Frequency-sweep Fourier transform ion cyclotron resonance spectroscopy (Reprinted from Chemical Physics Letters, vol 6, pg 489-490, 1974)

A single ion cyclotron resonance (ICR) absorption spectrum showing both CH3+ and CH4+ signals has been obtained by exciting both ion cyclotron resonances with a frequency-swept rf irradiation, followed by broad-band detection, digitization of the (time-domain) response, and finally discrete Fourier transformation to produce the (frequency-domain) spectrum. Pulsed-excitation Fourier transform ICR has demonstrated the use of broad-band detection in rapid generation of ICR spectra by Fourier transform methods; this paper demonstrates that frequency-sweep excitation can provide the broad-band irradiation required to excite ion cyclotron resonances throughout any desired mass range. It will thus be possible to obtain an ICR absorption spectrum of given mass range, signal-to-noise ratio, and resolution in an observation period which is two orders of magnitude shorter than that needed to obtain the same spectrum by conventional slow-sweep detection.