W. C. Wiley

W. C. Wiley worked on time-of-flight mass spectrometry at Bendix Aviation Corporation Research Laboratories. With I. H. McLaren, Wiley published a 1955 instrument study addressing the arrival-time spread of ions with the same mass-to-charge ratio. Their apparatus combined an ion-producing source, accelerating electric fields, an evacuated drift region and a collector; its analysis separated broadening from initial position and initial motion.^[ref]

The basic timing principle can be derived without the focusing details. An initially stationary ion of positive electric charge $q$ accelerated through an electric potential difference $V$ acquires kinetic energy $qV=m{v}^2/2$. Over a field-free drift length $L$,For a fixed charge state and instrument setting, differentiating $m\propto t^2$ gives the approximate mass resolving powerFor illustration, a $20\mu \mathrm{s}$ arrival time with a $20\mathrm{ns}$ timing width corresponds to $R\simeq 500$, if that width is the relevant small peak-width measure.

The focusing problem addressed by Wiley and I. H. McLaren is therefore substantive: a spread of initial conditions can broaden a peak even when the detector timing is precise. Their work on space focusing and time-lag focusing changes the ion trajectories to reduce that broadening, rather than merely measuring the same broad peak with a faster clock.