A molecular beam time-of-flight method for the observation of the velocity dependence of total collision cross sections

An application of the molecular beam time-of-flight technique is presented providing a physically simpler method of overcoming the principal uncertainties encountered in measurement of the velocity dependence of total collision cross sections. Explicit expressions are given for the velocity resolution and transmission of the time-of-flight (TOF) system. The considerations and procedure for design of a molecular beam TOF apparatus are detailed. This method gives greater velocity range and freedom of control of velocity resolution and transmission than traditional methods. The apparatus is described with emphasis on the considerations for optimizing the signal to noise ratio. An example of the method of extraction of the total cross section from the data is given, together with the observed velocity dependence and resulting intermolecular potential information. (author)