Molecular effect in the formation of the energy spectrum upon the transmission of low-energy hydrogen ions through ultrathin carbon foils

The energy spectra of ions transmitted through ultrathin diamond-like foils irradiated by H⁺, H⁺₂, and H⁺₃ ions with energies from 2 to 12 keV/nucleon are studied. For molecular ions incident on the target with identical velocities, a considerable broadening of the energy spectrum is observed with an increase in the ion mass. The spectrum halfwidth reduced to the identical particle velocity remains constant for each type of incident ion, irrespective of the foil thickness.     

Dissociative photoionization of l-menthone: An experimental and theoretical study

The dissociative photoionization mechanism of l-menthone has been investigated with photoionization mass spectrometry using synchrotron radiation. The adiabatic ionization energy (IE) of l-menthone and the appearance energies (AE) of its major fragment ions C₉H₁₅O⁺, C₉H₁₇⁺, C₈H₁₆⁺, C₇H₁₁O⁺, C₆H₁₀O⁺, C₆H₉O⁺, C₅H₈O⁺, C₅H₁₀⁺, C₄H₆O⁺, C₅H₉⁺, C₄H₈⁺, C₄H₇⁺, C₃H₇⁺, C₃H₆⁺, C₂H₂O⁺, and CH₃⁺ are determined with their photoionization efficiency (PIE) spectra in the photon energy region of ∼8−15.5 eV. Breakdown diagrams identifying the major products are presented. Dissociative photoionization channels for formation of these fragment ions are proposed based on comparison of determined experimental appearance energies and energies predicted with the DFT calculations. According to our results, the experimental dissociation energies are in fair agreement with the theoretical values of the possible photodissociation channels of C₁₀H₁₈O.     

Electron stimulated desorption of condensed,branched alkanes

Electron stimulated desorption of H⁺, CH₃⁺, H₂⁺ and D⁺ has been measured as a function of excitation energy for condensed phase neopentane, tetramethylsilane, 2-methylpropane-1-d₁, and 2-methylpropane-2-d₁. The data show that the processes which result in both H⁺ and CH₃⁺ production are initiated by the same excitation. The excitations which produce H⁺, CH₃⁺ and H₂⁺ appear to be largely localized on the methyl groups. The results indicate that multi-electron (hole) final states are responsible for H⁺ and CH₃⁺ desorption.     

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：     

Theoretical study of efficiency of metal cations (Mg+, Ca+, and Ag+) for effective hydrogen storage

The interaction between the metal cations and H₂ molecule has been investigated using dispersion-corrected and -uncorrected hybrid density functional and CCSD(T) methods in conjunction with the correlation consistent triple-ζ quality basis sets for the storage of the H₂ molecule. The molecular properties, potential energy surfaces, stability, binding energy and well-depth have been computed for the metal cation–dihydrogen (M⁺–H₂, M = Mg, Ca, and Ag) complexes in the gas phase. The results obtained by the dispersion-corrected hybrid density functional B2PLYP-D method agree very well with the earlier experimental and theoretical results wherever available. Different components of the interaction energy have been estimated by the symmetry adapted perturbation theory (SAPT) to get physical insight into the interaction energy. Among the three complexes, only Ag⁺–H₂ is the most stable complex and it accumulates more H₂ molecules as the interaction between the metal cation Ag⁺ and the H₂ molecule is the greatest.     

异戊二烯解离光电离理论研究

利用CBS-QB3理论计算方法研究了异戊二烯的可能解离通道.获得了主要碎片离子C₅H₇⁺,C₅H₅⁺,C₄H₅⁺,C₃H₆⁺,C₃H₅⁺,C₃H₄⁺,C₃H₃⁺的C₂H₃⁺的结构以及这些解离通道的解离能,并给出了相应的过渡态和中间体的结构和位垒.得到的异戊二烯电离势及主要碎片离子的出现势均与实验值符合的较好.最后,通过理论和实验结果的对比讨论了各通道的解离机理.     

1,4-二氧六环的真空紫外同步辐射光解离电离研究

The photoionization and photodissociation of 1,4-dioxane have been investigated with a reflectron time-of-flight photoionization mass spectrometry and a tunable vacuum ultraviolet synchrotron radiation in the energy region of 8.0-15.5 eV. Parent ion and fragment ions at m/z 88, 87, 58, 57, 45, 44, 43, 41, 31, 30, 29, 28 and 15 are detected under supersonic conditions. The ionization energy of DX as well as the appearance energies of its fragment ions C₄H₇O₂⁺, C₃H₆O⁺, C₃H₅O⁺, C₂H₅O⁺, C₂H₄O⁺, C₂H₃O⁺, C₃H₅⁺, CH₃O⁺, C₂H₆⁺, C₂H₅⁺/CHO⁺, C₂H₄⁺ and CH₃⁺ was determined from their photoionization efficiency curves. The optimized structures for the neutrals, cations, transition states and intermediates related to photodissociation of DX are characterized at the B3LYP/6-31+G(d,p) level and their energies are obtained by G3B3 method. Possible dissociative channels of the DX are proposed based on comparison of experimental AE values and theoretical predicted ones. Intramolecular hydrogen migrations are found to be the dominant processes in most of the fragmentation pathways of 1,4-dioxane.     

MeV氢微团簇离子与固体介质的电荷交换

利用静电加速器提供的0.6—1.8MeV的H⁺，H⁺₂，H⁺₃离子，轰击不同厚度的碳膜，分别测量这些离子通过碳膜后各种产物的产额. 得到了不同能量的H⁺通过碳膜后中性原子H和负离子H^-的产额随入射质子速度的变化关系；分别得到能量为1.2MeV,1.8MeV的H⁺₂，H⁺₃团簇离子通过不同厚度碳膜的透射产额及其与团簇离子在碳膜中驻留时间的关系；对结果进行了理论分析与讨论. 关键词： 团簇离子 电荷交换     

The reactions of Cl+ (3P) and Cl+ (1D) with hydrogen sulphide. A G2 molecular orbital study

G2 ab initio molecular orbital calculations have been performed to study the potential energy surfaces (PESs) associated with the reactions of Cl⁺ in its ³P ground state and in its ¹D first excited state with hydrogen sulphide. [H₂, Cl, S]⁺ singlet and triplet state cations present very different bonding characteristics. The latter are systematically ion-dipole or hydrogen-bonded weakly bound species, while the former are covalent molecular ions. As a consequence, although the Cl⁺(³P) is 34.5 kcal mol^?1 more stable than Cl⁺(¹D), the global minimum of the singlet PES lies 37.3 kcal mol^?1 below the global minimum of the triplet PES. Both singlet and triplet potential energy surfaces show significant differences with respect to those associated with Cl⁺ + H₂O reactions as well as with SH₂ reactions with F⁺. In both cases, the major product should be SH⁺ ₂; SH⁺ and HCl⁺ being the minor products, in agreement with the experimental evidence. The estimated heat of formation for the most stable H₂SCl⁺ singlet state species is 198 ± 1 kcal mol^?1.     

Balmer Hβ vs. Dβ line intensity in the collisions of H+, H2 +, H3 +, D+, D2 +, and D3 + ions with “realistic” metal surface at energies below 1 keV

The intensities of hydrogen H_β and deuterium D_β spectral lines of the Balmer series were measured as a function of collision energy when H⁺, H₂ ⁺, H₃ ⁺, D⁺, D₂ ⁺, and D₃ ⁺ ions impinged on Al, Ti, Cu, Mo, W, and Pb targets. The collision energies were kept in the 100–1000 eV range. The target surface was contaminated with hydrocarbons from the vacuum pumping system and possibly also by oxygen molecules due to limited vacuum conditions. At projectile velocities above 200 km/s the luminescence of backscattered deuterium atoms is about 30–50% weaker than that of hydrogen atoms.     

Herstellung eines neutralen Wasserstoffatomstrahls im MeV-Bereich

An arrangement is described to produce a neutral hydrogen beam by splitting an accelerated H ₂ ⁺ -Ion in a gas target. At 500 keV energy of the neutral H-atom, the ratio of H ₂ ⁺ -ions to neutral H-atoms is measured to be about 12%. In the energy domain of 300 to 650 keV this ratio decreases only very little with increasing energy. The cross sections σ₁, σ₂ and σ₃ for splitting inH ⁺+H°, 2H ⁺+e ^? and for electronloss of the neutral atom are given.     

Semiempirical valence bond potential energy surfaces for simple chemical reactions: 1 A′ states of H2O and H2F+

A semiemprical valence bond method is employed to study the potential energy surfaces (PESs) of the lowest ¹ A′ states of H₂O and isoelectronic H₂F⁺. The calculation is based on the search for the electronic configurations which play the most important rôle in the formation of the stable electronic states of the molecules and the relevant diatomic fragments. Several approximations are used to reduce the number of permutations in the calculation of the energy matrix. The Moffit atoms-in-molecule approximation is used to correct for the atomic errors arising from the poor basis set. The computed data for the lowest electronic states of OH, HF, HF⁺, H₂O and H₂F⁺, as well as the general behaviour of the PESs for different molecular geometries, are in good agreement with the available ab initio and experimental data.     

甲苯光电离解离理论研究

The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods.The geometries and frequencies of the reactants,transition states and products have been performed at B3LYP/6-311++G (d,p) level,and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level.The ionization energies of toluene and the appearance energies for major fragment ions,C₇H₇⁺,C₆H₅⁺,C₅H₆⁺,C₅H₅⁺,are determined to be 8.90,11.15 or 11.03,12.72,13.69,16.28 eV,respectively,which are all in good agreement with published experimental data.With the help of available published experimental data and theoretical results,four dissociative photoionization channels have been proposed:C₇H₇⁺+H,C₆H₅⁺+CH₃,C₅H₆⁺+C₂H₂,C₅H₅⁺+C₂H₂+H.Transition structures and intermediates for those isomerization processes are determined in this work.Especially,the structures of C₅H₆⁺ and C₅H₅⁺ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.     

Features of the variation in reflection spectra of the F4MB/Al coating under bombardment by H+, H 2 + and H 3 + ions

Variations of reflection spectra for the F4MB/Al coating, based on fluoroplastic film, occurring under bombardment by H⁺, H ₂ ⁺ , and H ₃ ⁺ , ions with energy 15 keV are investigated. It is established that the variations in the reflection spectra and integrated absorption coefficient are not proportional to the mass of the hydrogen ion and obey the different regularities depending on the energy of the absorption band.     

Fragmentation of polyatomic ions produced by electron-loss collisions of butane and isobutane molecules with ions of kiloelectronvolt energy

Fragmentation accompanying the loss of electrons by butane and isobutane (C₄H₁₀) molecules in collisions with energy H⁺, He²⁺, and Ar⁶⁺ ions of kiloelectronvolt energies is studied. The electron density functional technique is applied to C _n H_2n+2 alkane molecules and their respective C _n H _2n+2 ⁺ ions to carry out quantum-chemical calculations of the atomic spacing, electron total energy for the initial configuration of the ionizing molecules and ions in the ground state, and atomic bond breaking energy necessary to produce different ion fragments. The fragmentation energy is correlated with the fragmentation probability. It is shown that the relative cross sections of ion fragmentation depend primarily on the related energy consumption. However, the process cross section is also strongly affected by the initial configuration of C₄H₁₀ isomer molecules, as well as by the amount of dangling and arising atomic bonds involved in the formation of each ion fragment.     

Complexation of hydrogen by lithium: structures,energies and vibrational spectra of Li+ (H2) n (n = 1–4), Li-H(H2) m and Li-H + (H2) m (m = 1–3)

The interaction of metals with hydrogen is of importance in several areas of technology. Lithium-hydrogen complexes are particularly amenable to theoretical study. Although no stable compound of the Li atom and H₂ has been found, a weak dative interaction forms between the σ bond of H₂ and the positively charged Li atom for Li⁺, Li-H⁺, and Li-H. At least four H₂ molecules can be complexed by Li⁺, and three by Li-H⁺ and Li-H. The presence of the Li ion does not substantially weaken the H₂ bond, nor is the energy of dissociation affected; however, the Li ion does form stable complexes with the dissociated H atoms.     

Steady-state fluorescence and photo-isomerization study of 1-methyl-4′-(p-N,N dimethyl-amino styryl) pyridinium iodide

Photochemical and thermal trans/cis isomerization reactions are reported for 1-methyl-4′-(p-N,N dimethyl-amino styryl) pyridinium iodide, Cy, which is synthesized in the trans configuration. In a basic solution the trans form, Cy_tr, cannot isomerise directly to the cis form. Its protonated form, Cy_trH⁺, is active and reacts photochemically from trans to cis isomer, Cy_cH⁺. The quantum yields Φ_tc and Φ_ct are determined in water. Deprotonation process of Cy_cH⁺ yields the cis isomer, Cy_c, which can thermally revert to the stable trans form. The rate constant and the activated parameters of the thermal reaction are also determined. Due to irreversibility of the thermal reaction , a complete molecular reaction cycle is performed in one direction. To get more information on the spectral properties of protonated form, its absorption and fluorescence spectra were investigated in sixteen neat polar protic and aprotic solvents. Absorption energy correlates linearly with hydrogen bond acceptor ability of the solvent. Another linear correlation was found between fluorescence energy of CyH⁺ and free energy for transferring the proton to the surrounding solvent, ΔG_t^o.     

Luminescence in collisions of low-energy ions with graphite and Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Excitation of H⁺, H₂ ⁺, H₃ ⁺, He⁺, and Ar⁺ ions by impact on graphite and Al₂O₃ was investigated by means of emission spectroscopy in the 50–1000 eV energy range of the projectiles. Emission of Balmer series from excited neutral hydrogen is observed for both targets. In addition, for the Al₂O₃ target a continuum emission is observed. The continuum probably originates from excited M_nO_m molecules produced in the collision cascade, when surface atoms bound by ionic bonds are released after the bond breaking caused by neutralization. The spectra obtained under Ar⁺ -bombardment show Ar II lines emitted by backscattered ions.     

化合物和合金中离子投影射程分布矩的计算(Ⅱ)——轻离子(Z1≤10)的射程分布矩

本文根据离子在固体材料中电子阻止截面的实验资料,给出了低能Li⁺,Be⁺,B⁺,C⁺,N⁺,O⁺,F⁺,Ne⁺等离子在固体中电子阻止截面S_e的经验公式。这些经验公式既能够很好地反映电子阻止本领的Z₁和Z₂振荡、又能正确地给出S_e随离子能量E的变化关系。用这种以实验为基础的S_e经验公式和符合于WHB势的核散射函数,计数了从H⁺到Ne⁺十种轻离子在非晶Al₂O₃,SiO₂,20/25/Nb不锈钢,LiNbO₃和UO₂等材料中的投影射程分布的一次至三次矩。将计算值与近几年的实验测量及其他人的计算结果进行了比较,在低能端,我们计算的平均投影射程R_p与实验符合得更好。 关键词：