由飞行时间质谱峰形获取光解碎片平动能分布

An approach to obtain the photofragment translational energy distribution from time-of-flight profile

由于在魔角条件下测量的飞行时间 (TOF)质谱峰形与光解碎片的角分布无关 ,因而便于用含待定参数的平动能分布函数去拟合质谱峰形来获取光解碎片的平动能分布 .与通常的拟合法不同 ,提出一种峰形参量法 ,只需通过测量TOF峰形的半高宽 (t1 2 )、四分之一高宽 (t1 4 )和四分之三高宽 (t3 4 ) ,便可借助文中提供的曲线图或解析式得出碎片平均平动能 ,平动能分布特征宽度以及描述实验装置本身的特征峰宽等 .处理过程中 ,平动能分布及实验装置峰形均采用相应的高斯分布函数描述 .

At the magic angle, the time-of-flight mass-spectrometer (TOF-MS) profile depends only on the translational energy distribution of photofragment, and is independent of the angle distribution of recoil momentum, therefore, the translational energy distribution is usually determined by fitting the measured TOF-MS profile. Different from the above procedure, we take another approach in the present work. According to this method, by measuring three widths at half maximum (t(1/2)(1/4)(3/4)(), one-fourth Maximum (t)() and three-fourth maximum (t)) of the TOF-MS profile, the averaged translational energy, the width of translational energy distribution, as well as the width of instrumental function can be determined from numeric tables or mathematical expressions. In this method, both the translational energy distribution and the instrumental function are described by Gaussian functions.