Laser-induced quadrupoleben quadrupole collisional energy transfer in Xe-Kr

By considering the relative velocity distribution function and multipole expansion interaction Hamiltonian, a three-state model for calculating the cross section of laser-induced quadrupole-quadrupole collisional energy transfer is presented. Calculated results in Xe-Kr system show that in the present system, the laser-induced collision process occurs for ~4 ps, which is much shorter than the dipole-dipole laser-induced collisional energy transfer (LICET) process. The spectrum of laser-induced quadrupole-quadrupole collisional energy transfer in Xe-Kr system has wider tunable range in an order of magnitude than the dipole-dipole LICET spectra. The peak cross section decreases and moves to the quasi-static wing with increasing temperature and the full width at half peak of the profile becomes larger as the system temperature increases.     

Structural Deformation of CO22+ in Intense Femtosecond Laser Fields

The angular distributions of CO^＋ from the dissociation of CO2^2＋ and CO2^＋ in intense femtosecond laser fields （45 fs, about 5 × 10^15 W/cm^2） are studied at a laser wavelength of 800nm based on the time-of-flight mass spectra of CO^＋ fragment ions. The experimental results show that structural deformation occurs in the charge state of CO2^2＋ and the CO^＋ maintains linear geometrical structure.     

Xe-Kr laser induced collisional ionization system and experimental preparation of its initial state: Four-photon resonant excitation

This paper proposes a novel one-colour Xe-Kr laser induced collisional ionization system. Considering the level scheme of the system, it finds that the initial state of the reaction--the four 4f levels with even J of Xe-can be prepared through method of four-photon resonant excitation by dye laser with wavelength of -440 nm. Absorption of an additional photon （the transfer laser） of the same wavelength will complete the laser induced collisional ionization process. The resonance enhanced ionization spectrum of Xe by four laser photons at -440nm is measured through time-of-flight mass spectrometry, this aims at the preparation of the initial state of the system proposed. The Stark broadening of the measured spectrum is observed and consistent with the previous study. Analysis of the measured resonance ionization spectrum implies the feasibility of -440 nm four-photon resonant excitation of the initial 4f state of the Xe Kr system proposed in this paper, which prepares for a further experiment of laser induced collisional ionization.     

Laser-induced quadrupole-quadrupole collisional energy transfer in Xe-Kr

By considering the relative velocity distribution function and multipole expansion interaction Hamiltonian, a three-state model for calculating the cross section of laser-induced quadrupole-quadrupole collisional energy transfer is presented. Calculated results in Xe-Kr system show that in the present system, the laser-induced collision process occurs for ～4 ps, which is much shorter than the dipole-dipole laser-induced collisional energy transfer (LICET) process. The spectrum of laser-induced quadrupole-quadrupole collisional energy transfer in Xe-Kr system has wider tunable range in an order of magnitude than the dipole-dipole LICET spectra. The peak cross section decreases and moves to the quasi-static wing with increasing temperature and the full width at half peak of the profile becomes larger as the system temperature increases.     

Laser induced collisional energy transfer in Sr—Li system

A four-state model considering the relative velocity distribution function for calculating the cross section of laserinduced collisional energy transfer in a Sr-Li system is presented and profiles of laser-induced collision cross section are obtained.The resulting spectra obtained from different intermediate states are strongly asymmetrical in an opposite asymmetry.Both of the two intermediate states have contributions to the final state,and none of the intermediate states should be neglected.The peak of the laser-induced collisional energy transfer(LICET) profile shifts toward the red and the FWHM becomes narrower obviously with laser field intensity increasing.A cross section of 1.2 × 10-12 cm 2 at a laser field intensity of 2.17 × 10 7 V/m is obtained,which indicates that this collision process can be an effective way to transfer energy selectively from a storage state to a target state.The existence of saturation for cross section with the increase of the laser intensity shows that the high-intensity redistribution of transition probabilities is an important feature of this process,which is not accounted for in a two-state treatment.     

Ba-Sr系统激光感生碰撞能量转移的数值计算

以现有的激光感生碰撞能量转移的四能级理论模型为基础,通过直接积分态振幅的运动方程,对弱场、强场两种情况下Ba-Sr系统的激光感生碰撞能量转移过程进行了数值计算,得到了两种情况下的激光感生碰撞跃迁概率和碰撞截面的谱线线型.在弱场情况下的数值计算结果与近似解析解的计算结果符合很好.对强场情况下的数值积分计算结果表明：激光感生碰撞作用随转换激光强度的增大而增强;强场时激光感生碰撞截面谱线的峰值位置明显偏离了共振频率并向紫端移动,且碰撞截面谱线的半宽度(即调谐范围)较之弱场明显变小. 关键词： 激光感生碰撞能量转移 碰撞截面 Ba-Sr系统 强场