氢原子谱线与高质量金刚石薄膜

采用蒙特卡罗方法,对以CH₄/H₂混合气体为源气体的电子助进热丝化学气相沉积(EACVD)中的氢原子发射过程进行了模拟。在模拟中考虑了电子与H₂的弹性碰撞及振动激发、分解、电子激发(包括H_α, H_β, H_γ谱线的激发)、电离及分解电离等非弹性碰撞过程;与CH₄的碰撞考虑了弹性动量传输及振动激发、分解、电子激发、分解激发(包括H_α, H_β, H_γ谱线的激发)、电离及分解电离等非弹性碰撞过程。研究了不同实验条件下产生的H, CH₃的数目与氢原子谱线相对强度的关系,给出了一种利用氢原子谱线来获得最佳成膜实验条件的方法。对于有效控制工艺条件,生长出高质量的金刚石薄膜具有重要意义。     

EACVD中的Hα谱线与最佳生长条件

采用蒙特卡罗方法,模拟了CH4/H2混合气体为源气体的EACVD中的氢原子发射过程。考虑了电子与H2的弹性碰撞及振动激发、分解、电子激发、相应于Hα,Hβ,Hγ谱线的激发、电离及分解电离等非弹性碰撞过程;与CH4的碰撞考虑了弹性动量传输及振动激发、分解、电子激发、电离及分解电离等非弹性碰撞过程。研究了不同实验条件下产生的H,CH3的数目与Hδ谱线强度的关系,给出了一种通过Hα谱线来推断生长金刚石薄膜的最佳实验条件的方法。     

氢原子谱线测定EACVD中电子平均温度

采用蒙特卡罗方法,对以CH₄/H₂混合气体为原料气体的EACVD中氢原子的发射过程进行了模拟。在模拟中考虑了电子与H₂的弹性碰撞及振动激发、分解、电子激发、相应于H_α, H_β, H_γ谱线的激发、电离及分解电离等非弹性碰撞过程;与CH₄的碰撞考虑了弹性动量传输及振动激发、分解、电子激发、电离及分解电离等非弹性碰撞过程。研究了不同CH₄浓度下基片表面上电子平均温度与氢原子谱线相对强度的关系,给出了一种对EACVD中电子平均温度进行实时监测的方法。对于有效控制工艺条件,生长出高质量的金刚石薄膜具有重要意义。     

Comparative Study on Excitation Mechanism of Chromium Emission Lines in Argon Radio‐Frequency Inductively‐Coupled Plasma,Nitrogen Microwave Induced Plasma,and Argon or Nitrogen Glow Discharge Plasmas

Boltzmann plots of both atomic and ionic chromium emission lines are investigated to compare the excitation mechanisms in four different plasmas: an argon inductively‐coupled plasma (Ar‐ICP), a nitrogen high‐power microwave induced plasma (N₂‐MIP), an argon glow discharge plasma (Ar‐GDP), and a nitrogen glow discharge plasma (N₂‐GDP). The plots of the atomic lines and the ionic lines give both linear relationships as well as similar excitation temperatures in the case of the Ar‐ICP, the N₂‐MIP, and the N₂‐GDP. It implies that a thermodynamic process such as electron collision would control their excitations. However, only in the case of the ionic‐line plot in the Ar‐GDP, a departure from linear relationship is observed and the estimated excitation temperature is rather higher than that with the atomic lines, meaning that a specific excitation mechanism exists in the Ar‐GDP. A possible explanation for these results is that a charge‐transfer collision between chromium atom and argon ion plays a dominant role in exciting highly‐lying energy levels of chromium ion, especially in the Ar‐GDP.     

Atomic excitation by a simultaneous collision with another atom and with a photon

A new mechanism of atomic excitation is considered, a simultaneous collision with another atom and with a photon. The atomic excitation cross section is calculated. It is shown that for experimentally aehieveable electromagnetic field intensities and for other real parameter values the cross section is comparable to that of atomic excitation by electron impact.Presented in the V All-Union Conference in nonlinear optics and at the XVI scientific conference of the Moscow Physicotechnical Institute, November, 1970.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 66–71, September, 1972.     

Conditions for the indistinguishability of thermal equilibrium and single atomic collision relative level populations

Single atomic collision and thermodynamic equilibrium level populations are compared. The population distributions for relatively cascade free levels with similar lifetimes are shown to be easily described by a Boltzmann relation even if the excitation mechanism is non-thermal.     

Collision operator for relativistic electrons in a cold gas of atomic particles

The collision operator of relativistic electrons with a cold gas of atomic particles is derived consistently taking into account elastic interactions, excitation of electron shells, and ionization. The creation of secondary electrons is described accurately. In the range of energies exceeding the binding energy of atomic electrons, the operator implicates only the angular scattering by nuclei and the ionization integral that automatically allows for scattering by atomic electrons. The collision operator used earlier for studying the kinetics of avalanches of relativistic runaway electrons is analyzed. A more exact operator derived in the present study is simpler in form and saves time in computer calculations.     

Two-photon coherent control of atomic collisions by light with entangled polarization

We describe a new method of coherent optical control of internal dynamics of atomic collisions by means of two correlated light beams having entangled polarizations. We show that, if excitation of a colliding pair of atoms is by two photons having entangled polarizations, it is possible to redirect the output fragments of the collision into certain channels with a selected type of internal transition symmetry. The transition symmetry is defined in the body-fixed coordinate frame which has random and originally unknown orientation in space.     

NaK分子激发态的预离解和碰撞激发转移

用Ar+激光器固定频率488.0nm线激发Na-K混合蒸汽,NaK分子激发态通过自发辐射、预离解和与基态原子的碰撞激发转移而去布居,测量在不同K原子密度下原子荧光对分子荧光的强度比,结合NaK(E)态寿命,得到了预离解率和碰撞激发转移率.     

A comparison of gas-phase,plasma, sputtering and beam-foil excitations

A comparison of relative populations of ZnI and ZnII levels excited in equilibrium plasma, sputtering, gas-phase single collision, and beam foil sources is presented, and includes data on the first reported excitation studies under single collision conditions for a (transition metal atom)-(transition metal ion) interaction. A search for continuum emission from atomic chromium, like that seen during sputtering of chromium metal, produced a negative result.     

Study of the 2p 1/2 σ excitation probability in collision systems withZ 1+Z 2>150 using line width analysis

The 90°-line width ofK x-ray lines induced in heavy ion collisions is mainly determined by the kinematical broadening. Its conversion into mean impact parameters together with total excitation cross section allows to obtain mean excitation probabilities. Within the energy range (1.4–5.9) MeV/u mean excitation probabilities for 2p _1/2 σ-excitation are deduced. Collision systems in theZ-range (150–180) are investigated. A very poor agreement between experiment and theoretical predictions has been found. The excitation probabilities are larger than predicted and are nearly independent of the atomic numberZ of the united atom. The collision energy dependence is much weaker than predicted. Even a decrease of the mean excitation probabilities at high collision energies has been found.     

蒙特卡罗模拟四极阱中原子的参变激发

在中性原子的磁囚禁实验中,磁阱线圈的电流噪声会激发磁阱中的原子运动,势必对原子团的温度和寿命产生不可忽视的影响。对于非简谐阱,这种激发具有能量选择特性,它又取决于电流噪声的频谱分布。选择了实验中常用的四极阱为研究对象,用直接模拟蒙特卡罗方法来模拟四极阱中原子运动的参变激发现象,得到了原子温度与原子数损失随激发频率的变化关系,并进一步计算了两个共振峰处原子温度随调制时间和调制深度的变化曲线。此外,还研究了弹性碰撞速率对参变激发过程中原子温度上升的影响。这些结果对四极阱参变激发的实验有较好的参考价值。     

紫外激光烧蚀Cu产生等离子体辐射特性

通过时间分辨的光谱测量技术,测定了308 nm XeCl紫外激光烧蚀金属Cu在氮气环境中诱导产生等离子体的发射光谱及其强度随时间分布,实验结果表明等离子体辐射光谱线主要由原子光谱线、一价离子光谱线及连续辐射背景光组成,各种光谱线的数目、辐射强度、持续时间不同。结合实验结果对等离子辐射机理进行了探讨,认为电子通过逆韧致辐射获得较高的能量,连续辐射主要来自高能电子的韧致辐射,原子和一价离子的激发主要是通过电子与原子、离子的碰撞传能以及电子与离子的复合产生,并用其定性地解释了所观察的实验现象。     

Predicting secondary ion formation in molecular dynamics simulations of sputtering

We present a model to incorporate the excitation and ionization of sputtered particles into molecular dynamics simulations of ion bombardment-induced collision cascades in metals. The kinetic excitation of the solid is described by electronic friction experienced by all moving particles and electron promotion in close atomic collisions. Transport of the resulting excitation energy is treated by a nonlinear diffusion equation. The resulting space- and time-dependent electron temperature is then introduced into a rate equation model describing the ionization of ejected particles. This way, secondary ion formation is described by assigning an individual ionization probability to every sputtered atom. Averaging over the entire flux, this allows the prediction of measurable quantities like integral or spectral ionization probabilities as well as velocity spectra of secondary ions.     

激光烧蚀铜产生原子和离子光谱线的研究

通过测定Nd∶YAG脉冲激光烧蚀金属Cu诱导产生光谱线及其强度随时间与空间的分布,结果表明等离子体辐射光谱线由原子光谱线、离子光谱线及连续辐射背景光组成,Cu原子光谱线的数目不仅比离子光谱线多,而且辐射强度比离子光谱线的大,以连续辐射背景光的辐射强度为最弱;原子光谱线的发光范围最大,持续时间最长;离子光谱线发光范围中等,持续时间中长;连续辐射背景光的发光范围最小,持续时间最短.讨论了激光诱导发光的机理,认为等离子体羽中连续辐射背景光主要来自近靶处高能电子的韧致辐射和电子与离子的复合激发,原子和离子光谱线主要由等离子体中高能电子的碰撞传能激发所引起,并用之较好地解释了所观察的实验现象.     

On excitation and loss of an electron by incident ions in relativistic collisions with atoms

The excitation and loss of an electron by ions in relativistic collisions with atoms are studied in first-order perturbation theory. General expressions are obtained for the cross sections for the excitation and loss of an electron. In the limit of nonrelativistic collision velocities these expressions pass into the well-known nonrelativistic results. It is shown that, in contradistinction to the nonrelativistic collisions, in ultrarelativistic collisions the screening of the nucleus of the target atom by the atomic electrons is very important for excitation and loss of an electron by ions even for collisions of heavy ions with light atoms. Our computational results for the cross section for electron loss are in good agreement with existing experimental data.     

Atmospheric interaction radiation from high altitude rocket exhausts

A model for calculating the infrared radiation from rocket exhaust gases at high altitudes (typically above 200 km), caused by collisions between exhaust molecular species and atmospheric species is presented. At altitudes where the atmospheric mean free path is larger than a typical rocket exhaust plume lenght scale, the evolution in space and time of the exhaust gases is described by the kinetic theory of gases. In addition, the collision frequency between exhaust and atmospheric species is sufficiently low that excited molecules have time, on the average, to loose thsis excitation energy via radiative emission before experiencing another collision. Thus, the distribution of excited molecular states is nonthermal in this model. Two examples of such radiation are presented: one for the radiation from the CO₂ (υ₃) mode and the other for the H₂O(υ₃) mode. The atmospheric collision partner for excitation of both of these exhaust species is taken to be atomic oxygen, the dominant atmospheric constituent at high altitudes.     

高能离子原子碰撞

本文在Born一阶近似下,建立了一种能够方便计算各种过程的高能原子(或离子)碰撞截面的理论计算方法。对各种碰撞过程,进行了详细的理论分析,并对已有实验结果的H⁺,e,H,H^-四种入射粒子与Na(3s→3p)的碰撞激发过程进行了理论计算。与实验结果的比较是令人满意的。 关键词：