Method of determining presence of isotopes

A method of determining the presence of isotopes in a sample, comprising:

• providing a sample beam containing the sample;
• causing the sample beam to travel back and forth along a single longitudinal axis;
• ionizing the sample beam with one or more lasers, wherein ionizing the sample beam comprises operating the one or more lasers at a plurality of frequencies;
• and
• directing the sample beam out of the ion trap and subsequently determining time of flight data of a first part of the sample beam relative to a second part of the sample beam, wherein the first part of the sample beam has a different charge relative to the second part of the sample beam, and wherein determining the time of flight data of a first part of the sample beam relative to a second part of the sample beam includes detecting the first part of the sample beam and the second part of the sample beam with one or more detectors;
• determining an ionization time using the time of flight data;
• obtaining data relating to the frequency of the one or more lasers at the ionization time;
• and
• determining the presence of isotopes in the sample using the data relating to the frequency of the one or more lasers at the ionization time.