Pulsed field ionization-photoion spectroscopy using two-bunch synchrotron radiation: Time-of-flight selection scheme

We have demonstrated that the time-of-flight (TOF) selection method for pul sed field ionization (PFI) photoelectron detection [Jarvis , Rev. Sci. Inst rum. 70, 2615 (1999)] can also be applied for the detection of PFI-photoion s (PFI-PIs) using the two-bunch synchrotron radiation at the Advanced Light Source. By employing the supersonic beam technique to lower the translatio nal temperature of the sample gas, we show that background prompt ions form ed in direct and spontaneous autoionization processes arrive at the ion det ector in a pattern similar to that of the vacuum ultraviolet light bunches. The PFI-PIs formed at dark gaps can be designed to arrive at the detector in between adjacent prompt ion peaks, enabling the gating of the PFI-PI sig nal with only minor contamination from background prompt ions. This experim ent has revealed important considerations for the design of a general TOF s election scheme for PFI-PI detection using synchrotron radiation. (C) 2000 American Institute of Physics. [S0034-6748(00)03003-3].