Correlation phenomena in the Cherenkov radiation of accelerated multiply charged ions

Correlation phenomena occurring in Cherenkov radiation are considered which are related to fluctuations of the charge states of multiply charged accelerated ions in a medium. The additional correlation contribution to the radiation is determined by the root-mean-square deviation of the ion charge from its equilibrium value and is responsible for the nonzero radiation yield in the event that the threshold condition is not fulfilled. Numerical estimates of the radiation yield of heavy ions in the optical and X-ray frequency ranges are given. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 41–46, January, 2009.     

FAB-MS spectra from Teflon® surface: Peak pattern development with increasing bombarding dose

The potential of FAB-MS for characterization of Teflon® surface is investigated and the character of the spectra compared with SIMS results from several different experiments. The change in the spectral peak pattern with increasing atom bombarding dose is examined in light of the radiation damage accumulation in the surface layer of the polymer and surface morphology development at higher atom bombarding doses. The correlation of the fragment ion yield with surface morphology shows that the overall change of the bombarding geometry plays an important role in the decrease of signal intensity with time. An irregular development of the relative ion fragment yields with increasing bombarding dose indicates that processes in the surface region are more complicated than a simple radiation damage accumulation of the polymer fragments created by a polymer chain scissoring mechanism.     

辐照前处理木质纤维素的研究进展

本文对几种主要的辐照前处理木质纤维素方法的效果和特点进行较为全面的比较和总结,旨在阐述微波、紫外线、γ射线、X射线、电子束、离子束等方式辐照前处理木质纤维素对其结构改变的机理尤其重点探讨了重离子辐照前处理引起木质纤维素同质异形体（I_α → I_β）的转换机制。木质纤维素结晶度与酶消化率呈强相关性,重离子辐照前处理可使木质纤维素中木质素和半纤维素部分破坏,导致其相对结晶度增加,从而增强了纤维素酶与木质纤维素的可及度,提高了酶解产率。因而,通过适当剂量的重离子辐照前处理可以显著提高酶对木质纤维素的生物转化效率和还原糖的产量,这为辐照前处理提高木质纤维素的综合利用提供了理论指导。     

X-ray emission from betatron motion in a plasma wiggler

The successful utilization of an ion channel in a plasma to wiggle a 28.5-GeV electron beam to obtain broadband x-ray radiation is reported. The ion channel is induced by the electron bunch as it propagates through an underdense 1.4-meter-long lithium plasma. The quadratic density dependence of the spontaneously emitted betatron x-ray radiation and the divergence angle of approximately (1-3)x10(-4) radian of the forward-emitted x-rays as a consequence of betatron motion in the ion channel are in good agreement with theory. The absolute photon yield and the peak spectral brightness at 14.2-keV photon energy are estimated.     

强作用介质诱导的光子辐射和双轻子产生

考察了相对论性高能重离子碰撞中产生的硬部分子喷注穿过强作用介质时,喷注与介质中的部分子多次散射诱导的光子辐射与双轻子产生,得到了对应于opacity展开第一阶的光子横动量谱,辐射光子导致的喷注的能量损失以及双轻子的不变质量谱,结果表明,光子的产生率随横动量的增加而降低,双轻子的产生率随其不变质量的增加而减小,辐射光子导致的能量损失线性依赖强作用介质靶的厚度。     

Laser desorption of energetic sodium ions from single-crystal NaNO3 at 1064 nm

We report electron and Na⁺ ion emission from single-crystal sodium nitrate (~10 eV band gap) upon exposure to IR (1064 nm, 1.16 eV) laser radiation. The fluence dependence of both the ion and the electron yield is highly nonlinear, and the kinetic energies of the emitted ions can reach values up to 5 eV. The fluence dependence and the ion energy distributions can be understood by a previously presented model involving multiple photon charge transfer plus electrostatic ejection of adions siting atop electron traps. Further evidence for the role of defects in the observed ion emission are provided by two-beam experiments; one beam (UV laser) is used to generate defects and the second beam (IR laser) is used to photodesorb the ions. Such experiments demonstrate that exposure of the sodium nitrate surfaces to UV laser radiation significantly increases the ion emission due to IR laser radiation.     

Effect of heavy ion charge fluctuations on Cherenkov radiation

Correlation effects in the Cherenkov radiation due to ions charge fluctuations in the matter are considered. Stochastic process of charge exchange leads to the washout of a radiation wave front and to the transformation of spectral-angular density. The effect is determined by a root-mean-square deviation of an ion charge. The additional radiation yield gives the nonzero contribution at the violation of the Cherenkov threshold condition. The interference of an electromagnetic field generated in the matter by the different ion's charge states along the trajectory is the cause of the additional radiation.     

Polarization characteristics of the radiation of ions formed during dielectronic recombination

The polarization characteristics of the radiation emitted during dielectronic recombination of free plasma electrons are considered. It is shown that taking into account the correlation between the orders of the angular momenta of a doubly excited state of an ion leads to a significant difference in the dependence of the radiation polarization on the plasma parameters.     

Gd靶激光等离子体6.7nm光源的实验研究

本文对Gd靶激光等离子体极紫外光源进行了实验研究, 在 6.7 nm附近获得了较强的辐射, 并研究了6.7 nm 附近光辐射随打靶激光功率密度变化的规律以及收集角度对极紫外辐射的影响. 同时, 对平面Gd靶激光等离子光源的离子碎屑角分布进行了测量, 发现从靶面的法线到沿着靶面平行方向上Gd离子数量依次减少. 进一步研究结果表明采用0.9 T外加磁场的条件下可取得较好的Gd 离子碎屑阻挡效果.     

Dependence of the process of nonlinear two-electron ionization of the barium atom on the polarization of the laser radiation

Experimental results are presented on measuring the yield of Ba²⁺-ions versus polarization of neodymium—glass laser radiation. These results show that the resonance in the Ba²⁺ ion yield occurs with the bound two-electron state rather than with the autoionization state in the Ba-atom spectrum.     

Study of the process of formation of excited states of krypton atomic ions via electron-stimulated desorption of excited molecular ions

The processes of population of excited levels of a krypton atomic ion via electron-stimulated desorption are studied. The radiation yield per single exciting electron in the corresponding krypton spectral lines is measured by the optical time-of-flight mass spectrometric method. The efficiency of the processes studied is compared with that of electron-impact excitation of the same levels.     

Nonthermal desorption of molecular ions of polyatomic molecules induced by uv laser radiation

The paper presents the results of studies into ion desorption from the surface of adenine and anthracene molecular crystals and anthracene molecules adsorbed on a metal as the surface is irradiated by an uv laser at λ=249, 308, and 337 nm. A sharp increase in molecular ion yield has been revealed with a decrease in radiation wavelength down to 249 nm. At this wavelength the effect of molecular ion desorption is observed at the radiation intensity of 20∶50 kW/cm² and pulse duration of 20 ns, it cannot be explained by thermal mechanisms. The initial velocity distribution of photoions is nonthermal by character, with maximum velocity of 2·10⁵ cm/s in case of adenine. The mechanisms responsible for the effect observed are discussed.     

129Xe30+与Au作用激发的Au M-X射线 与Xe L-X射线

探测了动能为1.0——7.0 MeV的¹²⁹Xe³⁰⁺ 入射Au表面产生的X射线谱. 实验结果表明, 入射离子动能较高时, 不仅激发出很强的Au的M-X射线, 还激发出了Xe的L-X射线, 且X射线产额与入射离子动能有强相关性. 分析了X射线产额与入射离子动能的关系.     

Influence of the Stark effect on multiphoton ionization of atoms when the dynamic polarizability depends strongly on the laser frequency

The influence of the Stark effect on multiphoton ionization of Ba atoms under conditions when the dynamic polarizability depends strongly on the frequency of the laser radiation is investigated. It is found that for some electric field strengths ε of the laser radiation this effect gives rise to resonance peaks in the Ba⁺ ion yield as a function of the laser radiation frequency at frequencies corresponding to single-photon transitions between the excited states. These frequencies can differ substantially from the frequencies corresponding to the conventional multiphoton excitation of these states from the ground states of the atoms. Peaks in the ion yield as a function of ε behave differently from the conventional Stark effect—their position on the frequency scale does not depend strongly on ε. The conditions under which such an induced resonance structure appears are determined. Zh. éksp. Teor. Fiz. 113, 499–512 (February 1998)     

水稻植株高矮突变系材料的株高性状与产量等相关性分析

对利用N离子束和γ射线诱变获得的粳稻日本晴和籼稻“9311” 89份株高突变体的株高性状和产量性状进行了相关分析。 结果表明, 株高和水稻的产量与其构成因素: 穗粒数、 结实率、 千粒重以及穗长、 单株茎秆干重有着一定的相关性。 株高与穗长、 穗粒数、 千粒重、 单株茎秆干重、 单株生产力呈极显著的正相关, 与有效穗数呈极显著的负相关。 通过对株高与其他产量结构因素的相关分析, 进一步了解了株高的变异对于水稻经济产量因素的影响。 The total 89 plant height mutant lines induced from rice cultivars Nipponbare and “9311” by ion beam implantation and γ rays irradiation were used for analysis of the correlation between plant height and yield component. The results indicated spike length, ear grains, thousand grain weight, stem dry weight and yield have significantly positive correlation with the plant height, while the number of productive ear has significant negative correlation with it. The correlation analysis of the plant height and yield component will help to reveal the influence of the plant height and the factors of yield component.     

Photon-stimulated ion desorption from DCOO/Si(100) near the O K-edge

Photon-stimulated ion desorption from deuterated formic acid chemisorbed on Si(100) has been studied using pulsed synchrotron radiation in the energy region of the oxygen 1s electron excitation. The O 1s electrons of hydroxyl oxygen and carbonyl oxygen could be selectively excited in the O K-edge region because the chemical environments are different. It is found that the CDO⁺ yield is enhanced at the O 1s(C---O)→σ*(C---O) resonance and the CD⁺ yield at the O 1s(C=O)→σ*(C---O) resonance. The results indicate that ion desorption is related both to the antibonding character of excited molecular orbitals and the local character of core hole orbitals.     

12C6+束辐照引起的实验猪皮肤急性损伤反应的研究

探讨了正常皮肤对重离子辐照急性损伤反应的耐受性, 为重离子治癌临床应用提供安全性检测的实验依据。实验前10 min, 实验猪肌肉注射复方氯胺酮1.2 mg/kg进行麻醉, 然后在兰州重离子研究装置（HIRFL）辐照终端利用12C6+束照射, 辐照剂量分别为0, 12, 21和27 Gy, 辐照分3次完成, 剂量率约为1.2 Gy/min, Bragg峰区照射, 辐照后每隔7 d对照射野拍照并活检取样, 做HE组织病理学观察。不同剂量12C6+离子束辐照实验猪皮肤后, 皮肤外观反应随辐照剂量增大而加快, 表现为肿胀和色素沉积等; 皮肤组织结构的变化明显, 上皮细胞排列紊乱、 萎缩、 空泡变性; 基本恢复正常所需时间也越长, 且都存在明显的剂量效应关系。结果表明, 辐照剂量范围为0—27 Gy时, 重离子对正常皮肤的辐照是安全的。The tolerance of the normal skin to the acute radiation injury reaction induced by heavy ion beams has been studied experimentally. The experimental pigs were injected with 1.2 mg/kg ketamine in 10 min before irradiation and were irradiated with 0, 12 , 21 and 27 Gy 12C6+ ion at a dose rate of 1.2 Gy/min at the Heavy Ion Research Facility in Lanzhou（HIRFL）. The total radiation dose was finished by 3 times at Bragg Peak Region of Heavy Ion Beams.The radiation fields of skin were taken photo and performed biopsy. The contaneous tissues of radiation fields were stained by HE and examined histopatholo gical changes every seven days after irradiation. The results indicated that the cutaneous appearance reaction became more faster with radiation dosage rising and presented with swollen, melanin forming and so on after irradiated by the carbon ions at different dosage. The Pathological examination showed noticeable changes in histological and structural of experimental pigs skin, such as atrophy, vacuolation, denaturation and arranged irregularly in epithelial cells. Furthermore, the time for return to normality became longer with the increasing of radiation dosage. All indexes demonstrated correlation between the does and effects. It is concluded that the irradiation of heavy ion beams to normal skin is security when the radiation dose range is about 0—27 Gy.     

铝丝阵Z箍缩辐射产生机理初步研究

利用一维非平衡辐射磁流体力学程序研究了铝丝阵内爆过程中的能量转化规律和辐射产生机理.细致讨论了Z箍缩过程中脉冲功率驱动器电磁能馈入等离子体,等离子体动能转化为内能以及通过一系列原子过程电子内能转化为X射线辐射的能量转化机理.结合离子布居信息深入分析了Z箍缩过程中的辐射产生机理.结果表明,在内爆压缩阶段,电离和激发过程占优,线辐射占据总辐射的绝大部分.在滞止时,离子大都处于裸核离化度,连续谱辐射达到峰值.在滞止附近,线辐射出现两个峰值.在膨胀过程中,光电复合过程优于三体复合,线辐射占总辐射的份额逐渐下降.     

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.     

Photoionization cross section of Xe+ ion in the pure 5p5 2P3/2 ground level

Coupling an ion trap with synchrotron radiation is shown here to be a powerful approach to measure photoionization cross sections on ionic species relaxed in their ground state. The photoionization efficiency curve of Xe+ ions stored in a Fourier transform ion cyclotron resonance ion trap was recorded at ELETTRA in the 20-23 eV photon energy range. Absolute cross sections were derived by comparison of the photoionization yield of Xe+ with measurements from the ASTRID merged-beam experiment. Multiconfiguration Dirac-Fock calculations were performed for the interpretation of these new data.