Optimal approach to rotational state reconstruction of linear molecules

We present a simulation for the reconstruction of the rotational quantum state of linear molecules to retrieve the density matrix. An optimal approach in the sense of minimal error limit is proposed, in which a variable set of angular frequency is properly chosen and the least square inversion is then applied. This approach of reconstruction from time-dependent molecular-axis angular distribution is proved adaptable for various object states, which has a good numerical stability independent of the selected rotational space.     

2-溴噻吩和3-溴噻吩在267 nm的C-Br键解离机理

利用离子速度影像技术, 研究了2-溴噻吩和3-溴噻吩两种同分异构体在267 nm激光作用下的C—Br键解离机理, 获得了光解产物Br(2P3/2)和Br*(2P1/2)的能量和角度分布, 分析了两异构分子在267 nm 的C—Br键解离通道. 对于2-溴噻吩和3-溴噻吩, 产物Br来源于三个通道: (i) 从单重激发态系间窜跃到排斥的三重激发态的快速预解离; (ii)单重激发态内转化到高振动基态的热解离; (iii) 母体分子多光子电离后的解离. 2-溴噻吩的产物Br*具有类似的产生机制; 但对于3-溴噻吩, 从激发态内转换到高振动基态发生热解离成为产物Br*的主导通道, 而来自激发三重态的快速预解离通道则几乎消失. 定量地给出了各个通道的相对贡献、能量分配及各向异性分布信息. 实验发现, 随着溴原子在噻吩上取代位置远离硫原子, 来自通道(i)和(ii)产物之间的比例明显减小, 相应的各向异性分布有变弱趋势.     

空气中飞秒激光自聚焦等离子体通道的电导特性

 通过电学探测法,采用不同焦距的聚焦透镜,在不同激光能量、不同极性外加电压的条件下,对大气中的飞秒激光自聚焦等离子体电离通道特性进行了实验研究。发现激光脉冲经不同焦距的聚焦透镜作用后均存在较长的电离通道,通道的等效电阻率有所变化,通常电阻率的最大值出现在透镜的几何焦点附近,并且焦距越长,此电阻率的局部峰值点离几何焦点位置越近。在外加不同极性电压时,自由电子受到所加静电场作用力、洛仑兹力以及有质动力的共同作用。焦点前,通道电流变化不明显,加正向电压产生的电流略微大于加负向电压时的电流;焦点后则是加负向电压产生的电流大于加正向电压时的电流。     

2-溴噻吩和3-溴噻吩在267nm的C—Br键解离机理

利用离子速度影像技术,研究了2-溴噻吩和3-溴噻吩两种同分异构体在267 nm激光作用下的C-Br键解离机理,获得了光解产物Br(2P3/2)和Br*(2p1/2)的能量和角度分布,分析了两异构分子在267 nm的C-Br键解离通道.对于2-溴噻吩和3-溴噻吩,产物Br来源于三个通道:(i)从单重激发态系间窜跃到排斥的三重激发态的快速预解离;(ii)单重激发态内转化到高振动基态的热解离;(iii)母体分子多光子电离后的解离.2-溴噻吩的产物Br*具有类似的产生机制;但对于3-溴噻吩,从激发态内转换到高振动基态发生热解离成为产物Br*的主导通道,而来自激发三重态的快速预解离通道则几乎消失.定量地给出了各个通道的相对贡献、能量分配及各向异性分布信息.实验发现,随着溴原子在噻吩上取代位置远离硫原子,来自通道(i)和(ii)产物之间的比例明显减小,相应的各向异性分布有变弱趋势.     

State reconstruction of molecular spatial rotation

We establish a reconstruction approach for the rotational quantum state of linear molecules possessing a magnetic manifold. Our approximate method contains an iteration with generalized matrix inverses, processing the tomographic integral of the time-dependent molecular-axis distribution in a polar angle. As shown in a simulated example for an alignment state, the density matrix is determined in a high fidelity. An analytic tomographic formula is also derived for the symmetric top rotation. The state coherent in the quantum space of both the angular momentum and its magnetic projection can be approximately retrieved from the observable time-resolved solid-angle distribution of the molecular axis.