Cl2+离子R支跃迁光谱的理论研究

从双原子分子能级的物理表达式出发进行多次微分,建立了预测双原子分子体系R支高振转跃迁谱线的新解析公式. 使用新解析公式预测双原子体系R支高阶跃迁谱线的数据时,最多只需15条精确的实验跃迁谱线和该跃迁带中对应的上下 振动态的转动光谱常数B′_v 和 B″_v.将该解析公式用于预测Cl₂⁺ 离子 A²∏_u---X²∏_g跃迁系(3,7)带和(4,8)带的跃迁谱线,不仅精确的重复了实验给出的较低阶的跃迁光谱数据值, 而且正确预言了所研究体系中缺失的振转跃迁谱线,尤其是高阶的跃迁谱线数据.     

中能重离子碰撞中的各向异性流标度

用同位旋相关的量子分子动力学(IQMD)模型, 研究了25MeV/A的⁸⁶Kr+¹²⁴Sn碰撞系统在较大碰撞参数下的轻碎片的各向异性流(v₂和v₄), 发现横向动量依赖的椭圆流(v₂)存在对轻碎片核子数的标度律(number-of-nucleon scaling)现象, 以及不同轻碎片的v₄/v₂²比值都近似等于一个常数0.5. 这种标度律现象可以用核子层次碎片形成的组合(coalescence)模型来解释.     

大变形核中对力对内部激发的影响

本文提出了一个处理原子核中nn及pp对力的近似方法。这个方法避免了通常将BCS-Боголюбов方法应用于原子核所引起的困难,例如粒子数不守恒,假态的出现以及不同激发态波函数不正交等。但这个方法只有在所需考虑的粒子数n及能级数Ω不太大时(n≤10,Ω≤10)才能较方便地被应用,近似程度才比较好。在这个方法中,毋须引入准粒子的概念,激发的多体性质被明显地表示出来。系统的激发可分为两大类型。第一类型激发是一种以多体系为背景的单粒子跃迁,相应于一个准粒子的跃迁α_v⁺α_v,或两个准粒子的激发α_v⁺β_v′⁺,α_v⁺α_v′⁺(v≠v′)。第二类型激发是对激发,在这种激发中,各能级上共轭粒子对的填充几率改变了,相应于共轭的准粒子对的激发α_v⁺β_v⁺,α_v⁺β_v⁺α_μ⁺β_μ⁺,….本文还考察了对力在r及β跃迁中的影响。在β跃迁中,对力一般是使跃迁受阻。在r跃迁中,对力的效应随初末态间的相对激发类型不同而异,如相对激发属于第一类型,则跃迁受阻,受阻程度随跃迁的电磁性质不同而有所差别,如相对跃迁属于第二类型,则在无对力作用时跃迁是禁戒的,在对力作用下也只有由电荷电流所产生的电跃迁是允许的。最后本文以Hf¹⁷⁸为例,应用上述方法,初步分析了对力对偶偶核的内部激发能谱及β衰变的影响。     

激光诱导荧光确定NiB自由基一个新的电子激发态：在19000-22100 cm -1的2II态

Ni针放电产生的Ni原子与B₂H₆反应产生NiB自由基,得到了在19000～22100 cm^-1的激光诱导荧光光谱. 通过对激光诱导荧光激发谱和色散谱的研究,发现了一个新的电子跃迁序列[20.77]²II-X²∑⁺,序列共包括11个振动谱带,光谱分析得到了这个新的电子激发态和基态的跃迁寿命. 在光谱常数和跃迁寿命等数据的基础上,讨论了新发现电子激发态的电子构型.     

关于ψ(3770)的电偶极跃迁

本文采用一种以QCD为基础的势模型,计算了cc态的各种E1跃迁宽度.结果表明相对论修正效应相当重要.所得ψ(2s)→γχ_cJ和χ_cJ→γψ(1S)(J=0,1,2)的跃迁宽度与实验符合,但ψ(3770)→γχ_cJ跃迁宽度要比MarkⅢ实验组的新近结果小2倍左右.改善理论结果的一个可能性是考虑2³S₁—1³D1混合的效应.     

交叉分子束实验研究F+D2(v=1, j=0)反应

本文使用交叉分子束方法研究了氟原子和振动激发态氘分子D₂(v=1, j=0)的反应. 使用受激拉曼抽运的方法制备了振动激发的D₂分子. 实验中未观测到来自于旋轨耦合激发态氟原子F^*(²P_1/2)与振动激发态D₂分子的贡献. 观测到来自于旋轨耦合基态氟原子F(²P_3/2)和振动激发态D₂的反应信号,相应的产物DF分子布居于v''=2,3,4,5振动态上. 与振动基态反应F+D₂(v=1,j=0)相比,振动激发态反应F+D₂(v=1,j=0)生成的DF产物转动分布更“热”. 获得了振动激发反应的四个碰撞能在0.32至2.62 kcal/mol范围内的微分反应截面. 在最低的碰撞能0.32 kcal/mol下,所有振动态的DF产物都以后向散射为主. 随着碰撞能的增加,DF产物的角分布逐渐从后向转移到侧向. 测量了DF(v''=5)产物的前向微分散射截面随碰撞能变化的曲线. 前向散射的DF(v''=5)信号出现于1.0 kcal/mol. 在2.62 kcal/mol碰撞能下DF(v''=5)主要为前向散射.     

He-H2S复合物的六维从头算势能面和束缚态

采用[CCSD(T)]-F12a/aug-cc-pVTZ方法，同时在基组中引入中心键函数(3s3p2d1f1g)构建了He-H$_2$S复合物的高精度六维势能面. 除分子间振动坐标，同时考虑了H₂S分子内的v₁对称伸缩振动Q₁正则模、v₂弯曲振动Q₂正则模和v₃反对称伸缩振动Q₃正则模三种振动模式. 将计算得到的六维势能面在Q₁，Q₂和Q₃方向上分别做积分得到H₂S单体分别处于振动基态、v和v₃激发态下的He-H₂S的三个振动平均势能面. 计算结果表明，每个平均势能面都有一个T形全局极小值、一个平面局部极小值、两个平面内鞍点和一个平面外鞍点. 全局极小值的几何构型位于R=3.46 ?，θ=109.9°和φ=0.0°，势阱深度为35.301 ^-1. 在径向部分采用离散变量表象法和角度部分采用有限基组表象法并结合Lanczos循环算法计算了He-H₂S的振转能级和束缚态. 计算发现He-(para-H₂S)在H₂S的v₂和v₃区域的带心位移分别为0.025 cm^-1和0.031 cm^-1，而He-(ortho-H₂S)的带心位移分别为0.041 cm^-1和0.060 cm^-1，都表现为蓝移.     

硫化钴的激光诱导荧光光谱：一个来自基态的新激发态

采用激光诱导荧光技术在22400～24400 cm^-1研究了超声射流冷却下的硫化钴光谱,获得了一个包含六个振动带的电子跃迁序列,该电子跃迁序列为：[24.00]⁴△_7/2-X⁴△_7/2．新的电子态的电子组态很可能是core[10σ²][4π³][11σ²][1δ³][5π³],该电子态的所有的振动谱带都受到了其他电子态的严重微扰,通过转动分析得到了这些谱带的转动常数,同时也测量了这些谱带的寿命     

钒氧卟啉正负离子的结构畸变与电子-振动耦合的DFT研究

用PBE1PBE方法研究了钒氧卟啉一价阴离子([VOP]^-)、一价阳离子([VOP]⁺)的单态和三重态结构. 结果表明[VOP]^-和[VOP]⁺的最稳定电子态均为三重态,其未配对电子一个占据钒的d_xy轨道,另一个占据卟啉环的π轨道,因此两者均为π-自由基. 中性分子(VOP)的双重态最稳定,其未配对电子占据钒的d_xy轨道. 双重态VOP具有较高的C_4v对称性,而三重态[VOP]^- 离子由于发生姜-泰勒效应对称性降低为C_2v. 计算了[VOP]^-姜-泰勒活性振动模式的电子-振动耦合常数,并用前线KS轨道的节面分布解释了姜-泰勒畸变沿特定简正模式发生的原因. 三重态[VOP]⁺ 阳离子的卟啉环发生键长交替变化,构型畸变起源于电子态近简并引起的赝姜-泰勒效应,导致其对称性从C_4v降低为C₄,其结构变化可以用重组的前线KS轨道的节面分布解释.     

用云母弯晶谱仪探测Z箍缩等离子体X射线光谱

 为了研究Z箍缩等离子体辐射的X射线光谱,研制了可用于“阳”加速器上探测宽频谱范围的X射线椭圆弯曲晶体谱仪。该谱仪晶体分析器采用云母材料,椭圆焦距为1 350 mm,离心率为0.948 5,覆盖布拉格范围为30°~60°,可探测X射线波长范围为0.10~1.73 nm(0.86~1.00 nm除外),用X射线胶片接收光谱信号。探测实验在中国工程物理研究院“阳”加速器上进行,实验结果表明:谱仪获取了氩的类氢共振线L_ya及其伴线、类氦共振线(1s2p¹P₁-1s2¹S₀)w线及磁四级M₂2跃迁(1s2p³P₂-1s²¹S₀)x线、互组合跃迁(1s2p³P₁-1s²¹S­₀)y线、禁戒谱线(1s2p³S₁-1s²¹S₀)z线和K­_-a线,谱线分辨率达到564。实验证明弯晶谱仪适合于Z箍缩等离子体X射线光谱学诊断。     

晶体压致非晶化的拉曼散射研究

本文主要介绍压致非晶化研究的进展，其中包括我们对β—ＢａＢ＿２Ｏ＿４，ＬｉＢ＿３Ｏ＿５，Ｐｂ＿５Ｇｅ＿３Ｏ＿１１和Ｌｉ＿２Ｇｅ＿７Ｏ＿（１５）的拉曼散射研究结果。综述了压致非晶的结构特征，压致非晶转变机制和重新晶化过程。     

Volume changes of castor oil during its transformation to the high pressure phase

Abstract

Time dependencies p(t)_V,T, nd V(t),_P,T, at room temperature as castor oil phase transition indicators were investigated. The time after which the transition takes place, within the pressure range from 0.36 up to 1.05 GPa, strongly depends on pressure. Its minimum, at about 0.6 GPa is equal to 15 hours. Under the same conditions of experiment the largest change in volume (about ?2%) was detected. The relative changes of volume on pressure for the normal state of castor oil and for its new high pressure state have been found to be approximately the same. A large hysteresis of volume changes after the phase transition has also been observed.     

一种基于偏振态检测技术的单模光纤应力双折射测量法

针对光纤应力双折射理论与实际应用存在的差异,提出了一种简单而实用的基于偏振态检测技术的光纤应力双折射测量的方案,并用实验结果证明了其有效性.     

可调谐激光晶体GSGG∶Cr3+在低温下光谱压致移位的理论研究

采用单组态坐标模型,应用由对角化d3能量矩阵而获得的波函数,同时考虑了自旋-轨道相互作用和电-声子耦合,并定量计入了4T2与2T1各电子态对R线的影响以及局域压缩率和整体压缩率之间的差异,从微观的角度,研究了GSGG∶Cr3+低温下光谱结构的特点以及压力导致的R1线和4T2宽带的移位.理论计算的结果与实验符合较好,R线的常压位置及其分裂、R1线的压致移位及其"反转"现象和4T2宽带的压致移位都得到了合理的解释.     

Curvature sensor based on a pressure-induced birefringence single mode fiber loop mirror

An optical fiber curvature sensor based on a pressure-induced birefringence singlemode fiber loop mirror is presented. The birefringer SMF is made by applying a transverse force against a short length of singlemode fiber. The length of the sensing element for the curvature sensing is about 150 mm. The sensitivity of the curvature measurement experimentally is 0.0263 m⁻¹/pm. And the temperature effect of the proposed sensor is also analyzed. Comparing with the sensor of photonic crystal fiber, it is more convenient and simply.     

Comparative Study on Pressure-Induced Structural Changes between C 6 O 2 I 4 and C 6 I 6

We have investigated the pressure effects on the structural properties of C 6 O 2 I 4 up to 39 GPa by powder x-ray diffraction measurements, which were compared with those of C 6 I 6 . The diffraction patterns of C 6 O 2 I 4 indicated a phase transition starting at 26.8 GPa. The mixed state of the low- and high-pressure phases continued up to 39 GPa well above an insulator-to-metal transition pressure of 33 GPa. The C 6 O 2 I 4 molecule remains planar structure in the low-pressure phase below 26.8 GPa in contrast to the non-planar molecular structure of C 6 I 6 at ambient and high pressures.     

锗酸盐晶体压致非晶化的研究

高压拉曼散射研究表明．ＣｕＧｅＯ３，Ｌｉ２ＧｅＯ３和Ｌｉ６Ｇｅ２Ｏ７三种晶体分别在７，１２和１１ＧＰａ压力下转变为非晶。在高于起始转变压力以上一定范围压致非晶是可逆的，ＣｕＧｅＯ３，Ｌｉ２ＧｅＯ３和Ｌｉ６Ｇｅ２Ｏ７压致非晶的不可逆转变压力分别为１４．１，２０和２０ＧＰａ。压致非晶ＣｕＧｅＯ３的重新晶化温度在６００℃附近。锗酸及系列晶体的压致非晶化与它们的成份和结构有关，随着在这一系列晶体中Ｌｉ２Ｏ含量的增加，压致非晶化的压力趋于减小。     

Structural studies of AgSbTe2 under pressure: Experimental and theoretical analyses

The crystal structure of AgSbTe₂ has been refined using first-principles calculations, from which the ordering of the cations, Ag and Sb, was confirmed. The spontaneous formation of two (D4 and L1₁) phases at ambient and elevated pressure was demonstrated theoretically. The compound was also prepared and its high-pressure structural deformation sequence, ranging from ambient to 50.9 GPa, was observed with synchrotron radiation at room temperature. The compound underwent a pressure-induced amorphization (PIA) at 24.6 GPa and then started recrystallizing at 49.2 GPa. The bulk modulus (B₀) and pressure derivative of the bulk modulus (B_p) were determined experimentally to be 56.3 ± 5.1 GPa and 4.3 ± 0.8, respectively. We suggest that large displacements of Te atoms to Ag vacancy positions are responsible for PIA and the recrystallization.     

Cooling by adiabatic (DE)pressurization - the barocaloric effect

Abstract

The barocaloric effect reflects a new cooling principle at low temperatures without the need of liquefied gases nor magnetic fields as used in other cooling techniques. A pressure induced structural and/or magnetic phase transition is used to obtain a significant change in the system's entropy which leads to its cooling if done adiabatically. The effect is illustrated for the two rare earth compounds Pr₁ ? _xLa_xNio₃ and Ce_x(La,Y)₁ ? _xSb using a structural and a magnetic phase transition, respectively. In situ experiments on Ce_x(La,Y)₁?_xSb are presented and reveal a cooling rate of up to 2 K per 0·5 GPa pressure change at working temperatures below 20 K for x=1 and up to 0·42 K per 0·24 GPa for x=0·85 at around 10K.     

Symmetry systematics of pressure—induced phase transitions

Abstract

Most pressure induced phase transitions are diffusionless. Because of this, there exists a one-to-one correspondence between the positions of atoms in the parent and the product phases, which, therefore, show interesting symmetry relationships. In this paper, we have used these for discussing a symmetry classification of pressure induced phase transitions into four categories: iso-symmetric, group-subgroup, intersection group, and order-disorder transitions. Various examples illustrating this classification scheme are discussed. The importance of this classification is in understanding the mechanism of pressure indbced phase transitions, where both theoretical calculations and experimental measurements are employed to analyse related phenomena like softening of phonon modes, elastic instabilities, diffraction patterns, and orientation relations.