Comparative study on atomic ionization in bicircular laser fields by length and velocity gauges S-matrix theory

Ionization of atoms in counter-rotating and co-rotating bicircular laser fields is studied using the S-matrix theory in both length and velocity gauges.We show that for both the bicircular fields,ionization rates are enhanced when the two circularly polarized lights have comparable intensities.In addition,the curves of ionization rate versus the field amplitude ratio of the two colors for counter-rotating and co-rotating fields coincide with each other in the length gauge case at the total laser intensity 5×10^14 W/cm^2,which agrees with the experimental observation.Moreover,the degree of the coincidence between the ionization rate curves of the two bicircular fields decreases with the increasing field amplitude ratio and decreasing total laser intensity.With the help of the ADK theory,the above characteristics of the ionization rate curves can be well interpreted,which is related to the transition from the tunneling to multiphoton ionization mechanism.

Ultraviolet laser ionization studies of 1-fluoronaphthalene clusters and density functional theory calculations

This paper studies supersonic jet-cooled 1-fluoronaphthalene （1FN） clusters by ultraviolet （UV） laser ionization at 281 nm in a time-of-flight mass spectrometer. The （1FN）＋ （n=1-3） series cluster ions are observed where the signal intensity decreases with increasing cluster size. The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured. Using density functional theory calculations, it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds. The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first ＂shell＂ in geometric structure while the larger clusters are generated based on this fundamental unit.

Nonsequential double ionization of nonaligned diatomic molecules N_2 and O_2

Nonsequential double ionization （NSDI） processes of nonaligned diatomic molecules N2 and O2 are studied using the S-matrix theory. Our results show that the NSDI process significantly depends on the molecular symmetry and structure. The ratio of NSDI rate to single ionization rate as a function of the field intensity is obtained. It is found that N2 behaves closely with its companion atom Ar in the ratios over the entire intensity range, while O2 exhibits an obvious suppression effect, which is qualitatively consistent with the experiment.

Multiphoton and tunneling ionization of atoms in an intense laser field

We study the ionization probabilities of atoms by a short laser pulse with three different theoretical methods, i.e., the numerical solution of the time-dependent SchrSdinger equation （TDSE）, the Perelomov-Popov Terent＇ev （PPT） theory, and the Ammosov-Delone-Krainov （ADK） theory. Our results show that laser intensity dependent ionization probabilities of several atoms （i.e., H, He, and Ne） obtained from the PPT theory accord quite well with the TDSE results both in the multiphoton and tunneling ionization regimes, while the ADK results fit well to the TDSE data only in the tunneling ionization regime. Our calculations also show that laser intensity dependent ionization probabilities of a H atom at three different laser wavelengths of 600 nm, 800 nm, and 1200 nm obtained from the PPT theory are also in good agreement with those from the TDSE, while the ADK theory fails to give the wavelength dependence of ionization probability. Only when the laser wavelength is long enough, will the results of ADK be close to those of TDSE.

Ionization Potentials and Quantum Defects of 1s^2np^2p Rydberg States of Lithium Atom

Abstract In this work, ionization potentials and quantum effects of ls^2 np^2 P Rydberg states of lithium are calculated based on the calibrated quantum defect function. Energy levels and quantum defects for ls^2np^2P bound states and their adjacent continuum states are calculated with the R-matrix theory, and then the quantum defect function of the ls^2np （n ≥ 7） channel is obtained, which varies smoothly with the energy based on the quantum defect theory. The accurate quantum defect of the ls^2 7p^2P state derived from the experimental data is used to calibrate the original quantum defect function. The new function is used to calculate ionization potentials and quantum effects of ls^2np ^2P （n ≥ 7） Rydberg states. Present calculations are in agreement with recent experimental data in whole.

Theoretical approach to the study of vibrational effects on strong field ionization of molecules with alignment-dependent tunneling ionization rates

The tunneling ionization rates of vibrationally excited N2 molecules at the ground electronic state are calculated using molecular orbital Ammosov–Delone–Krainov theory considering R-dependence. The results show that molecular alignment significantly affects the ionization rate, as the rate is mainly determined by the electron density distribution of the highest occupied molecular orbital. The present work indicates that the ratios of alignment-dependent rates of different vibrational levels to that of the vibrational ground level increase for the aligned N2 at the angle θ = 0？, and suggests that the alignment-dependent tunneling ionization rates can be used as a diagnostics for the influence of vibrational excitation on the strong field ionization of molecules.

THE VARIATION OF K-SHELL IONIZATION PROBABILITY ACROSS A NARROW P-WAVE RESONANCE

The projectile energy dependence of K-shell ionization probability have been measured across the narrow resonance 2.522Mev with large ratio of Uk/Г=5.3 in the reaction^(56)Fe(p,p)^(56)Fe.The frame work of the theory proposed by Blair and Anholt was introduced to analyze the results.

Influence of Coulomb force between two electrons on double ionization of He-like atoms

In strong-field double ionization,two electrons are ionized by intense laser field.These two electrons move in the laser field and the state is described by a Coulomb-Volkov state,where the repulsive Coulomb state describes the relative motion of the two electrons and the Volkov state describes the center-of-mass motion of the two electrons in the laser field.In the frame of scattering theory,we derive a simple analytical formula of the double ionization of He-like atoms.The effect of the Coulomb force between two electrons on the double ionization process is discussed.Numerical studies disclose that the Coulomb force enhances the ionization rate of high-energy electrons but suppresses the ionization rate of the lowest-energy electrons.

Effect of gas pressure on ionization of ambient gas

An Nd: YAG pulsed laser (145 mJ) was used to ablate aluminum target and Ar was used as protecting gas. Time-and space-resolved spectra of the plasmas under pressure 100 Pa, 1 kPa, 10 kPa and 100 kPa were acquired with time- and space-resolved technique. The characteristics of the plasma radiating under each pressure were briefly described, and the laws of Ar characteristical radiaton were analyzed in detail. Based on the profile of Ar characteristical radiation under these pressure, the relation between protecting gas pressure and its ionization was briefly discussed, and explained with quantum theory. Farther more, the mechanism of ambient gas ionization was investigated. As the result, it was suggested that the main mechanism inducing protecting gas to ionize should be the absorption of the plasma continuum radiation by the gas.

Possible Evolutionary Models in the Initially Hydride Earth Theory

A modern view of the properties of chemical elements has confirmed the theory of the hot origin of the Earth. The next step in developing this theory was the hypothesis of the initial hydride Earth. In this work, we attempted to find additional evidence for this hypothesis and show additional effects that flow from it. The effect of the physical properties of atoms and ions on their behavior during the formation of the Earth was studied. The maximum contribution to the distribution of elements was made by those elements whose content in the original protoplanets of the disk was the maximum. Correlation dependence is obtained, which allows one to calculate the distribution of elements in the protoplanetary disk. It was shown that hydrogen was the main element in the proto substance located in the zone of the Earth’s formation. In this case, various chemical compounds formed, most represented by hydrogen compounds—hydrides. Since the pressure inside the Earth is 375 GPa, this factor forces the chemical compounds to adopt stoichiometry and structure that would not be available in atmospheric conditions. It is shown that many chemical elements at high pressure in a hydrogen medium form simple hydrides and super hydrides—polyhydrides with high hydrogen content. Pressure leads to a higher density of matter inside the planet. Given the possibility of forming polyhydrides, there is the possibility of binding the initially available hydrogen in an amount that can reach 49.3 mole%. Young Earth could contain about 10.7 mass% of hydrogen in hydrides, polyhydrides, and adsorbed form is almost twice higher than previous estimates. This fact additionally confirms the theory of the original hydride Earth. In hydrides, the occurrence of the phenomenon of superconductivity was discovered. Polyhydrides were shown as potential superconductors with a high critical temperature above 200 K. We, based on these data, hypothesized the presence of superconducting properties in the Earth’s core, which explains the presence of a magnetic field in the Earth, as well as the unevenness and instability of this field and the possibility of migration of the Earth’s poles. The fact that the Earth has a hydroid core causes its change in time due to the instability of hydrides. Arranged several possible models of the destruction of the Earth’s core. The calculations showed that both models give close results. These results give predictions that can be measured. The proposed models also made it possible to estimate the initial size of the Earth. Possible ways of further testing the hypothesis of the initial hydride Earth is shown.

浅谈离子的水化与缔合作用

电解质溶液中粒子并非简单的共存,体系中一般存在水化与缔合作用,溶液结构与性质通常与理想溶液存在差异比较复杂。为了解释复杂的溶液结构现象,分别采用Stokes-Robinson水化理论、BET模型水化理论、Debye-Hückel离子互吸理论、Bjerrum离子缔合理论和Pitzer电解质溶液理论阐述了离子的水化与缔合作用的存在原理及其发展简史,并通过举例实际数据证明在浓度较高的电解质溶液中离子水化与缔合作用的存在。

Dynamic development model for long gap discharge streamer-leader system based on fractal theory

Establishing a long air gap discharge model considering the streamer-leader transition and randomness of the discharge path is of great signiflcance to improve the accuracy of discharge characteristic prediction and optimize external insulation design.Based on fractal theory and thermal ionization theory of streamer-leader transition,this work establishes a dynamic development model for the long air gap discharge streamer-leader system,which includes streamer inception,streamer development,leader inception,development of streamer-leader system and flnal jump.The positive discharge process of a 3 m rod plate is simulated to obtain the fractal distribution of the discharge path and the law of leader development for comparison with the discharge test results.The results show that the simulation model is similar to test results in the development characteristics of leader path distribution,each stage time and leader velocity.Finally,a simulation calculation of a 50%breakdown voltage of the rod-plate gap and ball-plate gap is carried out,with results fairly consistent with test data,proving the effectiveness and practicality of the model.

Application of IPF Theory to the Study of lonization Equilibrium

This article is a theoretical study about ionization equilibrium. Taking the ionization equilibrium of acetic acid in a series of MeOH-water mixtures as an example, we calculated the ionization constant Ka according to the IPF theory, the Born theory and the vander Waals theory, respectively. The results indicate that the values obtained by the IPF theory are in best accordance with those from literatures. A brief discussion about the theories is given at the end.

再现知识产生过程:培养学生探究与质疑的科学精神——以电解质溶液为例

质疑精神是培养当代大学生具备创新精神和创新能力的重要基石,但教师在实际的教学过程中常常直接给出知识产生的结果,这对于培养学生探究与质疑的科学思维品质是不利的。在教学过程中,教师如果能引导学生再现教材知识中那些激动人心的发现、概括、抽象的创造过程,必然能激起学生的探究欲望,展现他们的创造才能,有效地培养其探究与质疑的科学思维品质,同时也能形成学生独立思考的良好习惯和创新思维能力。因此,该文以基础化学课程电解质溶液一章的教学过程为例,借助科学家们探索电解质溶液理论的历史事实再现知识产生、发展的过程,并与人的认知规律相结合进行创造性的教学设计,能改善教学效果,最终实现培养学生探究与质疑的科学精神。

Accurate electron beam phase-space theory for ionization-injection schemes driven by laser pulses

After the introduction of the ionization-injection scheme in laser wake field acceleration and of related high-quality electron beam generation methods,such as two-color and resonant multi-pulse ionization injection(Re MPI),the theory of thermal emittance has been used to predict the beam normalized emittance obtainable with those schemes.We recast and extend such a theory,including both higher order terms in the polynomial laser field expansion and non-polynomial corrections due to the onset of saturation effects on a single cycle.Also,a very accurate model for predicting the cycle-averaged distribution of the extracted electrons,including saturation and multi-process events,is proposed and tested.We show that our theory is very accurate for the selected processes of Kr^(8+→10+) and Ar^(8+→10+),resulting in a maximum error below 1%,even in a deep-saturation regime.The accurate prediction of the beam phase-space can be implemented,for example,in laser-envelope or hybrid particle-in-cell(PIC)/fiuid codes,to correctly mimic the cycle-averaged momentum distribution without the need for resolving the intra-cycle dynamics.We introduce further spatial averaging,obtaining expressions for the whole-beam emittance fitting with simulations in a saturated regime,too.Finally,a PIC simulation for a laser wakefield acceleration injector in the Re MPI configuration is discussed.

TM_(13-n)X_(n)(TM=Fe,Co,Ni;X=Si,Ge;n=1-3)团簇的结构和性质研究

研究二元过渡金属团簇的性质,对设计新型纳米材料、纳米电子元件和高密度磁存储器的制备具有重要意义。本文利用密度泛函理论方法对TM_(13-n)X_(n)(TM=Fe,Co,Ni;X=Si,Ge;n=1-3)团簇的几何结构、相对稳定性、电子性质以及磁性进行了系统的研究。结果表明,掺杂Si和Ge原子后的TM_(13-n)X_(n)团簇的稳定性均有所增强,掺杂团簇的非金属性提高,吸电子能力增强,而其磁性却都有不同程度的减弱。

Relativistic semi-classical theory of atom ionization in ultra-intense laser

A relativistic semi-classical theory (RSCT) of H-atom ionizationin ultra-intense laser (UIL) is proposed. A relativistic analytical expression for ionization probability of H-atom in its ground state is given. This expression, compared with non-relativistic expression, clearly shows the effects of the magnet vector in the laser, the non-dipole approximation and the relativistic mass-energy relation on the ionization processes. At the same time, we show that under some conditions the relativistic expression reduces to the non-relativistic expression of non-dipole approximation. At last, some possible applications of the relativistic theory are briefly stated.

Quantum-orbit theory of low-energy above-threshold ionization on and off axis

Intense-laser-induced above-threshold ionization of a bound electron into continuum states with low energy is investigated in the context of the strong-field approximation that allows for one act of rescattering of the re- visiting electron. The quantum orbits for forward and backward scattering are evaluated and generalized to arbitrary scattering angles. The velocity map of the liberated electron exhibits the well-known low-energy structure as well as other features off the polarization axis.

强激光能源系统新型放电回路研究

从理论上分析了强激光能源系统新型放电回路能量传输效率和氙灯能量分配均匀性问题 ,给出了预电离回路的实验研究结果 。

有机场致发光中能带模型与分子理论的讨论(英文)

在有机场致发光中,能带模型及分子理论从 20世纪就存在尖锐的矛盾。在分层优化方案中,经SiO2加速后的电子能量可以到达 10eV, 这足以激发发光材料发光,将分层优化方案应用到有机场致发光材料中。发现了固态阴极射线发光(SSCL),经过对它的交叉证明、普适性的验证,肯定了固态阴极射线的发光确实是在发光二极管,无机及有机场致发光之外的一种完全新型的电场诱导的发光。SSCL的特征是在它的光谱中出现短波发光峰,实验证明长波发光峰的减弱是由于电场离化效应。研究了这种效应出现的电压阈值并和SSCL的短波峰出现的电压相比,发现短波峰的出现是在激子的电场离化之后,从而找出了电子处于局域态与扩展态的分水岭,解释了在有机场致发光中能带模型和分子理论并不矛盾,只是适用的条件不同。激子的离化是随电场强度而渐进的变化,因此会有一个两种过程并存的范围。