Ion cyclotron resonance spectroscopy

摘要: Ion cyclotron resonance spectroscopy yields information on many aspects of ion-molecule chemistry. The method is ideally suited for experiments involving ion energies below several electron volts, and hence provides a valuable complement to other techniques (27). eyclotron double uniquely suitable establishing relationships between reactant ions their product in complex reaction sequences. double-resonance with isotopic species yield mechanisms the nature intermediate species. Ion-molecule reactions which occur at low are quite sensitive functional groups details molecular structure (28). Reactions or neutral molecules specific reagents spectrometer can thus be used characterize unknown Once systematic chemistry useful has been worked out, it should possible proceed manner directly analogous classical chemical methods. Suppose, example, that A+, B+, C+, D+ each have characteristic different groups. Then these all mixed an species, X, reactions, X + A+ → ?, B+ . examined. In contrast solution chemistry, added simultaneously unknown, since examined by resonance. occur, synthesized , products degradation then X. same methodology applied ionic epecies X+, through use A, B, C, D. For proton transfer neuteal studying mass 45 produced from various sources (29). order affinities reagent as follows: NH3 〉 isobutylene propene. Ions protonation ethylene oxide (see III), acetaldehyde IV), fragmentation dimethyl ether V). Those might expected have, respectively, three structures: Proton mass-45 III IV occurs readily, but not source V, occurs, Thus demonstrate different. This example only rudimentary version approach characterization unusual species; niore sophisticated applications follow when more available. ideal comparing nonclassical carbonium routes. Some very interesting rearrangements molecules, following impact. Such frequently result radical another elimination small (30). It run reverse check postulated mechanisms. An study finding affinity amines pyridine extremely high (31). Species such VI VII: stable; they fact so stable unreactive respect subsequent charge center. Thus, if there ion, important design presence little influence reactivity group. this case functions simply inert label makes neutral-neutral accessible resonance: Various routes development basic technique also appear promising. Echo phenomena sequences pulsed excitation observed (32). Analogous transient cvclotron resonances (33). Pulsed-cyclotron-resonance course intriguing analogies nuclear-magnetic-resonance spin-echo (34) may choice making accurate measurements ion-molecule-reaction cross sections function energy energies. Finally, excited electronic states (35). N2- CO N2 CO- (46) studied beam (36). A straightforward procedure observe optical emission placing window end cell (37). analyzed crude set filters, high-speed spectrograph. Optical originate sources. radiation selected radio-frequency-optical experiment. If, generai B *C+ D, (47) irradiated its frequency, number density emitters changed. If irradiating frequency modulated, will intensity modulated. When spectrograph photoelectric cell, output detected phase detector referenced modulation frequency. highly modulation-detection scheme discriminate against light cell.