 45° while the scattering angle (θ) ranged from 50 to 130°. The cleanliness of the surface during the measurement was maintained by simultaneous deposition of Ag atoms from an effusion source. The obtained distributions considerably differ from the corresponding distributions of noble ions. Firstly, for all measured values of E₀ and θ, an intensive hump is observed in the high energy part of the distribution. In certain cases this hump is transformed into a peak. Secondly, the low energy part of the distribution is very pronounced, especially for higher values of E₀ and θ.     

Radiation damage of material surfaces under prolonged irradiation with He+ and Ar+ ions with broad energy spectra

The results of studying the redistribution of Be, Al, Ti, Fe, Cu, Zr, Mo, and W atoms incorporated in polycrystalline metal samples under irradiation with He⁺, (He⁺ + Ar⁺), and Ar⁺ ion beams with a broad energy spectrum and an average energy of 10 keV at irradiation doses of 1 × 10²¹ ion/cm² are studied. It is discovered that irradiation at doses exceeding 1 × 10¹⁹ ion/cm² results in local small-crystal formations being produced in a near-surface substrate layer. Their typical dimensions are less than 1–5 μm, and their the density is up to 1–100. They contain incorporated atoms and impurity atoms with a concentration of 0.1–10 at %. Subsequent irradiation at a dose of 1 × 10²⁰ ions/cm² or more leads to disappearance of these formations, mainly because of sputtering processes.     

A molecular-beam investigation of the reaction H2 + 12O2 → H2O on Pd(111)

Using molecular-beam relaxation techniques and isotopic exchange experiments, the water-formation reaction on Pd(111) has been shown to proceed via a Langmuir-Hinshelwood mechanism. The reaction product H₂O is emitted from the surface with a cosine distribution. The rate-determining step is the formation of OH_ad in the reaction O_ad + H_ad → OH_ad. The activation energy for this step is 7 kcal/mole with a pre-exponential factor, v, of 4 × 10^?8 cm² atom^?1 sec^?1. This value for v lies well below that observed for simple second-order desorption of dissociatively adsorbed diatomic gases, but is roughly of the order of that obtained for the oxidation of CO on Pd(111). The formation of H₂O proceeds differently under conditions of excess O₂ or H₂. In an excess of H₂, the kinetics is dominated by the transport of atomic hydrogen between the bulk and the surface as was found for the H?D exchange reaction on Pd(111). In an excess of O₂, diffusion of hydrogen into the bulk is blocked by adsorbed oxygen and the hydrogen reservoir available for reaction at the surface is decreased by several orders of magnitude. This results in a drastic reduction of the reaction rate which can be reversed by increasing the partial pressure of H₂.     

He+和He2+离子与碱金属原子Li碰撞中的靶激发

本文在q×(20—150)keV的能量范围内,通过光学测量,对He⁺和He²⁺离子与碱余属原子Li碰撞过程中的靶激发过程进行了研究。由光学多道分析系统(OMA),测得LiI 670.8nm(2p→2s),LiI610.4nm(3d→2p),LiI460.3nm(4d→2p)和LiI812.6nm(3s→2p)谱线。给出所观察到的谱线的发射截面和相立的Li(2p)激发截面。对He⁺与Li碰撞过程,LiI670.8nm谱线发射截面与Aumayr 关键词：     

πo and π+ production with polarized photons in the energy range 1–2 GeV

The asymmetry of π^o and π⁺ photoproduction from hydrogen has been measured. The π^o-mesons were detected at 130° cms with E_γ ranged from 0.9 to 1.65 GeV, and the π⁺-mesons at 40° cms with E_γ ranged from 0.9 to 1.2 GeV. The results agree with model predictions of single pion photoproduction in the resonance region using fixed-t dispersion relations.     

Vibrational analysis of the a3Σ+-X1Σ+ and b3Π-X1Σ+ band systems of GeS

Spectra of GeS have been obtained in a chemiluminescent flame produced by the reaction Ge + OCS → GeS + CO. Neither of the known band systems, D¹Π-X¹Σ⁺ and E¹Σ⁺-X¹Σ⁺, was observed, but two new band systems in the regions 350–400 and 420–650 nm were obtained. By comparison with similar systems in isovalent molecules, these were assigned as b³Π₁-X¹Σ⁺ and a³Σ⁺-X¹Σ⁺, respectively. Vibrational assignments were made with the help of the germanium isotope effect and vibrational constants were obtained for the states involved. Approximate Morse potential Franck-Condon factors were computed and were shown to fit the general trend of the intensity distribution for both systems. Addition of active nitrogen to the flame was shown to increase the intensity of the b-X system by an order of magnitude while hardly affecting the a-X system. Constants (in cm^?1) obtained for the two new states are: a³Σ⁺: T_e = 21986.3 ± 2.3, ω_e = 388.9 ± 1.0, ω_ex_e = 1.35 ± 0.11; b³Π₁: T_e = 27192.0 ± 1.8, ω_e = 435.4 ± 1.1, ω_ex_e = 1.68 ± 0.20.     

Measurement of e+e− → e+e− and e+e− → λλ at energies up to 36.7 GeV

The differential cross sections of the reactions e⁺e^? → e⁺e^? and e⁺e^? → λλ are measured at energies between 33.0 and 36.7 GeV. The results agree with the predictions of quantum electrodynamics. A comparison with the standard model of electroweak interaction yields sin²θ_W = 0.25 ± 0.13.     

Laser-induced fluorescence and microwave-optical double-resonance study of the B1Σ+-X1Σ+ system of magnesium monoxide

Doppler-limited, laser-induced fluorescence spectra on the B¹Σ⁺-X¹Σ⁺ (v′ = v″ = 0 and 1) system of MgO have been obtained. The results of the optical analysis were merged with our microwave-optical double-resonance measurements to produce the following set of spectroscopic parameters for the B and X states, where the units are in cm^?1, and the uncertainties represent 95% confidence limits: T′_0.0 = 20003.594(2); B′₀ = 0.58004(3); D′₀ = 1.13(2) × 10^?6; B″₀ = 0.57198(3); D″₀ = 1.20(2) × 10⁶; T′_1.1 = 20043.423(2); B′₁ = 0.57528(4); D′₁ = 1.14(11) × 10⁶; B″₁ = 0.56674(4); D″₁ = 1.22(10) × 10⁶.     

Charge exchange in He++Li collisions

A two-state model, based on atomic wave functions and allowing for momentum transfer factors, is employed to calculate cross sections for the formation of excited states of He⁺ in collisions of He⁺⁺ ions with Li in the ground state, for energies in the range 5–64 keV. It is shown that the selective capture into the n=3 levels of He⁺, predicted at low energies by Shipsey et al., persists up to energies of ≈30 keV.