Ion Cyclotron Resonance Spectroscopy

Abstract

Ion cyclotron resonance spectroscopy has met with such wide acceptance that research groups utilizing this relatively new experimental technique now likely outnumber research groups which have used more traditional techniques, such as high pressure mass spectrometry, for the study of ion-molecule reactions. Since the previous review of ion-molecule reactions in Volume 1 9 o f the Annual Review of Physical Chemistry (1) there has been considerable development in the field. This development has been distributed among studies conducted with ion cyclotron resonance spectroscopy, drift tubes, high pressure mass spectrometry, flowing afterglows, tandem mass spectrometry, and beam experiments. Chemical applications of these techniques have been the subject of numerous recent reviews and monographs authored by principals in these investigations. In the present review an attempt will be made to chron­ icle the development of ion cyclotron resonance spectroscopy. Since this is the first review of the subject to appear in these volumes, the present article purports to be not only a review but an introduction as well. Sufficient back­ ground is developed to allow for a critical review of current experimentation in this field of endeavor. Ion cyclotron resonance spectroscopy is finding applications to the study of an increasing number of problems of general chemical interest. Recent developments promise an even wider range of applications. The technique is well suited for the routine study of ion-molecule reactions, which are readily identified using double resonance experiments (2). The identification of an ion-molecule reaction in a double resonance experiment provides useful information relating to the thermochemical properties of both ions and neu­ trals [including acidities (3-8) and basicities (9, 10) determined in the absence of complicating solvation phenomena], the identification of isomeric ion structures (1 1-16), and information concerning reaction mechanisms (17-23). Ion ejection techniques (11, 24) allow for the determination of product ion distributions in ion-molecule reactions even when other processes, such as