Multiphoton fragmentation and ionization of CF2HCl molecules and clusters by UV radiation

The results of experimental studies of multiphoton ionization of CF₂HCl molecules and clusters by UV laser radiation in the wavelength range 217–236 nm are reported. In the case of molecules, the main reaction products are CF₂H⁺ and CF⁺ ions as well as atomic chlorine. It is found that the spectra of the products of ionization of free molecules and molecules condensed into clusters differ qualitatively: multiphoton ionization of clusters does not yield CF₂H⁺ ions. The dependences of the ion yield on the intensity of laser radiation and its wavelength are measured. The effect of a constant electric field and the radiation spectral width on the multiphoton ionization process is demonstrated. The shape of the velocity distributions is determined for a number of products. A strong anisotropy is detected in the reaction of formation of CF₂H⁺ ions. Possible mechanisms for these processes are discussed.     

甲醛的态选择性多光子电离研究

我们在XeCl准分子激光多光子电离甲醛分子的研究中,获得了甲醛经过2+1和2+2光子共振激发过程而产生的母体离子和高能离解通道的离子CO⁺。在电子轰击和单光子电离中占优势的低能阈离解通道离子HCO⁺,由于态选择性激发的结果而未出现。 关键词：     

Laser multiphoton mass spectroscopy of organometallic compounds: State selective and mass resolved detection of neutral fragment tellurium atoms from C2H5TeC2H5

Typical features in laser multiphoton ionization of organometallic compounds are well evident in the case of the diethyltelluride C₂H₅TeC₂H₅ molecule. The use of a tunable dye laser coupled with time-of-flight (TOF) mass spectroscopy has allowed to establish that a large amount of tellurium is eliminated from the parent molecule as a neutral atom either in its ground or low excited states. Sharp two- and three-photon atomic Te resonances, which give origin to extraproduction of Te⁺ ions, have been identified in the optical spectra measured by varying the laser wavelength.     

Multiphoton ionization of CF<Subscript>3</Subscript>I clusters by ultraviolet laser radiation

The results of the investigation of the multiphoton ionization of (CF₃I) _n clusters by ultraviolet laser radiation are reported. The yields of the I₂⁺ and I⁺ ions, which are the products of the multiphoton ionization, have been measured as functions of the intensity of the ultraviolet radiation at the wavelengths of 308 and 232.5 nm. The degree of multiphoton ionization has been determined and appears to depend on the wavelength of radiation. The velocity distributions of the products have been measured in detail for various wavelengths and various polarizations of radiation. The anisotropy parameters of the velocity distributions of the produced ions and their kinetic energy have been determined. After analysis of the data, a mechanism of the multiphoton ultraviolet ionization of the clusters under investigation has been proposed. This mechanism depends on the used wavelengths.     

Nanochemistry – Chemical Reactions of Iron and Benzene Within Molecular Clusters

Molecular clusters represent a nanoscale test tube where chemical reactions can be examined in a unique way for the effects of the local environment and the possibility of size-dependent reactions. Previous experiments have shown that the ionization/dissociation of iron pentacarbonyl clusters can lead to the formation of iron ions and iron cluster ions and that these species can further react with dopant molecules to yield chemically rearranged products. The present experiments characterize similar reactions with benzene molecules and clusters. Heteroclusters of the form [Fe(CO)₅]_m(C₆H₆)_nAr_p are created in an expanding supersonic jet of the component molecules. Following ionization by a 30 ps, 266 nm laser pulse, extensive dissociation, aggregation, and chemical rearrangement occurs leading to ionic products which are characterized by mass spectrometry. Cluster ions of the type Fe_m(C₆H₆)_n ⁺ are observed as products. The stability of the sandwich form of the ion, Fe(benzene)₂ ⁺, is inferred from the data. Evidence for a similar special stability for the double-decker, Fe₂(benzene)₃ ⁺, is presented.     

Atomic and molecular ions in intense ultra-fast laser fields

The interaction of a 60 fs 790 nm laser pulse with beams of Ar⁺, C⁺, H₂ ⁺, HD⁺ and D₂ ⁺ are discussed. Intensities up to 10¹⁶ Wcm^-2 are employed. An experimental z-scanning technique is used to resolve the intensity dependent processes in the confocal volume.Received: 6 January 2003, Published online: 15 July 2003PACS: 32.80.Fb Photoionization of atoms and ions - 33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) - 42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift     

乙醚团簇的激光电离质谱及从头计算

应用激光多光子电离质谱与超声脉冲分子束技术研究了乙醚团簇，实验中观测到乙醚的碎片离子以及强度较小的(E)H⁺，(E)^＋₂和(E)₂H⁺(E代表CH₃CH₂OCH₂CH₃)，没有发现更大尺寸的团簇离子.结合从头计算理论，在B3LYP/6-311++G(d,p 关键词： 乙醚团簇 偶极-偶极相互作用 从头计算     

Strong optical fields induce ultrafast rearrangement of H-atoms in ethanol molecules

H-atoms in C₂H₅OH are rearranged by strong optical fields generated by intense, 100 fs long infrared laser pulses to form new bonds that lead to the H ₃ ⁺ molecular ion. This observation appears to be against the expectation that exposure of molecules to intensities of the order of 10¹⁵ W cm^?2 inevitably lead to multiple ionization of molecules followed by instantaneous Coulomb explosion into fragments. The polarization dependence of the H ₃ ⁺ signal and of the energy content of H ₃ ⁺ ions lead to believe that H-atom rear-rangement in ethanol occurs within a single 100 fs pulse.     

射频溅射微晶NiOxHy膜电致变色性能及其机理研究

研究了射频溅射制备的NiO_x膜的电致变色性能,发现富氧非理想化学配比的NiO _x(x>1)膜具有变色活性,这种膜出现Ni³⁺和Ni²⁺的混 合价态,当H^＋注入并占据Ni空位时,导致Ni³⁺的t_2g 能级被填满,Ni³⁺被阴极还原为Ni²⁺引起光学透明,即为漂白态; 反之,H⁺被萃取出NiO 关键词： xH_y膜')" href="#">NiO_xH_y膜 电致变色     

Luminescence detection of multiphoton ionization-fragmentation of the molecular CrO 4 2− anions adsorbed on the surface of dispersed SiO2

It is shown that luminescence detection of multiphoton ionization-fragmentation of the molecular CrO ₄ ²⁻ anions adsorbed on the surface of dispersed SiO₂ is possible under excitation with the fundamental frequency of a Nd:YAG pulsed laser (λ=1.064 μm). The structure and the process of formation of the adsorbed complexes under thermal activation of the surface and the nature of luminescence transitions in CrO ₄ ²⁻ anions are studied in detail. It is shown that luminescence is excited as a result of the recombination of photoelectrons and ionized chromate ions. Multiphoton ionization of the ions occurs under three-photon resonance conditions. The resonance level is an antibonding state of the adsorption complex formed with the participation of an oxygen vacancy on the SiO₂ surface. The dynamics of the multiphoton luminescence excitation process includes autoionization (stimulated by intercomplex electronic excitation) in superexcited states, fragmentation of chromate anions, and annealing of surface oxygen vacancies. The rate equations for three-photon-resonance multiphoton ionization are studied. The cross sections for two-and one-photon transitions on the nonresonance steps of multiphoton absorption are obtained. It is concluded that the nonlinear polarizability of the donor-acceptor adsorption bond in “chromate anion-oxygen vacancy” complexes is very important. Zh. éksp. Teor. Fiz. 111, 1748–1774 (May 1997)     

Secondary ion emission under the bombardment of Si by multiply charged Si q+ ions

The spectra of secondary ion emission under the bombardment of a B-doped Si target by multiply charged Si ^q+ ions (q = 1?C5) have been studied in the energy range of 1 to 10 keV per unit of charge. A multifold increase in the yield of secondary cluster Sk _n ⁺ ions, multiply charged Si ^q/+ ion (q = 1?C3), and H⁺, C⁺, B⁺, Si₂N⁺, Si₂O⁺ is observed as the charge of the multiply charged ions increases. The increase in the yield of secondary ions with increasing charge of the multiply charged-ion charge is most significant for ions with relatively high ionization potentials.     

On the origin of electron stimulated desorption of H+ from metal surface

The emission of hydrogen ESD ions from polycrystalline Nb is studied experimentally. The results demonstrate clearly that no ESD emission of H⁺ occurs from a pure H adsorbate. However, adsorption of H₂O, present as an impurity in H₂, and H₂ adsorption on Nb preceded by O adsorption, produce strong H⁺ ESD emission. It is shown that Auger ionization of O can account for the increased H⁺ yield and it is postulated that similar effects also occur on other metal surfaces.     

Independent electron theory of multiple ionization of xenon by intense laser pulses

The intensity dependence of the multiphoton ionization spectra of Xe atoms has been investigated with an improved accuracy and well-controlled laser parameters. In particular, we have examined the ionization rates for X³⁺, X²⁻, X⁺ as functions of the laser intensity and the pressure in the target chamber. The apparatus used for these measurements is characterized by a high-energy resolution (better than 200 meV) and a completely digital acquisition system. The time-of-flight spectra clearly show the contributions of the different isotopes present in Xe gas. The laser pulses have been characterized with great accuracy by monitoring the energy, pulse width and divergence shot by shot. The ionization rates of the different ions have been used for testing the basic assumption of the Geltman theory of multiple ionization based on the single electron ionization model. We have found that for the small intensity range investigated the quantity (dXe ⁺/dI)·(dXe ³⁺/dI)/(dXe ²⁺/dI)² appears to be quite close to the value 0.5 predicted by this model.     

N2O+离子A2Σ+电子态高振动能级的转动结构分析

利用一束波长为36055nm的激光,通过(3+1)共振多光子电离方法制备纯净的且处于X²Π_1/2,3/2(000)态的N₂O⁺离子,用另一束激光激发所制备的离子到第一电子激发态A²Σ⁺的不同振动能级,然后解离,通过检测解离碎片NO⁺强度随光解光波长的变化,得到了转动分辨的N₂ 关键词： 2O⁺离子A²Σ⁺电子态')" href="#">N₂O⁺离子A²Σ⁺电子态 共振增强多光子电离 光解碎片激发光谱 光谱常数     

H3PAuPh与(H3PAu)2(1,4-C6H4)2光谱性质的密度泛函研究

用密度泛函(DFT)方法优化了配合物H₃PAuPh(a),(H₃PAu)₂(1,4-C₆H₄)₂(b)的基态的几何结构,并用含时密度泛函方法计算了它们的吸收光谱.结果表明配合物a与 b的最低能量吸收谱线的波长分别为257.5 nm和307.6 nm,皆具有C(2p)→Au(6p)电荷转移参与下的p_π 关键词： 激发态 光谱 密度泛函 3')" href="#">AuPH₃     

Capture of an electron by ions in methionine and norleucine molecules

The relative cross sections of processes taking place when H⁺ and He²⁺ ions with an energy of 6z keV (z is the ionic charge) capture an electron from molecules of C₅H₁₁NO₂S methionine (proteogenic amino acid) and C₆H₁₃NO₂ norleucine (nonproteogenic amino acid) are measured by time-of-flight mass spectrometry (a methionine molecule transforms into a norleucine molecule by substituting the CH₂ group for the S heteroatom). The fragmentation pattern of resulting molecular ions is established from correlation analysis of the detection times of all fragment ions. The results are compared with experimental data for fragmentation of the same molecules ionized by electrons and photons. In these amino acids, the pattern of molecular ion fragmentation is found to depend on the type of molecule ionization. However, the detachment cross section of the COOH neutral group or residue (neutral or charged) R of a side chain of the amino acid is invariably among the largest. The relative cross sections of capture with single and double ionization of molecules are measured.     

Multiphoton ionization of molecules under the conditions of strong field-induced perturbation of Rydberg states

Multiphonon ionization of the H₂ molecule under the action of a weak (probe) field, which provides the initial population of the low-lying (working) level, and intense monochromatic linearly polarized radiation is studied. The multiphoton ionization process occurs under the conditions of strong field perturbation of two intermediate Rydberg series, np0(¹Σ _u ⁺ and np2(¹Π_u), of the optical R(0)branch which have different ionization potentials. The series are occupied simultaneously as a result of single-photon absorption by an excited H ₂ ^* molecule in the working state 4s σH′¹Σ _g ⁺ (v=0). As a result of the irregularity in the arrangement of the intermediate levels from a large group of states that are combined in the multiphoton ionization process a sharp and irregular change occurs in the dependence of the shifts and widths Γ_n of the levels on the intensity f of the strong field in a transition from one level to another. It is shown that for field intensities f such that the level widths remain much less than the splitting between the levels (Γ_n≪/n ³) the stabilizing effect (i.e., the field-induced narrowing of the levels as f→∞) in the form Γ_n ∝ 1/f ² (as happens in atoms with a structureless core) is not observed in molecular systems. Zh. éksp. Teor. Fiz. 115, 1987–2000 (June 1999)     

Synthesis and investigation of titanium diselenide intercalated with ferrocene and cobaltocene

Single crystals and polycrystals of titanium diselenide TiSe₂ intercalated with ferrocene Fe(η⁵-C₅H₅)₂ and cobaltocene Co(η⁵-C₅H₅)₂ are synthesized. The magnetic susceptibility and electrical resistivity of the intercalation compounds are measured. The results obtained demonstrate that the intercalation brings about the formation of an impurity band with a temperature-dependent width.     

Ions with strong symmetric H-bonds and their solvation in aqueous-ethanolic solutions of HCl

Ion-molecular interactions in the HCl-EtOH-H₂O system are studied by means of multiple frustrated total internal reflection IR spectroscopy over a wide range of concentrations of the components. It is demonstrated that, in the investigated solutions, the acid is fully bound into ions and uncharged complexes formed by strong symmetric or quasi-symmetric H-bonds. There is a competition between H₂O and EtOH molecules during the formation of the (H₅C₂(H)O…H…O(H)C₂H₅)⁺, (H₂O…H…OH₂)⁺, and (H₂O…H…O(H)C₂H₅)⁺ proton disolvates. In dilute solutions of HCl in 2: 1 and 1: 1 EtOH-H₂O mixtures, (H₂O…H…OH₂)⁺ proton dihydrates are mainly formed, whereas in concentrated HCl solutions, under conditions of a partial solvation of ions by solvent molecules, predominantly (H₂O…H…O(H)C₂H₅)⁺ mixed proton disolvates arise. In concentrated solutions of HCl in EtOH with low water content, the acid is partially bound into (H₅C₂(H)O…H⁺…Cl^?) uncharged complexes with the participation of the Cl^? anion.