Thomson received the 1906 Nobel Prize in Physics in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gasses. Thomson noticed that the ions move through parabolic trajectories proportional to their "mass-to-charge ratios.".
The time period from the late 1930's to the early 1970's was a time of great achievement in the field of mass spectrometry. By the end of World War I, the work of Francis W. Aston and Arthur J. Dempster brought improved higher accuracy mass spectrometers into reality. Later, Alfred Neir incorporated the developments in the accuracy along with advances in vacuum technology and electronics to greatly decrease the size of mass spectrometers. In 1946, William E. Stephens proposed the concept of time-of-flight analyzers, which also separated ions by measuring velocities as the ions move in a straight path toward a collector. The other analyzer in use today, the quadrupole analyzer, was developed in the mid-1950s by Wolfgang Paul. This analyzer is capable of separating ions with an oscillating electrical field further increasing the utility of mass spectrometers. Another Paul innovation was the quadrupole ion trap, which is a device specifically designed to trap and measure ions. The first ion trap became available commercially in 1983 and now both the quadrupole and quadrupole ion trap are the most widely used mass analyzers in the world and for his innovative work Paul was awarded the 1989 Nobel Prize in Physics. This era of rapid development fueled the enthusiasm that ushered in even greater discoveries during the 1980s and 1990s.
Two techniques developed in the mid 1980's, electrospray ionization (ESI) and matrix assisted laser desorption/ionization (MALDI), have had a significant impact on the capabilities of mass spectrometry. ESI is the production of highly charged droplets that are treated with dry gas or heat to facilitate evaporation, which eventually eject the ions in the gas phase.