电子与类锂离子碰撞激发截面和速率系数

用自编的扭曲波程序ＡＣＤＷ（９）和拟合程序ＦＩＴ（９），计算了一系列类锂离子的碰撞激发过程．找出了约化碰撞强度Ω_ｒｅｄ是约化电子能量ε_ｒｅｄ的慢变函数，约化速率系数因子γ_ｒｅｄ是约化电子温度Ｔ_ｒｅｄ的慢变函数．对某种离子的一个激发过程，可用１０个参数描述，由这１０个参数可以得到任意电子能量下的碰撞强度和激发截面，以及任意温度下的速率系数 关键词：     

C2H221分子转动角动量定向分布(Orientation)及其碰撞弛豫和转移

利用圆偏振激光受激Raman抽运,以 C₂H₂分子为样品选择性地制备了它的电子基态单一转动态(X¹Σ⁺_g,ν″₂＝1,J″的角动量定向布居(orientation)．并从圆偏振紫外激光诱导的A¹A_u(ν′₃＝1)←X¹Σ⁺_g(ν″₂＝1)的荧光（谱）,直接测定了 C₂H₂(X¹Σ^＋_g,ν″₂＝1,J″＝4,7,8,…,13）的角动量定向布居值．从时间分辨的荧光信号谱测定了角动量定向布居的碰撞弛豫速率常数,同时还研究了由各初始激励的转动态向其他邻近转动态碰撞诱导的角动量定向布居转移． 关键词：     

激发态铯原子间的碰撞能量转移

用激光抽运基态Cs₂分子,通过预离解或碰撞转移,由一部分的激发态Cs₂产生Cs原子6P,5D激发态。测量了Cs(5D)+Cs(6P)→Cs(7D_J)+Cs(6S)碰撞激发能量转移截面σ_(7DJ),以及Cs(7D_J)+Cs(6S)→除Cs(7D)外的态的截面σ_tr。结果是,对于J=5/2,3/2,σ_(7DJ)(以 关键词：     

激光诱导荧光法研究CH2Cl2分子的振动能量转移

本文中用激光诱导荧光法首次研究了有机分子CH₂Cl₂分子的振动能量转移。实验测得了CH₂Cl₂分子的ν₃和ν₃/ν₉振动模的激活和消激活速率常数,以及稀有气体分子对CH₂Cl₂分子的ν₃/ν₉振动模消激活的影响。用SSH理论计算了CH₂Cl₂-稀有气体碰撞,CH₂Cl₂分子ν₃/ν₉的V-T能量转移相对几率,分析讨论了CH₂Cl₂分子的振动能量转移的通道。 关键词：     

反散射理论应用于e-H2O碰撞

运用反散射方法研究了ｅ－Ｈ₂Ｏ碰撞。从ｅ－Ｈ₂Ｏ弹性散射微分截面的实验数据出发，运用反散射方法，ｅ－Ｈ₂Ｏ相互作用的球平均势已被导出，它是复数的，而且含有非定域的成分。所得的势能给出非常符合实验数据的结果。 关键词：     

激发态钠原子间的碰撞能量合并

对钠蒸气中的碰撞能量合并过程Na(3P_J)+Na(3P_J′)→Na(nL_J″)+Na(3S_1/2)进行了实验研究．在低钠原子密度条件下，用激光将原子分别激发到3P_1/2或3P_3/2态，测量从nL_J″态发出的荧光强度比和Na(3P_3/2)与Na(3P_1/2)的密度比，给出了J′=J=1/2或3/2，nL_J″=4D_3/2，4D_5/2,4F_5/2，4F_7/2，5S_1/2的速率系数对打的比值、当销原子密度足够高时，3P态以统计比率布居，得到了k_(nLJ″)(1/2,3/2)对k_5S(3/2,3/2)的比值． 关键词：     

推广Bethe公式：Au50+离子的偶极激发的碰撞强度和速率系数

快速算法结合推广的Bethe公式,可以为应用研究提供便于使用的偶极激发碰撞强度和速率系数.用准相对论平面波Born(QRPB)近似计算高能区Au⁵⁰⁺离子n₀l₀→nl偶极激发的碰撞强度,给出Bethe公式中动量转移截断参数k₀,从而确定激发过程的高能行为.快速计算方法中采用了Cowan所发展的准相对论方法,用统一的Hartree-Fock-Slater势计算束缚和连续态电子波函数.用准相对论扭曲波(QRDW)近似计算阈值附近的碰撞强度并外推阈值处的碰撞强度Ω₀,然后拟合到高能碰撞强度上.对于特殊情况还需增加三倍阈值点a的计算,用三个参数Ω₀,Ω_a和k₀拟合出全能域(出射电子能量ε_b=0—∞)的碰撞强度.由此可以得到全部温度范围(电子温度T_e=0—∞)的速率系数<σv>.这样得到的Ω和<σv>,在相应的感兴趣的能量和温度范围内有合理的精度. 关键词：     

He-H2(D2,T2)碰撞体系振转相互作用势及分波截面的理论计算

采用超分子单双迭代(包括非迭代三重激发)耦合簇理论CCSD(T)方法,选择由原子中心高斯函数和高斯键函数3s3p2d1f组成的大基组,计算了He-H₂(D₂,T₂)碰撞体系的H₂分子取不同键长时的相互作用势能面.运用Tang-Toennies势模型和非线性最小二乘法拟合构造了He与同位素分子H₂(D₂,T₂)在质心坐标系下的振转相互作用势.通过密耦计算得 关键词： 高斯键函数 Tang-Toennies势函数 分波截面 碰撞参数     

电子与类铍N3+和O4+离子碰撞激发截面的相对论扭曲波计算

采用全相对论扭曲波方法,系统地计算了类铍N³⁺和 O⁴⁺离子从基态到2s2p和2p² 的各激发态以及从亚稳态到2p²各激发态的电子碰撞激发截面,详细地讨论了靶态的关联效应对激发截面的影响.结果表明：对于2s-2p的单电子激发,在低能碰撞时,靶态的电子关联效应起非常重要的作用,且使得激发截面降低;而高能碰撞时,靶态波函数的描述对连续态波函数的影响比较小,对激发截面影响也比较小.对于2s²-2p²的双电子激发,其中基态2s²¹S₀到J=0的2p²³P₀,¹S₀的激发截面较大,其主要原因是末离子态波函数与基组态波函数的混合,但是其他几个激发的激发截面较小. 关键词： 全相对论扭曲波方法 电子碰撞激发 电子关联效应     

Raman紫外双共振研究C2H2分子的碰撞转动弛豫

本文利用受激Raman抽运,选择性地制备了C₂H₂分子电子基态的红外非激活振动能级的单一转动态(X¹∑_g⁺,v″₂=1,J″=9,11,13),并从紫外激光诱导的A¹Au(v′₃=1)←X¹∑_g⁺(v″₂=1)荧光谱,直接测定上述三个转动态的C< 关键词：     

超高泵浦功率下的Xe(6p[1/2]0, 6p[3/2]2, 和6p[5/2]2)原子的能量转移过程

本文研究了Xe(6p[1/2]₀, 6p[3/2]₂, and 6p[5/2]₂)原子在聚焦条件下的动力学过程. 激发能级的原子密度在聚焦条件下会显著地增加,因此两个高激发态原子之间的energy-pooling碰撞的概率也会增加. 这种energy-pooling碰撞主要有三种类型. 第一种类型为energy-pooling碰撞导致的电离. 一旦将激发激光聚焦,就可以从侧面的窗口观察到非常明显的电离现象,不论激发能级是6p[1/2]₀、6p[3/2]₂或6p[5/2]₂能级. 这种电离的产生机理是energy-pooling电离或者一个Xe^*原子再吸收一个光子产生电离. 第二种类型为跨越较大能极差的energy-pooling碰撞. 当激发能级为6p[1/2]₀能级的情况下,两个6p[1/2]₀原子碰撞会产生一个5d[3/2]₁原子和一个6s''[1/2]₀原子. 第三种类型为跨越较小能级差的energy-pooling碰撞. 以5个二次产生的6p能级为上能级的荧光强度都变得更强,并且这些荧光的上升沿都变得更陡峭. 产生这些6p原子的主要机理是energy-pooling碰撞并非简单的碰撞弛豫. 基于理想气体原子之间的碰撞概率公式,推导出两个6p[1/2]₀原子的energy-pooling碰撞速率为6.39x10⁸s^-1. 此外,6s原子在聚焦条件下的密度也会增加. 因此所有的荧光曲线会因为辐射俘获效应而出现非常严重的拖尾.     

Quenching of SO2 phosphorescence by a magnetic field

Phosphorescence excitation spectra of the ã³B₁← [Xtilde]¹A₁ transition of SO₂ were measured in the absence and presence of a magnetic field (B = 0?44 T², P(SO₂) = 0?7 Torr). The absorption and phosphorescence excitation spectra of the ã³B₁← [Xtilde]¹A₁ transition of SO₂ measured in the absence of a magnetic field show that the relative intensity of the bands of the phosphorescence excitation spectrum is smaller than the relative intensity of the corresponding bands of the absorption spectrum beginning with the (0, 2, 0) band. In the presence of a magnetic field, the intensity of the phosphorescence excitation band falls, for ν_exc> 26400 cm^-1. Under the direct excitation of the ã³B₁← [Xtilde]¹A₁ transition, the dependence of the magnetic quenching of the SO₂ phosphorescence on the excitation frequency (ν_exc) was studied at P(SO₂) = 0?7 Torr and B = 0?44 T. The dependence of the magnetic field effect on ν_excshows that only the vibrationally excited levels of the ã³B₁ state are sensitive to an external magnetic field. The magnetic field strength and the pressure dependence of the magnetic field effects were studied under indirect excitation of the ã³B₁← [Xtilde]¹A₁ transition at λ_exc = 308 nm. The magnetic field and the pressure dependence were investigated for pure SO₂ and for SO₂ + RH (RH n-C₅H₁₂) mixtures. It was found that the magnetic field effect was saturated at B ? 0?25 T. The saturation value (Gr = l(0?3 T)/l(0)) increases with increasing gas pressure. The magnetic field, the pressure and the excess vibrational energy (ν_excess) dependence of the magnetic quenching of SO2 phosphorescence show that the data observed can be explained by an indirect mechanism within the framework of a low level density approximation.     

High magnetic field properties of mixed terbium-yttrium ferrite garnets

Magnetization measurements in d.c. magnetic fields up to 180 kOe have been performed on polycrystalline specimens and on single crystals of mixed terbium-yttrium iron garnets: Tb _x Y_3–x Fe₅O₁₂ in the 4.2–300 K temperature range. On polycrystals (x=2.5; 2; 1; 0.37) the concentration dependence of both compensation point and spontaneous magnetization has been determined. In the single crystals (x=2; 1; 0.37) a strong magnetic anisotropy has been observed with a change of the easy direction of magnetization from [111] to [100] whenx decreases; abrupt field-induced transitions have been observed at low temperatures when the external field is applied along the [100] direction.     

Mössbauer spectra on [Fe(H2O)6]K2(SO4)2 exhibit slow electronic relaxation

Mössbauer spectra on single crystals of [Fe(H₂O)₆]K₂(SO₄)₂ in fields from 1.5 T to 5 T at temperatures from 4.2 K to 20 K show considerable line broadenings up to 0.95 mm/s. This broadening strongly depends on the specific line in the spectrum, the temperature, and the strength and direction of the external field. It is shown that these phenomena are due to electronic relaxation rates that are some-what slower (≈10^?8 s) than the fast relaxation limit.     

激光诱导荧光能级寿命检测中磁场的干扰

在孔阴极放电激光诱导荧光氩原子Ａｒ１５ｐ［３／２］２能级寿命检测中，当加强外碰场于其观察方向，被测能级寿命随磁场强度的增加而缩短。其自然能级寿命被确定为１２０ｎｓ。     

On the magnetic anisotropy of chromium

Magnetization and susceptibility measurements have been performed on a single crystal of chromium for field orientations parallel to the symmetry directions [100], [110] and [111] of the cubic unit cell. Particular emphasis is given to the weak temperature-orientation-and field-dependent contributions to the longitudinal (field parallel) susceptibility. For the high-temperature antiferromagnetic phase with transversally polarized spin-density wave (TSDW) the magnetic easy direction is along [100] and the magnetic hard one along [110]. In the low-temperature phase with longitudinal spin density waves (LSDW) the significance of these directions has reversed. The magnetization is not strictly a linear function of the field and shows a weak minimum atB ₀1.8 T in the TSDW phase. This minimum does shift discontinuously at the spin-flip transition (T _sf=132 K) to a value of 4.6 T in the LSDW phase. TheJ/B ₀-minimum is considered as due to the field induced change from the orientationally degenerated multidomain state into a state with only polarization directions perpendicular to the magnetic field.On leave from Academy of Mining and Metallurgy, Department of Solid State Physics, PL-30-059 Krakow, Poland     

Ni54Fe19Ga27单晶的形状记忆和超弹性

本文研究了单晶Ni₅₄Fe₁₉Ga₂₇不同方向的形状记忆效应、超弹性和磁性. 研究发现,单晶样品具有良好的双向形状记忆效应.不同晶体学方向的相变应变随着热循环次数的变化而改变. 在外应力作用下,通过应力诱发马氏体相变,样品在[001],[110],[111]方向分别产生了3.3%, 2% 和3%的可回复应变平台.磁性测量结果表明马氏体的磁晶各向异性能约为4.8× 10⁵ erg/cm³,远远小于变体孪生所需机械应力能,因此磁场的作用是使磁矩发生转动而不是使孪晶界移动, 成功揭示了不能在NiFeGa中获得大磁感生应变的物理根源.     

Anisotropic and large low-field magnetic entropy change in a La4/3Sr5/3Mn2O7 single crystal

We have studied the magnetocaloric effect (MCE) in a bilayered La_4/3Sr_5/3Mn₂O₇ single crystal with applied field along both ab-plane and c-direction. Due to the quasi-two-dimensional structure, the crystal exhibits a strong anisotropy in the MCE. The difference of magnetic entropy change between two crystallographic directions depends on external magnetic fields and has a maximum of 2 J/kg K. A large low-field magnetic entropy change, reaching 3.2 J/kg K for a magnetic field change of 15 kOe, is observed when the applied field is along ab-plane. This large low-field magnetic entropy change is attributed to the rapid change of magnetization in response to external magnetic fields in the easy magnetizing plane.     

Magnetic ordering in (110) Eu films in an applied magnetic field

Below its ordering temperature (T _N = 90 K), bulk bcc Eu has a helical magnetic state with propagation vectors along the three equivalent 〈100〉 directions. In contrast, epitaxial (110)Eu films exhibit a unique magnetic ordering: the domain with a magnetic helix propagating along the in-plane [001] direction vanishes on cooling, at the expense of other domains with helices propagating along [100] and [010]. This paper is devoted to the study of the stability of the magnetic domains in an external magnetic field using neutron scattering experiments and macroscopic magnetization measurements. The helix propagating along the [001] direction can be restored by the application of an external field along this direction. On the contrary, when a magnetic field is applied along an intermediate direction, specifically [10], the domain with a helix propagating along [001] is suppressed. Both effects depend on the film thickness. They are explained if one considers that, because of the low magnetic anisotropy of Eu, a helix with a propagation vector parallel to (or close to) the applied magnetic field is energetically more favourable than cycloidal structures with unchanged propagation vectors. Finally, the amplitudes of the propagation vectors and their directions (that are modified in films compared to bulk) do not vary under magnetic field.     

Nuclear Spin-Lattice Relaxation of 82BrFe

The field dependence of the nuclear spin-lattice relaxation (SLR) of cold implanted ⁸²Br (T ≤ 25 mK) in α-Fe single crystals was investigated with nuclear magnetic resonance of oriented nuclei (NMR/ON) at low temperatures as experimental technique. The SLR at the lattice sites with the hyperfine fields found by earlier NMR/ON experiments was measured as a function of the applied external magnetic field B _ext parallel to the three principle axes [100], [110] and [111] of the iron single crystal. The data were evaluated with the full relaxation formalism in the single impurity limit and for comparison also with the often employed model of a single exponential function with an effective relaxation time T ₁′. With a phenomenological model the high field values of the relaxation rates r _{∞, [100]′} = 6.6(2) · 10⁻¹⁵ T²sK⁻¹, r _{∞, [110]} = 5.4(2) · 10⁻¹⁵ T²sK⁻¹ and r _{∞, [111]} = 5.2(1) · 10⁻¹⁵ T²sK⁻¹ were obtained.