Photodetachment photoelectron spectroscopy of multiply charged anions using electrospray ionization

A magnetic-bottle time-of-flight (TOF) photoelectron spectrometer, coupled with an electrospray ionization source, has been developed for the investig ation of multiply charged anions in the gas phase. Anions formed in the ele ctrospray source are guided by a radio-frequency quadrupole ion guide into a quadrupole ion trap, where the ions are accumulated. A unique feature of this apparatus involves the coupling of a TOF mass spectrometer to the ion trap with perpendicular ion extraction. The ion trap significantly improves the duty cycle of the experiments and allows photodetachment experiments t o be performed with low repetition-rate lasers (10-20 Hz). This novel combi nation makes the photodetachment photoelectron spectroscopy studies of mult iply charged anions possible for the first time. Furthermore, the perpendic ular extraction of ions, pulsed out of the ion trap, to the TOF mass spectr ometer allows the ion energies to be conveniently referenced to ground, sim plifying the configuration of the TOF mass spectrometer and the subsequent magnetic-bottle TOF photoelectron spectrometer. The mass resolution ( M/Del ta M) achieved is about 800 for smaller ions. The magnetic-bottle photoelec tron spectrometer resolution is about 11 meV full width at half maximum for 0.5 eV photoelectrons with an overall resolution of Delta E/E similar to 2 %. The detailed design, construction, and operation of the new apparatus ar e presented. (C) 1999 American Institute of Physics. [S0034-6748(99)00804-7 ].