摘要
本文采用飞行时间质谱技术测定了在紫外(355nm)、可见(560nm)和近红外(1064nm)脉冲激光作用下,氯分子束与Ti表面反应产物的质量分布和速度分布.所得结果表明,不同波长激光诱导反应的主要产物相同,有Ti,TiCl,TiCl_2,TiCl_3和TiCl_4.在高能量密度的紫外激光作用下,首次测得具有很高动能的原生Ti^+.各种含Ti氯化物的飞行时间谱,能满意地用.单组分或多组分Maxwell-Boltzmann公式拟合和分析.上述激光诱导气-固表面反应的机理主要由氯分子在Ti表面上的解离吸附,吸附态氯原子在表面上生成TiCl_x(x=1～4)的连串反应以及激光诱导脱附所组成.近红外激光主要引起热脱附,而紫外激光的作用还可能有非热脱附过程.
A mass selected time-of-flight (TOF) technique has been used to determine the mass distribution and velocity distribution of the reaction products of C1_2 molecular beam reacted with a Ti surface under pulsed UV (355 nm), Vis(560 nm) and near IR (1064 nm) laser irradiation. The results show that the main reaction products, such as Ti, TiCl, TiCl_2, TiCl_3 and TiCl_4, are the same for different wavelength of laser radiations. The genuine Ti^+ ions with high kinetic energy have been detected for the first time under the UV laser irradiation at high laser fluence. All of the TOF spectra for the Ti-contained chlorides can be fitted satisfactory with single-or multicomponent Maxwell-Boltzmann distribution. A mechanism with three steps, which mainly involves the dissociative chemisorption of the Cl_2 molecules on the Ti surface, the consecutive reactions of the adsorbed Cl atoms to form TiCl_x(x = 1～4) on the surface and the laser-induced desorption processes has been employed to explain the results of these laser-induced gas-surface reactions. It is found that the laserinduced thermal desorption play a dominant role for the 1064 nm laser irradiation, while competing nonthermal desorption processes are also important for the 355 nm case.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
1993年第2期161-166,共6页
Acta Chimica Sinica
基金
国家自然科学基金
