Collision-induced dissociation of H 2 + ions into the fragmentations H+H(2p) and H++H(2p)

Using a photon-particle delayed coincidence method the energy distributions of H +H(2p) and H⁺+H(2p) fragment pairs have been measured arising from collisional dissociation of 10 keV H ₂ ⁺ ions incident on various target gases. H fragments in their 2p state are identified by the Lymanα radiation emitted. The distribution of H+H(2p) fragment pairs arising from dissociative charge exchange reveals a sharp increase below 0.2 eV in the center-of-mass frame of the H ₂ ⁺ ion. This is ascribed to predissociation of vibrational levels of higher H₂ Rydberg states close above then=2 dissociation limit by those H₂ Rydberg states which separate into H+H(2p) fragments. Only direct transitions into the continuum of theGK ¹ ∑ _g ⁺ state may compete. Some structure at 0.3–0.5 eV is attributed to the three statesI ¹ П _g,i ³ П _g, andh ³ bE _g ⁺ having potential barriers of this height. The distributions for H⁺+H(2p) have maxima at 3.4, 3.8, and 4.2 eV for a H₂, Ar, and He target, respectively, indicating that the 2pπ _u state as well as the 3dσ _g state ofH ₂ ⁺ is excited. The H+H(2p) process has a greater probability than the H⁺+H(2p) process for Ar and H₂ targets, though all electronic H₂ states under consideration are bound.     

Collision-induced dissociation of alkyl alcohols

collision-induced dissociation of aliphatic alcohols by I₂⁺, I⁺ and Xe⁺ ions is studied using a double mass spectrometer of the longitudinal type. The fragmentation patterns are compared with those resulting from pure charge exchange obtained with a double mass spectrometer of the perpendicular type. Important differences are pointed out, the former reactions being more complicated than the latter.     

Collision-induced dissociation of hydrated adenosine monophosphate nucleotide ions: protection of the ion in water nanoclusters

Fragmentation of singly charged anions of adenosine 5'-monophosphate (AMP-) induced by collisions with neutral atoms (Ne, Na) has been studied at a collision energy of 50 keV. The experiments were performed with isolated AMP- as well as with AMP- anions nanosolvated in a cluster with a given number m of water molecules. In the first case, the dominant fragmentation channels concern the loss of adenine, PO3- and H2PO4-. In the latter, loss of water molecules becomes the dominating process, and the AMP- ion is fully protected when m is larger than approximately 13. The observed fragment distributions are well described with the model of an evaporative ensemble.     

H3+团簇离子与固体相互作用

报道了H3+团簇通过碳膜对产生的各种产物的测量结果.分析讨论了三原子离子团簇与固体相互作用中的电荷交换过程.证明在产物的形成中,电荷交换过程起关键作用.分析研究了H3+团簇与固体作用中的团簇效应和尾流效应. 关键词： H3+团簇 电荷交换 团簇效应 尾流效应     

Collision-induced dissociation studies on gas-phase titanium oxide cluster cations

Titanium oxide cluster cations $\mathrm{Ti}_{x}\mathrm{O}_{y}^{+}$ are produced in a molecular beam by combining laser ablation of titanium with the supersonic expansion of oxygen into vacuum. The size distribution of the clusters produced is analyzed by time-of-flight reflectron mass spectrometry. The stable clusters appearing in the mass spectrum can be described by the general formula $(\mathrm{TiO})_{m}(\mathrm{TiO}_{2})_{n}(\mathrm{O}_{2})_{k}^{+}$ (with m,n=0,1,2,?? and k=0,1). Additionally, collision-induced dissociation studies of mass selected clusters colliding with Kr atoms in a gas cell have been performed. The results show that the clusters lose neutral O₂, TiO and/or (TiO₂) _n units, and the remaining charged fragments are those with the lowest ionization potentials. From these results the fragmentation cross section of the selected clusters is obtained.     

The interaction of fast H 3 + ions with a clean Ni-surface

Scattering of H ₃ ⁺ ions from a clean Ni(111) surface is observed at energies below 1 keV and grazing incidence in a time-of-flight system. The interaction with the surface leads to neutral particles mainly which are identified from the energy distributions as H and H₂. The neutralisation/dissociation mechanism is probably a resonant charge transfer of Ni electrons into the non-binding ground state of H₃.     

H+2,H+3团簇离子在沟道条件下的背散射质子产额测量

采用卢瑟福背散射方法,测得了每质子能量为650 keV的H+2,H+3团簇离子在Si晶体<100>和<110>沟道条件下的质子背散射能谱.结果发现,由于H+2,H+3团簇在晶体中的库仑爆炸和团簇效应,H+2的背散射质子产额大于H+的背散射产额,而H+3的背散射质子产额又大于H+2的背散射质子产额.通过计算,分别得到了H+2,H+3在<100>和<110>沟道方向的背散射质子产额相对于随机方向背散射产额之比随深度的分布.     

Discussion on the dissociation of fast HD+2 ions traversing thin foils

the discussion is on the following experimental results: The energy distribution of the H+ and D+ fragments resulting from the dissociation of HD+2 molecular ions at energy 1.497 7 MeV has been measured using the Coulomb explosion technique. The spectra were used to determine the binding energy of HD+2 and its structure. There existed differences between the spectral structures for proton and for deuteron.     

Highly efficient cooperative energy transfer from Ho3+ and Tm3+ ions to Ce3+ ions in crystals

A phenomenon of highly efficient cooperative energy transfer from Ho³⁺ and Tm³⁺ ions to two-particle (2Ce³⁺) cooperative acceptors in crystals of solid solutions of La_1?x Ce _x F₃ is revealed. The rates of cooperative energy transfer in Ho³⁺→2Ce³⁺, Tm³⁺→2Ce³⁺, and Tb³⁺→ 2Yb³⁺ systems are measured, as well as their dependence on the magnitude of the matrix elements of donor transition.     

Electric field dissociation of H+ 2: close-coupled scattering calculations

Close-coupling scattering calculations have been carried out to predict the magnitude of electric fields required to dissociate specific vibration—rotation levels in H⁺ ₂. Results for electric fields up to 40 kV cm^?1, which may dissociate levels up to 25 cm^?1 below the dissociation limit, are presented. The results are used to simulate spectra which are compared with experimental spectra. A method for extracting the eigenphase sum from a coupled channel scattering calculation is described in the appendix and used in the calculations.     

Discussion on the dissociation of fast HD^＋2 ions traversing thin foils

the discussion is on the following experimental results:The energy distribution of the H^ and D^ fragments resulting from the dissociation of HD^ 2 molecular ions at energy 1.4977 MeV has been measured using the Coulomb explosion techoique,The spectra were used to determing the binding energy of HD^ 2 and its structure,There existed differenoes between the spectral structures for proton and for deuteron.     

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.     

Photoluminescence of LiNbO3 crystals doped with Er3+ and Yb3+ ions

Results of cooperative phenomena investigations in the impurity subsystem of lithium niobate crystals doped with Er³⁺ and co-doped with Yb³⁺ impurity ions under continuous wave and pulsed excitation at 975 nm and 1064 nm wavelengths are presented. Dependences of some spectroscopic characteristics on the intensity of laser pumping are studied. Based on the pair centers model the analysis of the cooperative luminescence behavior in LiNbO₃:Yb³⁺+Er³⁺ crystals is performed.     

Study of sensitization of Cr4+ ions by Yb3+ ions in yttrium-aluminum garnet crystals

The possibility of using ytterbium ions as sensitizers of luminescence of tetravalent chromium in yttrium-aluminum garnet single crystals is studied. It is found that average values of the microparameters of electronic energy transfer between ytterbium and chromium ions are C _DA=7.05×10^?36 cm⁶/s and C _DD=4.55×10^?43 cm⁶/s.     

Optical transitions of Pr3+ and Er3+ ions in LiYF4

The optical absorption, emission, and excitation spectra of Pr³⁺ and Er³⁺ ions in LiYF₄ have been measured and energy level schemes established which agree with previous work. The temperature dependence of the emission lifetimes were investigated and analyzed using the Huang-Rhys and Struck-Fonger treatments of multiphonon decay. The non-radiative processes in LiYF₄: Er³⁺ were shown to follow the same “gap law” behavior as Er³⁺ in LaF₃ and MnF₂. Theoretical fits to the Huang-Rhys model allowed the construction of a configuration coordinate diagram for the Er³⁺ system. The non-exponential temperature dependence of the ¹D₂ lifetime in Pr³⁺ can be understood as a non-radiative transition from higher levels.