Pulsed field ionization-photoelectron

Several methods exist that allow the determination of the standard enthalpies of formation of the ionic species. The reader is referred to two recent rigorous and detailed chapters by Lias and Bartmess and Ervin. The vast majority of the experimental data reported here are obtained by means of Fourier transform ion cyclotron resonance spectroscopy (FT ICR), high-pressure mass spectrometry (HPMS), selected ion flow tube (SIFT), and pulsed-field ionization (PFI) techniques, particularly pulsed-field ionization photoelectron photoion coincidence (PFI-PEPICO). All these experimental techniques have been examined quite recently, respectively, by Marshall, Kebarle, B6hme," ° Ng" and Baer. These chapters appear in a single (remarkable) issue of the International Journal of Mass Spectrometry. An excellent independent discussion of the thermochemical data of ions, with a careful survey of these and other experimental methods, is given in Ref. 37. 

PFI-PEPICO pulsed field ionization photoelectron-photoion coincidence technique... 

ZEKE-PEl zero kinetic energy pulsed field ionization photoelectron spectroscopy... 

B. Pulsed field ionization-photoelectron spectroscopic studies, 88... 

In recent high-resolution, pulsed-field ionization-photoelectron (PFI-PE) spectroscopic studies of laser-initiated radicals, such as SH [61] and CHjS [54] formed in the laser photodissociation of H2S and CH3SH and CH3SSCH3, respectively, we have demonstrated that the PFI-PE spectroscopic technique is potentially useful for probing nascent state distributions of primary products formed in photochemical or reactive processes. 

B. Pulsed Field Ionization-Photoelectron Spectroscopic Studies... 

Beattie et al. [98Bea] have carried out zero kinetie energy pulsed field ionization photoelectron spectroscopy (ZEKE-PFI) using coherent two-photon exeitation (C2P) via a repulsive intermediate state. Vibrational progressions were observed, but rotational struetures eould not be resolved. Parameters, for both ionie spin-orbit ground state components, have been determined as follows (all values in units of cm )... 

B. Zero Kinetic Energy Threshold Photoelectron Spectroscopy and Pulsed Field Ionization (ZEKE-PFI)... 

D. -S. Yang, M. Z. Zgierski, D. M. Rayner, P. A. Hackett, A. Martinez, D. R. Salahub, P.-N. Roy, and T. Carrington Jr., J. Chem. Phys., 103, 5335 (1995). The Structure of NbjO and Nb30 Determined by Pulsed Field Ionization-Zero Electron Kinetic Energy Photoelectron Spectroscopy and Density Functional Theory. 

ADE = adiabatic detachment energies ESC A = electron spectroscopy for chemical analysis HOMO = highest occupied molecular orbitals MAES = metastable atom electron spectroscopy MIES = metastable ionization electron spectroscopy OAT = oxygen atom transfer PES = photoelectron spectra PEI = pulsed field ionization PIES = Penning ionization electron spectroscopy QM = quantum-mechanical REMPI = resonantly enhanced multiphoton ionization SC = semiclassical VDE = vertical detachment energies XPS = x-ray photoelectron spectroscopy ZEKE = zero electron kinetic energy Cp = cyclopentadienyl, Ph = phenyl, CeHs Tp =... 

The improved numerical stability of the new deMon2K version also opened the possibility for accurate harmonic Franck-Condon factor calculations. Based on the combination of such calculations with experimental data from pulsed-field ionization zero-electron-kinetic energy (PFl-ZEKE) photoelectron spectroscopy, the ground state stmcture of V3 could be determined [272]. Very recently, this work has been extended to the simulation of vibrationaUy resolved negative ion photoelectron spectra [273]. In both works the use of newly developed basis sets for gradient corrected functionals was the key to success for the ground state stmcture determination. These basis sets have now been developed for aU 3d transition metal elements. With the simulation of vibrationaUy resolved photoelectron spectra of small transition metal clusters reliable stmcture and... 

S. Willitsch, F. Innocent , J.M. Dyke, F. Merkt, High resolution pulse-field-ionization ZEKE photoelectron spectroscopic study of the two lowest electronic states of the ozone cation O. J. Chem. Phys. 122, 024311 (2005)... 

LASER-BASED PULSED FIELD IONIZATION-ZERO ELECTRON KINETIC ENERGY PHOTOELECTRON SPECTROSCOPY... 

An extension of ZEKE spectroscopy is mass-analysed threshold ionization (MATI), photoelectron spectroscopy without photoelectrons . This is effectively the same experiment for every ZEKE electron produced, there must be a cation, and in MATI detection a signal is recorded from these ions. It is much harder to separate the ions produced from pulsed-field ionization of the ZEKE Rydberg states from the ever-present directly produced ions. Ions are much heavier than electrons and hence move more slowly, so a higher-voltage extraction pulse is required for the separation and the subsequent extraction and selection of the cations. The obvious advantage of this combination of ZEKE with mass spectrometry is the ability to select the cations on the basis of their mass. 

A successful modification to the technique involves delayed pulsed-field extraction which allows discrimination between zero and near-zero kinetic energy electrons. About 1 ps after the laser pulse has produced photoelectrons, a small voltage pulse is applied. This has the effect of amplifying the differences in fhe velocities of fhe phofoelecfrons and allows easy discrimination befween fhem as a resulf of fhe differenf times of arrival af fhe defector. In fhis way only fhe elections which originally had zero kinetic energy following ionization can be counted to give fhe ZEKE-PE specfmm. 

This completes our brief description of the computational methods used in these studies. In the following sections some recent results will be presented and discussed. We will cover the calculation of ionization rates, the photoelectron energy distributions, the determination of the residual excited state populations remaining after excitation by a short pulse and finally show some photoemission spectra. The shape of the pulse envelope clearly can affect all these observable quantities. For example, the final state populations are found to be very sensitive to the pulse width and the peak intensity. Such results emphasize the point that in a strong, short pulsed field, the time dependence of the field envelope is reflected in the time evolution of the excitation dynamics. During the pulse. 

In the experiment, we measured photoelectron spectra from strong-field excitation and simultaneous two-photon ionization of K atoms with BWL (unmodulated) IR pump pulses, as a function of the pulse energy W [68]. The results for energies ranging from W = 0.35 to 2 pj are shown in logarithmic representation in Figure 6.13. All photoelectron spectra exhibit the AT doublet as a signature of the... 

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