Ultrafast photoelectron spectroscopy: Femtosecond pump-probe coincidence detection of ammonia cluster ions and electrons

Analysis of the ultrafast photodissociation of electronically excited CF2I2 molecules by femtosecond time-resolved photoelectron spectroscopy

“…A small amount of benzene gas has been added for calibration purposes. After passing a skimmer ͑diameter 1 mm͒, the molecular beam reached the ionization region of the combined ion mass and electron spectrometers 10 where the molecules interact with the pulses of the weakly focused copropagating pump and probe laser beams. These were generated by a commercial Ti-sapphire laser and amplifier system ͑Clark MXR͒ the output of which, tuned to 800 nm, was split into two parts.…”

“…Then we obtained total coincidence rates below 0.05 per laser pulse which have been found necessary to keep the contribution of uncorrelated coincidences below 10%. 10 In the coincidence experiments the ions were detected by a time-of-flight ͑TOF͒ mass spectrometer whereas the electrons were analyzed by a TOF ''magnetic bottle'' electron spectrometer. The ion and electron signals were recorded by microchannel plate ͑MCP͒ detectors and were registered in a multihit time-to-digital converter ͑Le Croy 4208͒ started by the laser pulses with a repetition frequency of 1 kHz and stored and processed in a computer until a sufficient amount of coincidences was accumulated.…”

“…As different ion masses have to be analyzed simultaneously the combination of the pump-probe technique with the coincidence detection of photoions and photoelectrons as has been recently developed by us was necessary. 10 In the following after recapitulation of the fs time-resolved ion spectra we present the results of the photoelectron spectroscopy. Here, particular efforts are undertaken to detect selectively the neutral I atoms as fragmentation products of the CF 2 I 2 molecules.…”

Electronic continua in time-resolved photoelectron spectroscopy. II. Corresponding ionization correlations

“…Femtosecond time-resolved photoelectron spectroscopy ͑for a recent review, see Ref. 17͒ has been applied to wave packet dynamics in simple systems, 12,13,[18][19][20] nonadiabatic intramolecular 11,[21][22][23][24][25][26][27][28] and photodissociation 23,29 dynamics, spin-orbit coupling dynamics, 30,31 intracluster reaction dynamics, 32 excited state proton transfer dynamics, 33 and model molecular switches. 34 The outgoing photoelectron may be differentially analyzed as a function of time not only with respect to kinetic energy but also with respect to angular distributions [35][36][37][38][39][40] and spin polarization.…”

Electron Energy Spectra from Intense Laser Double Ionization of Helium

“…By detecting only one ion and one or more electrons in coincidence, it can be determined with some level of certainty that the detected ion and electrons were involved in the same ionization process. This level of certainty manifests itself in the number of "true" counts that are accumulated (the electrons and ion are positively correlated) versus the number of "false" or accidental counts (the electrons and ions are not correlated) [19]. The resulting true:false ratio can be calculated and used in the interpretation of the data.…”